Catalytic Degradation of Unsaturated Polyester Resins Using p ‐Toluenesulfonic Acid and n ‐Butanol for High‐Value Chemical Recovery

Unsaturated polyester resin (UPR) is one of the three major thermosetting resins. It has a three‐dimensional structure that is insoluble and non‐meltable. Owing to its outstanding mechanical performance and corrosion resistance, it has been widely applied in the domain of composite materials. However, its waste is difficult to degrade and traditional disposal methods (landfill and incineration) can easily cause environmental pollution and resource squandering. This study proposes a catalytic degradation strategy. By using an efficient catalytic system, the UPR waste can be directly converted into high‐value‐added chemicals under mild conditions. The experiments show that in the p ‐toluenesulfonic acid/ n ‐butanol system, under optimized conditions (such as a catalytic dose of 5 wt%, 200°C, and 5 h), the degradation rate of UPR can reach 100%, and the styrene‐ b ‐dibutyl maleate copolymer, dibutyl phthalate, and 1,2‐propanediol can be successfully recovered. The catalytic degradation mechanism was revealed, and it was confirmed that the cleavage mainly occurred at the ester bonds, and the main reaction mechanism was the transesterification. This technology provides a new way for the resource utilization of thermosetting UPR waste, with both environmental benefits and economic value, and is expected to promote the development of the circular economy of UPRs.