The role of crosslinking agents and chain extenders

They are active substances that can enter the polymer structure through chemical reactions. In order to produce foamed plastics with high load carrying capacity, cross-linking within the polymer is sometimes necessary.
In general, chain extender and crosslinking agent are not used in general-purpose soft foam, but are used in high resilience soft foam, self skinning foam, semi hard foam and RIM. Low molecular weight or monomer diols and diamines are generally referred to as chain extenders or chain extenders, while low molecular weight polyols and polyamines belong to crosslinking agents. Among them, MOCA (i.e. 3,3-dichloro-4,4-diaminodiphenylmethane) is an important crosslinking agent, and its reaction activity is relatively moderate due to the steric hindrance of adjacent chlorine atoms. Therefore, it is widely used in soft foam (mainly high resilience soft foam), semi hard foam, self skinning foam and RIM, which can make foam with TDI and polymeric MDI as basic raw materials mature quickly. And it effectively improves the load-bearing capacity of the product.
High resilience foam can also use diol with relative molecular weight less than 400 as chain extender, which helps to improve the resilience of foam.