Types of plastic

Plastics are polymers. These are large molecules that are formed by chains of smaller molecules called monomers. The properties of plastic depend on the length of the polymers. For example Polyethylene (PE) has long chains of polymers and is hard and rigid. The chemical industry produces different types of plastic. There are seven primary groups.

In 1988 The Society of the Plastics Industry (SPI) created a coding system that assists recyclers with the recycling of plastics. Virtually all plastic products have the recycling symbol (a triangle of arrows). The number inside the triangle indicates the type of synthetic.

1-125x150

1. PET (polyethylene terephthalate)

i.e. PET bottles for soft drinks.

 
2a-125x1502. HDPE (high density polyethylene)

i.e. plastic containers and pipes.

 

 

3a-125x1503. PVC (polyvinylchloride)

i.e. sewage pipes and synthetic window frames.

 

 

4-125x1504. LDPE (low density polyethylene)

i.e. soft plastics such as cling film, plastic drycleaner covers, carry bags.

 

 

5-125x1505. PP (polypropylene)

i.e. plastic furniture, jerry cans, car parts, bottle tops.

 

 

6-125x1506. PS (polystyrene)

i.e. disposable cups, meat trays, packaging for electronics.

 

 

7-125x1507. Miscellaneous and mixed synthetics

i.e. PC (polycarbonate), PU (polyurethane), acrylics, polyamide, bioplastics and many other combinations.

 

Notes on the Recycling Code

  • The number in the triangle suggests that plastic is been recycled by category of product. In reality this is not the case (yet).
  • Whereas the number indicates the type of synthetic, it does not tell its durability, form or consistency. For example the same type of synthetic can be used for plastic bags or bottles.
  • Not every type of plastic can be adequately recycled and only a low percentage of plastic is in fact recycled.
  • The regulations that reflect the symbols leave much to be desired. Often the symbols are punched in too small, are hard to find and difficult to read (especially when the plastic is transparent).
  • Code 7 is a miscellaneous category that nobody can do anything with.

Recycling code and plastic soup

On 14 February 2013 an article was published in the science magazine Nature in which it was suggested to classify as harmful substances those types of plastics that are made of toxic materials and which are the most difficult to recycle. Named were PVC (code 3), polystyrene (code 6), polyurethane and polycarbonate (both code 7). In the United States a number of cities have banned polystyrene (mostly known as styrofoam). This insulating plastic is used especially in the fast food industry for packaging. Much ends up as litter and breaks up quickly.

As long as certain plastics and/or additives are not prohibited, it is for consumers to use the recycling codes to decide what types of plastic they want to purchase or not.

For plastics fished out of the ocean (as by fishing for litter) the codes are of no use. In the ocean plastic breaks up into smaller fragments, is subject to fouling deposits and the code becomes quickly unreadable.

Recycling code and safety

The code can also be used by consumers to distinguish between plastics that are safer to use than others.

The site www.greenjump.nl has published an overview with the following classification:

  • PET (code 1) is relatively safe. You should not refill PET bottles as the risk of additives leakage increases.
  • HDPE (code 2) is considered safe and is easy to recycle.
  • PVC (code 3) is to be avoided. In the manufacturing process the toxic dioxin is released and softeners are often added.
  • LDPE (code 4) is considered safe.
  • PP (code 5) is considered safe.
  • PS (code 6) is to be avoided because of possible leakage of styrene.
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