The Influence of the Solubility of Accelerators on the Vulcanization of Elastomer Blends

Abstract

Abstract The various results obtained in the course of this study show that the solubility of the curing ingredients exercises an influence on the properties of the vulcanizate of a blend of elastomers when the latter are incompatible. If, in the preparation of the blend, the two elastomers contain the same levels of the curing ingredients, the latter undergo rapid migration at the temperature of vulcanization from the phase in which they are less soluble toward the phase in which they are more soluble. This unbalances their distribution, and the impoverished phase vulcanizes more slowly and less completely. In the limiting case, it cannot vulcanize at all and, hence, plays the role of diluent filler. if, on the contrary, the phase with the higher solubility of the curing ingredients at the vulcanization temperature is saturated initially, migration does not occur, and the two phases can covulcanize. However, for obvious reasons, such a procedure is not technically feasible and is useful only in demonstrating the principle. The solution lies rather in use of accelerators which have the same solubility in each of the elastomers of the blend. This is the way which has been followed by certain investigators, but the products have not yet been commercialized. One might equally envision an investigation of combinations of accelerators which will form eutectic mixtures having identical solubility in the two different elastomers.