Identification of glycerol as a novel accelerator for sulphur vulcanization of unsaturated rubbers

Different organic polyols were investigated as accelerators for different type of vulcanization system such as sulphur, metal oxide, peroxide with different rubbers such as natural rubber (NR), styrene butadiene rubber (SBR), butadiene rubber (BR), butyl rubber (IIR), nitrile rubber (NBR) and chloroprene rubber (CR). Among all the polyols studied, glycerol found to be the most efficient accelerator for sulphur vulcanization of unsaturated rubbers. Moreover, from rheometric study glycerol was found to be reversion free and scorch safe accelerator. A detailed study was performed with glycerol for sulphur vulcanization of silica filled, SBR + BR-based standard passenger car radial (PCR) tire tread compound and plausible mechanism of acceleration was proposed. Finally, from the PCR tyre tread compound 70% of conventional accelerators, namely N-cyclohexyl-2-benzothiazole sulfenamide (CBS) and di-phenyl guanidine (DPG) were replaced with 5 phr (parts per hundred gram of rubber) of glycerol and properties of the vulcanized compounds were measured. The results evidenced that glycerol could efficiently replace 70% conventional accelerators (CBS + DPG), with additional improvement of scorch time by 68%, tensile strength by 31.5%, elongation at break by 75.6% and tear strength by 9.4% of the PCR tyre tread compound. The increase in mechanical properties was due to the improvement in compatibility between silica and rubber in presence of glycerol. Moreover, glycerol is an environmentally benign (nitrogen free, halogen free), fossil free, low-cost material.

THE EFFECT OF GLYCEROL CONTENT ON MECHANICAL PROPERTIES, SURFACE MORPHOLOGY AND WATER ABSORPTION OF THERMOPLASTIC FILMS FROM TACCA LEONTOPETALOIDES STARCH

Tacca leontopetaloides is a new plant source of starch and has high potential to produce film of thermoplastic. In this study, thermoplastic starch (TPS) derived from T.leontopetaloides was developed with glycerol as plasticizer through casting method at temperature range from 85 °C to 90 °C and enhanced with sulphur vulcanization method. It was found that the addition of 5%, 10%, 15%, 20% and 25% (v/v) of glycerol into T.leontopetaloides starch had affected the mechanical properties, surface morphology, and water absorption of the thermoplastic films. In the mechanical properties study, the TPS films have the highest tensile strength (47.96 MPa) at 5% glycerol content in the formulation. Conversely, the TPS films have increasing value of elongation at break (EAB) with increasing glycerol concentration with the higher EAB obtained at 25% glycerol content (52.90%). The morphology of thermoplastic film was examined by using Scanning Electron Microscopy (SEM). As glycerol content increased, thermoplastic films showed smoother surface, homogenous and good distribution. In water absorption test, TPS films showed lower affinity to water absorption at lower glycerol content. The weight of the TPS films increased ranging from 80.3% to 107.4% after 12 hour of immersion in water. It can be concluded that, glycerol significantly affected the properties of TPS film within the range of glycerol concentration studied.

Investigating the Effect of Vulcanization in Tread Rubber Applications

Retreading has many potential applications in tyre manufacturing industry. There is a critical need for optimization of vulcanization processes used in tread manufacturing. Not much work hitherto has been reported for optimization of efficient sulphur vulcanization process of the tread manufacturing. The present experimentation work highlights approach to macro-model strength, elongation and hardness during vulcanization of rubber. Relationship between strength, elongation, hardness and other parameter has been deduced by using Taguchi L9 orthogonal array (OA). Results indicate that the hardness, elongation and strength of tread rubber while vulcanization depends significantly on the natural: synthetic rubber ratio (NR: SR), curing time and curing temperature of the rubber.