Tensile properties of biaxially drawn polyethylene

The tensile properties of simultaneously biaxially drawn soln.-crystd. ultrahigh-mol.-wt. polyethylene films were investigated as a function of draw ratio and were related to the data obtained for uniaxially drawn tapes. The Young's modulus of a biaxially drawn film with a random in-plane orientation appears to amt. to 3/8 of the Young's modulus of a tape drawn to the same extent uniaxially. Furthermore, the tensile strength depends solely upon the draw ratio and not upon the drawing geometry since at the point of fracture the orientation in the film has become approx. uniaxial. These relationships are only valid for draw ratios £10, whereas for draw ratios >10 the tensile properties of the biaxially drawn film are not significantly improved in contrast to those of uniaxially drawn tap