Research on the change of mechanical characteristics under the influence of ultraviolet in rigid polyurethane foams

Abstract

The paper investigated the influence of ultraviolet (sunlight) as a degrading factor on the change in the mechanical characteristics of rigid polyurethane foams (PPU). Experimental studies were performed for groups of samples obtained in laboratory conditions. Mechanical characteristics were determined based on the results of tests of experimental samples under the action of a compressive load simulating static deformation.  Polyurethane foam was obtained by pouring a two-component polyol-polyisocyanate mixture with weight fractions of components 1:2. The appearance of PPU compositions is described.

Mechanical characteristics were determined based on the results of tests of experimental samples under the action of a compressive load simulating static deformation. According to the load diagrams under static compression, Young's modulus, proportional limit, plastic limit, and relative residual deformation were determined  5 min after unloading the sample. The studies were conducted for two series of samples, one of which was freshly manufactured and without exposure to ultraviolet light, and the second series of samples was exposed to ultraviolet light for three months. The results of the studies of two series of samples were compared, and changes in the mechanical characteristics of rigid polyurethane foams caused by the influence of UV radiation were established.

The state of the surface of the cross-section of the UV-irradiated sample was assessed and it was found that the inner part of the UV-irradiated samples, unlike the outer surface, did not undergo yellowing of the material, which may indicate the preservation of the chemical structure of the polyurethane foam and its components in the inner layers of the material. The thickness of the degraded surface layer of the foam due to the influence of ultraviolet light for 3 months was determined.

It was established that the effect of UV radiation (exposure duration 3 months) causes a slight but not critical change in the mechanical characteristics of rigid polyurethane foams. However, it is recommended to protect PPU elements from prolonged exposure to ultraviolet light to prevent their degradation, preserve functional properties, and prevent premature aging.