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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.

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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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