Structure and physical properties of polyurethanes

Abstract

AbstractThe relations between structure and physical properties of polyurethane elastomers, particularly elastic properties, were studied. Polyurethanes with various structures were prepared by a prepolymer technique. Among the conceivable structural factors the substituted urea group, which was introduced by the use of a diamine‐type curing agent, had a remarkable reinforcing effect. This was attributed to the strong hydrogen‐bonding effect between urea groups. In this connection, softening occurred during repeated deformation of diamine‐cured polyurethane elastomers. It was proved that this is due not to the melting of crystallite but to the slip of hydrogen bonding between urea groups. On the other hand, urea groups did not have much influence on equilibrium rubber elasticity. The contribution of the force caused by the internal energy to the total force was independent of curing agents, being determined by the principal segments of network chains.