Polymer composites are widely used in the space industry for the manufacture of spacecraft, satellite panels, antennas, thermostatically controlled coatings, etc. In space, they are subjected to harsh environmental con-ditions, such as ultraviolet, deep vacuum, atomic oxygen, charged particles, anthropogenic debris, micrometeoids, electromagnetic radiation and thermal cycles that cause severe degradation of the material. One of the most important environmental effects of materials based on polymers is the thermal cycle, in which the composite undergoes a large temperature difference from -170˚C to + 200˚C. The paper presents an assessment of the use of composites based on a polyalkane-rich matrix and a filler in the form of an SiO2 amorphous and crystalline structure under thermal cycling conditions. The data on the change in tensile strength, modulus of elasticity in tension and relative elongation in tension of materials after several cycles of a sharp differential temperature (from -190 to +200°C) are presented. The thermal cycle was repeated 5, 10 and 20 times. It is shown that the sample polyalkanimide has a large value of tensile strength and elastic modulus compared with highly filled composites.However, during thermal cycling there is a significant decrease in these parameters.For a highly filled composite sample with 65% crystalline SiO2 content, the decrease in tensile strength and elastic modulus after thermal cycling is insignificant and is within the measurement error. A composite with amorphous SiO2 is more susceptible to a change in mechanical properties after thermal cycling in comparison with a composite containing crystalline SiO2.