Extruded polystyrene rod was first annealed, and then stretched hot to elongations as high as 12,000 per cent. Tests were made in tension, flexure, and torsion at temperatures ranging from 0 to 80 C. Tests included creep and relaxation as well as tests at strain and load rates ranging as high as 1.0 in/in/min and 10,000 lb per min to determine the effect of orientation upon these mechanical properties. Tensile and flexural strengths increased two to threefold, depending upon rate and temperature; torsional strength decreased; and modulus of elasticity increased moderately. Fracture changed from a sharp break to a fibrous separation. Birefringence measurements revealed marked orientation of the material, but low-angle x-ray diffraction studies revealed no “crystalline” structure.

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