Types of Plastic

For all the different types of plastics that exist in the world, there are various ways to group similar types of plastic. Below are some of the ways.

How to sort it all

Natural vs Synthetic

• Natural - easily obtained from plants and animals, known as bioplastics.

  • Cellulose is a natural polymer used for making sticky tape (among other things)
  • Bioplastics—artificially made from natural ingredients)

• Synthetic - artificially made by complex chemical processes in a factory or lab.

  • Nylon is a synthetic polymer made in a factory.

Monomer structure

As covered in previous section, (Link to How plastic is made) Polymers are made from various monomer configurations. Materials like:

• polyesters
• polyethenes
• polyurethanes

and many others are named so based on their make up and resulting properties.

More on this in the next section: Plastic Recycling codes

Behavior when disposed of

Biodegradable

Photodegradable

Behavior when heated

Thermoplastics

Thermoplastics soften when they're heated.

Thermoplastics are easy to melt down and recycle.

• In a thermoplastic, the long polymer molecules are joined to one another by very weak bonds, which easily break apart when we heat them, and quickly reform again when we take the heat away.

• Everyday examples:

  • polyethylene/polythene - plastic bottles and sheets
  • polystyrene - crumbly white packaging material
  • polypropylene - plastic ropes
  • polyvinylchloride/PVC - toys and credit cards
  • polycarbonate hard plastic windows and car headlamps
  • polyamide - nylonn used for stockings, swimming shorts, toothbrushes, and umbrellas.

Thermosets

Thermosets never soften after they're initially molded, they cannot be heated to remold or reform.

Once they're "set" (cured) during manufacture, they stay that way.

• Thermosets are usually made from much bigger polymer chains than thermoplastics. When they're initially manufactured, they're heated or compressed to form a dense, hard, structure with strong cross-links binding each of these long molecular chains to its neighbors.

  • That's very different from thermoplastics, where the polymer chains are held to one another only by very weak bonds.

• Everyday examples:

  • Polyurethane - insulating material in buildings
  • Polytetrafluoroethylene/PTFE - nonstick coatings on cooking pots and pans
  • Melamine - hard plastic crockery
  • Epoxy resin - tough plastic used in strong adhesives and wood fillers

Plastic recycling codes

Expained in the next section....