Effect of γ radiation on the long-term strength of polyethylene terephthalate

By analyzing the results of a study of the long-term strength and isometric heating diagrams of polyethylene terephthalate exposed to radiation it has been established that irradiation leads to a decrease in the short-time and long-term strength of the polymer and to the misorientation of its structural elements. The coefficient in the long-term strength equation increases with the radiation dose, while U₀ varies along a curve with a maximum at small doses.Lenin Tadzhik State University. Translated from Mekhanika Polimerov, No. 2, pp. 239–243, March–April, 1973.     

Effect of annealing temperature on the mechanical properties of polyethylene terephthalate fiber

The mechanical properties of polyethylene terephthalate fibers stretched at 45 and 110° C have been investigated in relation to annealing temperature. It is shown that for fibers with the maximum degree of stretch the annealing temperature has no effect on mechanical strength. Reduction in the stretch of the fibers leads to an increase in strength upon annealing, and this may be associated with densification of the amorphous zones due to the formation of a large number of intermolecular bonds between the links of the polymer chains.Mekhanika Polimerov, Vol. 3, No. 3, pp. 503–506, 1967     

Study of a polyethylene terephthalate film by an acoustic method

The effect of orientation on the acoustic properties of a polyethylene terephthalate film is examined. In a crystallized, uniaxially oriented film the velocity of ultrasound measured along the orientation axis is lower than in an amorphous oriented film, while the velocity of ultrasound measured at angles of over 35° to the direction of orientation rises after crystallization. Evidently the supramolecular organization of the polyethylene terephthalate film before and after heat treatment is quite different.Scientific-Research Institute of Plastics, Moscow. Voronezh Branch of the Experimental Design Office of Automation. Translated from Mekhanika Polimerov, No. 4, pp. 759–761, July–August, 1972.     

Theoretical calculation of the thermal expansion of the polyethylene crystal

Temperature dependences of the polyethylene crystal lattice parameters, in good agreement with the experimental data, are calculated on the basis of an expression for the intermolecular gap using molecular characteristics taken from literature sources.     

Experimental investigation of low cycle fatigue of metallized polyethylene terephthalate films

Conclusion The destruction of the coating of a loaded metallized film is a process that includes the stages of formation of point defects, formation and development of a network of cracks. In proportion to the increase of the load or of the number of load cycles the density of the network of cracks increases. When an element of the network has attained the critical dimension, crumbling ceases. Measurement of the light transmission is an effective method of investigating the damage to metallized films, even if they are opaque in the undamaged state.Translated from Mekhanika Kompozitnykh Materialov, No. 6, pp. 787–795, November, 1992.     

Elasticity of the crystal lattices of novel polyimides and fragments of polyimide chains

Conclusions 1. The elasticity modulus of the crystal lattices along the c axis, the pliancy of the repeated links, and the force f needed for stretching a single chain in the lattice by 1% were determined from the displacement of meridional x-ray reflexes produced by loading of PMPF and PMB polyimide filaments.2. Thanks to the similarity and simplicity of the conformations and chains of the polymers examined in the crystal lattice, and also thanks to the similarity of their chemical structure, the pliancies and the forces f for the various fragments of the chains could be experimentally determined. The pliancies calculated for the repeated links and their fragments agree satisfactorily with the experimental data.3. Addition of phenylene groups to the dianhydride fragment should not lead to a noticeable change of the pliancy of the chain as a whole.Institute of High-Molecular-Weight Compounds, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 5, pp. 771–776, September–October, 1976.     

Creep of polyethylene terephthalate with variable stresses under conditions of uniaxial extension

The results from experimental and theoretical investigation of the creep of polyethylene terephthalate film during stepwise varying stresses under conditions of uniaxial extension are given.Izhevsk Mechanical Institute. Translated from Mekhanika Polimerov, No. 5, pp. 929–933, September–October, 1972.     

Large deviation and the tangent cone at infinity of a crystal lattice

We discuss a large deviation property of a periodic random walk on a crystal lattice in view of geometry, and relate it to a rational convex polyhedron in the first homology group of a finite graph, which, as we shall observe, has remarkable combinatorial features, and shows up also in the Gromov-Hausdorff limit of a crystal lattice.To the memory of our late friend Robert Brooks     

Correlation of the elastic characteristics of Arimid PM with the elasticity modulus of its crystal lattice

Studies were made of the elastic characteristics (longitudinal elasticity modulus, elastic recovery) of Arimid PM fibers and of the longitudinal elasticity modulus of the crystal lattice of these samples. The elasticity modulus of the crystallites was determined by x-ray diffraction studies of loaded fibers. It is shown that the studied samples practically instanteneously recover their starting length after removing the load; the sample and its crystal lattice have comparatively low elasticity moduli with nearly identical values. Based on this data, reasons are discussed for the high elastic recovery of Arimid fibers and for the low elasticity modulus of its crystal lattice.Leningrad Branch, All-Union Scientific-Research Institute of Synthetic Fibers. Translated from Mekhanika Polimerov, No. 5, pp. 771–773, September–October, 1972.     

Effect of a lattice defect on the local plastic deformation mechanism of a polymer crystal

A computer has been used to calculate twinning curves for a rhombic model containing a vacancy for different directions of the hydrostatic component. Energy plastic deformation curves are calculated for a 24-particle model of a polymer crystal with a vacancy. The local deformation characteristics of the unit cells in the presence of a lattice defect are analyzed.