Abstract: An improved magnetic recording medium comprising a flexible support consisting of at least about 70 mol % of p-oriented aromatic polycarbonamide units. The polycarbonamide may include substituent groups on the aromatic nuclei. The support has a density of more than about 1.41 g/cm.sup.3 at 25.degree. C and 0% relative humidity, and a tensile modulus higher than about 800 kg/mm.sup.2 in at least one direction, combined with a thin layer of magnetically susceptible material deposited electrically or dispersed in a nonmagnetic binder. The magnetic recording medium in this invention shows excellent running performance and has superior dimensional stability both thermally and hygroscopically.

Abstract: Polyester compositions suitable for fiber and film formation contain from 0.2 to 3.0% by weight of fine particles of uniform size and possess sufficient slippery tendency, appropriate opacity and crystallizing potential; said particles containing lithium and phosphorus as a lithium salt of a phosphoric acid ester constituent of short chain polyesters.

Abstract: Aromatic polyamide-hydrazide films, consisting of p-benzamide p-phenylene terephthalamide and/or terephthaloyl hydrazide recurring units, as major chain constituents, are removed from inorganic residue by an aqueous mixture which dissolves or swells the films, and are heated up to their crystallization temperatures in tension, giving rise to high tensile strength and modulus, good hygroscopic dimensional stability and excellent electrical insulation properties.