They behave very differently from thermoplastics. When heated for the first time, the polymer softens and can be shaped under pressure. However, due to the heat, a chemical reaction begins in which the molecules bond permanently. This reaction is known as degradation. As a result, the polymer becomes permanently rigid, and if heated, it will not soften but will instead be destroyed.
Some examples of thermosets:
BAQUELITE (phenolic resins)
It was the first plastic to be artificially manufactured from chemicals. It was named after the man who first produced it (Leo Baekeland).
It is a hard, brittle plastic with a dark, glossy color. It is a thermosetting plastic, meaning it resists heat without softening—but only up to a certain temperature, because at very high temperatures it decomposes and becomes charred.
Bakelite is a good thermal and electrical insulator, which explains its uses and applications in electrical accessories, such as handles for pots and pans, kitchen knobs, soldering iron handles, etc.
MELAMINE (FORMALDEHYDE)
It is a colorless polymer that can be dyed with color pigments. It is harder than Bakelite, is tasteless and odorless, and is a good thermal and electrical insulator.
It is used to manufacture unbreakable tableware, door handles, kitchen countertops, etc.
POLYESTER
It is in resin form and must be mixed with a product called a hardener. It solidifies and forms a rigid, hard, and brittle plastic.
To make it stronger, it is reinforced with a layer of fiberglass.
Applications: fiberglass coatings (airplanes, boats, swimming pools, etc.) and as transparent panels for canopies and roofs.