Recycling waste thermosetting unsaturated polyester resins into oligomers for preparing amphiphilic aerogels

The styrene-maleic acid copolymer (SMC) was obtained by selective and complete cleavage of ester groups from waste thermosetting unsaturated polyester resins (WTUPR). The degradation was performed in glycol at 180 °C for 5 h with potassium carbonate as a catalyst and the resultant potassium salt of SMC (SMC-K) can be very easily separated by precipitation using ethanol with a yield of 63.8%. The SMC-K was integrated with polyvinyl alcohol to form amphiphilic aerogels via freeze-thaw and freeze-drying processes. The aerogel exhibits a low density of 0.024 g·mL^-1 due to hierarchical pore structures with a size range from nanometer to micrometer scale. Besides, the good compressibility and resilience of the aerogel are demonstrated. The amphiphilic aerogel displayed high absorption of both water and oily liquids (over 30 g.g^-1 and 20 g.g^-1 for water and dichloromethane respectively), together with a good recycle adsorption efficiency (>90% after 10 cycles). This work provides a new strategy on upcycling of WTUPR.