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CHEM 121 Studioby Learn4Less · UBC CHEM 121

CHEM 121 glossary

Thermoset

A polymer whose chains are joined by extensive covalent cross-links into one rigid network. Heating cannot make the chains slide past each other, so a thermoset does not melt; it chars or decomposes instead and cannot be remoulded.

Thermoplastic versus thermosetLeft: in a thermoplastic the chains are separate and held only by intermolecular forces, so on heating they slide past each other and the plastic can be remelted. Right: in a thermoset, covalent crosslinks join the chains into one network, so it does not melt when heated.thermoplasticseparate chainsremelts on heatingthermosetcrosslinked (red bars)does not remelt

Example

Epoxy adhesives and Bakelite (a phenol–formaldehyde resin) are thermosets: once cured, they stay hard when heated.

See alsoThermoplasticCross-linkingCovalent-network solid