The Carbon Reinforcement of Rubber

Abstract

Abstract Evolution Discovered in England in 1910 where, however, insufficient quantities were used, and developed commercially in Akron in 1912, its evolution may be roughly divided into three periods: 1913–1920, during which time the art led the science; 1920–1927, during which time science led the art, and 1927–1934, when the art once more overtook the science, leading to the empirical employment of 50 per cent or more of carbon on the rubber. At the present time there is needed a fresh theoretical approach. The Course The scope of carbon reinforcement may conveniently be defined as the region of positive Delta A values. The shape of the Delta A curve is in itself interesting as to symmetry, the presence of a well-defined maximum, and the extraordinary extent of positive values compared to other reinforcing pigments. Position of Maximum The published data on carbon Delta A functions have been assembled together with fresh data, the latter including both litharge and Captax accelerated mixings. Considerable discrepancies appear. A mean curve has been drawn to include the recent data, and previous work in which fatty acids were employed. This mean Delta A curve for carbon black shows a maximum at 26.3 per cent by volume of carbon on the rubber, corresponding to 51 per cent by weight. This mean curve cuts the base-mixing energy axis at 53.6 volumes of carbon, or approximately 105 per cent by weight.