Modification of polyurethane with wholly-rigid poly (m-phenylene isophthalamide)

Abstract

Flexible polyurethane (PU) was reinforced by wholly-rigid aromatic polyamide poly (m-phenylene isophthalamide) (PmlA) (Nomex) by physical polyblending and chemical copolymerization. Three polyurethane elastomers were blended physically with various amounts of high molecular weight Nomex to form twelve PU/Nomex polyblends in order to modify their physical properties. Also three multiblock copolyamides (PU-Nomex)were synthesised with a low molecular weight diamine-terminated Nomex prepolymer as a hydrogen donor for chain extending. From differential scanning calorimetry and Rheovibron measurements it was shown that both the polyblends and multiblock copolyamides exhibited a glass transition temperature under 0 °C and had a higher storage modulus, E′, than those of the polyurethane. Scanning electron microscopy revealed that the polyblends and multiblock copolyamides had a dispersed phase structure. From the wide-angle X-ray diffraction pattern of the polyurethane and multiblock copolyamides it was found that the degree of stress-induced crystallization was dependent on the composition of the soft and hard segments and also the degree of its stretching. With regard to mechanical properties, it was found that both the tensile strength and elongation of the multiblock copolyamides had a more significant reinforcing effect than those of the polyblends and polyurethanes.