Microplastics generation behavior of polypropylene films with different crystalline structures under UV irradiation

•The time of secondary microplastics generation under natural forces was predicted by a new method.•The UV irradiation experiment results were connected with mechanical damage modeling.•Crystalline structures are critical for the morphology and amount of microplastics.•Guidance for material design with less microplastics and lower environmental impact. Microplastics are receiving extensive attention worldwide, however very scarce studies have been conducted to estimate the secondary microplastics generation behavior and the effect of different crystalline structures on the microplastics generation. Here, we present a method to assess the time of microplastics generation through quantitatively matching material aging behavior with mechanical failure. The aim of this study is to recycle plastic products in time and reduce the pollution caused by the microplastics into the environment. It has been applied to evaluate the differences in microplastics generation behavior of α and β crystalline-structured polypropylene (α-PP, β-PP) under conditions of ultraviolet (UV) irradiation and natural forces. The results indicate after UV aging for 1470–1500 h and 1670–1700 h respectively, α-PP generates 71% of microplastics, including 44% for 1–5 mm and 27% for less than 1 mm, and β-PP generates 25% of microplastics, including 23% for 1–5 mm and 2% for less than 1 mm. Moreover, more microplastics below 150 μm are generated by α-PP compared to β-PP which is not easily broken and exists in larger sizes. This work opens an avenue toward the quantitative study of secondary microplastics generation behavior and the reduction of microplastics generation through material structural design with lower environmental impact. [Display omitted]