Photodegradation behavior of different polyurethane: A comparison study of foam and leather

Polyurethane (PU) is a type of widely used plastics. However, its raw materials, diisocyanates, are highly carcinogenic, rendering potential hazard of released PU microplastics (MPs) and leachates throughout its lifecycle. This study used foam polyurethane (PU-S) and leather polyurethane (PU-L) as representatives of polyether-based (EPU) and polyester-based (SPU) polyurethanes, respectively, to investigate the photodegradation behavior of PU and the impact of soft segment composition on its overall degradation process. A series of physical and chemical characterizations demonstrated that PU-S degraded faster than PU-L, showing a greater propensity for further fragmentation and aging. Moreover, after 300 h aging, the cumulative total organic carbon (TOC) release of PU-S exceeded that of PU-L by 58.9 ± 2.52 mg/g, which might be attributed to the decarboxylation reaction in the polyester structure of PU-L that imparted the resistance of PU to ultraviolet ‌(UV) irradiation and resulted in delayed aging characteristics. Two-dimensional infrared spectroscopy revealed differences in functional group changes, elucidating the disparities in aging reaction procedure between PU-S and PU-L. Additionally, PU-S released more nanoscale plastic particles and dissolved organic matter (DOM) than PU-L. These findings provide insights into the photodegradation of non-olefinic MPs and offer a theoretical basis for understanding and mitigating PU MPs pollution.