Crosslinkable

Crosslinkable is a term used in polymer science to describe materials that can form bonds between individual polymer chains under suitable conditions, creating a network structure. In crosslinked polymers, the links connect chains at multiple points, reducing mobility and often transforming a soluble or melt-processable polymer into a thermoset or gel.

Crosslinking can be covalent, ionic, or physical in nature. In most practical contexts, covalent crosslinks are the primary focus, formed through chemical reactions that join reactive groups on different polymer chains. Activation methods include thermal curing, irradiation (such as UV or gamma rays), or chemical processes using crosslinking agents or catalysts. The degree of crosslinking depends on functionality (the number of reactive groups per molecule), crosslinker concentration, and reaction conditions, which together determine network density and final material properties.

Benefits of crosslinkability include increased modulus, strength, thermal stability, chemical resistance, and dimensional stability, along with reduced solubility and swellability. Drawbacks can include reduced ductility or toughness, processing difficulties, and potential brittleness if the network is overly dense.

Industrial examples encompass epoxy and phenolic resins, silicone elastomers, and vulcanized rubbers, as well as UV-crosslinked polymer resins used in coatings, adhesives, and photoresists. In biomedical contexts, crosslinkable hydrogels form networks for encapsulating cells or delivering drugs. Reversible or dynamic crosslinking, via non-permanent bonds, enables reprocessability and self-healing in some materials.