SEM COMPARISON OF TRADITIONAL AND MODULUS GRADIENT-INDUCED PARTICULATE COMPOSITES OF POLYURETHANE NANO POLYMER

The microstructure of polyurethane (PU) nano material comprising hard-block urethane linkages and soft-segment prepolymer chains is presented and discussed. Two types of micro composites of the nano material are fabricated by reactive processing. A generic particle-doped composite is supplanted by the one in which a modulus gradient is deliberately introduced at the particle-matrix interface. SEM examines the morphology of the respective composites. Cryofracture surfaces of these composites reveal good interfacial adhesion in the modified composite without the attendant processing constraints and the visible particle pull out observed in traditional composites. The results are compared with parallel work comprising liquid crystalline polymer (LCT)-PET blend and a rubber-toughened epoxy. It is found that securing micro-particles to the host nano-matrix serves to increase the cohesive energy density, reduce the non-linear response and improve the fracture energy of the fabricated assembly.