blown film workbook draft

Higher Institute for Plastics Fabrication

WORKBOOK

for

Blown Film Extrusion

Practical Course

Prepared by

Blown Film Extrusion Department

1st Edition 2009

Workbook for Blown F i lm Pract ica l Course

ACKNOWLEDGEMENT

In its program to continuously improve the quality of instructions at the

Higher Institute for Plastics Fabrication, the Curriculum Steering Committee

initiated the creation of the workbooks for all practical courses being offered

in the Institute. The Committee is headed by Dr. Khaled Al-Ghefaili, and the

members are Dr. Ahmad Al-Ghamdi, Mr. Hiroshi Takeshita, Engr. Issa Al-

Khormi, Mr. Sumio Iwase, Mr. Kazuhiko Sawada, Mr. Sanjay Rawat, Mr.

Zakaria Musa, and Mr. Virgilio Calpe.

This is the HIPF Workbook for Injection Molding for Practical Course. The

contents of this workbook were compiled through the efforts of the members

of the Blown Film Department, namely, Raul R. Clave (Head of the

Department), Isagani Aldover, Philip Floyd Yumul, Jovanny Quilala, Jovef

Pangue, Alfred Bacosa, Kirankumar Daraji (Senior Instructors) and Mr.

Sumio Iwase and Mr. Takuma Nakashima (Blown Film Expert Advisers).

Editing, formatting and design by Virgilio Calpe.

February 2009


TABLE OF CONTENTS

Introduction … … … … … … … … … … … … … … … … … … . 4

Course Objectives … … … … … … … … … … … … … … … … . 5

General Safety Guidelines … … … … … … … … … … … … … ... 6

Grades Summary Sheet … … … … … … … … … … … … … … ... 7

Workshop Activities

Activity 1—Basic Theory of Blown Film Extrusion … … … … … .. 8

Activity 2—Polyethylene Films… … … … … … … … … … … … 14

Activity 3—Emergency Stop and Safety Devices … … … … … … . 19

Activity 4—Blown Film Die … … … … … … … … … … … … … 26

Activity 5—Blown Film Air Cooling Ring … … … … … … … … .. 31

Activity 6—Blown Film Width and Thickness… … … … … … … .. 37

Activity 7—Corona Treatment … … … … … … … … … … … … . 42

Activity 8—Flexographic Printing … … … … … … … … … … … 48

Activity 9—Bag Making … … … … … … … … … … … … … … . 55

Activity 10—Polyethylene Film Recycling … … … … … … … … . 64

Glossary … … … … … … … … … … … … … … … … … … … . 92

References … … … … … … … … … … … … … … … … … … ... 110

Activity 11—Practice Plant Operations (LDPE) … …. … … … … .. 73

Activity 12—Practice Plant Operations (LLDPE) … …. … … … … . 81

Formulas … … … … … … … … … … … … … … … … … … … 89

Activity 13—Practice Plant Operations (HDPE) … …. … … … … .. 85


INTRODUCTION

Blown film extrusion is one of the most commonly used thin-gauge

fabrication processes in the world. The majority of the commodity films

such as grocery bags, agricultural films and other flexible packaging films

used by consumers are produced by this method. The process of producing

film by extruding molten resin into a continuous tube is simple. Yet, in fact

the system is one of the most complex and sensitive of all the plastics

fabricating technologies and it presents many inherent difficulties.

A simple blown film line consists of an extruder, die, air ring, iris or bubble

cage, collapsing frame, and a winder.


COURSE OBJECTIVES

The purpose of this workbook is to enable the trainees to understand and

carry out important activities being done in a blown film extrusion process.

Focus will be on the most important functions of the machine and the

terminologies used in the enterprise.

Upon successful completion of this course, the trainee will be able to:

• Know the main components of film extruders and their purposes.

• Describe blown film extrusion process.

• Identify common polyethylene films.

• Perform emergency stop using emergency switches.

• Know the operation of an air ring, die, nip rolls and gusseting equipment.

• Know the operation of a simple flexographic in-line printer.

• Know the basic operation of a recycling machine.


GENERAL SAFETY PRECAUTIONS

Instead of starting operations carelessly, all trainees should discuss the

following before starting any activity:

(1.) What types of activities are we going to do?

(2.) What kind of risks are hidden behind those types of activities?

(3.) What should we do to avoid those risks?

Here are some safety reminders to always keep in mind:

• Keep the work area clean at all times.

• Use proper hand gloves. Avoid using loose hand gloves.

• Use the appropriate tool and wear protective dry gloves when you throw

away purged resin.

• Do not lean against the cage guard of the ladder when you work.

• Pay attention to where your hands are to ensure that your hands are not

pinched between rollers and other rotating equipment.

• Do not run the machine without the protective covers on rotating parts.

• Avoid clothing or accessories that could easily be pinched or caught in

machines.

• Specifically, do not wear items that hang far from your neck such as long

necklaces and IDs’. Do not wear rings or loose bracelets. Do not wear

clothing that is pleated, sags or has strings. Make sure that you button or

fasten your shirt and jacket cuffs, pant cuffs and jacket hem.

• Do not stand in front of the die.


GRADES SUMMARY SHEET

Trainee Name: _________________________ Group: ________

Semester ___ School Year ___________

ACTIVITIES GRADE

Activity 1—Basic Theory of Blown Film Extrusion

Activity 2—Polyethylene Films

Activity 3—Emergency Stop and Safety Devices

Activity 4—Blown Film Die

Activity 5—Blown Film Air Cooling Ring

Activity 6—Blown Film Width and Thickness

Activity 7—Corona Treatment

Activity 8—Flexographic Printing

Activity 9—Bag Making

Activity 10—Polyethylene Film Recycling

Activity 11—Practice Plant Operations (LDPE)

Activity 12—Practice Plant Operations (LLDPE)

Activity 13—Practice Plant Operations (HDPE)

AVERAGE GRADE


THEORETICAL BACKGROUND

Blown films are created by feeding plastics pellets into an extruder where

they are melted and homogenised before they are pumped through a circular

blown film die. The melted plastics form a continuous tube which is drawn

from the die. It is inflated and simultaneously cooled by rapidly moving air.

The tube, also called a “bubble,” is then flattened as it passes the collapsing

frames and drawn through nip rolls and over idler rolls to a winder which

pulls and winds the finished rolls of film.

A typical film blown film machine consists of the following five major units:

• Extruder unit—converts the solid pellets into hot melt.

• Die unit—forms the hot melt into tube.

• Cooling unit—cools down and solidifies the hot melt.

• Take-off unit—pulls and flattens the tube at constant speed.

• Winding unit—winds-up the flattened tube into finish rolls.

WORKSHOP ACTIVITY #1

Basic Theory of Blown Film Extrusion


OBJECTIVES OF THE ACTIVITY

1. To learn the basics of operating a blown film machine

2. To identify the parts of the five major units of a blown film and their

elements

PROCEDURE

PART I—The Basic Operations of Blown Film Machine

1. Go to the Workshop floor and observe any of the blown film machine

that is being run by your Instructor.

2. Using data sheet on the following pages, list down accordingly the steps

of the blown film process you have observed.

Example:

Step 1. Put material in the hopper.

Step 2. etc…

PART II—The Five Major Units of a Blown Film Machine

1. Using the drawing of Blown Film Machine in your data sheet, label the

following:

a. name of the part/s of each major units.

b. name the other elements needed in the process.

WORKSHOP ACTIVITY #1—Basic Theory of Blown Film Extrusion

DATA SHEET

PART I—The Basic Operations of Blown Film Machine

Steps in Blown Film Operations

ACTIVITY #1—Basic Theory of Blown Film Extrusion

TRAINEE NAME GROUP NO.

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Report Form Report Form Report Form Report Form ---- Page 1 of 4 Page 1 of 4 Page 1 of 4 Page 1 of 4

Description of the Step Step No.

DATA SHEET

PART II—The Five Major Units of a Blown Film Machine

ACTIVITY #1—Basic Theory of Blown Film Extrusion


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Properly label the Blown Film

Proce

ss Diagram


QUESTIONS & EXERCISES

A. Choose the correct answer.

1. What is the most common material used for blown films?

(a.) PVC (c.) Nylon

(b.) PET (d.) PE

2. What is the common type of blown film used all over the world?

(a.) Downward BF (c.) Upward BF

(b.) Horizontal BF (d.) None of the above

3. What part of the blown film machine makes the screw rotates?

(a.) blower (c.) haul-off

(b.) main motor (d.) winder

4. What is the process of feeding a single die with two or more different

polymer melt streams?

(a.) blower (c.) haul-off

(b.) main motor (d.) none of the above

B. How does blown film differs from other plastics fabrications?

Check (�) if applicable, and cross out (�) if not applicable.


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PROCESS Die Mould Screw and

Barrel

Haul-off /

Take-off Winder

Blown Film

Extrusion

Blow

Molding

Pipe

Extrusion

Injection

Molding


CONCLUSION & RECOMMENDATIONS

INSTRUCTOR’S COMMENTS


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TRAINEE’S GRADE

FOR THIS ACTIVITY

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INSTRUCTOR’S SIGNATURE

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DATE: __________________

DATE: __________________

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TRAINEE’S SIGNATURE



• The ethylene polymer is available in three main grades, low, medium and

high density film.

• Polyethylene, PE, film is slightly opaque, the opacity increasing with

density.

• PE film is waxy to the touch, and is a good moisture barrier.

• Low and medium density PE films are flexible even when cold.

• PE is readily heat sealed.

• High density PE film is suitable for boil-in-the-bag packs, whereas low

and medium density films are not.

• PE film that has a lower MFR means a higher molecular weight and

better mechanical strength.


Polyethylene Films



1. To learn the physical properties of Polyethylene (PE) films

2. To compare the differences among the three common types of PE films

used in blown film packaging

PROCEDURE

PART I—Physical Characteristics of PE Films

1. Collect three samples for each type of the PE films from the plant

• LDPE @ 400mm & 30microns

• LLDPE @ 400mm & 30microns

• HDPE @ 400mm & 30microns

2. Correctly label the different films.

3. Each film sample should have the same thickness, length and width.

4. Try to stretch each film and write your observation in your data sheet.

PART II—Process Parameters for PE Films

1. Try to find the Melt Temperature and Pressure for processing each type

of PE films.

2. Write your data in the table provided in your data sheet.

3. Compare MFR, Density, Melt Temperature, and Pressure for each type of

PE films.

4. Which materials do you think is the easiest to process?

WORKSHOP ACTIVITY #2—Polyethylene Films

DATA SHEET

PART I—Physical Characteristics of PE Films

Stretch the plastics samples:

PART II—Process Parameters for PE Films

ACTIVITY #2—Polyethylene Films


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PE Sample

MFR Density Extruder Melt Temperature

Extruder Melt Pressure

LDPE 0.2 to 5 0.912 to 0.925

LLDPE 0.5 to 2 0.912 to 0.925

HDPE 0.03 to 0.1 0.945 to 0.955

PE Sample Observations

LDPE

(400mm, 30microns)

LLDPE

(400mm, 30microns)

HDPE

(400mm, 30microns)

Based on the above data, which materials is easy to process?

Why?



Choose the correct answer and mark ( � ) the correct ones.

1. Which of these films has a better clarity?

a. LDPE

b. LLDPE

c. HDPE

2. Which is the toughest among these polyethylene films?

a. HDPE

b. LDPE

c. LLDPE

3. Which blown film bag is suitable for carrying more weight?

a. LLDPE

b. LDPE

c. HDPE

4. Choose the correct application of LDPE film.

a. food packaging

b. shopping bag

c. garments packaging

d. floor covering

5. Which of these films can be stretch more?

a. HDPE

b. LDPE

c. LLDPE


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FOR THIS ACTIVITY

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DATE: __________________

DATE: __________________

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MACHINE SAFETY GUARDS & DEVICES

Safety devices in facilities, machinery and equipment are an essential means

of ensuring worker safety. Foolproof devices, failsafe devices and others are

used to ensure intrinsic (essential) safety. These devices are usually built

into facilities, machinery and equipment so that workers cannot easily

remove them.

The foolproof function is a safety mechanism designed with a focus on

human factors. On the other hand, the failsafe function is a safety

mechanism designed with a focus on the protection of facilities, machinery

and equipment.

Types of safety devices typically used in blown film machine:

• Mechanical Interlock

• Electrical Interlock

All Dangerous spots of the blown film line must be secured by suitable

protective devices. If proper guards cannot be mounted due to the conditions

at hand, these areas are secured by Emergency devices.

Guarding and Barriers

The purpose of machine guarding and barrier is to protect the machine

operator and other employees in the work area from hazards created by

moving parts, rotating parts, flying chips & sparks. Some examples of this

are barrier guards, safety gates, etc.


Emergency Stop and Safety Devices


THEORETICAL BACKGROUND … continued

WORKSHOP ACTIVITY #3—Emergency Stop and Safety Devices

Pull-Down

Electrical Interlock

Safety Interlock Switch

Push

WARNING SIGN WARNING SIGN

SAFETY COVER GUARD RAILS

EMERGENCY STOP EMERGENCY STOP

SAFETY SWITCH SAFETY GATE



1. To know the purposes of each of the safety devices installed in a blown

film machine

2. To learn how to pause or stop the blown film machine in emergency

cases

3. To develop awareness of the dangers of blown film machine if safety

devices are tampered or by-passed

PROCEDURE

Types of Safety Devices Typically Used in Blown Film Machines

Walk around the blown film machine assigned to you by your Instructor and

try to locate all the safety devices and the emergency stop buttons.

PART I—Safety Devices and their Functions

1. In your data sheet, write down the names of the safety devices and their

functions and answer the questions.

PART II—Emergency Stops

1. In your data sheet, indicate all the emergency stop buttons of the blown

film machine available in WS02 and answer all the questions.


DATA SHEET

PART I—Safety Devices and their Functions

Safety Devices of Blown Film Machine, where are they?

ACTIVITY #3—Emergency Stop and Safety Devices


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SAFETY DEVICES of BLOWN FILM MACHINE

1.

2.

3.

4.

5.

1. Do these safety devices really help by reminding you of the danger if

they are not activated?

2. How?

YESYESYESYES NONONONO

DATA SHEET

PART II—Emergency Stops

Emergency stop buttons of Blown Film Machine, where are they?

ACTIVITY #3—Emergency Stop and Safety Devices


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1. When are we going to use the emergency stop buttons, is it during

scheduled shutdown?

2. Why?

3. If something happens to the machine or to the operator and we need to

stop immediately, are we going to use the emergency stop?

4. Why?





Choose the correct answer.

1. What type of emergency device is installed above and across the

width of the winding station?

(a.) emergency stop button (c.) emergency stop cord

(b.) warning alarm (d.) none of the above

2. What warning sign is available in the machine indicating danger of

being burn?

3. What will you do to stop the machine in case of emergency?

(a.) switch off the main switch

(b.) leave the machine

(c.) press the “Emergency Stop” push button

(d.) follow the shutdown procedure

4. Which mandatory safety sign that informs operator to wear hand

protection?

5. Which of the following is an example of safeguarding devices?

(a.) printing gear cover (b.) railings

(b.) winder gates (c.) all of the above


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(a.) (b.)

(c.) (d.)

(a.) (b.)

(c.) (d.)





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FOR THIS ACTIVITY

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DATE: __________________

DATE: __________________

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In various kinds of plastics fabrication processes, molten resin that leaves the

extruder is forced through an orifice (opening, slit) called a die. By this die

the molten resin is given its final shape appropriate for the end product.

A die used for blown film extrusion has an annular (ring-shaped) outlet

(called a lip) through which the molten resin passes. Such a die is called a

circular die. The size of a die is expressed by the lip diameter. The lip

diameter ranges from a small diameter of about 30 mm to a large diameter of

about 1,500 mm.

The Two Types of Die Lip Gap Adjustments: Figure 4.1


Blown Film Die

Upper Die Goes that way

Tightening the bolt

Upper Die

Tightening the bolt

Upper Die Goes that way

Upper Die

A

B



1. To learn the basic principles of die mechanisms

2. To understand the die mechanisms and how to adjust the lip gap

PROCEDURE

PART I—Die Lip Adjustment

1. Prepare the half die head available in the Workshop.

2. Examine carefully what type of die lip gap adjustment the die has.

3. Confirm the movement of the die lip. Confirm whether it is A- or B-type

lip gap adjustment.

4. When making adjustment, loosen the bolt on the other side first. Refer to

Figure 4.1:

• For A type, tightening the bolt will widen the gap.

For this type, when the die ring is screwed in, the ring is moved in a

way that pulls the ring with the bolt to widen the lip gap (see Figure

4.1).

• For B type, tightening the bolt will narrow the gap.

For this other type, when the die ring is screwed in, the ring is moved

in a way that pushes the ring with the bolt to narrow the lip gap (see

Figure 4.1).

5. Try turning the bolts of your die and observe the outer lip movement of

the die. Answer all the questions in your data sheet.

PART II—Parts of the Die

1. Properly label the parts of the die using the drawing found in your data

sheet.

WORKSHOP ACTIVITY #4—Blown Film Die

Important!

Before you adjust the gap, you should know which type of adjust-you should know which type of adjust-you should know which type of adjust-you should know which type of adjust-able die ring is used for the die able die ring is used for the die able die ring is used for the die able die ring is used for the die available. You should also under-stand that the adjustable die ring just moves horizontally as a as a as a as a

whole whole whole whole by rotating the adjusting bolt.

DATA SHEET

PART I—Die Lip Adjustment

ACTIVITY #4—Blown Film Die


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1. Referring to the Figure 4.1, what type of die do we have in Workshop 02

Blown Film?

2. What happens when you tighten the bolt of this type?

3. In your own opinion, if you widen the die lip gap, does this makes the

corresponding blown film wall thicker?

4. Why?

PART II—Parts of the Die

AAAA----TypeTypeTypeType BBBB----TypeTypeTypeType




1. It is the part of the Blown Film machine where the molten resin is forced

through its round opening slit and forms a tube.

a. screw and barrel

b. adapter

c. die

d. none of these

2. Describe briefly how the material flows as it enters the spiral and outside the

spiral.

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4. When the die is not properly centered, why is a thinner film produced from the

wider die gap and a thicker film from the narrower gap?

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FOR THIS ACTIVITY

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DATE: __________________

DATE: __________________

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Blown film air rings are used primarily to stabilize the bubble and

secondarily to cool the melt. In plastics forming, a circular manifold

distributes an even flow of cool air into a hollow tubular form passing

through the manifold.

An air ring is installed just above the die in an upward air cooling blown film

machine. The air outlet called a lip (or slit) has an annular shape that

surrounds the molten resin extruded from the die. Air is introduced into the

ring by the blower, and the air is turned into a uniform flow inside the air

ring. Then the air is blown through the lip against the molten resin for

cooling. If the flow of air blown out of the lip is not uniform, it leads to non-

uniform cooling. As a result, film thickness will be uneven. To prevent this,

the air ring is designed to ensure uniform air flow over the entire lip.

As the molten resin is cooled, it becomes “frosty,” or less clear (transparent),

and a solidification border appears. This borderline is called a frost line.


Blown Film Air Cooling Ring


WORKSHOP ACTIVITY #5—Blown Film Air Cooling Ring

PA

RT

S O

F A

SIN

GL

E L

IP B

LO

WN

FIL

M A

IR R

ING



1. To know the importance of air ring to blown film extrusion

2. To understand the construction of an air ring and how to adjust it

PROCEDURE

1. Run the blown film line assigned to you by your Instructor.

2. With the supervision of your Instructor, set the parameters to produce a

30microns by 300mm lay flat width film.

3. Once the process has stabilized (as checked by your Instructor), adjust

the threaded adjusting ring of the air ring by the doing the following

trials:

• Trial 1—Turn the adjusting ring one-fourth ( ¼ ) down

• Trial 2—Turn the adjusting ring another one-fourth ( ¼ ) down

• Trial 3—Turn the adjusting ring still another one-fourth ( ¼ )

down

• Trial 4—Turn the adjusting ring one-fourth ( ¼ ) upward

• Trial 5—Turn the adjusting ring another one-fourth ( ¼ ) upward

4. Allow 5minutes intervals for each trial and ensure that the bubble is

stable each time.

5. For each trial, observe what will happen to the bubble and take note of

what happens to the height of the frost line.

6. Write all your observations on the table provided in your data sheet, and

answer all the questions.


DATA SHEET

OBSERVATIONS

ACTIVITY #5—Blown Film Air Cooling Ring


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Trial

No.

Number of Turns

and Direction

Pressure

Reading Bubble Observations

1 ¼ turn down

2 another ¼ turn down

3 another ¼ turn down

4 ¼ turn upward

5 another ¼ turn upward

1. When the threaded adjustable ring is adjusted downwards, what happens

to the frost line height? goes up or down?

2. What type of air ring does workshop 02 blown film has,

Is it single lip or dual lip?

3. How did you know that it is a _____________lip?

4. If the inside of the air ring is dirty and causing obstruction, will you have

an even flow of air in the bubble, yes or no?

5. Does this obstruction cause uneven thickness of the film, yes or no?

goes upgoes upgoes upgoes up goes downgoes downgoes downgoes down

single lipsingle lipsingle lipsingle lip dual lipdual lipdual lipdual lip

yesyesyesyes nononono




1. _______________________is the part of the Blown Film machine that

uniformly cools and then evenly solidifies (make solid) the molten resin

extruded from the die.

2. The blowing angle should be appropriately set depending on the type of

resin is used, the type of product being made, and other factors.

True or False?

3. In the given drawing below, the air ring is called a dual lip because it has

_______________, _________________, and ____________________.

4. In the given drawing below, which of these two air rings is used for

LLDPE and which is for HDPE?

_________ is for LDPE _________ is for HDPE


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DATE: __________________

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The width (lay-flat width) and thickness of the film to be made are always

specified in blown film extrusion. The operators need to set the width and

thickness to the specified values correctly and maintain them within the

target level during the processing. Once the process is started, first adjust the

lay-flat width to the specified value. The screw rotation speed shall be set to

the predetermined speed and the amount of air to be introduced into the

bubble shall be adjusted. Then the film thickness shall be next step.

In blown film extrusion, there are various kinds of operation requirements

that directly influence on the shape of the bubble. Examples of these

requirements are extruder take-off speed and the amount of air that enters

the bubble. In particular, they affect the bubble size and vary the film

thickness and lay-flat width.


Blown Film Width and Thickness

D

Rolled Film

W t

tttt = thickness of film

W= width of film



1. To learn how to adjust the width and thickness of a blown film bubble

PROCEDURE

1. Run the blown film line assigned to you by your Instructor.

2. With the supervision of your Instructor, set the parameters to produce a

30microns by 300mm lay flat width film.

3. Once the process has stabilized (as checked by your Instructor), record

the take-off speed and winder tension on the table in your data sheet

under Trial 0.

4. Then do the following trials, each time observing what will happen to the

film thickness and film width. Record the new thickness and width on

the table in your data sheet.

5. Answer all questions relating to each trial.

WORKSHOP ACTIVITY #6—Blown Film Width and Thickness

TRIAL No. ACTION

Trial No.1 Increase the take-off speed by 2m/min. Slightly add

tension on winder to adjust the film tension.

Trial No.2 Open the air valve and let air enter the bubble for at

least 2 minutes. Wait for another 3minutes. Let your

instructor stabilize the bubble. Observe what will hap-

pen to the bubble.

Trial No.3 Increase the take-off speed by 2m/min. Slightly add

tension to winder to adjust the film tension. Observe

again what will happen to the thickness of the film.

Trial No.4 Open the air valve and let air enter the bubble for at

least 2minutes. Wait for another 3minutes. Try to sta-

bilize the bubble by yourself while the instructor

guides you. Observe what will happen to the bubble.

DATA SHEET

DATA & OBSERVATIONS

ACTIVITY #6—Blown Film Width and Thickness


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Trial

#

Take-off Speed,

m/min

Film Thickness,

µm

Winder

Tension, N Width, mm

0 30 microns 300mm

1

2

3

4

1. When the haul-off speed is increased in Trial No.1, did the thickness also

increased, yes or no?

2. When you add some more compressed air in Trial No.2, did the width of

the film increased, yes or no?

3. What happened to the bubble when you increased again the haul-off

speed in Trial No.3?

4. What happened to the width when you add more compressed air in Trial

No.4?





A. Choose the correct answer.

1. What happens to the lay-flat width if more air is introduced into the

bubble?

(a.) no change (c.) increase

(b.) decrease (d.) none of the above

2. If the extruder screw speed is increased, what happens to the film

average thickness?



3. What happens to the film average thickness if the take-off speed

increased?



4. If the extruder screw speed is decreased, what happens to the film

average thickness?



5. What happens to the film average thickness if the take-off speed

decreased?




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B. How do you decrease the width of lay flat tube?

C. How do you increase the thickness of the film?





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• If a corona discharge is generated in air, ozone (O3) is created from the

oxygen (O2) in the air. Ozone is a powerful oxidizing gas. This ozone

oxidizes the surface of plastics film to make it easier for the ink to stick

to the film. This method of treating a plastics film surface is called

corona discharge treatment.

• The corona discharge treatment equipment is made up of a high

frequency generator, an electrode, and a treater roll.

• The wetting tension of PE film and PP film that have not been surface

treated is around 30 to 35 mN/m. The tension appropriate for printing on

these kinds of film is said to be normally around 40 to 45 mN/m. So,

what is wetting tension?

• Treated film surface can be checked by measuring the wetting tension of

the film surface. The wetting tension is an indication of the wettability of

a solid surface.

• Normally, wetting tension of a film that is not surface treated is around

30 to 35 mN/m compared to a treated film which has 40 to 45mN/m.


Corona Treatment


Theoretical background … continued

• This activity will explain how wettability works with the polyethylene

film. Below is the schematic drawing of a corona discharge machine

(corona treater).

WETTING TENSION MEASUREMENT

• The approximate wetting tension of a film can measured by using wetting

ink supplied by Polyrema. The ink is used to write on the surface of the

film and the ink value where there is no “run-off” corresponds to the wet-

ting tension of the film.

WORKSHOP ACTIVITY #7—Corona Treatment



1. To know the importance of corona treater in blown film printing

2. To know how corona treater affects the film quality during secondary

processes

PROCEDURE

1. Run a blown film line.

2. Produce a 30microns by 300mm lay flat width LLDPE film. Make sure

film passes the corona discharge machine.

3. Once the blown film is stabilized and checked by your instructor, get

film samples without the corona treatment, and then with corona

treatments at different corona treatment settings.

4. Properly label each sample.

5. Check the wettability of each sample using the wetting ink supplied by

POLYREMA.

6. Follow the following settings for the trials:

7. Your Instructor will demonstrate how the wetting ink is used. Start from

the lowest wetting ink value to the highest, and record the trial results in

your data sheet for each of the sample.

8. Record whether “run-off” occurs or not when the sample is tested with

each wetting ink values.

9. Answer all questions regarding your observations.


TRIAL NO. CORONA TREATER SETTING

1 0% treater setting (no corona treatment)

2 40% treater setting



DATA SHEET

RUN-OFF OBSERVATIONS

ACTIVITY #7—Corona Treatment


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Trial

No.

Did the line “run-off”?

Wetting Ink 42 Wetting Ink 44 Wetting Ink 46

1 0%

2 40%

3 70%

4 90%

Treater

Setting













1. What happened to the wetting ink applied on the first film sample? Did

the liquid line run-off? What does this broken line shows?

2. For the 2nd sample (Trial #2) how did the wetting ink behave in the

film? Did it run-off too? What does this mean?

4. For the 3rd sample (Trial #3), do you think the value of the corona dis-

charge is very good for printing? Why?

4. For the 4th sample (Trial #4), do you think the value of the corona dis-

charge is very good for printing? Why?

5. What about sealing this film from Trial #4, do you think that the seal

will be very good?



1. The method of treating film surface is called

a. gusseting

b. sealing

c. corona discharge treatment.

2. What is the normal surface tension for untreated PE films?

a. 20-30 mN/mtr

b. 30-35 mN/mtr

c. 40-45mN/mtr

3. Using the wetting liquid application and marking a line on the film, if

the line breaks-off or runs-off this means the film is

a. untreated

b. treated

4. Write down the three major parts of a corona discharge machine.

a. ______________________________

b. ______________________________

c. ______________________________


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DATE: __________________

DATE: __________________

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Rotary Printing—is a printing technique in which the impressions are

carved on a rubber plate and stuck on a cylinder, or carved on the cylinder

itself, so that the printing can be done on long continuous rolls of paper,

cardboard, plastic, or a large number of other substrate.

Often Used Printing Processes for Blown Film:

• Flexographic Printing

• Rotogravure Printing

FLEXOGRAPHIC PRINTING

Flexographic printing has an advantage over rotogravure in that it can use a

wider range of inks, water-based rather than oil-based inks, and is good at

printing on a variety of different materials like plastics, foils, acetate films,

brown paper, and other materials used in packaging. Typical products

printed using flexography includes flexible packaging, including retail and

shopping bags, food and hygiene bag, etc.

A flexographic print is made by creating a positive mirrored master of the

required image as a 3D relief in a rubber or polymer material. Flexographic

plates can be created with analog and digital plate-making processes. The

image areas are raised above the non-image areas on the rubber or polymer

plate. The ink is transferred from the ink roll which is partially immerged in

the ink tank. Then it transfers to the anilox roll (or meter roll) whose texture

holds a specific amount of ink since it is covered with thousands of small

wells or cups that enable it to meter ink to the printing plate in a uniform

thickness evenly and quickly.


Flexographic Printing


Theoretical Background … continued

PARTS OF A FLEXOGRAPHIC PRINTER

WORKSHOP ACTIVITY #8—Flexographic Printing

Impression

Cylinder

Plate

Cylinder

Anilox

Roller

Fountain

Roller



1. To learn the basic operation of a flexographic printing machine for blown

film

2. To know the parts and functions of a flexographic printing machine

PROCEDURE

1. Pre-heat a blown film machine that has in-line flexographic printing

machine.

2. Prepare a rubber cliché for flexographic film print run and the schematic

drawing of a flexographic printing machine.

3. Mount the rubber plate on the plate cylinder. Make sure of the alignment

by following the groove etched on the cylinder surface. See the drawing.

4. Move gear 1 (for Roll 1) towards gear 2 (for Roll 2) and mesh their teeth

by about 3mm by turning knob C clockwise.

5. Pour ink in the ink pan. Ink level at least a few millimetre of the fountain

roller lower portion.

6. Switch-on the printing drive.



Procedure … continued

7. Move the fountain roller 3 towards the anilox roller 4 by turning knob A

clockwise. Observe the ink between these rollers. Putting more pressure

between roller 3 and 4 means reducing the ink on the anilox concave

surface and lesser ink will be transferred to the rubber plate.

8. Move carriage of 3 & 4 towards 1 by turning the knob B until ink from

the anilox is transferred to the rubber plate.

9. Activate the pneumatic cylinder for the carriage D and observe the

printing on the film.

10. If print does not appear yet, turn knob C slower clockwise until print

appears.

10. When you feel you have attained the best print, take a sample printed

film and cut the printed portion.

11. Attach the printed film in your data sheet.


Note:

Each of the specific knobs has to be adjusted to attain

a good ink tone balance and better quality print.

DATA SHEET ACTIVITY #8—Flexographic Printing


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ATTACH ATTACH ATTACH ATTACH

YOUR YOUR YOUR YOUR

PRINTED FILM PRINTED FILM PRINTED FILM PRINTED FILM

HERE!HERE!HERE!HERE!

FLEXOGRAPHIC PRINTED FILM

1. When you pressed the fountain roller with the anilox roller, does this

mean we are reducing the ink being transferred to the printing plate?

2. What is the function of knob A?

3. When you pressed carriage 3 & 4 to roller 1, did the image appear on the

film?

4. What is the function of knob B?





Choose correct answer.

1. Which type of printing is done on polyethylene blown film?

a. Screen printing

b. Rotogravure printing

c. Laser printing

d. Flexographic printing

2. Which process is done before printing the polyethylene film?

a. Heat treatment

b. Chemical treatment

c. Corona treatment

d. Laser treatment

3. Why do plastics surfaces require pre-treatment for printing?

a. To make plastic thicker

b. To make plastic stronger

c. To make plastic more decorative

d. To make strong ink bonding on surface

4. What type of chemical (thinner) is used to make printing ink thin and

dryable during flexographic printing?

a. Acid

b. Kerosene

c. Petrol

d. Alcohol

5. What is that rubber-like material we use in flexographic in making a

printing plate?

a. PVC

b. Photopolymer

c. Polyethylene

d. None of these


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DATE: __________________

DATE: __________________

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Every day, our lives are touched by plastics packaging

products. Polyethylene bag is one of the best applications of packaging

products.

Polyethylene bag is used for various purposes like shopping, grocery,

laundry, food packaging, garments, textiles, agriculture, industrial products

packaging, garbage, waste management, etc.

There are mainly two types of methods to make polyethylene bags.

• Bottom sealed bag

• Top and bottom sealed bag


Bag Making

Examples of Bottom Sealed Bag Products

Examples of Top and Bottom Sealed Bag Products



WORKSHOP ACTIVITY #9—Bag Making

BOTTOM SEALING DIAGRAM

BOTTOM SEALING PROCESS FLOW




DOUBLE SEALING DIAGRAM

DOUBLE SEALING PROCESS FLOW




TYPES OF BAGS

EXAMPLES OF BAG MAKING PRODUCTS



1. To learn making polyethylene poly bags for various applications

2. To learn the proper adjustment of sealing temperature to come up

with acceptable product

3. To determine the effect of product type on the production output rate

PROCEDURE

PART I—Sealing Temperature for LDPE and HDPE Bags

1. Familiarize yourself with the bag making machine assigned to you by

your Instructor.

2. Determine the effect of changing the sealing temperature to final product

by changing the temperature setting.

3. Make 5 trials with 5 different temperatures using LDPE film.

4. Each time you change the temperature, record the bag cutting speed and

inspect the product if acceptable or not.

5. Record all your data in your data sheet.

6. Do the same for HDPE film.

PART II—Production Output

1. Run five (5) different bag products (different sizes and materials) at

constant speed using the machine assigned to you by your Instructor.

2. For each run, record the bag cutting speed and the production output

(bags/min).

3. Record all your data in your data sheet.


DATA SHEET

PART I—Sealing Temperature for LDPE and HDPE Bags

SEALING TEMPERATURE FOR LDPE BAGS

ACTIVITY #9—Bag Making


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Trial No.

Sealing Temperature

Bag Cutting Speed Sealing Quality

1

2

3

4

5

acceptedacceptedacceptedaccepted rejectedrejectedrejectedrejected





Trial No.

Sealing Temperature

Bag Cutting Speed Sealing Quality

1

2

3

4

5






SEALING TEMPERATURE FOR HDPE BAGS

DATA SHEET

PART II—Production Output

ACTIVITY #9—Bag Making


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Trial Trial Trial Trial No.No.No.No.

MaterialMaterialMaterialMaterial Bag Size Bag Size Bag Size Bag Size (length)(length)(length)(length)

Bag Cutting Bag Cutting Bag Cutting Bag Cutting SpeedSpeedSpeedSpeed

Product RateProduct RateProduct RateProduct Rate (bags/min)(bags/min)(bags/min)(bags/min)

1111

2222

3333

4444

5555



1. Which of these three are the bottom seal and the top & bottom seal bag?

____________ is the bottom seal bag.

____________ is the top & bottom seal bag.

2. In the given drawing, why did they call this a top and bottom sealing?

Explain briefly.

___________________________

___________________________

___________________________

___________________________

___________________________

___________________________

___________________________

___________________________

3. Give at least two applications of this top & bottom sealed bags.

Clue: bags that can be found in a market.

Applications: _______________________________

_______________________________


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DATE: __________________

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Recycling Procedure for Polyethylene Film


Polyethylene Film Recycling

1. Start machine heat-up. Set the temperature according to the required set-ting for the type of material to be recycled.

2. Check the cooling water supply in/out and ensure that it is ON.

3. Set the shredder temperature at 60°C initially, then increase up to 100°C, as temperature increases after shredder start.

4. Start feeding scraps in shredder drum, ensuring that no metal or foreign matter is present. Set shredder speed to 45rpm maximum. The load must not exceed 22amps.

Scrap MaterialScrap MaterialScrap MaterialScrap Material LDPELDPELDPELDPE LLDPELLDPELLDPELLDPE HDPEHDPEHDPEHDPE

Temperature Settings Temperature Settings Temperature Settings Temperature Settings ºC 180 180 180 180 ---- 200 200 200 200 190 190 190 190 ---- 210 210 210 210 195 195 195 195 ---- 220 220 220 220

OUTOUTOUTOUT ININININ

Shredder Shredder Shredder Shredder TemperatureTemperatureTemperatureTemperature

Speed Speed Speed Speed ControlControlControlControl



WORKSHOP ACTIVITY #10—Polyethylene Film Recycling

5. After reaching to the set barrel temperature, clean the screen or change if required and check breaker plate also.

6. Connect conveyor to the shredder and after ensuring metal detector is functioning, put conveyor in auto mode. Also connect the cooling water chamber to die-face cutter and tighten the screw properly.

7. When shedder drum temperature reaches 90°C, and barrel temperature, 185°C to 220°C, start oil pump, water pump, vibrator, blowers, and cen-trifuge.

Screen CleaningScreen CleaningScreen CleaningScreen Cleaning Screen Change ControlsScreen Change ControlsScreen Change ControlsScreen Change Controls

Up/DownUp/DownUp/DownUp/Down




8. Start die face cutter and set speed to 1500 initially. Increase die face cut-ter speed in order to maintain pellet size of 2mm. Monitor the size of pellets and adjust the speed when needed.

9. Start extruder at 25 rpm initially, then increase gradually up to 45 rpm. Observe the ampere meter to control motor load (max 40 amps).

10. Observe smooth operation.

Variable Speed Variable Speed Variable Speed Variable Speed

ControlControlControlControl

Extruder Speed Extruder Speed Extruder Speed Extruder Speed

SettingSettingSettingSetting

Extruder Amps Extruder Amps Extruder Amps Extruder Amps

MeterMeterMeterMeter



1. To learn recycling machine operation

PROCEDURE

.Observe the recycling machine start up procedure and write start-up steps in

the given work sheet.(worksheet#9.1)

Write your observations and fill data in process parameter sheet

( work sheet #9.2)

PART I—Recycling Machine Startup Procedure

1. Observe the startup procedure for the recycling machine as performed by

your Instructor.

2. In your data sheet, write down the steps on the table provided.

PART II—Recycling Machine Process Parameters

1. Observe the actual recycling run for different plastics materials.

2. Use the Process Monitoring Sheet provided in your data sheet to record

your data on the actual machine run.


DATA SHEET

PART I—Recycling Machine Startup Procedure

ACTIVITY #10—Polyethylene Film Recycling


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START PROCEDURE STEP OBSERVED

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

DATA SHEET

PART II—Recycling Machine Process Parameters

ACTIVITY #10—Polyethylene Film Recycling


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SCRAP MATERIALS

LLDPE LDPE HDPE

Barre

l Temperature

Cylinder 1

Cylinder 2

Cylinder 3

Cylinder 4

Joint

Filter

Die

Shredder Tempera-ture

Shredder Speed

Shredder Motor Load (Amps)

Extruder Speed

Extruder Motor Load (Amps)

Cutting Speed

PROCESS PARAMETERS

Process Monitoring Sheet—Recycling Machine



Choose correct answer.

1. What are the advantages of recycling plastics?

a. By recycling we can make more plastics

b. Making plastics cheaper

c. Recycling machinery business can grow up

d. Reduce the consumption of energy and less pollution

2. What is the “STANDARD MARKING CODE” for HDPE?

3. Why are “STANDARD MARKING CODES” developed?

a. To identify the strength of each plastics

b. To identify the cost of each plastics

c. To understand the number of times the plastics can be recycled

d. To help consumers identify and sort the main types of plastic

4. What is the consumption of plastics in packaging industries?

5. What is the importance of oil circulation in the gear box of the extruder?

a. To provide lubrication and reduce friction

b. To increase the speed of an extruder

c. To save power consumption of machine

d. For cooling the gear box

6. Select the barrel temperature (ºC ) range for HDPE scrap material

a. 195, 200, 205, 210, 215, 220, 225

b. 165, 170, 175, 180, 185, 190, 195

c. 175, 180, 185, 190, 195, 200, 205

d. 170, 180, 180, 187, 190, 190, 195

7. Why is a metal detector provided on the conveyor?

a. To sense metal and allow it to go into the shredder and extruder

b. To sense metal and save the extruder from damage

c. To measure the weight of plastics fed into the shredder

d. To avoid dust to go inside

8. How do you increase or decrease the size of plastics pallets?

a. By adding or reducing material to the shredder

b. By increasing or decreasing the barrel temperature

c. By increasing or decreasing the speed of die face cutter

d. By increasing or decreasing cooling temperature


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a. c. d. b.

a. 35% c. 30% d. 15% b. 25%





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DATE: __________________

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PRACTICE YOUR OPERATIONS SKILLS!

1. Now that you have learned the basics of the Blown Film Extrusion

process, it is time to practice your skills in running the plant and

producing acceptable products.

2. Strictly follow the Standard Operating Procedures (SOP) for each

plant operations that you are going to perform.

3. Use the worksheet tables and forms in the next pages to record your

data.

4. After each practice operations, write your general comment on the

how well you have done your practice in the Conclusion &

Recommendations page.

5. Write down what you have done well, and what you should improve

for the next practice.

6. Enjoy practicing while being safe!

WORKSHOP ACTIVITY #11-13

Practice Plant Operations


STANDARD OPERATING PROCEDURES (SOP)

PART A—SOP for Plant Run Preparations

1. Read and understand carefully the JOB INSTRUCTIONS given by

your instructor. (See Job Instruction #1).

2. Switch on main power and pre-heat the blown film machine

according to the temperature listed in the Job Instruction.

3. Check the condition of the following:

• Chilled water for barrel and reduction gear cooling (optional).

• Air supply for downstream equipments like nip rolls, winder and

pressure roll.

4. Prepare the materials to be used according to the Job Instruction.

5. Prepare the following tools and equipments:

6. Prepare bobbins according to the width of the roll to be produced.

7. Set the bobbin to the shafts of the winder and wrap around adhesive

tape with the sticky surface exposed. Two turns are enough just to

stick the film during change roll. Have at least five bobbins for

replacements during roll change.

8. Prepare the guide twine to the web path from the die to winder.

9. Fill the hopper with the required materials.

10. Change the screen in the screen changer if necessary.

WORKSHOP ACTIVITY #11-13—Practice Plant Operations

• Dial thickness gauge

• Tape measure

• Cutting knife for film

• Silicon spray

• Cotton rags for die cleaning

• Guide twine or flat rope

• Allen wrench for die adjust-

ment

• Cotton Gloves

• Brass or copper spatula

• Scouring paste

• Scouring pad


Standard Operating Procedures … continued

11. Check the following blown film major parts’ conditions:

• Sizing basket — up and down movement

• Haul-off unit — roll rotation and air pressure and functions

• Collapsing device — functional adjustments

• Corona treater — if flexo printing will run

• Printing unit — functional adjustments and rolls rotations

• Winder — air pressure required for pressure roll and test for roll

change

11. Wait for 1.5 hours till the “ready” indicator light lights up and verify

again the temperature settings if the actual display temperatures

correspond to the set temperatures. If yes, machine is ready to run. If

not, check settings. If actual temperature is low, extend preheating

time.

PART B—SOP Startup

1. Open the shutter of the hopper.

2. Switch-on the main motor and adjust the screw rpm to 10.

3. Caution: Avoid facing the die during this stage. Melt material may

spurt-out.

4. Remove the initial extruded melt. This contains air trap in a material

that should be removed.

5. Increase screw speed to 30 rpm and remove the molten materials in

the die. Wait until the high melt pressure drops.

6. Do item 5 for 50, 75, and 100 rpm and back to 0.

7. Clean the die and the die lip using scouring pad and scouring paste.

8. Check die gap alignment. Align if off-centered by loosening and

tightening centering screws. Use Allen wrench for adjusting the

screws.




9. Open the blower damper at 30 degrees. Minimal air blown at the

film for initial start.

10. Open compressed air supply for inflating the bubble at minimum

only.

11. Make a loop on the film guide twine and have it ready.

12. Switch-on again the main motor and set the screw speed to 25 rpm.

13. Switch-on the haul-off nip and set the nip roll speed to 6-8 rpm.

14. As the melt comes out let it cool to solidify and tie the film guide

twine loop on that cooled lump.

15. Pull gently the melt as it continue forming into a bubble.

16. After the solid lump passes between the nip rolls, close the nip roll

and let it do the pulling of the bubble.

17. Temporarily closed the compressed air.

18. Just pull the flat tube gently till it reaches the printing unit.

19. Using the cutting knife, cut diagonally the film to make a pointed

end.

20. Insert this pointed end between the plate and impression roller of the

printer.

21. Pass the film between the open pressure roll and winder roll.

22. Close the pressure roll pinching the film.

23. Immediately, start the winder. Set minimum winding tension.

24. Insert the film in between the rotating winder roller and bobbin with

caution and start winding the film.

25. Increase screw rpm gradually to the target rpm. (See Job Instruction.)

26. Increase bubble diameter to its required lay-flat tube width. (See Job

Instruction.)

27. Increase nip roll speed according to the required film thickness. (See

Job Instruction.)

28. Switch-on corona treater if printing unit will run.




PART C—SOP for Shutdown

1. Close the shutter of the hopper.

2. Switch-off corona treater if printing unit is running.

3. Wait till the bubble starts to rattle. It is better to have a little material

inside the barrel and die to seal-off the barrel form air getting inside.

4. Gradually bring down the screw speed to 0 rpm.

5. Switch-off the main motor.

6. Bring down nip roll speed to 0 and switch-off.

7. Open the nip roll.

8. Bring down winder speed to 0 and switch-off.

9. Open the pressure roll.

10. Close the chilled water supply valve.

11. Start lowering the temperature for 30 minutes.

12. Switch-off the main power.

13. Bring good rolls to the bag making area. Record the total roll weight

produced in the Job Instruction.

14. Bring all scrap to the recycling area. Record the total weight of the

scrap in the Job Instruction.

15. Return all tools and equipment to their proper places.

16. Fill-up all the information needed in the Job Instruction.

17. Submit the Job Instruction to your instructor.


DATA SHEET

BLOWN FILM EXTRUSION PRODUCTION REPORT

ACTIVITY #11—Practice Plant Operations (LDPE)


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No. Type Resin Name / Grade Blending Ratio (%)

1

2

Material Specifications

Machine Running Condition Monitoring

1. 2. 3.

Actu

al T

emperature ( oC

)

Heater Zone 1.1

Heater Zone 1.2

Heater Zone 1.3

Heater Zone 2.1

Heater Zone 2.2

Heater Zone 3.1

Heater Zone 3.2

Heater Zone 3.3

Heater Zone 3.4

Heater Zone 4.1

MT

Extruder Screw Speed (rpm)

Extruder Melt Pressure (bar)

Air Ring Pressure (KPa)

Temperature (oC)

Haul-off Speed (mpm)

Corona Treater Power (%)

Printing Unit Motor Load (%)

Winder Tension (N)

Lay-on Pressure (bar)

Contact Pressure (bar)

Lot Number 4.

5.

Machine No.

Date:

Product Description:

DATA SHEET

BLOWN FILM EXTRUSION PRODUCTION REPORT … continued

ACTIVITY #11—Practice Plant Operations (LDPE)


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Output Monitoring

Quality Check Monitoring

Roll Number

Thick

ness P

rofile

(µm)

Measuring Point 1

Measuring Point 2

Measuring Point 3

Measuring Point 4

Measuring Point 5

Measuring Point 6

Measuring Point 7

Measuring Point 8

Average Thickness (µm)

Lay Flat Width (mm)

Gusseted LFW (mm)

Left Gusset Width (mm)

Right Gusset Width (mm)

Treating Level (OK/NOK)

Tape Test (OK/NOK)

Print Centering (OK/NOK)

Print Repeat Length (mm)

Clarity (OK/NOK)

Color (OK/NOK)

Defects (W/WO)

Roll Disposition

(Pass / Reject / On-Hold)

Lot Number 1. 2. 3. 4. 5.

Dismount Time

Roll Number

Length (m)

Weight (kg)

Total Scrap Weight (kg)



1. If you want to raise the frost line height, what part of the machine are

you going to adjust?

a. winder tension

b. the haul-off

c. Air adjusting ring

2. If you want to decrease the film thickness, what control are you going

to adjust?

a. haul-off speed

b. winder speed

c. main motor speed

3. How are you going to adjust the speed in question #2?

a. increase speed

b. decrease speed

4. If you want to reduce the lay-flat width, what are you going to do

with the bubble?

a. increase air inside

b. decrease air inside

5. How are you going to increase or decrease the air inside the bubble?

Describe in your own words.

______________________________________________________

______________________________________________________

6. Is it necessary to use a film guide twine during start-up? Why?

______________________________________________________

______________________________________________________

7. Give at least 3 important speed adjusting controls of the blown film

control panel.

_________________________________________________

_________________________________________________

_________________________________________________

WORKSHOP ACTIVITY #11—Practice Plant Operations (LDPE)

� Cut R

eport F

orm

and Submit to

Instru

ctor





WORKSHOP ACTIVITY #11—Practice Plant Operations (LDPE)

___________________________________________________________

___________________________________________________________

___________________________________________________________

___________________________________________________________

___________________________________________________________

___________________________________________________________

___________________________________________________________

___________________________________________________________

___________________________________________________________

___________________________________________________________

___________________________________________________________

___________________________________________________________

TRAINEE’S GRADE

FOR THIS ACTIVITY

________________________


� Cut R

eport F

orm

and Submit to

Instru

ctor


DATE: __________________

DATE: __________________

________________________


DATA SHEET


ACTIVITY #12—Practice Plant Operations (LLDPE)


� Cut R

eport F

orm

and Submit to

Instru

ctor



1

2



1. 2. 3.

Actu

al T

emperature ( oC

)

Heater Zone 1.1

Heater Zone 1.2

Heater Zone 1.3

Heater Zone 2.1

Heater Zone 2.2

Heater Zone 3.1

Heater Zone 3.2

Heater Zone 3.3

Heater Zone 3.4

Heater Zone 4.1

MT




Temperature (oC)




Winder Tension (N)



Lot Number 4.

5.

Machine No.

Date:


DATA SHEET


ACTIVITY #12—Practice Plant Operations (LLDPE)


� Cut R

eport F

orm

and Submit to

Instru

ctor


Output Monitoring


Roll Number

Thick

ness P

rofile

(µm)

Measuring Point 1

Measuring Point 2

Measuring Point 3

Measuring Point 4

Measuring Point 5

Measuring Point 6

Measuring Point 7

Measuring Point 8


Lay Flat Width (mm)

Gusseted LFW (mm)




Tape Test (OK/NOK)



Clarity (OK/NOK)

Color (OK/NOK)

Defects (W/WO)

Roll Disposition


Lot Number 1. 2. 3. 4. 5.

Dismount Time

Roll Number

Length (m)

Weight (kg)

Total Waste (kg)



1. What does melt pressure indicate?

a. The pressure before the screen

b. The pressure after the screen

2. What does indicator means if the reading is high (500)

_______________________________________________________

_______________________________________________________

3. What happens to the output if the screen is clogged-up, increase or

decrease? Why?

_______________________________________________________

_______________________________________________________

4. If the cooling of the barrel is not working, what do you think will

happen to the bubble?

_______________________________________________________

_______________________________________________________

_______________________________________________________

5. If the rolled film in the shaft is hard to removed, what must be the

probable cause?

_______________________________________________________

_______________________________________________________

6. How are you going to prevent the problem in #5 from happening

during operations?

_______________________________________________________

_______________________________________________________

7. Give at least 2 causes why bubble is pulsating.

_______________________________________________________

_______________________________________________________

_______________________________________________________

_______________________________________________________

WORKSHOP ACTIVITY #12—Practice Plant Operations (LLDPE)

� Cut R

eport F

orm

and Submit to

Instru

ctor





WORKSHOP ACTIVITY #12—Practice Plant Operations (LLDPE)

___________________________________________________________

___________________________________________________________

___________________________________________________________

___________________________________________________________

___________________________________________________________

___________________________________________________________

___________________________________________________________

___________________________________________________________

___________________________________________________________

___________________________________________________________

___________________________________________________________

___________________________________________________________

TRAINEE’S GRADE

FOR THIS ACTIVITY

________________________


� Cut R

eport F

orm

and Submit to

Instru

ctor


DATE: __________________

DATE: __________________

________________________


DATA SHEET


ACTIVITY #13—Practice Plant Operations (HDPE)


� Cut R

eport F

orm

and Submit to

Instru

ctor



1

2



1. 2. 3.

Actu

al T

emperature ( oC

)

Heater Zone 1.1

Heater Zone 1.2

Heater Zone 1.3

Heater Zone 2.1

Heater Zone 2.2

Heater Zone 3.1

Heater Zone 3.2

Heater Zone 3.3

Heater Zone 3.4

Heater Zone 4.1

MT




Temperature (oC)




Winder Tension (N)



Lot Number 4.

5.

Machine No.

Date:


DATA SHEET


ACTIVITY #13—Practice Plant Operations (HDPE)


� Cut R

eport F

orm

and Submit to

Instru

ctor


Output Monitoring


Roll Number

Thick

ness P

rofile

(µm)

Measuring Point 1

Measuring Point 2

Measuring Point 3

Measuring Point 4

Measuring Point 5

Measuring Point 6

Measuring Point 7

Measuring Point 8


Lay Flat Width (mm)

Gusseted LFW (mm)




Tape Test (OK/NOK)



Clarity (OK/NOK)

Color (OK/NOK)

Defects (W/WO)

Roll Disposition


Lot Number 1. 2. 3. 4. 5.

Dismount Time

Roll Number

Length (m)

Weight (kg)

Total Waste (kg)



1. Give at least 2 causes of die lines.

_______________________________________________________

_______________________________________________________

2. Give at least 2 causes of uneven film thickness.

_______________________________________________________

_______________________________________________________

3. What are you going to do with the die if the film wall at the right side

is thicker than the left side?

_______________________________________________________

_______________________________________________________

_______________________________________________________

_______________________________________________________

4. Give at least 2 causes of film blocking.

_______________________________________________________

_______________________________________________________

5. Give at least 3 common problems of blown film process.

_______________________________________________________

_______________________________________________________

_______________________________________________________

Good Luck!!!!!

WORKSHOP ACTIVITY #13—Practice Plant Operations (HDPE)

� Cut R

eport F

orm

and Submit to

Instru

ctor





WORKSHOP ACTIVITY #13—Practice Plant Operations (HDPE)

___________________________________________________________

___________________________________________________________

___________________________________________________________

___________________________________________________________

___________________________________________________________

___________________________________________________________

___________________________________________________________

___________________________________________________________

___________________________________________________________

___________________________________________________________

___________________________________________________________

___________________________________________________________

TRAINEE’S GRADE

FOR THIS ACTIVITY

________________________


� Cut R

eport F

orm

and Submit to

Instru

ctor


DATE: __________________

DATE: __________________

________________________



Formulas for Blown Film Computations

Blow Up Ratio (BUR)

Theoretical Bag Film Weight

D2

D1

Die

1

2

D Diameter, Die

D Diameter, Bubble BUR =

π

2LFW D2 ×=

LFW 0.637 D2 ×=

where:

LFW = Lay Flat Width, cm

D1 = the die diameter, cm

D2 = the bubble diameter, cm

W

Film Bag L

t =thickness, cm

where:

Wbag = theoretical bag film

weight in grams

w = width of the bag, cm

L = cut length of the bag, cm

t = thickness of the film, cm

ρ = material density, gm/cm³

ρ××××= 2Wbag tLw



Theoretical Roll Weight

Theoretical Output

• Computing for Output Rate per RPM of a Given Output:

Output Rate = ___________ kg/hr/RPM

• Getting the Needed Output of a Desired Screw RPM

Target Output = __________ kg/hr

where:

Wbag = theoretical bag film

weight in grams

w = width of the bag, cm

L = cut length of the bag, cm

t = thickness of the film, cm

ρ = material density, gm/cm³

ρ××××= 2Wbag tLw

Rolled Film

w t

RPM Speed, Screw

hourper kg Rate,Output RPMper RateOutput =

RPMper RateOutput RPM Speed, Screw Desired Output Target ×=



Theoretical Take-off Speed

DensityThickness2th LayFlatWid

RateOutput Speed off-Take lTheoretica

×××=

)(g/cm (cm)t 2(cm)LFW

(g/min) RateOutput (cm/min) Speed off-Take lTheoretica

3ρ×××

=


Glossary of technical terms for Blown Film

Air-ring A circular component of a blown film system that directs cool air

up the sides of a tubular blown film bubble to cool and solidify

the melt.

Alloy Plastics made by mechanically blending two or more different

polymers.

Additive Substance compounded into a resin to modify its characteristics

(i.e., antistatics, stabilizers, plasticizers, flame retardants, etc.).

Aging The process of exposing the film to a controlled environment for

an interval of time.

Ambient conditions The existing conditions of temperature and humidity in

any building or room.

Amorphous A polymer is said to be amorphous when its molecules are in long

random or coiled chains. Amorphous plastics tend to be

transparent, and are more soluble than crystalline plastics.

Having no crystalline structure.

Anilox Roll Mechanically or laser-engraved roll for transfer of ink to printing

plate. Specifications are in lines per inch and cell volume (ex.

800-line anilox will transfer a thinner film of ink than a 300-line

anilox).

Antiblock An additive used in plastic, generally at 1 or 2% that roughens the

film surface from adhering to each other. The most common anti-

blocks are based on clay by-products.

Antioxidant Additives that prevent oxygen from causing molecular breakdown

in polymers.

Anti-static agent A substance that can be applied to the surface of a plastic

article, or incorporated in the plastics from which the article is to be

made. Its function is to render the surface of the plastic article less

susceptible to accumulation of electrostatic charges which attract

and hold fine dirt or dust on the surface of the plastic article.

Auxiliary equipment The types of equipment used to enhance, support or add

to the precision and efficiency of injection, extrusion or other

primary processing machinery. (Continued on page 93)


Arc A luminous glow by the flow of electric current through ionized

air, gas or vapor between two separated electrodes or contacts.

Band heater Electrical heating units fitted to extruder barrels, adaptors, dies,

nozzles, etc., utilized for heating the polymer to a desired

temperature.

Barrel A metal tube that houses a rotating screw, or sometimes a ram, in

which plastic is heated before extrusion or moulding.

Barrier layer A layer of material in film, sheet or a blow molded container that

prevents the passage of moisture, flavors or certain gases.

Biaxial Orientation The process of stretching a hot plastic in two directions

under conditions resulting in molecular orientation in two

directions.

Bleed (1) To give up color when in contact with water or a solvent. (2)

Undesired movement of certain materials in a plastic (e.g.,

plasticizers in vinyl) to the surface of the finished article or into

an adjacent material; also called migration. (3) An escape passage

at the parting line of a mold, like a vent but deeper, that allows

material to escape or bleed out.

Blocking Substrate sticking to itself after being printed and rewound. Image

often transfers to back-side of other label.

Bloom (1) A non-continuous surface coating on plastic products that

comes from ingredients such as plasticizers, lubricants, antistatic

agents, etc., which are incorporated into the plastic resin. It is not

always visible. Bloom is the result of ingredients coming out of

solution in the plastic and migrating to its surface.

Blooming Migration of additives to the surface of the film

Blown film Film made by extruding molten plastic through a circular die, and

forming an inflated, tubular bubble that moves through a cage as

it cools, to be sliced open, collapsed and formed into rolls.

Breaker plate A metal plate installed across the flow of the stock between the

end of an extruder screw and the die, with openings through it

such as holes or slots. It usually is used to support a screen pack.

Bubble In blown film referred to as the inflated molten tube.

(Continued from page 92)

(Continued on page 94)


Cage, blown film A structure, usually with rollers or roller beads, through

which a bubble of blown film passes at it is extruded and cooled.

Calcium carbonate (CaCO3) A filler and extender used in thermoplastics. It

occurs naturally in the form of minerals such as calcite, chalk,

limestone, marble, and whiting.

Calendering The making of sheet or film with high-quality surface

characteristics by passing molten plastic from a kneader over a

series of rollers that flatten and/or emboss it.

Caliper The thickness of the substrate usually measured in thousandths of

an inch (mils). "Microns" (metric) are specified for some

substrates.

Cartridge heater Cylindrical electrical heater used to heat nozzles, hot

runners and moulds in injection and compression molding.

Cast film A film process, used where good cosmetics are needed, in which

molten plastic flows over a chilled roll or through a quench bath.

Chiller A self-contained system comprised of a refrigeration unit and a

coolant circulation mechanism consisting of a reservoir and a

pump. Chillers maintain the optimum heat balance in

thermoplastic processing by constantly re-circulating chilled

cooling fluids to molds, machines, etc.

Coefficient of friction, COF A measure of how slippery a film is. Coefficient

of friction is a number that expresses, for a given surface, the ratio

of the force required to slide an object over a frictionless surface

to the force required to slide the same object over the actual

surface. The COF, or slip properties, of film are important in

determining how that film will perform on conversion equipment

and in final form such as in open ability or stacking. This test

determines the ability of film to slide over itself and is used to

determine the effectiveness of slip additives incorporated into

resins. Both static (starting) and kinetic (sliding) friction are

measured.

Coextrusion A process whereby two or more plastics are extruded through one

die, to produce a material combining their properties.

Collapsing frame A pair of frames that gradually collapse the film tube and

guide this flattened tube smoothly into the nip rolls.




Compound Plastics that has colorants, additives or reinforcements added in a

compounding extruder or mixer.

Compression ratio In an extruder screw, the ratio of volume available in the

first flight at the hopper to that in the last flight at the end of the

screw.

Concentrate A measured amount of additive (e.g., dye, pigment, foaming

agent, anti-static agent, flame retardant, glass reinforcement, etc.)

that is incorporated into a predetermined small amount of plastic.

This (the concentrate) then can be mixed into larger quantities of

plastic to achieve a desired color or end-property.

Copolymer A polymer produced by reacting two different monomers together

to form long chains.

Crystallinity Polymers are said to be crystalline when their molecules are in a

regular, repeated lattice arrangement that makes them relatively

dense; non-transparent (because the crystals scatter light);

resistant to solvents or to chemical attack; and having a very sharp

melting point.

Dart impact strength A measure of a plastic's resilience, especially film's,

measured with a special dart or steel ball dropped on it.

Degradation A deleterious change in the chemical structure or physical

properties of a plastic, caused by exposure to heat, light or other

agent.

Density Weight per unit volume of a substance, expressed in grams per

cubic centimeter. Also called Specific Gravity. Polyethylene

ranges between .9100 - .9650. Water = 1.000, anything less than

that floats; greater than that will sink. LDPE is low density

polyethylene, HDPE is high density polyethylene.

Density is a basic molecular property that can affect many

essential physical properties of a polymer. Density, in part, is a

function of the crystalline structure of the polymer. It is an

excellent means of identifying a product, following physical

changes, and determining uniformity.

Die Line A line or series of lines on the film surface that run in the machine

direction. If there are numerous die lines , it is generally due to

the build-up of oxidized materials on the die. If the die line is a

single, deep line it is generally due to a foreign object on the die.




Die-lip In blown film, the edge of the circular dies.

Discoloration Any change from the original color, often caused by overheating,

light exposure, irradiation, or chemical attack.

Dispersion Finely divided particles of a material in suspension in another

substance.

Doctor blade Thin, flexible steel, plastic or composite blade that passes over a

gravure plate cylinder or flexographic anilox roll wiping off

excess ink before ink is transferred to substrate or plate.

Downstream equipment In extrusion, winders, haul-offs, saws, vacuum

sizing tanks and other equipment that trims, cuts and finishes

extruded film or shapes.

Draw down ratio The ratio of the thickness of the die opening to the final

thickness of the product.

Drive The entire electrical and mechanical system used to supply

mechanical energy to the input shaft of a gear reducer. This

includes the motor, constant or variable speed belt system,

flexible couplings, starting equipment, etc.

Dryer A device to absorb and/or drive off moisture from resin powder or

pellets that, if heated while still containing traces of moisture,

would make defective parts.

Dynes A unit of energy, also a unit of measure for surface tension (treat).

Elastomer A plastic with some of the elastic, flexible properties of natural

rubber.

Elasticity The elasticity of material by virtue of which it tends to recover its

original size and shape after deformation. If the strain is

proportional to the applied stress, the material is said to exhibit

Hookean or ideal elasticity.

Elongation The fractional increase in length of a material stressed in tension.

Environmental Stress Cracking (ESC) The susceptibility of a thermoplastic

article to crack or craze when stressed, in the presence of surface-

active agents or in other environments.

Extruder A machine that melts plastic powder, pellets or flake, possibly




with colorants and additives added. The basic machine consists of

a barrel, heater units around it, a drive system, and a fluted screw

inside to move and pressurize the plastic from the throat to the

extruder die.

Extrusion The process of melting plastic pellets, flake or powder by means

of heat and pressure, then forcing the melt through a die to

produce film or a three-dimensional profile shape.

Fabricate To work a material into a finished form by machining, forming or

other operation.

Feedstock Chemical source from which monomers for polymers are derived.

Feed throat The point at which resin or additives is added into an extruder or

injection unit.

Feed section First section or zone of an extruder screw, which is fed from the

hopper and conveys solids to the melting zone.

Feed zone A passage wherein a material passes through going down the

screw.

Filler Material such as calcium carbonate or wood flour used with

plastics to reduce costs and to impart additional mechanical

properties.

Fines Very small particles (usually under 200 mesh) accompanying

larger grains, usually of molding powder.

Fish-eye An unmelted lump of plastic in a melt, especially visible in clear

films.

Flexography A form of rotary web letterpress using flexible rubber or

photopolymer plates and fast-drying solvent, water-based or UV

inks. Photopolymer plates with raised surfaces that transfer ink to

the substrate are mounted to print cylinders using double faced

adhesive (stickyback).

Frost line The point in a blown film bubble at which the film tube reaches

its maximum diameter, and acquires a frosted appearance as the

plastic falls below its softening temperature.

Friction The resisting forces that arise when a surface of the film slides or

tends to slide over an adjoining surface of itself.




Flame retardant A chemical compounded into a resin to make it fire-

resistant.

Flight The outer surface of the helical ridge of metal on an extrusion or

injection molding screw.

Gauge Film thickness express in mils or microns (µ).

Glass Transition Temperature The temperature below which a given plastic

behaves like glass, being strong but brittle.

Gear Reducer A combination of gears enclosed in a case.

Gel Count Gels are hard, unmelted particles randomly distributed throughout

the film. Gels are unattractive and, in most cases, will be

detrimental to film downgauging. The types of imperfections

vary, but four of the most common are pinpoint, arrowhead,

fisheyes, and oxidized or discoloured gels. As different

applications will tolerate varying levels of film purity, a gel count

test gives the producer or extrusion shop indications as to end-use

expectations. This test is very useful as a quality control tool.

Gloss A measure of the reflectivity (shininess) of a film's surface of

light from a given angle, in this case - 45 degrees. The higher the

number, the shinier the film. Gloss can impact desirability of

consumers to purchase the film product or something packaged

within it. Gloss in film can be optimized by adjustment of

extrusion parameters. Once processing conditions are perfect,

changing resins to a higher melt index and higher density at a

constant MW and MWD will generally results in better gloss.

Gusset A fold on the sides of an extruded film tube. May also be done at

the bottom of the formed bag.

Haze A measure of the clarity or transparency of film. It is expressed as

the amount of light that is not transmitted through a film sample.

The lower the number, the higher the clarity. In certain

applications, high clarity and minimal haze or frostiness is

desirable. This is the case in many packaging applications where

good clarity enhances the sales. Both surface roughness and

polymer structure diffuse light as it passes through film and cause

the hazy appearance. Extrusion parameters can be optimized to

improve haze along with proper resin selection.




Half-tone A printed image of a continuous-tone original (like a photograph)

that is composed of tiny dots to create the illusion of continuous-

tone though printed with only single density. Halftones are

reproduced in screen values for flexographic printing from 80 line

(carton, fiber board and course papers) to 300 line (high gloss,

smooth finish papers). The majority of high quality flexographic

printing uses 133 to 150 lines screened halftones.

Heater band A band, normally of ceramic, mica or metal that is heated, and

transfers its heat to the barrel of an extruder.

Hopper dryer A combination feeding and drying device for extrusion and

injection molding of thermoplastics. Hot air flows upward

through the hopper containing the feed pellets.

Hydrophilic Tending to absorb water.

Hydrophobic Tending to absorb little or no water.

Hygroscopic Tending to absorb atmospheric moisture.

Impact resistance A measurement of the strength of film and its ability to

withstand the shock of a falling "dart" without breaking, in other

words, puncture resistance. Expressed as the gram weight of the

heaviest dart which doesn't break the film when dropped from a

specific height. The impact strength of film can be determined

and applied to end-use properties through a number of different

impact tests. Knowing these results aids in determining which

particular resins are best suited for high-strength applications such

as the construction and agriculture market.

Internal Bubble Cooling, IBC Injection of cold air into a tubular bubble of a

blown film, so that it cools and solidifies.

Laminate Product made by bonding two materials or two layers of one

material.

L/D ratio The length-to-diameter ratio of a screw, which affects how it

melts a given plastic.

Land (1) The bearing surface along the top of the flights of a screw in a

screw extruder. (2) The surface of an extrusion die parallel to the

direction of melt flow.

Lay flat Measurement of a film sample in the TD on a flat ruler or tape




measure.

Lay Flat Width, LFW The width of the tubular film when it is flattened.

Light resistance The ability of a plastics material to resist fading after

exposure to sunlight or ultraviolet light.

Light transmission The amount of light that a plastic will allow to pass.

Linear Low Density Polyethylene, LLDPE A process variation of low

density polyethylene. It enables high draw down-gauging in

extruding, while maintaining high film strength.

Low Density Polyethylene, LDPE A partially crystalline, lightweight

thermoplastic, polymerized form ethylene gas at controlled

temperature and pressure.

Lubricant Additive to plastic resin to promote mixing and improve flow

properties.

Machine Direction, MD The direction of the film which corresponds to

the way it came out of the extruder. On rolled film it is the length

of the film. Some film properties vary according to film direction.

Masterbatch A plastics compound that includes a high concentration of an

additive or additives. Masterbatches are designed for use in

appropriate quantities with the basic resin or mix so that the

correct end concentration is achieved. For example, color

masterbatches for a variety of plastics are used extensively, as

they provide a clean and convenient method of obtaining accurate

color shades.

Melt Term to describe molten plastic.

Melt fracture An instability in the melt flow through a die, starting at the entry

to the die. It leads to surface irregularities on the finished article

such as a regular helix or irregularly spaced ripples.

Melt Index The amount, in grams, of a thermoplastic resin that can be forced

through a 0.0825 inch orifice when subjected to 2160 grams force

in 10 minutes at 190ºC.

Melt strength The strength of a plastic while in the molten state.

Melting Point The temperature at which a resin changes from a solid to a liquid.




Melt zone The main section of a screw, which handles plasticising by heat

and pressure.

Metallocene catalyst A category of Ziegler-Natta catalysts for polymerizing

polyolefin. The structure of its own molecules orients the olefin

monomers into polyolefin polymers with tightly repeatable shapes

and properties.

Metering zone The relatively shallow discharge end of a screw.

Metering screw An extrusion screw that has a shallow constant depth and

a constant pitch section over, usually, the last three to four flights.

Metering section A relatively shallow portion of an extruder screw at the

discharge end with a constant depth and lead, and having a length

of at least one or more turns of the flight.

Mica Natural, plate-like silicate mineral used as a reinforcement or

mineral filler.

Mil One thousandth of an inch (0.001" or 0.001in.). Measure of the

film thickness.

Melt Index, MI Melt index is commonly used to classify polymeric

resins. Melt index uniformity is essential in maintaining control of

processing parameters, and melt index is inversely proportional to

molecular weight or polymeric chain length. Melt index heavily

influences physical properties.

Modulus of Elasticity The ratio of stress to strain in a material that is elastically

deformed.

Moisture Vapor Transmission The rate at which water vapor permeates through

a plastic film or wall at a specified temperature and relative

humidity.

Moisture resistance The ability of a material to resist absorbing ambient

moisture.

Molecular weight The sum of the atomic weights of all atoms forming a

molecule.

Molecular Weight Distribution A measure of the relative amounts of

polymers with different molecular weights within a batch of

material. This measure may be indicated by the ratio of the




weight-average molecular weight to the number-average

molecular weight.

Monomers Single molecules, in gaseous or liquid form, that can be joined in

chains to form polymers, the building blocks of plastics.

Nip Line of contact between two rollers.

Nip rollers A pair of rolls at the top of a blown film tower that close the film

bubble, and also, by their action, regulate the rate at which molten

plastic is pulled from the extrusion die. A set of rollers used to

compress the plastic bubble into a sheet, or to feed the film to the

winder at the proper tension.

Nitriding Hardening process for steel screws and barrels, also referred to as

ion nitriding.

Nylon Term for the family of polyamide polymers, first synthesized by

DuPont scientists in 1938. These crystalline plastics are tough and

offer good heat and chemical resistance.

ODR Term used in pouching material - Odor Transmission Rate. How

fast the odor will pass through the substrate.

Olefins A group of unsaturated hydrocarbons of the general formula

CnH2n, and named after the corresponding paraffin by the

addition of “ene” to the stem. Examples are ethylene and

propylene.

Opacity The amount of light that will penetrate through a colored item.

Opacity is higher with thicker films or with greater loading of

color. It has nothing to do with the particular shade or color of the

film.

Opaque Description of a material or substance that will not transmit light;

opposite of transparent. Materials that are neither opaque nor

transparent sometimes are described as semi opaque, but are more

properly classified as translucent.

Oscillating nip rollers Collapsing system on top of a blown film tower that

rotates back and forth to randomize, or distribute, gauge

variations in the film being blown.

Orientation The direction in which polymer chains lie, or are made to flow, in

plastic film, sheet or parts.




Overs/Unders Copies printed varying from the specified quantity. Depending on

the quantity ordered, the standard in our industry is usually 10%,

unless otherwise specified.

Oxidation A chemical process where a compound combines with oxygen to

form a different compound.

Pitch The distance from any point on the flight of a screw line to the

corresponding point on an adjacent flight, measured parallel to the

axis of the screw line or threading.

Plastic A material of organic origin, of high molecular weight, that can

be shaped by being made to flow through the application of heat

and/or pressure, and that will set solid after the forming process.

The word derives from a Greek root, plassein, which means to

mold.

Photopolymer A plastic that cures in response to ultra violet or another form of

light.

Permeability (1) The passage or diffusion of a gas, vapor, liquid or solid

through a barrier without being physically or chemically affected.

(2) The rate of such passage.

Pigment A coloring agent mixed with plastic material prior to processing

to provide a uniform color.

Pin holes Small random holes found in a film.

Plate cylinder The cylinder of a press on which the plate is mounted.

Plate Gap The space left when the plates are wrapped around the cylinder.

No copy or image can be printed in this area that is usually 1/8"

wide.

Plastics tooling Tools (e.g., dies, jigs, fixtures, etc.) for the metal forming

trades constructed of plastics, generally laminates or casting

materials.

Polymer Compound forming a chain of chemically linked monomers, or

single molecules; a chemist's description for a basic plastic.

Polyethylene In its pure form, a chemically stable plastic material. Used in film

form to make sleeves for photographic materials and other uses. A

cheaper alternative to polyester film.




Polyester A thermoset or thermoplastic material, made by polymerizing any

of a range of ester monomers, usually with properties of

toughness, stiffness and/or a high melting point.

Polyvinylchloride, PVC Plastic usually abbreviated as PVC, or sometimes

'vinyl'. Not as chemically stable as some other plastics. It can emit

acidic components which damage cellulosic materials. Added

chemicals called plasticizers are also used to make PVC more

flexible. These also damage library materials.

Preheating The heating of a compound prior to molding in order to facilitate

the operation, reduce the cycle, and improve the product.

Primary processing equipment Machinery that actually moulds, extrudes or

initially forms plastic parts and products.

Proof A facsimile image of the final printed piece created before

presswork begins. Used for evaluation by production staff and

customer prior to printing.

Purging Cleaning one color or type of material from the cylinder of an

extruder by forcing it out with a new color or material to be used

in subsequent production. Purging materials also are available.

Recycle Material from flash, trimmings, scrap, rejects, etc., that can be

ground up or repelletized and fed back into the processing

machine.

Register The fitting of two or more images on top of each other in exact

alignment.

Reprocessing Recycling of plastics back into processible material, usually

through pulverizing or re-extrusion.

Resin Term for plastics raw materials in powder, pellet or flake form.

Rewinding The process of rewinding a roll of substrate to produce a proper

size for the customer, to splice the ends together and/or to remove

defects.

Rheology The scientific study of the deformation and flow of matter,

particularly as it moves through a processing line.

Rotogravure The printing process that involves the principal of engraving. An

engraved cylinder is immersed in a fluid ink; the ink is wiped or




doctored from the surface of the cylinder; and the ink left in the

recessed area of the cylinder is transferred to the substrate.

Scrap Any product of a molding operation that is not part of the primary

product. Scraps in blow molding such as rejected parts and sprues

usually can be reground and remolded.

Screen A mesh plate that eliminates impurities from a melt stream.

Screen changer A device for replacing filtering screens without

interrupting the extrusion process.

Screw The rotating, flighted part of an extruder or injection unit, which,

in turning rapidly helps to melt, and convey, the plastic from the

hopper throat to the die or nozzle.

Shear An effect whereby parts of a melt separate and move against each

other. This is desired and essential in the heating stage, but

excessive shear produces breakdown of a plastic's properties.

Shrinkage A measurement of the percent of film shrinkage under a

controlled temperature and time interval. As a result of the

manufacturing process, internal stresses may be locked into the

film which can be released by heating. The temperature at which

shrinkage will occur related to the processing techniques

employed to manufacture the film and may also be related to a

phase transition in the base resin. The magnitude of the shrinkage

will vary with the temperature of the film Shrinkage of a

particular material produced by a particular process may be

characterized by this test method by making measurements at

several temperatures through the shrinkage range of the material.

This property is important to consider when handling film in

downstream equipment that requires heating.

Silicone spray Chemical derived from silica; used in molding as a release agent

and a general lubricant.

Silicone Chemical derived from silica; used in molding as a release agent

and a general lubricant.

Slip agents Substances added to make the sliding action easier. These

additives are designed to bloom to the surface and provide an

invisible coating on the film, reducing the coefficient of friction.

Fatty acid amines are an example which is widely used in film




extrusion.

Slitting Cutting printed sheets or webs into two or more sections by

means of cutting wheels on a press or rewinder.

Smear Film surface defect, usually V-shaped, and protrude from the film

surface.

Spiral die A die used for blown film that brings the molten plastic through

spiral channels from an extruder to the die-lip, ensuring a

homogeneous melt when the melt emerges to form the bubble.

Solvent Any substance, usually a liquid that dissolves other substances.

Liquid that dissolves a solid. In ink, the evaporation of solvent

leaves the solids behind as an ink film on the substrate.

Specific gravity The density (mass per unit volume) of any material divided by

that of water.

Spider A term used to denote the membranes supporting a mandrel

within the head/die assembly.

Stabilizer An ingredient used in the formulation of some plastics to assist in

maintaining the physical and chemical properties of the

compounded materials at their initial values throughout the

processing and service life of the material.

Stabilizer, heat A chemical additive that prevents deterioration of plastic

during heating.

Stabilizer, light A chemical additive that helps screen plastic from the

deleterious effects of ultra-violet light.

Substrate Any printing surface (paper, polypropylene, polyester, PVC,

PETG, etc.).

Surface treating Any method of treating a material so as to alter the

surface and render it receptive to inks, paints, lacquers, and

adhesives, such as chemical, flame, and electronic treating.

Surging Unstable pressure build-up in an extruder leading to variable

throughput.

SWS, Single Wound Sheeting One single thickness of plastic being wound on a

core.




Talc A natural, hydrous magnesium silicate used in plastics as

reinforcing filler.

Tear strength A measurement of the strength of a film and its ability to resist

tearing under specific conditions. Tear strength is the force

required to continue an initially started slit across a film

specimen. This widely used test has some value in quality control

of film production, but is not a very useful indicator of the

strength of film in service.

Tensile properties A measurement of the strength of a film and its ability to

withstand stretching or pulling. Tensile properties which include

tensile strength at yield, ultimate tensile (or break tensile

strength) , and elongation, are tests used to determine relative

strength of different films. Yield strength measures the point at

which the film, when, stretched, will not resume its original

shape. Ultimate tensile is the measure of a load that will cause the

film to rupture. Both yield and ultimate measurements are

measured in lb/ in2 of a cross-sectional area of useful information

on how polymers process and perform. For example, polyolefin

generally tend to process with easier and wider MWD and

improved drawdown. Within a given family of resins, many film

properties can be correlated with molecular properties.

Telescoping Lateral shifting of layers of film, causing the edge of the roll to

have a conical shape appearance.

Thermal Stress Cracking Crazing and cracking of some thermoplastic

resins that results from overexposure to elevated temperatures.

Thermocouple A temperature-sensitive device consisting of a pair of wires of

dissimilar metal welded together at one end. The electric current

created at different temperatures is measured by a calibrated

potentiometer.

Thermoplastic A polymer that can be heated and reformed any number of times.

Thermoset A polymer that, once heated and formed, cannot be re-melted

without fundamental degradation, because its polymer chains are

heavily cross-linked.

Tint A small amount of color added to a plastic film. You can see

through the film, yet there is still a noticeable color




Tower A rigid metal frame or structure that holds the collapsing frame

and the nip rolls.

Transducer An input/output electronic device that can measure load or

pressure when placed in a sensor cell adjacent to the flow path of

a melt.

Translucent Descriptive term for a material or substance capable of

transmitting some light but not clear enough to be seen through.

Transparent Descriptive term for a material or substance capable of a high

degree of light transmission (e.g., glass).

Traverse Direction (TD) The direction at right angle to the direction of the

extrusion (MD). Film is tougher in this direction.

Treat The process of using high frequency electrical discharge to

oxidize the film surface, thereby making the surface more

acceptable of printing and other substances.

Tube Shape of molten plastics extruded from the die during blown film

process.

UV Inhibitor Used to inhibit or prevent degradation of the film from ultraviolet

radiation sources such as sunlight and fluorescent lighting.

Ultraviolet (UV) Stabilizer A chemical additive that selectively absorbs or

filters out light waves at the ultra violet end of the spectrum,

protecting plastics from their harmful effects (embrittlement,

discoloration, crazing and disintegration).

Vicat Softening Temperature Measurement of the heat distortion temperature

of a plastic material. Also called the heat deformation point.

Vinyl Common abbreviation for polyvinyl chloride, a plastic used for

some packaging and house wares but particularly for construction

items such as pipe, window frames, doors and siding for houses.

The term is also sometimes applied to other plastics in the range

of vinyl copolymers.

Virgin resin Plastic resin that has never been previously heated or formed.

Viscosity The property of an ink defined as the resistance to flow or simply

the fluidity or thickness of the ink.

Water absorption The ability of a thermoplastic material to absorb water




from an environment.

WVTR, Water Vapor Transmission Rate Term used in pouching material -

Water Vapor Transmission Rate. How fast moisture passes

through the substrate

Weld Lines Also Weld Marks or Flow Lines. Marks on a molded plastic piece

made by the meeting of two flow fronts during the molding

operation.

Wetting Tension The ability of polyolefin films to retain inks, coatings,

adhesives, etc. is dependant upon the character of the surface and

can be improved by surface treating techniques such as corona

discharge or flame treatment. Wetting tension is utilized to

determine the degree or level of treatment applied by establishing

a correlation between surface tension (wetting tension) and

treatment level.

Winder A mechanical equipment of blown film machines that wind up the

lay flat tubular film that has been taken off.

Wrinkles Imperfections in plastic sheeting that has the appearance of a

wave or a crease

Yellowness Index A measure of the tendency of plastics to turn yellow upon

exposure to heat or light.

Yield The area of film at a given thickness produced from a given

weight of resin.

Yield Value (Yield Strength) The lowest stress at which a material undergoes

plastic deformation. Below this stress, the material is elastic;

above it, the material is viscous.

Young’s Modulus of Elasticity The modulus of elasticity in tension; the ratio of

stress in a material subjected to deformation.

Ziegler-Natta catalysts Large family of polymer catalysts discovered by Karl

Ziegler, and developed by Giulio Natta, with whom he shared the

Nobel Prize for their work in 1963.

Zippering An effect seen in blown film where a puncture or defect results in

a visible tear line appearing in the film surface.



REFERENCES

1. CT-1-6 Introduction to Plastics Fabrication Technology, Version 3,

July 2007, SPDC Ltd.

2. PT-3-6 Blown Film Extrusion PGM, Version 3, July 2007, SPDC

Ltd.

blown film workbook draft

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