According to technicians, crosslinking agents are commonly used additives for some polyurethane foam plastics, such as high resilience foam, microporous elastomer, semi-rigid foam, etc. They play a great role in improving and adjusting the performance of polyurethane foam plastics. In the plastic industry, crosslinking agents are mainly used for plastics such as epoxy resins, unsaturated polymers, phenolic resins, polyethylene, polyvinyl chloride, etc. Commonly used crosslinking agents include imidazole crosslinking agents, phthalic anhydride, diethylenetriamine, tert butyl peroxyethane, hexamethylenetetramine, etc.
Crosslinking agents are mostly active hydrogen compounds containing multiple functional groups, such as polyols and polyamines with smaller molecular weights. Polyols containing amino groups and tertiary nitrogen atoms can also be used as crosslinking agents. They also have a certain catalytic effect on the reaction between isocyanates and polyols. For example, ethanolamine, bis—2— Hydroxypropyl aniline, triethanolamine, and alkyl alcohol derivatives of piperazine. Ethanolamine compounds such as triethanolamine and diethanolamine are commonly used as crosslinking agents for high resilience foam and semi rigid foam systems. Low viscosity polyols with a relative molecular weight of several hundred, obtained by polymerizing small molecule polyols or alcohol amines with ethylene oxide, can be used in formulations such as RIM semi-rigid foam. Low molecular weight aromatic polyols obtained by adding aniline, toluene diamine, and ethylene oxide have high activity and can also be used in formulations such as RIM microporous elastomers and semi-rigid foam.
The purpose of adding crosslinking agents to plastics is to create crosslinking between resin molecules with linear or branched linear structures, resulting in a transition from linear to mesh or bulk molecular structures, thereby altering the physical and mechanical properties of plastics and the rheological properties of plastic melts.
In most cases during plastic processing, polymer crosslinking occurs through reactions between active centers (functional groups or sites) on macromolecules or between active centers and crosslinking agents. These active centers are reactive functional groups that, under certain conditions, such as the presence of initiators or catalysts, can cause cross-linking reactions in resin molecules, thereby forming a bulk structure.
