The widespread use of polyethylene terephthalate in the production of soft drinks and oil packaging results in a large amount of waste accumulating in landfills. In landfills, waste is exposed to sunlight, heat, and various aggressive environments. The most harmful of these in Central Asian conditions is high solar radiation, which promotes photo- and photo-oxidative degradation. This study evaluates how intense Central Asian ultraviolet (UV) radiation affects secondary PET (SPET). Post-consumer PET sheets were exposed up to half a year of natural sunlight and accelerated ultraviolet radiation. The structure and thermochemical analysis of PET samples were studied. The most resistant to photooxidative degradation was undyed (transparent) RPET. Over half a year, its average molecular weight decreased by 8.8%. It was also found that the degradation rate of RPET containing pigments of other colors also decreased. The data presented show that the highest degradation rate during this aging period was observed in RPET used for the production of brown bottles - 36%. Apparently, the depth of degradation is also affected by the initial molecular weight of RPET. In addition, the presence of dyes in RPET cannot be ruled out. The dark brown pigment contributes to the complete absorption of ultraviolet rays, which leads to a deeper destruction (36%).
Samida Ernazarova (2026) studied this question.