The invention of Nylon‐6/clay nanocomposites by the Toyota Research Group of Japan heralded a new chapter in the field of polymer composites. This article highlights the work done in the field of rubber/clay nanocomposites. The preparations of rubber/clay nanocomposites by solution blending, latex compounding, and melt intercalation are covered and a thorough discussion of the mechanical properties of the various rubber/clay nanocomposite systems is presented. Other properties such as barrier, dynamic mechanical behavior, and thermal properties are also discussed. Finally, the future trends in the rubber/clay nanocomposites are mentioned. POLYM. ENG. SCI., 47:1956–1974, 2007. © 2007 Society of Plastics Engineers

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synopsisThe effect of oxidative and thermal aging of EPDM raw rubber and rubber vulcanizate on gelation, network structure, and technical properties has been studied over a wide range of temperaand tin~ea of aging. Three grades of EPDM having different types of dime have been conaidered. The kinetics of aging of both raw rubber and vulcanizates has also been reported. Different network structures have been produced due to different reactivity of tmonomers. Cmselink density, -link effiaency, polysulfidic linkage, zinc sulfide sulfur, combined sulfur, free sulfur, and sulfur ine5aency change with aging time and temperature. T h e number of polysulfidic crosklinks deerenam continuously with increase in time or temperature of aging.Them is no definite trend in other structurd features. It is quite evident that p t c u r i n g reactions as well as destruction of crars-links are t &~~g place in the aging proceso. The predominance of the former or latter depends on the structure of the diene.Tensile and tear strength of the compounds decreases or increases with time or temperature of aging. At high temperature, it always decrease? with time. Changes in these properties can be approximately correlated with changes in structure only at high temperature. At lower temperature, relations between network structure and technical properties are complicated owing to the competing reactions discuseed above. In general, retention of properties of ENB-EPDM vulcanizate is the beat. The propertier, after aging do not exclusively depend on the network structure, nature of. croas-link. rank of sulfur, or pendant or cyclic sulfide. The backbone structure is important in all thew cChanges are less drastic on aging in nitrogen. but a similar trend is found. Raw EPDM rubber forms a gel, which increase? with temperature of aging. The activation energy for gelation has been found to be 98 kJ/mol, similar to the oxidation of dienecontaining rubbers.The activation energy for desulfunzation of various grades of EPDM vulcanizates is 60-85 kJ/mol. The activation energy for fracture calculated from aging data is, however, 30-36 kJ/mol from tenaile measurement and 32-46 kJ/mol from tear strength measurement.

In this study an attempt has been made to utilise marble powder derived from the marble slurry produced by gangsaw machines while cutting marble blocks in the northwest of India. The marble powder has been used; 1) as a cheap filler, 2) as a semi reinforcing filler, by doing chemical treatment of the slurry and 3) as partial replacement of carbon black filler to reduce the cost of the compounds, subsequently for products and also to find suitable disposal of the powder, which is creating a serious threat to the local environment. The methodology in this study is as follows: collection of marble powder and characterisation, evaluation of rubber compound including partial replacement of carbon black filler, treatment of the marble powder to enhance the reinforcing characteristics and evaluation of the product. It was found in this study that the marble powder can be used as a cheap filler, in place of other commercial fillers like whiting. However, no significant improvement was obtained by chemical treatment of the marble powder. Marble powder can also be used as a partial replacement of carbon black (up to 10 phr) in various rubber products, which operate under static conditions.

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