Crossbond

Crossbond is a term used in polymer science and materials engineering to describe covalent bonds that link separate polymer chains or components, forming a three-dimensional network. It is often used interchangeably with crosslinking, though crossbond can emphasize connections between distinct molecular entities in a composite or adhesive context.

Crossbonding occurs mainly through chemical crosslinking with bifunctional or multifunctional crosslinkers, or by irradiation (thermal, UV, gamma, or electron beam). Physical associations such as hydrogen bonding or crystallite interactions may contribute but do not form durable covalent networks as crossbonds.

The resulting networks exhibit higher modulus, strength, solvent and heat resistance, and altered thermomechanical behavior. Crosslink density is a key driver: more crossbonds increase stiffness and temperature resistance but can reduce toughness and elongation.

Common applications include vulcanized rubber, epoxy and silicone systems, crosslinked polyolefins for heat resistance, hydrogels for biomedical uses, ion-exchange resins, coatings, and dental materials.

Crosslink density is typically assessed by swelling experiments and gel fraction measurements, supported by spectroscopic or thermal methods and dynamic mechanical analysis.

Safety and processing considerations: curing conditions, residual reactants, and uniform network formation affect performance and safety.