What is PET ?
Some Facts about PET?
Recycling Material Codes?

PET was invented in England in the 1940's and primarily used for fibre manufacturing. In the 60's it also began to be used for film production. In 1973 the PEt bottle was patented in the USA. Due to development of technology for pre-form blowing, impact resistance and design choice as well as the relatively low cost, today PET is mainly used for bottle manufacturing.THE bottles are used for soft drinks, juices, mineral water, beer, vegetable oil, mayonaise, cosmetics, cleaning liquids, food and non - food containers etc.

There is a rapidly increasing demand for PET bottles worldwide. During the 1990's in Europe the consuption has increase from 300,000 tons to 1.5 million tons. Similiar trends are also seen in other parts of the world. In Europe the amount of PET bottles being recycled is growing rapidly.

In many countries PET bottles are still thrown away with the household waste and burnt, or often just left on the streets, contaminating the environment. The growing concern about the environment and the limited natural resources demands implementation of systems for collecting and recycling of PET into valuable materials and new products.

There are different collecting systems for PET bottles, for example: refund deposits installed in supermarkets, railway stations etc; selective waste containers installed on the streets; sorting conveyors and lines on the disposal fields for seperation of PET bottles from other domestis wastes. For easy identification and sorting, PET bottles are usually stamped with an international code "1"(see page 11-1/1)

Collected bottles are usually baled and then sent for processing into secondery PET plastic. The market for secondery PET is almost unlimited and has a great growth potential. The price depends on various factors, such as the quality of the flakes, current world prices, the collecting system , etc.

What is PET?

The Physical properties of PET make it an ideal material for many applications: pacakaging (containers, bottles, etc) films, fibres, mouldings, etc. PET (Polythylene Terephtalate) is a thermoplastic polyether of terephtalic acid and ethylene glycol. It is a Rigid, durable and light material.

PET items are resistant to impact loads and cracking. PET is stable in conditions of diluted acids, oil, spirits (alcohol), mineral salts and most organic compounds except strong alkalines and some solvents. It has a very small water absorption which guarantees a high stability of properties and dimensions of the products made of PET.

PET has no smell, no taste, is not poisonous and has a minimum absorption of smell. It also acts as a good gas barrier. PET esists in both amorphous and crystalline states. During processing it converts into amorphous state by means of fast cooling of the melted material from the melting point(+260 degree c) to below the glass temperature (+73 degree c), thereby obtaining a transparent and translucent form.

During the processing PET has a low melt viscosity. It is processed by extrusion, vaccum pnuematic shaping, injection moulding, pulling or spinning from the melt, etc . FOr protection against destruction (oxidizing) PEt is processed as a composition with thermostabilizers and other additives. THe moisture content must not be higher than 0.02%, otherwise PET tends to get hydrolysed.

Result of Tests
Samples of clean flakes from a bottle recycling plant were tested in a plastics institute for the following parameters:

• Intrinsic viscosity = 0.79dL/g (ASTMD4603)
  (By comparison the intrinsic viscosity of primary PET is 0.8-0.82dL/g. The conclusion is that the material does not lose much in molecular weight.)
• Melt viscosity of 270 degree c
  (in flow index of 270 degree c and load 0.75 kg. The sample was first dried in a vaccum dryer in 150 degree c for 5 hours)
• Humidity = 0.6% defined by manometrical method.
• Acetaldehyde content = 2.5ppm (ASTMD4526 and 4509)
• Glass TEmperature = 78 degree c (ASTMD3418)
• Melting Temperature = 248 degree (ASTMD3418)
• Temperature of starting crystallisation = 127 degree c (ASTMD3418)
• Temperature of maximum crystallisation = 146 degree c (ASTMD3418)
• Specific energy of crystallisation = 32 j/g (ASTMD3418)

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Some Facts

• 20 pieces of 2 litre PET bottles weigh approx 1 kg
• 5 pieces of 2 litre bottles are enough to manufacture fobre for one large T-Shirt
• 20 pieces of 2- litre bottles are enough for filling of a winter jacket.
• 20 pieces of 2- litre bottles are needed to manufacture fibre for a sweater
• 35 pieces of 2 - litre bottles are needed to manufacture fibre for a sleeping bag.
• 60 pieces of 2 - litre bottles are needed for lm 2 carpet.

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Annexure II : RECYLING MATERIAL CODES
SPI : Society of Plastic Industry (USA)

SPI introduced 10 years back Resin Identification codes by symbols form 1 - to - 7

Remaining materials including engineering plastics canbe accommodated by ISO Standared (ISO - 11469 ) for making plastics. This adapts the SPI triangular arrows symbol by removing numer & adding recognised abbrevation of polymer like.

Compatibility Table for PET :

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