MECHANICAL-PROPERTIES OF BIAXIALLY DRAWN FILMS OF ULTRA-HIGH-MOLECULAR-WEIGHT POLYETHYLENE DRIED GELS

Mechanical properties of biaxially drawn films of ultra-high molecular weight polyethylene dried gels were studied and were compared with the results of uniaxially drawn films prepared from the same gels. Although the tensile storage modulus (E') of biaxially drawn films is much smaller than that of uniaxially drawn films, their temperature dependence is similar. The largest attainable shear storage modulus of biaxially drawn film is 1.1 GPa at 20-degrees-C for the specimen with a draw ratio of 16 x 16, while E' is 7 GPa for the same specimen. The tensile creep rate of biaxially drawn films at 25-degrees-C is much bigger than that of uniaxially drawn films, although it decreases with increasing draw ratio. The large creep rate of biaxially drawn films is supposed to be mainly due to the easy orientation of fibrils in the strained direction.