Characteristics of Reinforcing Furnace Blacks Processing Shrinkage

Abstract

Abstract A major technical development in the rubber industry has been the recent introduction of furnace blacks possessing rubber reinforcing properties in the range of channel blacks. The literature on the subject of reinforcing furnace blacks is rapidly expanding to satisfy the need for information on the compounding and rubber properties of these new products. Types of reinforcing furnace blacks are available which duplicate closely the usual rubber properties observed with channel blacks in vulcanized stocks. However, because of the flexibility of operation and the different types of raw material adaptable to the continuous furnace process, it is also possible to produce grades of reinforcing furnace blacks which differ markedly from channel blacks in rubber properties. The range of rubber stiffness and hardness obtainable with reinforcing grades of furnace blacks is much greater than with channel blacks, and although final approval of a grade of black for a particular application is based on service testing, the useful range of rubber product quality has been broadened by the introduction of new varieties of furnace blacks. Processing characteristics of carbon blacks may be described as the relative workability factors of rubber stocks in the sequence of operations preceding the completed manufacture of cured rubber articles. In those compounds where carbon black is a substantial component of the stock, the properties of the black would be expected to exert a major influence on processing. The work reported here is concerned with the effect of carbon black properties on the forming step of semifinished stocks, and includes a study of the processing shrinkage properties of carbon black loaded stocks.