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LIBRARY REFERRENCE
PROJECT
ON
Biaxially Oriented Poly Propylene
Submitted By:
Shaikh Md. Izhar
PG/K/2010/03
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CONTENT
PA
GEIntroduction 3
BOPP 4Manufacturing process 5
Features of BOPP 8
BOPP uses 10
Breathable BOPP 13
Testing 18
Ecological aspects 21
Referrence 23
INTRODUCTION
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BOPP films is classified in the clear film category along with cello, PET, PP &
UPVC film which are popularly used by the packaging industry and convertors.
Polypropylene is an attractive candidate material for packaging applications
because of its low cost and good thermal stability. Opp, oriented polypropylene, is
a flexible material derived from melting and orienting a polymer calledpolypropylene. Commercial polypropylene films are typically oriented by a
tentering process or tubular process in which an extruded film is quenched,
reheated, and biaxially drawn into a film. Orientation improves both the
mechanical and gas-barrier properties of the films.
The worldwide film demand is steadily growing. Growth in biaxially-oriented
films for the packaging industry is especially strong. Biaxially-oriented films can
be divided into two categories:
Commodity films, which need to be produced as cost-efficiently as possible
due to strong price pressure from the market
Specialty films, where a higher price is possible, however this is usually
related to higher demands in technology and therefore also higher
production costs
Bi-axially Oriented Polypropylene (BOPP)
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Biaxially Oriented "means that the polypropylene film is stretched in both the
machine direction (MD) and across machine direction (AMD). Because of its
superior strength at low gauges, flatness, clarity and excellent printability,
BOPP film is rapidly becoming the benchmark for quality.
RAW MATERIALS
The four resin categories used for OPP films are: homopolymer, co-polymer,
terpolymer & modified resins. Homopolymer resis are made by polymerzing PP
monomer with a variety of catalyst. Co-polymer incorporates 0.1%-1.5% ethylene
as a comonomer with PP. The amount of comonomer used depends on the films
end use. Terpolymer production uses butene along with the ethylene and PP feeds.
PP homopolymer resins are also modified with terpenes to give them certain heat
sealing properties and to improve moisture barrier and film production. Thehomopolymer PP, is typically isotactic PP, & advances in molecular architecture
control has permitted improvements in film properties and productivity.
Due to advance catalyst technology, syndiotatic PP, is now available and has been
used in OPP shrink film production but has not resulted in any broad change in
OPP film.
MANUFACTURING PROCESS
There are three different techniques to produce biaxial oriented films: The
sequential tenter frame process, the simultaneous tenter frame orientation as well
as the double-bubble process, which is also a simultaneous stretching method.
Thereby for different film types certain processes have prevailed: For example4
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BOPP and BOPET are mainly produced by the sequential process, whereas for
BOPA all three techniques are used at about the same shares.
Tenter process
Polymer is extruded as a sheet directly onto a chilled chrome roller. The film is
then passed through a stretching unit by rollers moving faster than the rate at which
the material is extruded. This orients the film in the machine direction.
The film is then fed into a tenter frame for transverse direction orientation. In the
tenter, the film is gripped along each edge by clamps that are attached to moving
chains. These move outwards to stretch the film in the transverse direction. After
stretching, the film is heat-set to hold the orientation and then reeled up.
Two stage orientation
The simultaneous tenter frame orientation
The two operations can also be carried out simultaneously, as in shown in figure.
The film is gripped by its edges as it leaves the casting rolls and is then moved
forward at an increasing speed while being strenched transversely by the diverging
grips. Mechanically, this type of operation can be carried out by a tenter frame in
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which the clips are moved by a srew of increasing pitch. The magnitude of the
transverse draw would then be controlled by the angle of divergence of the clips, in
the usual way, while the magnitude of the forward draw would depend on the rate
of increase of pitch.
Simultaneous orientation process using a tenter
The Bubble Method
A circular die is used from the extruder to form a thick walled tube of
polypropylene. This is then blown under air pressure, orienting the film in the
transverse direction. At the same time, an equal orientation in the machine
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direction is achieved by the speed at which the tube is pulled downwards and
collapsed. After orientation, the film is heat-set.
The bubble method produces film which is "balanced", that is to say it has the
same mechanical properties in both the machine and transverse directions. Films
produced in this way can have process advantages during conversion over tenter-made films. The tubular process is thus another method of obtaining simultaneous
transverse and forward orientation.
If oriented PP film is heated about 100c immediately after drawing, it will shrink
unless it is restrained in some way. This can be prevented by a process of
annealing or heat setting. The film is heated, under controlled conditions, and
while held under restraint. After cooling, the film will not shrink if heated to below
annealing temperature and the film is said to be eat set. The physical and optical
properties of the film remain unchanged.
Features of Biaxially Oriented Polypropylene Film
The important properties of Biaxially Oriented Polypropylene (BOPP) film are:
It has a high tensile strength that facilitates high-speed conversion
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It has a high gloss and clarity
It has good puncture and flex-crack resistance over a wide range of
temperatures
It is a good barrier to water vapour
It is resistant to oils and greases It is not affected by moisture and does not wrinkle or shrink with environmental
changes
Advantages of Biaxial Oriented PP film versus Cast PP film
- Improved barrier properties
- Improved mechanical properties
Benefits of Bubble BOPP film versus Stenter film
- Balanced Orientation
- Excellent shrink tightening properties
- Improved film cutting (including die cutting)
- Access to both thin and thick film technology (down to 15 m and up to 250 m)
- High Machine Direction (MD) stiffness, high tensile strength (MD) and low
elongation (MD) for conversion.
Bopp Films Features
The main feature of Bopp films are improved stiffness, high tensile strength,
excellent optics and good water barrier properties. They range from 15 to 50
microns and are most commonly 15 to 30 microns. These bopp packaging films
can be monolayer or coextruded structures, and transparent, opaque, or metalized.
They also have the advantage of being non-toxic and fully recyclable.
Bopp films are printed out of new printing technology, Indigo Omnius. Theyprovide excellent UV light protection, humidity, aroma and light barriers. Bopp
films have superior strength at low gauges, flatness, clarity and excellent
printability. They can be treated with acrylic and PVDC PVDC coatings for better
sealability and barrier properties. The Bopp films use mainly homopolymer PP and
random copolymer PP.
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Applications: BOPP Films and Packaging
Bopp films are ideal for twist-wrap applications and in laminations for use
over vertical and horizontal machines.
Bopp films also can be used for decorative purposes.
They are used in an a almost limitless array of flexible packaging
applications,pressure sensitive tapes, labels, stationery, metalizing,
consumer products and a wide variety of packaging uses.
Bopp packaging films are widely used for gift and flower wrapping, paper
lamination, textile packaging, release film for melamine plates and plate film
packaging.
These films are also used as the anti-counterfeit covering film on the
packaging cases.
Various packaging products like packaging pouches, packaging bags,
electronic packaging, industrialpackaging are produced by Bopp films.
BOPP Films Uses
BOPP films are the high growth films in the world market and are available in a
wide range of film variations for usage as packaging,pressure sensitive tape, label,
stationery, metalizing and decorative tapes and films etc. Some of the popular
BOPP films usage have been described here.
BOPP BagsBOPP bags made from Biaxially Oriented Polypropylene (BOPP) films have high
tensile strength and physical properties like good dimensional stability, water
proofing, transparency etc. BOPP bags manufacturers make these bags available at
highly competitive prices with customization done as per the requirement of the
clients. Some of them use Dotted Seal Technology to give BOPP bags extra
sealing (perforation) on sides to strengthen them and remove the initial tear-off
from the edges to retain the product for longer periods. These BOPP film bags are
used for different products & various applications such as for packaging garments,hosiery, stationery, toys, combs and other products.
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BOPP Tapes
BOPP JUMBO ROLLS
Many types of BOPP tapes are used for various packaging needs- industrial,stationery for offices and homes as well as decorative packaging. BOPP Tapes are
commonly used for medium and heavy carton sealing. The BOPP self adhesive
tapes provide high tackiness, greater holding power and adhesion strength and
have good wear out resistance and shockproof character. The BOPP self adhesive
tapes come in various widths, colors, thicknesses ranging from 40 micron to 52
micron. Various colors of BOPP tape include white, brown, blue, black, yellow,
red, green etc. as well as transparent (some colored transparent too such as orange
transparent.) The special grade BOPP tapes include those used in packing and
storage in cold storage conditions. Hand tear tapes too are available in all widths
and lengths. BOPP Adhesive Jumbo rolls are made from high quality water acrylic
adhesive and BOPP film. They are widely used for slit medium and heavy-duty
carton sealing tape. The size of BOPP jumbo roll can vary from 980mm, 1040mm
and 1280mm to other customized sizes for export market.
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BOPP Lamination Film
BOPP lamination films are specially designed to protect printed image from
moisture & rough handling damage. The films are of glossy clear BOPP coated
with a permanent pressure sensitive acrylic adhesive & backed with an ultra
smooth clear transparent film. These BOPP films are used for various laminatingpurposes for posters, labels, sticker, paper printed material etc. BOPP lamination
films are also used for all types of documents such as catalog sheets and sales
leaflets, price lists and menus, security / identity / luggage tags, engineering
manual, industrial sheets, technical diagrams, educational and visual aids, show
cards, maps, charts, notices, etc. as well as presentation materials, id cards /
prestige business cards, photographs, graphics, computer graphics, planning
calendars, pocket calendars, record and library cards, press clippings among other
customized uses.
BOPP Pouches
The present food and beverage industry prefers to use pouches for their high
transparency, clarity, better tensile strength and durability. The BOPP pouches
prove to be very cost-effective and are available in unique and trendy styles that
help companies showcase their products while ensuring their packed safely. The
BOPP laminated display bags and pouches not only provide visibility for the
products but the companies can also repack the items after display as many of them
come with reusable adhesive tapes.
BOPP Woven Bags
BOPP woven bag is primarily made of woven fabric with BOPP lamination and
are widely used in many industries. The BOPP woven bags are even available in
custom designs. They come in various types including Valve Bag; Sewn Open
Mouth Bag; Bottom Open Mouth Bag etc. BOPP Woven Bags are extensively used
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in storage and packaging of food material. These bags are mostly resistant to dirt,
moisture and abrasion. Woven bags made of BOPP films also come in various
options of length, width, denier range, colors, designs and patterns for various
industrialpackaging usage.
New Range Of Non-Perforated 'Breathable' BOPP Film
Breathable BOPP Film for Fresh Produce Packaging
The permeable and non perforated breathable BOPP films are a quite a break
through for packaging the fresh harvests. Fresh foodpackaging needs breathable
films that are also laden with anti mist advantages. The ability to expand the shelf
life of the fresh food packaging is a big step in making it available to places thatare far and distant. Also it allows a longer storage life, with the assurance for
freshness being intact and preserved.
The new range of non perforated breathable BOPP film is a great innovation for
reducing the food wastage and enjoying the fresh produce. Consumers can now
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buy more of freshly packaged food and store it for longer durations as these films
help keep it fresh with high quality breathable films packaging and refrigeration.
Breathable film has today emerged as a very popularpackaging material.
Breathable films are produced by compounding a PP or PE resin with mineral
filler. The film is then stretched mono or bi axially to create micro pores in the cast
film. In a subsequent process this breathable film can be laminated with a
nonwoven web using adhesive or a point-bonding calendar
to produce a soft, textile like composite. Breathable films, the ability of extruded
films to allow the gases to escape, but retain the larger water molecules, inhibiting
the dehydration process.
Characteristics
The film offers high strength and high resistance to puncture.
They are flame retardant and provide UV stability.
They provide additional comfort without reducing the barrier properties of
the film.
They extend shelf life by limiting oxygen supply, slowing the live products
respiration rate, and thus retarding spoilage. They have excellent resistance to hydrolysis and remarkable mechanical
strength.
Applications
These are widely used for roofing applications in the construction industry. They
are also used for sanitary articles. They are also required in the medical industry
for bandages, wound dressings, surgical drapes, and gown fabrication. They arealso used in textile industry. They are utilized for cost-effective tack bonding,
combination tack bonding and lamination, for lamination, or for surface
modification.
Breathable films and packaging
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One common use for such films is to make packaging materials. Salad mixes and
other vegetables can be packaged in breathable films tailored to their respiration
rates for a couple of years. Packaging materials are available in varied forms like
packaging pouches, packaging rolls, packaging bags which can be used for packing
vegetables and fruits so as to keep them fresh and hygienic. Retailers have
nowadays gone for increased use of breathable films for packaging.
Choosing Suitable Breathable Film for Medical Applications
The breathable film in use should guard against any kind of contamination in the
wound. By any contamination, we here refer to bacteria and any other kind or
liquid or solid contamination. It has to essentially be skin friendly as it comes in
close contact to the skin, that too when it is extremely sensitive. Physical properties
required of these adhesive coated breathable films for medical applications are as
follows:
Transparency: It can be any color, but the breathable films required for
wounds need to be relatively clear as a close look at the wounds is often
required.
Thickness: There is a specified range of thickness, 0.01 mm to 0.075 mm
that needs to be met. In general, thicker the films, stronger it is.
Other Properties: Other properties like tensile, strength, softness,
drapability and tear resistance are some of the other important factors thatneed to be considered while choosing a suitable breathable film for medical
applications. Usually, it becomes challenging when two opposite or
competing characteristics are required in the same film. For example,
softness & drapability.
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Moisture Vapor Transmission: The most important of all the above
requirements of suitable films for medical applications is the moisture vapor
transmission. This is perhaps an important condition that makes adhesive
coated breathable films, a more appropriate choice as compared to other
kinds of films. Usually thinner breathable films allow more moisture vapor
transmission. This quality is important as it protects the covered wound from
a lot of infections that can be caused by the locked moisture in the wound.
The above discussion makes it clear that with high moisture vapor
transmission properties adhesive coated breathable films make suitable films
for medical applications. Guidelines have been set to help the manufacturers
produce high quality breathable films for all sorts of medical applications,
optimizing moisture vapor transmission, softness, strength and drapability of
these films.
Oxygen permeability of biaxially oriented polypropylene films
Polypropylene is an attractive candidate material for packaging applications
because of its low cost and good thermal stability. Biaxial orientation, by
means of a tentering process, for example, imparts mechanical robustness to
the film. Other key requirements for beverage and food packaging are
optical transparency and atmosphere control. In a previous contribution, we
reported that the loss of optical transparency of biaxially oriented
polypropylene (BOPP) films correlated with surface roughness on the 100-
[micro]m. The effect could be minimized by proper choices of thermal
history and orientation temperature. We now examine the oxygen
permeability of the same films.
Orientation reduces the gas permeability of polypropylene.
However, the relationship between orientation and gas permeability is not well
understood. For example, permeability does not exhibit a simple relationship with
optical birefringence, which reflects the total combined molecular orientation of
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the crystalline and amorphous phases whereas gas transport is seen as occurring
only through the amorphous regions. Indeed, one report, with very limited data,
demonstrated a correlation between oxygen permeability and the Herman's
amorphous phase orientation function in the transport direction.
Permeability is the product of two factors: diffusivity and solubility. A recent study
identified decreased diffusivity, the dynamic component of permeability, as being
responsible for decreased permeability of oriented polypropylene films, and
moreover suggested that reduced mobility of the oriented amorphous chains was
responsible. Orientation of polypropylene involves a morphological transformation
of the spherulites into a network of micro-fibrils. The process of orienting the
partially crystalline film stretches and tightens the amorphous tie molecules that
connect the crystals and transfer the stress.
Biaxial Stretching of Compression-Molded Sheets
The stretching characteristics were tested in the temperature range between
the onset of melting and the peak melting temperature in the DSC
thermograms. Good film uniformity, as indicated by the uniform
deformation of a stamped-on grid pattern and uniform birefringence over a
circular area with a 25-cm diameter in the center of the film, was obtained at
draw temperatures between 140 and 144[degrees]C regardless of the thermal
history of the sheet.
Oxygen Transport Properties of BOPP Films
Biaxial orientation resulted in a decrease in the oxygen permeability. The
lowest permeability was consistently obtained with the lowest draw
temperature. Also, a lower permeability was obtained by increasing the draw
ratio from 4 X 4 to 5 X 5. Surprisingly, there was no consistent relationship
between the oxygen permeability and the thermal history of thecompression-molded sheet. In contrast, thermal history of the compression-
molded sheet had a very strong effect on the transparency of the same BOPP
films.
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TESTINGS
BOPP testing is very important for BOPP quality control. BOPP (Biaxially
Oriented Polypropylene) cigarette film, with is excellent moisture barrier property,
optical performances, heat seal property as well as high heat seal strength,reasonable shrinkage rate and good stiffness, is the first choice for cigarette film.
The testing items of BOPP are the judgment for BOOP film performance. In order
to better control the quality of BOPP cigarette film,
A. Moisture Barrier Property Testing of BOPP Cigarette
Film
High moisture barrier property performance is a must for cigarette package so as to
avoid deterioration caused by moisture. At present, this factor is not fully noticed
by the cigarette manufacturers. According to ASTM E96, ISO 2528 and other
standards to test moisture transmission rate for materials. The lower WVTR the
better. But, higher barrier property means more costs. Therefore, the common data
is less than 10g/m2.day or 5g/m2.day.
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B. Thickness of BOPP
Thickness of BOPP cigarette film is the basic film performance index. Uneven
thickness would influence the tensile strength and permeability as well as the
following procedures. Thicker cigarette film would have better stiffness with bettervisual performance. But, the cost would also be great. When testing thickness in
different directions, deviation must be controlled within 3% usually. Meanwhile,
the edge thickness of BOPP film has to be measured.
C. BOPP Cigarette Film Tensile Strength, Elongation andElastic Modulus
Cigarette package requires high tensile strength of BOPP films, which can greatly
reduce the breakage during packaging process. Generally, 140N/mm2 vertically
and 200N/mm2 crosswise are required. Elongation rate is for analysis of incision
easiness of films. Cigarette packaging industry is different from other industries.
Higher elongation rate is not better.
D. The Heat Seal Strength of BOPP Cigarette Film
BOPP is required to have high heat seal strength and wider heat seal scope by the
cigarette industry, so as to improve packing speed and proper operation. If the heat
seal temperature is higher, it would lead to wrinkle because of increased BOPP
film shrinkage. Therefore, proper heat seal temperature should be chosen so as to
avoid unstable heat seal, wrinkle and other phenomena. The heat seal style of
BOPP cigarette film is heat-pressure seal, that is, to heat seal at certain heat seal
temperature, pressure and period. The heat seal testing is to test the minimum heat
seal separating force after heat sealing. The heat seal strength of cigarette is
normally required to be above 2.0N/15mm. Now, with the development of
cigarette packing machine, low temperature heat seal film becomes more popular,
which requires the heat seal strength above 1.5N/15mm.
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E. BOPP Cigarette Film Coefficient of Friction Testing
The smoothness of BOPP cigarette film is one important index for BOPP films
with is the testing requirements coming along with the high speed packing.
There are four kinds of situations that need coefficient of friction testing, namely,the coefficient of friction of the film and the metal side of the machine or the
transfer belt; the inside side between films; the film inner side and the cigarette
outer package; and the outer film side and the outer package. Of these four
coefficients of friction, the first should be low so as to better transfer the cigarette
package and improve packing speed.
F. The Heat Shrinkage Testing for BOPP Cigarette Film
BOPP film heat shrinkage is mainly used for the evaluation of heat stability under
different conditions or different factors. For rigid cigarette package, such rigid
package has good support effect, around which high shrinkage film can be applied
so as to achieve even and beautiful visual effects. Therefore, rigid package requires
the heat shrinkage of BOPP cigarette film to be up to 8% to 12%.
G. BOPP Cigarette Film Abrasion Resistance TestingWith stricter requirements for abrasion resistance, inferior abrasion resistance
performance would greatly influence the beauty of the cigarette package. The
testing of abrasion resistance is to avoid scratch on the surface of the product
caused by the contact of film surface and the machine; and to avoid wounds caused
by film and outer package.
Above all, there are many BOPP cigarette film testing items. Whentesting, relevant standards must be applied; or unified testing conditions
for data comparison.
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ECOLOGICAL ASPECTS
These days recycling of plastics have been most important as plastics are
not bio-degradable causing environmental hazards. Due to this most ofthem are being re-cycled and in the case of BOPP it can be recycled too
but when it is in the form of thin films as there would not be any scrap
value it can be used in laying of roads as this acts as it forms a thin layer
on the roads hence improving the quality of roads
Biaxial Polypropylene Geogrids are commonly used to improve the performance
of weak subgrades. By distributing dynamic loads over a wider area, pumping and
shear failures are minimized, resulting in increased load bearing capacity of thesubgrade. Biaxial Polypropylene Geogrids are also very effective in base
reinforcement applications. The openings in the geogrid interact with base
materials, confining them and preventing lateral dispersion. The result can be up to
a 30% reduction in base course materials. GSI offers a full array of Biaxial
Polypropylene Geogrids.
Paved Roadways
Unpaved Roadways
Port Terminals & Distribution Centers
Haul Roads
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In soil stabilization applications, Biaxial Polypropylene Geogrids distribute loads
over a larger area, reducing pumping and shear failures while maximizing the load
bearing capacity of the subgrade.
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In base reinforcement applications, Biaxial Polypropylene Geogrids prevent lateral
dispersion of base materials improving their structural performance. This can result
in up to a 30% reduction in base course materials.
REFERRENCE
FUNDAMENTAL OF PACKAGING TECHNOLOGY, 3rd
Edition WALTER SOROKA, CCP.
PLASTIC FILMS, 2nd
Edition-JOHN BRISTON.
PLASTICS IN PACKAGING by I.I.P
PACKAGING TECHNOLOGY VOL I by I.I.P
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