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Dispersion of filler such as carbon black into the rubber greatly affects the durability of the rubber products. The necessity of determination of the filler dispersion, especially, has been frequently discussed. On the other hand, in comparison with the evaluation method of the vulcanized rubber for the CB dispersion, evaluation methods of the unvulcanized rubber is very limited.The evaluation methods of the filler dispersibility are prescribed in standards of ISO and ASTM, but standards of JIS does not include them. In this paper, I comment on test methods about the processability of unvulcanized rubber and describe the influence of filler dispersion on rubber processability.

Gas permeability of high polymer is important as a physical property in the gas barrier evaluation of vehicle tires and some fuel hoses from the viewpoint of energy-loss. The precise measurement of permeability rate of oxygen and steam is recently required in the field of organic EL display and fuel cell.This review describes the well-known mechanism of the gas permeability in the elastomers and the classification of gas transmission rate measuring methods as standard testing methods. The relationships between gas permeability and manufacturing process factors are also introduced. By using L18 orthogonal array, the results allow not only specifying effective factors and levels but also optimizing those for gas barrier property. Among the eight factors examined, primary factor of gas permeability is found to be the type of polymer, followed by the shape of inorganic filler, while the crosslink density of vulcanized rubber is not so influential.

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