Devulcanisation of natural rubber vulcanisate through solid state mechanochemical milling at ambient temperature

Abstract

The devulcanisation of natural rubber (NR) vulcanisate was carried out with the self-designed pan mill type mechanochemical reactor that can exert fairly strong shearing force on the milled materials. The experimental results indicate that gel fraction of the devulcanised NR is substantially reduced, and the reduction of molecular weight of the sol part of devulcanised NR is not significant. The mechanical properties of the revulcanised NR increase with increasing milling cycle. After mechanochemical milled 30 cycles, the tensile strength increased to 7·1 MPa, which is about 60% of that of the virgin NR vulcanisate. Elongation at break as high as 973·0% was obtained, which is the same as that of the virgin NR vulcanisate. Solid state mechanochemical milling is a simple, low cost method for the devulcanisation of cross-linked rubber vulcanisates at ambient temperature without the use of any chemicals and is feasible to be industrialised.