Molecular composites of poly(p-phenylene terephthalamide) anion and poly(ethylene oxide): Mechanical properties

Molecular composites were prepared by the solution blending of poly(ethylen e oxide) (PEO) of three different molecular weights with low concentrations of poly(p-phenylene terephthalamide) (PPTA) anion serving as a rigid-rod r einforcement. For all of the composites, the tensile strength, stiffness, a nd fracture energy were enhanced relative to values for the three PEO homop olymers. Composites made with PEO of high molecular weight (similar to 10(6 ) or higher) exhibited good extensibility and improved resistance to stress relaxation and attained maximum values of strength and toughness at a PPTA -anion content of about 6 wt %. The enhancement in mechanical properties is primarily attributed to good miscibility between the components arising fr om the presence of intermolecular, ion-dipole interactions between the ioni c units of the PPTA anion and the dipole units of the PEO. Some considerati on is also given to possible effects of a nucleating agent and an annealing treatment, both of which lead to additional increases in the tensile stren gth of the composites. (C) 2000 John Wiley & Sons; Inc.