There are two main types of plastics.
1. Thermoset or thermosetting plastics. These are rigid plastics and retain their shape after cooling. They are hard and durable. Thermosets are used for car parts, aircraft parts and tyres. Examples include polyurethanes, polyesters, epoxy resins and phenolic resins.
2. Thermoplastics are less rigid or are flexible.
a. Polyethylene terephthalate (PET or PETE): PET is a thermoplastic that can be drawn into fibers (like Dacron) and films (like Mylar). It’s the main plastic in ziplock food storage bags.
b. Polystyrene (Styrofoam): Polystyrene can form a hard impact-resistant plastic for furniture, cabinets (for computer monitors and TVs), glasses and utensils. When polystyrene is heated and air blown through the mixture, it forms Styrofoam. Styrofoam is lightweight, moldable and an excellent insulator.
c. Polyvinyl Chloride (PVC): PVC is commonly used for pipes and plumbing because it’s durable, can’t be corroded and is cheaper than metal pipes. Over long periods of time, however, the plasticizer may leach out of it, rendering it brittle and breakable.
d. (Teflon): The polymer is stable, heat-resistant, strong, resistant to many chemicals and has a nearly frictionless surface. Teflon is used in plumbing tape, cookware, tubing, waterproof coatings, films and bearings.
e. Polyvinylidine Chloride (Saran): This plastic can be drawn into films and wraps that are impermeable to food odors. Saran wrap is a popular plastic for packaging foods.
f. Polyethylene, LDPE and HDPE: Low-density polyethylene (LDPE) because it will float in a mixture of alcohol and water. In LDPE, the polymer strands are entangled and loosely organized, so it’s soft and flexible. It was first used to insulate electrical wires, but today it’s used in films, wraps, bottles, disposable gloves and garbage bags.
g. High-density polyethylene (HDPE). HDPE is a harder plastic with a higher melting point than LDPE, and it sinks in an alcohol-water mixture. HDPE was first introduced in the hula hoop, but today it’s mostly used in containers.
h. Polypropylene (PP) The various forms of polypropylene have different melting points and hardnesses. Polypropylene is used in car trim, battery cases, bottles, tubes, filaments and bags.