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.

Morphology and physical properties of composite foams based on low‐density polyethylene and ground tire rubber

“…The crosslinked structure of GTR makes it difficult to achieve fine dispersion in the polymer matrix, owing to the incompatibility characteristic. Stress‐induced devulcanization of rubber vulcanizates through solid‐state mechanochemical milling has been well‐confirmed by our earlier studies . The partial devulcanization and surface activation (introduction of oxygen‐containing polar functional groups onto the GTR surface) may facilitate intermolecular entanglement and improve the compatibility between GTR and LDPE.…”

Mechanochemical preparation of devulcanized ground fluoroelastomers for the enhancement of the thermal stability of nitrile–butadiene rubber vulcanizates

“…Because of the presence of nearly 30% of carbon black, which could not be dissolved in ethyl acetate, the 18.4% increase in the sol fraction suggested an efficient devulcanization of the ground FKM after mechanochemical milling. The stress‐induced devulcanization of rubber vulcanizates, including FKM vulcanizates, through solid‐state mechanochemical milling was well confirmed in our earlier studies 24–28. The structural development of various rubber vulcanizates during pan milling was also reported in detail.…”

“…Because of its unique structure, the pan‐mill equipment acted as pairs of three‐dimensional scissors during milling, exerting very strong shear forces on the milled materials and showing multiple functions, including pulverizing, dispersion, mixing, and activation 16–23. Our previous investigations24–28 on the mechanochemical devulcanization of waste rubbers by pan milling suggested that the three‐dimensional network in rubber vulcanizates can be effectively broken up to form decrosslinked structures in the presence of fairly strong shearing and squeezing forces. These mechanochemically devulcanized rubbers are softened and can be reprocessed, shaped, and revulcanized in a manner similar to that employed with virgin elastomers.…”

Preparation of thermoplastic vulcanizates based on waste crosslinked polyethylene and ground tire rubber through dynamic vulcanization

“…The previous work31–33 carried out in our laboratory demonstrated that scrap rubber vulcanizates could be partially devulcanized through high‐shear mechanical milling with a pan‐mill type mechanochemical reactor. The pan‐mill equipment was designed in the authors' laboratory for solid state mechanochemical reactions of polymers, on the basis of a traditional Chinese stone‐mill 34, 35.…”