The temperature dependence of tensile modulus in anisotropic polyethylene sheets

Abstract

Abstract The mechanical anisotropy of polyethylene has been investigated by making measurements of tensile modulus on thin strips cut at various directions in the plane from anisotropic polyethylene sheets with a wide range of physical structures. Conventional sheets possessing fiber symmetry were made by uniaxial stretching of high- and low-density polyethylene sheets, in some cases accompanied by heat-annealing. Sheets of lower orthorhombic symmetry were made from oriented low-density sheets by rolling and annealing processes recently established by Hay and Keller [1]. In all cases the moduli in directions making angles of 0, 45, and 90° with the initial draw direction were measured over the temperature range −125 to 50°C. The most remarkable feature of the results is that the patterns of anisotropy change with temperature, the relative values of E0, E45, and E90 altering in a manner which produces crossover points. These results generalize the result previously established by Takayanagi et al. [2] that...