What are thermoplastics?
They are molten when heated and harden upon cooling. These characteristics, which lend the material its name, are reversible so that it can be reheated, reshaped, and frozen repeatedly. As a result, thermoplastics are mechanically recyclable. Some of the most common types of thermoplastics are polypropylene, polyethylene, polyvinyl chloride, polystyrene, polyethylene terephthalate and polycarbonate.
Properties of thermoplastics
Thermoplastics have a simple molecular structure comprising chemically independent macromolecules. They are softened or melted on heating, then shaped, formed, welded, and solidified when cooled. Multiple heating and cooling cycles can be repeated, allowing reprocessing and recycling.
How thermoplastics are used
Thermoplastics have been around for a long time and are an important component of everyday life today. For example:
Acrylonitrile butadiene styrene (ABS) is a thermoplastic used to manufacture:
- Sports equipment
- Toys (for instance, LEGO® blocks)
- Various automobile parts
Polycarbonate is used to make:
- Reusable drinking bottles
- Food storage containers
- Eyeglass lenses
Polyethylene is probably the most common thermoplastic and is used to make:
- Milk bottles
- Cleaning products
- Plastic grocery bags
Polypropylene (PP) is used in a wide range of applications, including:
- Packaging for food, and chemical and cleaning products
- Electrical cabling
- Automotive components
- Medical items, e.g. syringes, petri dishes and specimen bottles
- Polypropylene can also be used in fibre form for clothing, upholstery and carpets
The use of thermoplastics in 3D printing has brought about new opportunities for medical device companies and hospitals. Applications of 3D-printed medical-grade polymers range from trial implants and instruments to short- and long-term implants. Implants previously relied on more expensive metals and conventional production methods. 3D-printed implants using polymers such as polyphenyl sulfone (PPSU) can save medical companies up to 50% compared with milled titanium, providing opportunities to find more economically feasible solutions to various medical challenges and consequently enable better patient care.
The USA’s National Renewable Energy Laboratory has been exploring using thermoplastic composite materials for large-scale tidal power turbines, providing a clean energy generation opportunity that, unlike wind and solar, is not dependent on weather. Thermoplastic composite blades will improve fatigue performance over epoxy blades, can be manufactured faster and more energy-efficiently, and can be recycled.
Recycling and reuse of thermoplastics
Thermoplastics are 100% recyclable through mechanical and chemical recycling and can be repeatedly transformed into new products. However, the extent to which thermoplastics are recycled depends on economic and logistical factors, including collection schemes, available infrastructure, and consumer behaviour.