This study investigated the suitability of epoxidized vegetable oils as additives in place of aromatic processing aids and activators in natural rubber based truck tyre tread compounds. The processability and cure characteristics of the compounds and physical properties of the vulcanizates were compared with those of the standard vulcanizate, which was prepared with a standard mineral oil-Dutrex R. Epoxidation of the oils was carried out (formed in situ) using the peracetic acid method and epoxidation was confirmed using 1 H NMR and 13 C NMR spectra. Epoxidized vegetable oils (EVO) were used at a fixed dose in the compounding process as processing aids. These oils were used in the compounding process to ascertain the possibility of using them as activators and processing aids. Epoxidized palm oil (EPO) showed better processing properties, polymer filler interaction and dispersion properties and best heat resistance ability. Epoxidized sunflower oil (ESFO) can be used as an accelerator with the combination of sulphenamide to overcome the problem of reversion. Epoxidized soya bean oil (ESBO), EPO and ESFO were better alternative processing aids than petroleum based aromatic oils, which have been reported as carcinogenic. The cure characteristics and physical properties of the vulcanizate based on EPO suggested that this oil could be used as an activator in rubber compounding.

The potential of naturally available oils as additives instead of processing aids and activators in carbon black filled natural rubber was investigated in this study. Physical properties and cure characteristics of the vulcanizates containing the natural oils were compared with those of the standard vulcanizate which was prepared using an aromatic oil. Soybean oil, palm oil and sunflower oil were selected as the natural oils and used at a fixed dose (5phr) in the compounding process as processing aids. The natural oils were incorporated in the compounding process, to examine their potential as activators and processing aids simultaneously. The results indicate that soybean oil, palm oil and sunflower oil are better alternative processing aids than petroleum based aromatic oils which have been reported to be carcinogenic. In addition, palm oil has the best heat resistance ability. Further, the cure characteristics and mechanical properties of the vulcanizate based on soybean oil suggest that it could be used as a co-activator for rubber compounding.

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The objectives of this study were to develop a cost-effective, environmental-friendly, mechanochemical reclaiming process for compounded nitrile rubber (NBR) latex waste generated from the dipping and treatment plants of the glove manufacturing process and evaluate properties of reclaimed NBR and virgin NBR/reclaimed NBR blend compounds. Initially, compounded NBR latex waste containing NBR latex mixed with compounding ingredients was dried and reclaimed mechanically by varying the milling time from 0 min to 12.5 min at 2.5-min time interval. Properties such as initial plasticity, Mooney viscosity, swelling, and cross-link density of the mechanically reclaimed NBR samples were evaluated. Also, a series of mechanochemically reclaimed NBR samples were produced using urea and varying its amount from 0 phr to10 phr at 2 phr intervals and milling according to the selected milling time. The mechanochemically reclaimed NBR samples were also tested for the above properties. Finally, a reclaimed NBR sample was prepared by applying the best urea loading and the optimum milling time. Further, a series of virgin NBR/reclaimed NBR blend compounds was prepared by varying the reclaimed NBR from 0% to 70% at 10% interval. Cure characteristics of the above blend compounds were evaluated and compared with those of the 100% virgin NBR (control) compound. Initial plasticity and Mooney viscosity of mechanochemically reclaimed NBR revealed that urea is effective as a reclaiming agent for dried compounded NBR latex waste. Results in overall indicated that 5 min is the optimum milling time and 6 phr is the optimum loading of urea required to produce the best reclaimed NBR in terms of properties and energy consumption. Minimum torque and cure time of the 50:50 virgin NBR/reclaimed rubber blend compound were higher compared to the control, whereas scorch time, maximum torque, and cure rate index of the former were lower compared to the latter.

in non-uniformity of the composite and hence changes its properties. This non-uniformity could be overcome by incorporating a suitable adhesion promoter and/or a coupling agent. Although titanate coupling agents are used in this study was aimed at incorporating a CA to natural rubber (NR) and low-density polyethylene (LDPE) blend through calcium carbonate (CaCO 3 effect of CA loading on properties of the composites. In this hundred parts of polymer). CaCO 3 loading was kept constant at 20 pphp. Brabender plasticorder was used to prepare o of 60 rpm. Physico-mechanical properties were evaluated according to ISO standards. Degree of swelling and gel content and dynamic properties of the composites were investigated. composites increased with the addition of CA and showed the best properties at a CA loading of 0.7 pphp. Hardness of tensile properties and water resistance were also shown at 0.7 pphp showed better compatibility and the best properties. coupling agent.

Use of reclaimed rubber as a component of a blend with virgin rubber or as a replacement for the virgin material in most rubber applications, especially in tyre components, has increased in the recent past. This is due to the increase in prices of natural and synthetic rubbers and growing concern about environmental issues. This research is aimed at evaluating the properties of rubber compounds produced by blending virgin natural rubber (NR) with ground rubber tyre (GRT), which was modified using a readily available, environmentally friendly, low-cost amino compound. Initially, reclaiming of 40 mesh GRT in the presence of rubber processing oil was studied at four different concentrations of the amino compound and two milling time periods. Mechanochemical reclaiming/devulcanisation was performed at a temperature of 30-70°C, using a laboratory two-roll mill. Properties such as initial plasticity, swelling ratio, crosslink density, and molecular weight between two crosslinks (M c) of the reclaimed rubber samples were evaluated. Rubber compounds were prepared in the second stage by blending the reclaimed GRT samples with virgin NR in a ratio of 15:85. Mooney viscosity, initial plasticity, cure characteristics, and dynamic properties of the above blend compounds were evaluated and compared with those of the control compounds. This study shows that the amino compound acts as a devulcanising/reclaiming agent for GRT. Rubber compounds prepared by blending virgin NR with novel reclaimed rubber exhibit higher stock viscosity, lower scorch resistance, and lower hysteresis in comparison with the control compounds.

An outstanding interest on elimination of nitrosamine generation in traditional sulfur vulcanization systems has led to introduce nitrosamine safe accelerator/s to produce safe natural rubber (NR) vulcanizates. It is an effective way to prevent formation of carcinogenic N-nitroso compounds during manufacture of rubber products. In the present study, behavior of nitrosamine safe binary accelerator system consisting of diisopropyl xanthogen polysulfide (DIXP) with commonly used non-regulated accelerator N-tert-butyl-2-benzothiazole sulfenamide (TBBS) was investigated in efficient sulfur vulcanization of NR. Cure characteristics, physico-mechanical properties and crosslink density of vulcanizates prepared with different combinations of the accelerator system were evaluated and compared with those of individual accelerators. The study reveals that moduli and strength properties of the vulcanizate prepared with DIXP accelerator are inferior to those of the vulcanizate prepared with TBBS accelerator. Nevertheless, optimum cure time of the DIXP compounds is lower in comparison to TBBS compounds. Moreover, progressive replacement of DIXP with TBBS in the accelerator system showed a synergistic effect in regard to cure characteristics and physico-mechanical properties.

Natural rubber (NR)/low density polyethylene (LDPE) composites are utilised to manufacture rubber-based articles. Properties of these composites become inferior if they are used alone due to the incompatibility of the base polymers. Peroxides help to cross-link both NR and LDPE, and the addition of peroxide to the composite at its optimum loading may enhance properties by developing a stable phase morphology. Therefore, the present work investigates the effect of dicumyl peroxide (DCP) loading on physicomechanical properties of calcium carbonate (CaCO 3 )-filled NR/LDPE (70/30) composites. The composite preparation was based on varying the DCP loading from 0 to 0.9 parts per hundred parts of polymer (phpp) at 0.1 phpp intervals. The composite at DCP loading of 0.3 phpp indicated the highest physicomechanical properties, gel content, the hardness of gel, and degree of crystallinity and the lowest degree of swelling. Properties of the composites with DCP were better than those of the control (without DCP). Water absorption decreased with the addition of DCP up to 0.3 phpp and increased after that with the rise in DCP loading. Scanning electron microscopic (SEM) image of the composite at DCP loading of 0.3 phpp revealed a smooth fracture surface. Therefore, 0.3 phpp was identified as the optimum DCP loading for the NR/LDPE (70/30) composite.