Abstract: A polyurethane elastomer which comprises a reaction product of (A) a polymeric diol having a molecular weight of about 800-5000, (B) a mixture of organic diisocyanates wherein about 2-70 mol % is composed of aliphatic diisocyanate (said aliphatic diisocyanate having no direct bond between an aromatic ring and an isocyanate group) and wherein the balance 98-30 mol % is composed of aromatic diisocyanate which includes a direct bond between an aromatic ring and an isocyanate group, and (C) a chain extender comprising hydrazine and/or a derivative having the formula NH.sub.2 NHR and another chain extender having two functional groups constituting amino and/or hydroxyl groups,and wherein about 30-80% of the carbon atoms which are bonded to nitrogen atoms constituting the ureylene and/or urethane bonds of said polyurethane elastomer constitute benzene and/or naphthalene ring skeletons.

Abstract: A biaxially oriented poly-p-phenylene sulfide film comprising recurring units of the formula ##STR1## a melt viscosity of more than 100 poise and less than 600,000 poise at a shear rate of 200 sec.sup.-1 and at 300.degree. C., and a specific gravity of which is more than 1.330 and less than 1.400. The film has improved mechanical properties, thermal dimensional stability and high temperature durability. Typical applications of the film are as electrical insulation, capacitor, magnetic recording medium, packaging material, and so forth.