Structure-microhardness relationship in semi-interpenetrating polymer networks

Two series of single-phase, semi-interpenetrating polymer networks (semi-IPNs) based on the same linear polyurethane (LPU) and two different heterocyclic polymer networks (HPNs), respectively, were characterized by the room temperature microhardness H measurement. It is shown that the H value linearly increases with both the mass content of the stiffer component (HPN) and the glass transition temperature of a semi-IPN. The latter dependence can be justified on the assumption that the excess enthalpy of the glass with respect to a hypothetical melt state is a measure of the yield strength of the glassy quasi lattice.