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CHEM 121 Studioby Learn4Less · UBC CHEM 121

CHEM 121 glossary

Cross-linking

Covalent bonds that join one polymer chain to another. A few cross-links make a polymer elastic; many make it rigid and unable to melt (a thermoset).

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

Vulcanizing natural rubber with sulfur adds a few S bridges between chains, so the rubber snaps back after being stretched instead of flowing.

See alsoThermosetThermoplasticPolymer