ABSTRACT:The synergistic activity of binary accelerator systems in rubber vulcanization is well known. Binary accelerator systems are being widely used in industry and are becoming increasingly popular because of the fact that such mixed systems can produce a vulcanizate with superior mechanical properties compared to those of stock cured with a single accelerator. The authors have studied the performance of a binary accelerator system based on cyclohexyl benzothiazole sulfenamide (CBS), tetramethyl thiuram disulphide (TMTD) in the sulfur vulcanization of nitrile rubber. The amount of sulfur and accelerator was varied to change the network crosslink density of vulcanizates. The observed mutual activity has been discussed based on the mechanical properties and crosslink density. The physical crosslink density of the various nitrile rubber mixes was estimated using the Kinetic Theory of Elasticity. The mechanical properties of the various rubber compounds were related to the corresponding crosslink density estimated for each compound.

SynopsisA number of factors which influence the penetration rate of motor oils in polychloroprene rubber have been investigated. These are relevant to carbon black concentration, carbon black particle size and oil characterization.

No abstract

SynopsisThe penetration rate of chloroform (highly volatile solvent) in chloroprene rubber vulcanizate, based on different carbon black type and loading, has been studied. The results relevent to carbon black loading have shown an increase in the penetration rate with the increase in loading percentage. Other factors affecting the penetration rate, such as particle size and aggregate structures of carbon black, have shown some confusing results, such as the decrease in penetration rate with the increase of particle size and the decrease in penetration rate at a higher degree of equilibrium volume swelling. These results were attributed to the wrinkles formed at the surface of the rubber at these high equilibrium swellings.

No abstract

No abstract

Abstract. The modulus of filled and unfilled Ethylene-propylene diene rubber (EPDM) vulcanizates was used to predict the shape-factor of carbon black aggregation in the polymer. Four types of carbon black that vary in particle size and structure were used in this study. Quadratic curves relating the carbon black volume concentration and the modulus ratio of filled and unfilled rubber vulcanizates were used to adopt the shape factor of certain carbon black type. The shape factor of MT, HAF, SRF and Lampblack were 3, 3.75, 4 and 4.25 respectively. X-ray diffraction technique (XRD) was also used to evaluate the relative size of crystallite on the filler surface to that of the rubber and correlating it to the shape factor of carbon black aggregation in the polymer. Effect of the pH values and structure of carbon blacks used on the shape factor of filler aggregates were also studied. It was found that the shape factor is independent on the particle size while it is dependent on the pH value and structure of carbon black. Also the crystallites size of the filler is proportional to the shape factor.

No abstract