Effect of planar drawing on the properties of poly(pyromellitimide) films

The deformation-strength and; thermomechanical characteristics of poly(pyro mellitimide) films upon planar orientational drawing (lambda = 1-1.65) at 4 00 degrees C were studied. Mechanical properties of the oriented samples we re studied by tensile tests in the temperature range 20-250 degrees C and u pon thermal aging at a temperature of up to 350 degrees C. After the orient ational drawing, the ultimate strength, forced rubberlike elasticity, and m odulus of elasticity of the films markedly increased. The elongation at bre ak somewhat decreased, but still remained on the level of 35-40% not limiti ng the field of possible practical applications. Mechanical properties of t he oriented films are markedly more stable with respect to thermal aging th an the properties of initial films. The data obtained were used to estimate the degree of orientation of macromolecules in the samples studied.