© GNU Su-Jin Kim

Plastics

Material Science

Polymer (Plastics)

고분자재료

Associate Professor Su-Jin Kim

School of Mechanical Engineering

Gyeongsang National University

© GNU Su-Jin Kim

Plastics

Material Science

OCW

Plastics and Polymers (Kids)

https://youtu.be/tAYPxxdIQQc

Polymers (BBC)

https://youtu.be/BgILS0UBUvA

The 7 Thermoplastics

https://youtu.be/29Az-dPwtg8?list=PLDE5A69832ECC4D26

Thermoset

https://youtu.be/-cyTDZmkbYc

© GNU Su-Jin Kim

Plastics

Material Science

OCW

Polymers (TED 5min)

Monomer, Polymer, Natural, Syntactic(Addition reaction, ) Bakelite, Rubber, Styropone

https://youtu.be/UwRVj9rz2QQ

LG Chemical http://www.lgchem.com

© GNU Su-Jin Kim

Plastics

Material Science

Contents

1. Plastics (Polymers, 고분자재료) • Thermoplastics (열가소성수지) • Thermoses (열경화성수지) • Rubbers (고무)

2. Physical Properties

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Plastics

Material Science

Automotive Plastics and Composites Use Exterior

• doors, light, bumper covers

Interior

• instrument panels, door trim, seats, consoles

Engine

• valve covers, intake manifolds, fluid containers

© GNU Su-Jin Kim

Plastics

Material Science

Recreational Plastics and Composites Use Snow Equipment

• skis, snow boards, snow mobiles, etc.

Water Sports Equipment

• water skis, water crafts, snorkel equipment, fishing gear

• diving equipment and clothes

Land Sports Equipment

• shoes, roller blades, skate boards, tennis, golf, etc.

© GNU Su-Jin Kim

Plastics

Material Science

Commercial Plastics Usage

Packaging

• Wrapping, bags, bottles, foams, shrink wrap.

Textiles

• Clothing, carpets, fabrics, diapers, netting for sports

Furniture, Appliances, House wares

• Telephones and other communication equipment, computer housings and cabinets, luggage, seating, components for

• washers, dryers, etc.

• Musical instruments, CDs, VCRs, TVs, cases

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Plastics

Material Science

Medical Plastics and Composites Use Containers

• Bottles, bags

Drug delivery

• IV bags, syringes

• tubing and tools for surgery

• Implants, artificial skins

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Plastics

Material Science

Solid Materials

Metals Plastics Ceramic

Thermoplastics Thermosetts Elestomers

Plastic means to form or mold (from plastikos in Greek)

Polymer: Poly (many) + mer (structural unit)

Plastic = Polymer

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Plastics

Material Science

Chemical Structure of Polymer

• A monomer is the basic building block of a polymer.

• Polymers are long-chain molecules.

• Monomers linked in repeating units by polymerization reaction.

Ethylene

/Monomer

Polyethylene-[C2H4]n-

/Polymer

Polymerization

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Plastics

Material Science

Chemical Structure of Polymer Monomer Polymer

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Plastics

Material Science

Degree of Polymerization

1. Molecular weight

- M = n M0 , n: degree of polymerization

2. Degree of polymerization, n

- the higher the n, the longer the chain and the higher polymer’s viscosity.

Ex) Polyethylene -[C2H4]n- plastic

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Plastics

Material Science

Covalent (primary) bonding

• Occurs when two nonmetal atoms are in close proximity.

• Both atoms share outer electron shells.

• Strong Bond

Carbon 2C + hydrogen 4H

C

-

-

- -

H

-

H

-

H

-

H

-

Ethene C2H4

C

- -

- -

- -

H

H

C

- -

- -

- -

H

H

C

- -

- -

- -

H

H

Polyethylene -[C2H4]n-

C

-

-

- -

C

- -

- -

- -

H

H

C

- -

- -

- -

H

H

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Plastics

Material Science

Van der Waals (secondary) bonding

• Due to the Interaction between molecules called intermolecular force. It is much weaker than covalent bonding.

C C

C C

C C

C C

C C

C C

C C

C C

C C

C C

C C

C C

C C

C C

C C

C C

Covalent bonding

Van der Waals bonding

© GNU Su-Jin Kim

Plastics

Material Science

Structure of Polymer

1. Linear

- Thermoplastic such as acrylics, nylons, polyethylene, polyvinyl.

2. Branched

- polyethylene.

3. Cross-linked & Network

- Thermosets; epoxis, phenolics silicones, rubbers, elastomers

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Plastics

Material Science

Amorphous vs. Crystalline

• Amorphous region: polymer chains exist random. (Polyvinyl chloride, Polystyrene)

• Crystalline region: Uniform (regular) arrangement of molecules. It is stiffer, harder, less ductile. (Polyethylene, Polypropylene)

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Plastics

Material Science

Thermoplastics(열가소성)

• little crosslinking, ductile

• soften with heating

ex) polyethylene, polypropylene, polycarbonate, polystyrene

Thermosets(열경화성)

• large crosslinking (10~50%), hard and brittle

• do not soften with heating

ex) rubber, epoxies, polyester resin, phenolic resin

Thermoplastics vs. Thermosets

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Plastics

Material Science

Thermoplastics

• Linear and branched polymers will weaken secondary bonds.

• When above glass-transition temperature, polymers is easier to mold into shapes.

• Small increasing in temperature drops strength and increase ductility.

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Plastics

Material Science

Thermoplastics

PET Polyethylene terephthalate (high toughness, transparent )

Water & sports drink bottle

HDPE High density polyethylene (hard)

Milk, water, juice bottle; yogurt tub; retail bag

LDPE Low-density polyethylene (squeezable)

Bread and frozen food bag and squeezable bottle

PP Polypropylene (-110°C, high strength, transparent)

Flip-top bottle, plastic bag

PS Polystyrene (low strength, low elongation, transparent)

Yogurts cup, styrofoam

PVC Polyvinyl chloride

Flexible cables ; pipe

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Plastics

Material Science

Thermoplastics

PC Polycarbonate (high toughness, transparent)

Baby bottle, Phone, Laptop, Safyglass, Canopy

ABS Acrylonitrile Butadiene Styrene (high strength & toughness)

Electric, Home, Automotive

0.523" Polycarbonate

0.190" Spall Polycarbonate

0.025" TPU Interlayer

Abrasion Resistant Coating

Abrasion Resistant Coating

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Plastics

Material Science

Properties

Max usage Temperature°C

Optical Features

Mechanical properties

PS 60-70 Transparent Low strength & elongation

PE 60-80 Translucent to opaque

Low strength, Soft to rigid

PP 100-110 Translucent High strength & rigidity

PC 115-125 Transparent High strength

© GNU Su-Jin Kim

Plastics

Material Science

Thermosets

• Polymerization: linear chain(liquid) +(heat, pressure)-> cross-linking(cured permanently, no recycled)

• Epoxy resins - coating, adhesive

• Phenolic resins - tool handles, billiard balls

• Polyester resins - FRP

• Epoxy or Polyester +Fiberglass = FRP

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Plastics

Material Science

Thermosets

• Acrylic: transparent

• Melamine

• Polyimide(PI): high temperature

• Teflon(PTFE): non-stick coating

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Plastics

Material Science

Elastomers (Rubbers)

• An elastomer is capable of recovering substantially in shape and size after its load has been removed.

• Rubber is capable of quickly recovering from large deformations(<500%).

• Elastomers encounter hysteresis loss in stretching or compression. During the deformation energy is lost.

Elongation

Load

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Plastics

Material Science

Elastomers (Rubbers)

• Natural rubber

• SBR(styrene butadiene rubber)

• Silicone

• Polyurethane: insulating foams

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Plastics

Material Science

Polymer Additives(첨가제)

Improve mechanical properties, processability, durability, etc.

• Fillers (충진제)

– Added to improve tensile strength & abrasion resistance, toughness & decrease cost

– ex: carbon black, silica gel, wood flour, glass, limestone, etc.

• Plasticizers (가소제)

– Added to reduce the glass transition temperature Tg

– commonly added to PVC - otherwise it is brittle

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Plastics

Material Science 27

Polymer Additives

• Stabilizers (안정화제)

– Antioxidants

– UV protectants

• Lubricants (윤활제)

– Added to allow easier processing

– “slides” through dies easier – ex: Na stearate

• Colorants (색소제)

– Dyes or pigments

• Flame Retardants (방염제)

– Cl/F & B

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Plastics

Material Science 28

Stress-strain curve (응력-변형율)

Strain >10 possible (metals < 0.1)

brittle polymer

plastic

elastomer

Str

ess 1

0%

of m

eta

l

Network linked

Amorphous chain

• Stress 0.1xmetal, Strain 10xmetal

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Plastics

Material Science 29

Stress-strain curve (응력-변형율)

• Strength: PMMA>ABS>PP>PE

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Plastics

Material Science 30

↑Temperature

↓Elastic modulus, ↓ Tensile strength

↑Ductility

Sensitive to Temperature

0 0 0.1 0.2 0.3

4°C

20°C

40°C

60°C to 1.3

str

ess

strain

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Plastics

Material Science

Viscoelastic (점탄성)

Stress relaxation(응력이완)

strain to ε0 and hold stress decrease with time.

Relaxation modulus(이완계수) Er(t) = σ(t)/ ε0

time

str

ain

, str

ess

Strain ε0

Stress σ(t)

© GNU Su-Jin Kim

Plastics

Material Science

Glass-transition(유리천이) temperature

• Relaxation modulus drop large at Glass-transition temperature, Tg.

glassy

(rigid, brittle)

Tg Tm

rubbery

E

G

elastic solid

(탄성고체)

viscous liquid

(점성유체)

dy

dv

Viscoelastic

(점탄성체)

leathery viscous

mC

Log R

ela

xation m

odulu

s E

r

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Plastics

Material Science 33

Drawing

• Drawing (ex: monofilament fish line) - stretches the polymer prior to use - aligns chains in the stretching direction • Results of drawing: - increases the elastic modulus (E) in the stretching direction - increases the tensile strength (TS) in the stretching direction - decreases ductility (%EL) • Annealing after drawing - decreases alignment - reverses effects of drawing.

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Plastics

Material Science

Injection molding (사출성형)

Hopper

Barrel

Mold

• Plastics are melted in a heated cylinder and forced into a mold by hydraulic plunger of rotating screw.