Molecular composites of poly(p-phenylene terephthalamide) anion and poly(propylene oxide): mechanical properties

Molecular composites have been prepared by mixing rigid rod molecules of PP TA anion (K-salt) and poly(propylene oxide) in a common solvent and compres sion molding the precipitated material. As the PPTA anion content of the co mposites is increased, an upward shift occurs in both the glass transition temperature and the decomposition temperature. The tensile strength, stiffn ess and resistance to stress relaxation of the composites are significantly increased, even at relatively low concentrations of the rigid rod reinforc ement. The enhancement in mechanical properties results from a good dispers ion of the rigid PPTA anion molecules and from the presence of ion-dipole i nteractions between the ionic groups of the PPTA anion and the dipolar unit s of the poly(propylene oxide) matrix. Additional increases in strength and rigidity may be achieved by changing the counterion from monovalent K+ to divalent Ca2+. (C) 2000 Elsevier Science Ltd. All rights reserved.