A Study of the Utilization of Reclaimed Natural Rubber Prophylactic in Blend with Epoxidized Natural Rubber and Silica

Abstract

On the basis of rubber rejects becoming a major environmental and social issue, scrap latex rejects must be considered as a potential candidate for recycling. This is because of the high quality and lightly crosslinked nature of the rubber hydrocarbon obtainable from such rejects. The authors have conducted a study of utilization of reclaimed natural rubber prophylactic in blend with epoxidised natural rubber with 50 mole% epoxidation (ENR-50) and silica. The vulcanization characteristics and dynamic mechanical analysis of the vulcanizates have been carried out. It has been observed that the optimum cure time shows a gradual decrease with natural rubber prophylactics as well as silica, indicating cure activation. The damping behaviour has been found to be strongly dependent on the presence of silica filler in the sample. The dynamic modulus values have been increased with the addition of silica, both below and above the glass transition region. Addition of natural rubber prophylactics as well as silica filler has been found to be increasing the glass transition temperature of epoxidised natural rubber. Increase in frequency also increases the glass transition temperature of epoxidised natural rubber. The analysis of the relative distribution of silica among the components of the mix reveals that a major portion of silica remains in the prophylactics phase while it can interact with the epoxy groups in epoxidised natural rubber phase. The evaluation and variation of network density in the vulcanizates carried out using storage modulus–temperature plots and solvent sorption method reveals an increasing trend with the addition of natural rubber prophylactics and silica filler. The energy of activation values show a decrease at 40 phr loading of natural rubber prophylactics after an initial increase at 10 phr loading. Addition of silica to epoxidised natural rubber/natural rubber prophylactics mixes have been found to be causing different variations in energy of activation values depending on the composition of the mix.