The designing of degradable unsaturated polyester based on selective cleavage activated hydrolysis and its application in recyclable carbon fiber composites

In recent years, the extensive application of unsaturated polyester resins (UPRs) and their composites has resulted in an increasing environmental problem and it is necessary to find a simple and efficient recycling method especially for the high-value reinforced fibers. Here a self-polymerizable dimethacrylate monomer containing a cleavable unit, β-carbonyl hindered urethano, was designed for a degradable UPR which has a good flexible strength of 79 MPa and T g of 119.7 °C. Moreover, through the hydrolysis of ester that was previously activated by selective cleavage of hindered C–O bond in urethano, the resin could be directly degraded in an aqueous solution (4/1 M ratio of hydrazine and NaOH and 0.04 mol/mL of total concentration) at 80 °C in 4 h, and the degraded products could be simply separated by solubility. Furthermore, its carbon fiber composite was degraded in only 2.5 h and the recycled carbon fiber fabrics well maintained their original woven structure, surface chemical composition, graphitized structure and mechanical strength. This work provides a new method for efficient degradation and recycling of fiber reinforced thermosetting resin composites .