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Joint effect of high-energy electrons, mechanical loads, and temperature on polyimide films of thicknesses in the range 30-130 µm is investigated. The films were preliminary irradiated by electrons in air using an ÉLU-6 linear accelerator with energy of 2 MeV and doses D = 1, 5, 10, 20, 30, 40, and 100 MGy and then subjected to uniaxial mechanical tension at temperatures (Т) from 293 to 593 K. It is established that at Т = 293-450 K and D = 20-40 MGy, the mechanical load causes almost the same deformations (ε l max ) of nonirradiated and irradiated samples; at Т = 450-550 K, deformations of films sharply increase, and the character of their dependence changes. The ε l max value of the initial sample increases almost linearly with temperature by a factor of 10, whereas the character of changing ε l max (Т) of the irradiated films is more complex, and its value increases approximately by a factor of 4. For Т > 500 K, the deformation reaches limiting values. Irradiation increases the intensity of IR-spectra by 2-6 times and essentially increases the widths of absorption bands at 720, 1380, and 1775 cm -1 , which is caused by the formation of hydrogen bonds and cycles with nitrogen as well as by the formation of nitrogen oxides. External loading applied to film rupture causes an increase in the EPR signal amplitude from 3·10 3 to 5·10 3 , which is connected with an increased concentration of radicals =N-H and -NH 2 . The electron irradiation of the polyimide films with their subsequent mechanical loading causes the spectrum lines to displace from 3475.0 to 3512.5 cm -1 with simultaneous reduction of the signal amplitude from 6·10 3 to 4·10 3 .

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Experimental studies on the effect of electron irradiation with energy of 4 MeV to the mechanical strength of the film of Mylar type were conducted. It is found that the strain and stress dependences on the radiation dose are satisfactorily described by the proposed exponential models.

The paper is devoted to the study of the influence of factors on the rate of return deformation of polytetrafluoroethylene. The dependence of the rate of return strain (ε'r) on time (t), the dose of electron irradiation (D) and mechanical stress (σ) in thin films of polytetrafluoroethylene has been experimentally investigated. Significant variations of ε'r have been found dependingon on t, D and σ. A decrease in the rate of return deformation during irradiation of the material is associated with the frictional properties between macromolecules and a change in the structure, which leads to a weaker straightening of the polymer and their poor sliding. The resulting curves for both unirradiated and irradiated material are satisfactorily described in the exponential and linear models. For dependencies ε'r on D, these are decreasing functions, and for ε'r on σ, these are increasing functions.