Understand plastics — thermoplastics and thermosets
The two main groups and why the difference matters everything in production
Plastic is not one material but a large family. The most important division you encounter in the trade is between thermoplastics and thermosetting plastics. They behave differently when heated and determine how they can be shaped and recycled — and what machines and methods you work with.
§Thermoplastic – can be melted again
Thermoplastic becomes soft when heated and hard again when cooled. It can be melted again and formed again multiple times. It is this property that makes injection moulding and extrusion possible, and it is also what makes thermoplastic relatively easy to recycle. A large part of the plastic parts you encounter daily are thermoplastic.
§Thermoset plastic — sets once
Thermoset plastic hardens through a chemical reaction and cannot be melted and reshaped after — it remains hard even when heated. This makes thermoset plastic suitable for items that must withstand high heat and heavy loads but it cannot be recycled the same way as thermoplastic. Fiber-reinforced composites often fall into this category.
§Why the difference matters
- 01Different machines and methods for the two groups.
- 02Thermoplastic can typically be recycled; thermoset not in the same way.
- 03Thermoset plastic often withstands more heat and load.
- 04Your specialty at the plastics technician level targets the one group.
§Additives
Plastic is rarely used entirely pure. Colour fillers and substances that make the plastic stronger softer or flame-retardant are added. Understanding what is in the material is part of the trade — both for quality and safety because some additives must be handled with care.