Plastic Identification Code
Five groups of plastic polymers, each with specific properties, are used worldwide for packaging applications (see table below). Each group of plastic polymer can be identified by its Plastic Identification code (PIC) – usually a number or a letter abbreviation. For instance, Low-Density Polyethylene can be identified by the number "4" or the letters "LDPE". The PIC appears inside a three-chasing-arrow recycling symbol. The symbol is used to indicate whether the plastic can be recycled into new products.
The PIC was introduced by the Society of the Plastics Industry, Inc., to provide a uniform system for the identification of different polymer types and to help recycling companies separate different plastics for reprocessing. Manufacturers of plastic products are required to use PIC labels in some countries/regions and can voluntarily mark their products with the PIC where there are no requirements. Consumers can identify the plastic types based on the codes usually found at the base or at the side of the plastic products, including food/chemical packaging and containers. The PIC is usually not present on packaging films, as it is not practical to collect and recycle most of this type of waste.
| Plastic Identification Code | Type of plastic polymer | Properties | Common Packaging Applications | Glass Transition and Melting Temperatures (°C) | Young's Modulus (GPa) |
|---|---|---|---|---|---|
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Polyethylene terephthalate (PET, PETE) | Clarity, strength, toughness, barrier to gas and moisture. | Soft drink, water and salad dressing bottles; peanut butter and jam jars | Tm = 250; Tg = 76 | 2-2.7 |
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High-density polyethylene (HDPE) | Stiffness, strength, toughness, resistance to moisture, permeability to gas. | Water pipes, hula hoop rings, five gallon buckets, milk, juice and water bottles; grocery bags, some shampoo / toiletry bottles | Tm = 130; Tg = -125 | 0.8 |
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Polyvinyl chloride (PVC) | Versatility, ease of blending, strength, toughness. | Blister packaging for non-food items; cling films for non-food use. Not used for food packaging as the plasticisers needed to make natively rigid PVC flexible are usually toxic. Non-packaging uses are electrical cable insulation; rigid piping; vinyl records. | Tm = 240; Tg = 85 | 2.4-4.1 |
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Low-density polyethylene (LDPE) | Ease of processing, strength, toughness, flexibility, ease of sealing, barrier to moisture. | Frozen food bags; squeezable bottles, e.g. honey, mustard; cling films; flexible container lids. | Tm = 120; Tg = -125 | 0.17-0.28 |
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Polypropylene (PP) | Strength, toughness, resistance to heat, chemicals, grease and oil, versatile, barrier to moisture. | Reusable microwaveable ware; kitchenware; yogurt containers; margarine tubs; microwaveable disposable take-away containers; disposable cups; plates. | Tm = 173; Tg = -10 | 1.5-2 |
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Polystyrene (PS) | Versatility, clarity, easily formed | Egg cartons; packing peanuts; disposable cups, plates, trays and cutlery; disposable take-away containers; | Tm = 240 (only isotactic); Tg = 100 (atactic and isotactic) | 3-3.5 |
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Other (often polycarbonate or ABS) | Dependent on polymers or combination of polymers | Beverage bottles; baby milk bottles. Non-packaging uses for polycarbonate: compact discs; "unbreakable" glazing; electronic apparatus housings; lenses including sunglasses, prescription glasses, automotive headlamps, riot shields, instrument panels; | Polycarbonate: Tg = 145; Tm = 225 | Polycarbonate: 2.6; ABS plastics: 2.3 |
Read more about this topic: Plastic Recycling
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