Mechanochemical devulcanization of ground tire rubber and its application in acoustic absorbent polyurethane foamed composites

The use of recycled rubber in preparation of acoustic absorbent materials will help to combat the existing environmental problems of both waste disposal and noise pollution. The focus of this work is to investigate the influence of mechanochemical pretreatment of ground tire rubber (GTR) on the acoustic absorption properties of polyurethane (PU)/GTR foamed composites. GTR subjected to pan-milling could be mechanochemically devulcanized by breaking up the crosslinked structures through inducing fairly strong shearing and compressing forces. The significant increase in sol fraction of GTR confirmed the partial devulcanization during pan-milling. Moreover, thermal gravimetric analysis indicated that rubber content in the soluble part of GTR was also remarkably increased. The devulcanization increased flexible chains of the GTR particles, which could help to improve damping properties as well as acoustic absorption ability of the PU/GTR foamed composites. Dynamic mechanical analysis and acoustic absorption measurements well confirmed this hypothesis. The loss modulus and sound absorption coefficient of PU/GTR foamed composites were remarkably increased through the mechanochemical pretreatment of GTR. The mechanochemical pretreatment also enhanced foamability of the composites as revealed by cell morphology. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013