Effect of concentrated solar radiation on the accelerated degradation of poly(ethylene terephthalate) using a compound parabolic concentrator (CPC)

Abstract

The effects of concentrated solar radiation on the thermal, chemical, and mechanical properties of post-consumer poly(ethylene terephthalate) (PET) films are studied in the present research work. The films were exposed to solar radiation using a compound parabolic concentrator (CPC), and the results are compared with those obtained from exposing PET films to conditions established in an accelerated weathering chamber (QUV). The CPC and QUV were evaluated on specimens measuring 2 × 13 × 0.5 cm³. Exposure in the CPC was carried out over one year during the periods of February–April, May–July, and October–December. Additionally, in the QUV, the equivalence in hours of exposure to that used in the CPC was sought. The results obtained by differential scanning calorimetry (DSC) indicate a significant increase in crystallinity in the material exposed within CPC, while specimens in QUV exhibited effects related to physical aging. Information obtained from thermogravimetric analysis (TGA) showed a decrease in thermal stability and maximum degradation temperature of the exposed specimens, with a trend consistent with DSC. Intensity decreased in the infrared spectra of films exposed in the CPC, without absorption bands of photo- or thermodegradation. The intrinsic viscosity of specimens exposed to degradation showed a maximum reduction of 17%, attributed to polymeric chain cleavage due to photodegradation. The dynamic mechanical analysis (DMA) evidenced a deterioration in the elastic response of the material, particularly in the one subjected to solar concentration, which is aligned with the surface cracking observed by scanning electron microscopy.