Plastic Recycling

Did you know?

• Over 1,400 tonnes of plastics were collected for recycling in Canberra in 2005-06
• In Australia, about 21% of plastic packaging containers are recycled

Introduction

Plastics, first invented by Alexander Parkes in 1860, have only been used widely in the past few decades. Plastics production worldwide now exceeds 80 million tonnes a year. In Australia, plastics production is about one million tonnes a year.

Manufacture

The sources of plastics today are mainly crude oil, gas and coal. According to the Plastics and Chemicals Industries Association, "Much of the raw material for plastics comes from waste in petroleum refining - some of which would otherwise be flared off and wasted."

Plastics are polymers, that is, long chain molecules, made from smaller molecules called monomers. The polymers are made in large vessels under special conditions of temperature and pressure, using special catalysts. At this stage, the polymers are in the form of resin pellets or powders. There are about forty different plastics or polymers used today. Each has a different chemical composition and set of properties that makes it suitable for certain applications.

PLASTIC PRODUCTS ARE MADE IN THREE STAGES

1. The resin pellets or powders are heated to soften them.
2. The softened material is formed into a certain shape
3. The product is cooled, retaining the shape

There are several ways that plastic products are formed. These include injection moulding (for specially shaped objects, such as cups, toys and plumbing fittings), extrusion moulding (for plastic sheets, pipes and tubes) and blow moulding (to make bottles and drums). Other techniques are used to manufacture fibres, biscuit trays, margarine tubs and foam trays.

To help identify different plastics, manufacturers stamp a Plastics Identification Code on their products. This code is a number inside a triangle with chasing arrows. These codes serve only to identify the product, not to indicate that the product can be recycled.

Recycling

In the ACT all rigid plastic containers can be placed in the recycling bin. For example soft drink, milk, cordial and detergent bottles, laundry and cleaning bottles, ice cream, yoghurt, margarine and takeaway containers.

At the Materials Recovery Facility plastics collected for recycling are sorted and separated into polymer types. The codes help recycling contractors to do this. Bales of different types of plastic are then returned to factories for reprocessing. The steps in the reprocessing process are: · Large contaminants are removed manually · The plastics are either shredded, chopped or ground and then washed to remove further contaminants · The material is dried and formed into pellets or powder, ready for remaking into new plastic products.

Sources

Beverage Industry Environment Council, 1996, Recycling Audit and Garbage Bin Analysis, June-September.

Gould League, 1993, Plastic Recycling Kit.

Plastics and Chemicals Industries Association 1992, Manufacturing Plastics, and information brochures.

Recycling and Resource Recovery Council, 1994, Recycling and Resource Recovery in Victoria, Annual Report.