Structure-microhardness relationship in semi-interpenetrating polymer networks

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