Types Of Plastics

Types of Plastics • • • • • • •

PET (polyethylene terephthalate): plastic soft drink bottles, water bottles, beer bottles, mouthwash bottles and many more HDPE (high density polyethylene): milk bottles, detergent bottles, oil bottles, toys, plastic bags PVC (polyvinyl chloride): food wrap, vegetable oil bottles, blister packaging LDPE (low density polyethylene): bread bags, frozen food bags, squeezable bottles, fiber, tote bags, bottles, clothing, furniture, carpet, shrink-wrap, garment bags PP (polypropylene): margarine and yogurt containers, caps for containers, wrapping to replace cellophane PS (polystyrene): egg cartons, fast food trays, disposable plastic silverware Other: This code indicates that the item is made with a resin other than the six listed above, or a combination of different resins.

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PET (polyethylene terephthalate) is a thermoplastic polymer resin of the polyester family and is used in synthetic fibers; beverage, food and other liquid containers; thermoforming applications; and engineering resins often in combination with glass fiber. PET has good barrier properties against oxygen and carbon dioxide. Therefore, it is utilized in bottles for mineral water. PET exists both as an amorphous (transparent) and as a semi-crystalline (opaque and white) thermoplastic material. Generally, it has good resistance to mineral oils, solvents and acids but not to bases. The semi-crystalline PET has good strength, ductility, stiffness and hardness. The amorphous PET has better ductility but less stiffness and hardness. HDPE is the high density version of PE plastic. It is harder, stronger and a little heavier than LDPE, but less ductile. Dishwasher safe. HDPE is lighter than water, and can be moulded, machined, and joined together using welding (difficult to glue).

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The appearance is wax-like, lustreless and opaque. The use of UVstabilizators (carbon black) improves its weather resistance but turns it black. Some types can be used in contact with food. PVC is a heavy, stiff, ductile and medium strong amorphous (transparent) material. By adding softeners a range of softer materials can be achieved, ranging from a flexible to an almost rubber-like elastic soft material. Softeners also help to increase the manufacturability. PVC has brilliant resistance to acids and bases, but is affected by some solvents. Soft PVC is exceptionally resistant to most chemicals. Tubes made of PVC have the unique ability that they do not kink, i.e. stop

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the flow if bent. The poor weather resistance can be improved using additives. PVC has good barrier properties to atmospheric gasses. LDPE is the low density version of PE. This has less hardness, stiffness and strength compared to HDPE, but better ductility. It is opaque and only thin foils can be transparent. LDPE is used for packaging like foils, trays and plastic bags both for food and non-food purposes. Used as protective coating on paper, textiles and other plastics, for instance in milk cartons. PP is an inexpensive, ductile, low strength material with reasonable outdoor performance. The material surface is soft wax-like and scratches easily. Stiffness and strenght are often improved using reinforcement of glass, chalk or talc. The colour is opaque and white, but it can be dyed in many colours.

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In many ways, PP is similar to HDPE, but it is stiffer and melts at 165-170 C. PP can be manufactured by all the methods used for thermoplastics. Polystyrene is an inexpensive amorphous thermoplast that is vitreous, brittle and has low strength. However it is also hard and stiff. Foamed PS is used for packaging and insulation purposes. It is not weather resistant, and therefore not suitable for outdoor uses. PS is transparent (it transmits about 90% of the sunlight) and has unlimited dyeing possibilities. Assembly can be done with glueing.

Resin identification code The code system was developed to meet recyclers' needs while providing manufacturers a consistent, uniform system that could apply nationwide. Because municipal recycling programs traditionally have targeted packaging – primarily bottles and containers – the resin coding system offered a means of identifying the resin content of bottles and containers commonly found in the residential waste stream. Recycling firms have varying standards for the plastics they accept. Some firms may require that the plastics be sorted by type and separated from other recyclables; some may specify that mixed plastics are acceptable if they are separated from other recyclables; while others may accept all material mixed together.