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Natural weathering of polystyrene (PS) was performed at six exposure sites with various climate types along the coastal line from China to Europe, including Qionghai (typical hot-humid climate), Sansha (island hot-humid climate), Chennai (savanna hot-humid climate), Jeddah (xerothermic climate), Sanary-sur-Mer (mediterranean climate), Hoek van Holland (warm-temperate climate). The chemical structure, morphology and color changes of PS after weathering were characterized by FTIR, DSC, SEM and Color spectrometer, and relative weathering severity of different climates on PS were compared. Results show that Sansha has the highest severity value while the severity value of Hoek van Holland is the lowest. The degradation degree of PS at the sites of Qionghai, Sansha, and Chennai is higher than that at other sites, resulted in a deterioration of the optical properties and serious damage of the sample surface. In the xerothermic climate, the optical properties of PS decrease drastically during the process of natural weathering, while only slight change in hydroxyl index and carbonyl index is observed, and micrographic surface does not differ from the surface of un-weathered materials. For other climates, the degradation degree was low, resulting in a relative slow change of optical properties and long time for the appearance of surface defects. In order to quantify the relative severity of these climates, a mathematic model was proposed based on the basic degradation principle of polymer materials, which could predict the failure time of PS. The failure time was predicted by the model using gloss loss of PS as failure index, with an accuracy up to 99.2%.

Due to its high strength, toughness, corrosion resistance and wear resistance, long chain polyamide (LCPA) has attracted broad interest. Nevertheless, its wide application in industrial fields is still being restricted because the starting material acquisition step involving diacid and diamine remains a major obstacle. Herein, we circumvent this obstacle by developing a novel polymer with similar properties by a green and efficient copolymerization process of carbon dioxide (CO2)-based dicarbamate with diamide diol under vacuum conditions, named poly(urethane-co-amide) (PUA). The semi-crystalline PUAs with high number-weight-average molecular weights (Mn, up to 41.3 kDa) were readily obtained, and these new polymers show high thermal stability (above 300 °C). Thanks to its unique chain structure, the amide, urethane and urea groups can endow the polymer with a high density cross-linking network via hydrogen bonds and high crystallinity that can result in high strength, up to 54.0 MPa. The dynamic thermomechanical analysis (DMA) results suggest that the phase separation exists within the new polymers, endowing the PUAs with a toughness higher than that of long chain polyamides. Consequently, this work not only develops a useful new polymer like commercial polyamides with high performance as a long chain polyamide candidate, but also provides a new way of utilizating CO2.

Artificial accelerated aging tests, which usually expose materials to artificial light sources and simulated environment conditions, are commonly conducted to evaluate weatherability and service life of polymeric materials. However, one main limitation of these methods is that the testing protocols usually ignore a significant amount of environmental effects which may change failure mechanisms of polymers caused by natural factors, such as seasonal variations, microorganisms, ozone, airborne chemical pollutants and salt. As a result, the polymeric materials verified by the artificial aging acceleration tests quickly show degradation phenomena, including discoloration, fading, cracking, and brittle fracture after exposed to the real service environment. Besides, these degradations could make the service life of industrial equipment and products much shorter than the expected one. Alternatively, sunlight tracking concentrator testing (STCT) which accelerates aging under natural exposure has been widely used for weatherability and service life evaluation of polymeric materials. The testing method not only takes natural aging effects into account but also achieves a high aging acceleration rate. This review article aims to summarize various structures and principles of sunlight tracking concentrator (STC), correlation and acceleration of STCT, the research progress of weatherability, and the investigation of service life prediction for polymeric materials such as plastics, coatings, and solar energy conversion materials using STCT over the years. The aging behavior and mechanism of testing materials and the corresponding correlation between STCT and natural weathering are also discussed. In addition, existing problems and future development direction of STCT are prospected as well.