BoPET,full form is Biaxially-oriented polyethylenee terephthalate,is a kind of flexible film,which has high importance in flexible packaging. Commonly called polyester film made from stretched PET.Generally known as supreme properties film regarding barrier to Gas,aroma,any many others which will be nerrated later.

History:

BoPET(Biaxially oriented polyethylene terephthalate)first time developed in 1950s,NASA used Metallized BoPET during its projects in 1960 and 1964.

Manufacturing process:

Manufacturing process starts with a sheet of molten polymer polyethylene terephlate being extruded on a chilled roll,quenches there and gets amorphous state,then biaxially orientation process starts,During orientation ,film first drawn in the machine direction(MD)travlling through heated rollers,2ndly film drawn in the transverse direction(TD),Drawing into both direction can also be made simultaneously.Ratios for draw are typically about 3 to 4 in both directions.
After completion of drawing process film becomes crystallized,becuase of tension and heat (more than200°C) in the orientation oven.This process stop film to reurning back to its original shape.This orientation process of the polymer’s molecular chains gives high strength,stiffness and excellent clarity to BoPET film.
Now film passes through scanning area to be verified regarding required guage,then passes through Corona treatment station for surface tension,to avoid layers sticking,same like sticking of clean glass plates during stacking.Finally reaches the winder to be wound into big rolls.

Other processes

Metallized BoPET:film can also be metallized throgh metal evaporation process,in which a very thin layer of Aluminium,gold etc depsited on the film.Metallizd BoPET become highly suitable for food packaging because of it’s enhanced barrier properties towards Gasses and light.
Metallized or non metallized film can also be laminated with other substrates like polyethylene,Cast polypropylene or Bopp(Biaxially oriented polypropylene)to get sealability,polyethylene lamination appearance maybe dull but improves puncture resistance.

Special characteristics of BoPET:

Barrier properties : It has excellent barrier properties towards chemicals,air,aroma/fragness,oil,non-toxic,and tasteless.
Mechanical properties: It has excellent mechanical properties like high tensile strength,rigidity,stiffness hardness,toughness,puncture resistance,friction resistance,high and temperature resistance.

Application:

Bangs,lamination for food packaging,packaging for pharma items,Anti fog film for food trays,Rigid film used for silk screen printing and thermoforming,electrical insulation etc.

stretch film

It comes in varying gauges, colors and can be used in numerous applications.The main

differences of stretch films are blown versus cast.

Difference is below..
Blown stretch film, also known as blown Pe stretch wrap, is manufactured by blowing

heated resin out vertically into a bubble. It is cooled by the inner and surrounding air,

called IBC system. Pulled by Take-Off nip roller,

Cast stretch film, also known as cast Pe stretch wrap is manufactured by feeding a sheet of heated resin along with a rolling path with chilled rollers. The cooling solidifies the film sheet, and it is made into large rolls.
now a days cast pe stretch wrap film is being used mostly because of its special characteristics than Blown pe stretch wrap film.

Extrusion process

Cast pe stretch wrap, is created using a cast extrusion process. The Cast extrusion process is a continuous process by which the Polymers are melted and extruded as molten sheet through a flat T-die onto a Cast chilled roll, where it is quenched and re-

solidified. which gives Cast Pe stretch film excellent clarity, low force to stretch, increases tear resistance, unwind quietly from machines, and offer an excellent cling. There are both machine grade and jumbo cast stretch film rolls available.(which can be converted to hand rolls afterwards)

Resin for manufacturing

Most commonly used LLDPE (Linear low density polyethylene) to have good elastic properties,Elongation,punctured resistance,Tearing Etc. Cling agent and processing aids also being used to enhance the film appearance and cling properties.

Uses/Benefits of stretch film

• It is used to hold the wrapped/packed package while transporting.
• It improves stability of the product/package.
• It is used to keep the package safe from dust and foreign body damages.
• It also keep product/package safe from UV Rays,with the use of UV stabilizer while processing.
• white opaque stretch wrap enhance package appearance.also great
• for colour coding products.
• It can be used with manual,semi automatic and automatic machines.

It is also a kind of flexible packaging product with its revolutionary benefits in packaging field.without any risk while package transportation,storage,damaging from rain-dew-and dust.at the end we can even recycle it,because is made of LLDPE.

Properties should considered while using/purchasing..
Stretch ability
Elongation
Dart impact
Puncture resistance
Tearing
Cling

Introduction

Pe Blown film extrusion is a technology that is the most common method to make Pe films, especially in the flexible packaging industry. The process involves extruding a tube of molten substance(polymers) through a die and inflating to several times its initial diameter to form a thin layer bubble. This bubble is then collapsed and used as a lay-flat tube or can be made into bags, also can be used in many more different packaging items.

Extrusion process

Typically, Pe blown film extrusion is carried out vertically upwards,which is different than Cast Polypropylene (CPP film) however horizontal (Cast Pe Stretch wrap film)and downward extrusion processes are now becoming more common . Figure shows a schematic of the set-up for Pe blown film extrusion. This procedure consists of four main steps:

1. The polymer material starts in a pellet form, which are successively compacted and melted to form a continuous, semi liquid . This molten plastic is then extruded through an annular die.
2. Air is injected through a hole in the center of the Die unit, and the pressure causes the extruded melt to expand into a bubble. IBC and OBC (inner bubble cooling and outer bubble cooling)works in automatic way with setting parameters, so that even and constant pressure is maintained to ensure uniform thickness of the film .
3. The bubble is pulled continually upwards from the die and a cooling ring blows air onto the bubble. The bubble can also be cooled from the inside using internal bubble cooling. which brings bubble temperature down, while maintaining the bubble diameter.
4. After getting cooled at the frost line, the film moves into a set of nip rollers which collapse the bubble and flatten it into two flat layers. The set of rolls pull it onto windup rollers. Then it passes through idler rolls during this process to ensure that there is uniform tension in the film. Between the nip rollers and the windup rollers, It may pass through a Corona treatment station for surface tension, depending on the application. During this stage.

Advantages and Disadvantages of Pe blown films.

Pe Blown film generally has a better balance of mechanical properties than flexible packaging because it is drawn in both the transverse and machine directions. Mechanical properties of the thin film include tensile , elongation and toughness properties. approximate stable properties gives maximum toughness .

Pe Blown film requires lower melting temperatures than cast extrusion. Measured at the die opening, the temperature in cast is about 220-260°C(depends on m/c output), where as the temperature in blown process is about 145-200°C(depends on m/c output).

following are some common disadvantage in Pe blown film techniques..

low transparency ,low output,more thickness variation,less optical properties(gloss and haze)

classification of R.material grades

The most important polyethylene grades used for Pe blown films are HDPE, LLDPE and LDPE. details as under with relevant grades names…

• High density polyethylene(HDPE)

• Linear low density polyethylene (LLDPE)
• Medium linear low density polyethylene(mlldpe)

Classification of Pe Blown film types
Here we will know only names of the types in short.

• Pe(polyethylene)lamination
• pe shrink wrap
• pe stretch wrap (also can be produced via T-die cast process)

Since the creation of flexible films, the packaging industry has been propelled to astonishing heights.
Through the development and utilization of these films, manufacturing practices, and continual innovations, the field of packaging has been able to grow and evolve to adapt to the needs of products around the globe.

What is Flexible Packaging
Bags, envelopes, pouches, sachets, wraps etc, made of easily yielding materials, such as
Film, Foil, paper sheeting which, when filled and sealed, acquires pliable shape.
Due to flexible film’s many desirable characteristics, implementation of various manufacturing methods and polymer additions provides the means to increase appeal to a broad spectrum of products.
These films have an illustrated history in packaging, and there are continually enhancements and improvements, as well as new products being marketed.
HERE, THE HISTORY, MANUFACTURE, AND RECENT INNOVATIONS OF THESE FILMS WILL BE ADDRESSED,AS WELL AS THE IMPORTANCE AND IMPACT BY THESE FILMS HAS HAD ON THE PACKAGING INDUSTRY AS A WHOLE, AND WHAT THE PACKAGING FUTURE HOLDS FOR FLEXIBLE FILMS.
INTRODUCTION :-
With the united states 135 billion dollars in the worldwide packaging industry (Flexible packaging Association), this industry is the second largest sector of the business with flexible
Packaging offering Consumers extensive desirable characteristics, it is easy to see why. From ease of handling and storage, overall cost savings, and convenience, flexible packaging has cemented itself in the packaging world, and has undoubtedly been a key contributor to packaging’s continued success.
The popularity of utilizing these films for packaging is largely based on the numerous technical developments that have been made in the field. packaging film possess good barrier properties from gasses, light, germs and moisture etc. on their own, but with the aid of coatings, film types, and manufacturing methods, the positive attributes skyrocket.
Main products
While there are many types in this industry, the most common are polypropylene (pp), polyethylene(PE),which is known as Pe blown film (lamination/printing and shrink for wrapping)Cast Pe Stretch wrap,Biaxially-oriented polyethylene terephthlate(B0PET) and Biaxially oriented polypropylene(BOPP). But Pvc, polyamid(nylone),and polyestrene(PS) are also standing there.