STRUCTURAL-CHANGES IN RIGID-CHAIN POLY(AM IDE BENZIMIDAZOLAMIDES) DURING THE FORMATION OF ULTIMATELY REINFORCED-PLASTICS

The texture and phase transitions in poly(p-phenylene benzimidazole te rephthalamide) and in a copolyamide of (p-phenylene benzimidazole tere phthalamide) and p-phenylene terephthalamide during the formation of u ltimately reinforced plastics by sintering fibers under pressure were studied by X-ray diffraction. In the heat-treated fibers of poly(p-phe nylene benzimidazole terephthalamide), in which a smectic structure or iginally prevails, an accelerated crystallization of polymer with the formation of crystallites in alpha form is observed on heating under p ressure. In the case of as-spun copolyamide fibers the tendency to cry stallization in the gamma-form is observed, for which the lattice para meters and the crystal symmetry are determined. The degree of axial or ientation of macromolecules in the plastics prepared from as-spun fibe rs has extremal dependence on the pressure, and sintering at an optimu m pressure allows highly oriented plastics to be obtained with high el asticity and strength characteristics. Orientation and mechanical char acteristics of plastics prepared from heat-treated fibers by sintering in the investigated interval of pressures (up to 64 MPa) vary insigni ficantly.