On the theory of biaxial orientation of amorphous polymers

The macromolecule orientation distribution function for biaxial orientation is calculated on the basis of a network model of a linear amorphous polymer. The dependence of the distribution function on the biaxial stretch ratio, orientation temperature, and certain other factors is investigated. A relation is established between the distribution function and the experimentally observed birefringence. The birefringence of biaxially oriented polymethyl methacrylate is measured in relation to the degree of deformation. The experimental data are compared with theory.Moscow Lenin State Pedagogical Institute, Problem Laboratory of Polymer Physics. Translated from Mekhanika Polimerov, No. 5, pp. 771–779, September–October, 1970.     

Biaxial orientation of amorphous linear polymers

The mechanical properties of biaxially oriented polymethyl methacrylate, obtained on a broad range of stretch ratios and under a variety of orientation conditions, have been investigated. There is a fundamental difference between the variation of the forced elastic limit with increase in stretch ratio, which is monotone increasing, and the variation of such properties as the brittle strength, brittle temperature, true strength and elongation at break, which have an optimum at a certain stretch ratio. It is shown that the presence of an optimum is associated with the transformation of the supermolecular structures in the process of biaxial high-elastic deformation. A relation is established between the mechanical properties of biaxially oriented polymethyl methacrylate (orientation hardening) and the density of the molecular network.For communication 1 see [3].Moscow. Translated from Mekhanika Polimerov, No. 4, pp. 586–593, July–August, 1971.     

On the theory of orientation of linear amorphous polymers

The previously derived orientation equations are solved for uniaxial extension at constant true stress, unloading, stress relaxation, and biaxial orientation at constant strain rate. The dependence of the birefringence of biaxially oriented PMMA on the magnitude and conditions of preliminary orientation has been experimentally investigated. There is good qualitative agreement between the theoretical and experimental results.For communication 1 see [1].Lenin Moscow State Pedagogic Institute. Translated from Mekhanika Polimerov, No. 1, pp. 14–21, January–February, 1973.     

Effect of biaxial orientation on the fracture kinetics of polymethyl methacrylate

Biaxially oriented PMM is shown to have important advantages as a structural material over unoriented PMM owing to a difference in fracture kinetics. Under identical conditions primary cracks appear later in the oriented PMM, their growth is impeded, and the rate of crack propagation in the avalanche stage of failure is much lower. This accounts for the greater resistance of biaxially oriented PMM to stress raisers and its higher fracture energy under biaxial loading.All-Union Scientific-Research Institute of Aviation Materials, Moscow. Translated from Mekhanika Polimerov, Vol. 5, No. 2, pp. 274–281, March–April, 1969.     

Biaxial orientation of amorphous linear polymers

The dependence of the birefringence and orientation stress on the biaxial stretch ratio and orientation conditions has been experimentally investigated. The temperature dependence of these characteristics is explained in terms of the network structure of amorphous polymers. It is shown that the transformations of the supermolecular structures in the process of biaxial orientation depend on the orientation temperature — at higher temperatures better organized structures are formed. There is a formal relationship between the effect of orientation temperature on supermolecular structure formation and on the relaxation process responsible for the formation of a more thermally stable molecular network.Moscow. Translated from Mekhanika Polimerov, No. 5, pp. 17–23, January–February, 1971.