Plastics can be divided in two categories based on how they react when exposed to heat:
1) Thermosetting plastics
2) Thermoplastics
Thermosetting Plastics:
A thermosetting plastic (‘thermoset’) is a polymer that is irreversibly hardened by heat and can not be reshaped. The polymer is initially a liquid or a soft solid and the heat provides energy for chemical reactions that increase the cross-linking bonds between polymer chains that cures the plastic. These thermosetting plastics tend to be stronger than thermoplastics due to the strength of the internal cross-linking via covalent bonds which increase during the curing process.
For example: fiberglass (a fiber-reinforced thermoset); polyurethane; silicone resin; vulcanized rubber
Thermoplastics:
A thermoplastic is a plastic material which melts into a soft and pliable form when heated above a certain temperature and then solidifies upon cooling. No chemical bonding takes place. They can be re-melted and re-shaped any number of times. Thermoplastics can be recycled as they can be re-melt and then re-used.
For example: acrylic; polyester; polypropylene; polystyrene; polyethylene; nylon.
Thermoplastics are used in foot orthotic manufacture for shells as the plastic sheet can be heat molded to a positive model of the foot via vacuum forming.
Page last updated:
Comments are closed.