The size of cryofracture figures in the network of segmented polyurethane elastomers

Cross-linked segmented polyurethanes were broken below brittle ductile tran sition and their fracture surfaces were analysed by optical and electron mi croscopy. Shapes of polygonal appearance were present on the whole surface of the broken sample, and a radial texture with the fracture origin in the middle of polygons was observed. The average distance between cryofracture and origins (L) was measured for each polyurethane studied. The swelling de gree was measured and junction-point density calculated. A correlation betw een L and the junction-point density, v, has been found to exist.