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Kamis, 29 Maret 2012

Recycling rates

The quantity of post-consumer plastics recycled has increased every year since at least 1990, but rates lag far behind those of other items, such as newspaper (about 80%) and corrugated fiberboard (about 70%). Overall U.S. post-consumer plastic waste for 2008 was estimated at 33.6 million tons; 2.2 million tons (6.5%) were recycled and 2.6 million tons (7.7%) were burned for energy; 28.9 million tons, or 85.5%, were discarded in landfills.

Economic and energy potential

In 2008, the price of PET dropped from $370/ton in the US to $20 in November. PET prices had returned to their long term averages by May 2009.

Consumer education

United States

Low national plastic recycling rates have been due to the complexity of sorting and processing, unfavorable economics, and consumer confusion about which plastics can actually be recycled. Part of the confusion has been due to the recycling symbol that is usually on all plastic items. This symbol is called a resin identification code. It is stamped or printed on the bottom of containers and surrounded by a triangle of arrows. (See the table in Plastic.) The intent of these arrows was to make it easier to identify plastics for recycling. The recycling symbol doesn’t necessarily mean that the item will be accepted by residential recycling programs.

United Kingdom

In the UK, theamount of post-consumer plastic being recycled is relatively low, due in part to a lack of recycling facilities.
The Plastics 2020 Challenge was founded in 2009 by the plastics industry with the aim of engaging the British public in a nationwide debate about the use, reuse and disposal of plastics, hosts a series of online debates on its website framed around the waste hierarchy.

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 reecycling 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., which provides a uniform system for the identification of different polymer types and helps recycling companies to 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)
Plastic-recyc-01.svg
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
Plastic-recyc-02.svg
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
Plastic-recyc-03.svg
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
Plastic-recyc-04.svg
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
Plastic-recyc-05.svg
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
Plastic-recyc-06.svg
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
Plastic-recyc-07.svg
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

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