ANISOTROPIC POLYARAMIDE POLYOL DISPERSIONS - NEW COMPONENTS FOR THE PREPARATION OF POLYURETHANE MICROCOMPOSITES

Polymerization of N-(p-aminobenzoyl)-caprolactam (PAC) in melts of polyols such as dihydroxy-terminated oligo(oxytetramethylene) with M(n)=2000 g/mol at 200-degrees-C afforded stable dispersions of poly(p-phenylenebenzamide) whiskers in polyol. In spite of the low molecular weight of the polyaramide, which was isolated by solvent extraction, the microparticles are efficient reinforcing agents of polyurethanes because of the excellent interfacial adhesion resulting from covalent attachment of the polyols onto the microparticle surfaces. The role of the competing formation of p-aminobenzoate-terminated polyols via esterification of PAC was investigated. Morphological and mechanical properties of polyurethane microcomposites, prepared from poly(p-phenylenebenzamide)/poly(oxytetramethylene)diol dispersions and 4,4'-diisocyanatodiphenylmethane, were determined as a function of the microparticle content. When compared to conventional polyurethanes, containing equivalent amounts of spherical organic and inorganic fillers, the microcomposites give higher Young's modulus, tensile strength without sacrificing high elongation at break.