The crosslinking of polymer chains is of primary importance in controlling many polymer properties. Large increases in the degree of crosslinking make amorphous polymers more rigid and cause them to have higher softening points and a higher modulus.The properties of polyurethane are influenced by the method of crosslink

the structure of crosslink agent and the crosslink density. Therefore

it is very important to research the way of crosslink

the measurement of crosslink density and the relationship between the property and crosslink density of polyurethane. In this paper

several two-step methods based on linear prepolymer to prepare crosslinked polyurethane are reviewed

after that the common used methods to determinate the crosslink density are summarized. Furthermore

the works about the effects of crosslink density on the properties of polyurethane network are introduced as well.