Cross-linked refers to the process of forming chemical or physical bonds between polymer chains in a thermoplastic material, converting it into a thermoset compound with greater strength, heat resistance, and chemical stability.
In wire and cable manufacturing, cross-linking is a process that enhances the performance of polymeric insulation and jacketing materials. It involves bonding molecular chains within a thermoplastic, such as polyethylene (PE), using chemical agents or radiation. This creates a three-dimensional molecular network, transforming the material into a thermoset polymer that retains structural and electrical integrity even under heat or stress.
Once cross-linked, the material no longer softens when reheated, making it ideal for high-performance applications that require long-term durability, thermal stability, and dielectric strength. One of the most common examples is Cross-Linked Polyethylene (XLPE), widely used in power, control, and communication cables for its ability to handle higher operating temperatures and voltage levels. Cross-linked compounds also provide superior tensile strength, abrasion resistance, and protection against chemicals and environmental stress cracking, key advantages for cables in harsh or industrial settings.
Cross-linked insulation materials, including XLPE, are governed by standards from UL (Underwriters Laboratories) and ASTM (American Society for Testing and Materials). Additional guidelines from IEEE (Institute of Electrical and Electronics Engineers) and ICEA (Insulated Cable Engineers Association) define performance, thermal limits, and safety criteria for cross-linked cable applications.
The development of cross-linked polymers began in the mid-20th century, driven by the need for materials capable of operating under higher electrical and thermal stress. Early innovations in chemical and radiation cross-linking revolutionized cable insulation technology, allowing for longer service life, improved heat resistance, and enhanced reliability in power and industrial systems.