EXTENSIBILITY OF BLACK-FILLED ELASTOMERS

It has been known that curatives, fillers, resins, and processing oils are the major variables which determinine the modulus level of elastomers by changing the degree of crosslinking and reinforcement. Attempts have been made to relate the tensile strength of elastomers to the network structure and the molecular characteristics. Unique empirical relations are found to exist between the extension ratio at break and the crosslink density in the absence and in the presence of gross strain-induced crystallization. With black-filled elastomers, the modulus at 100% strain is proportional to the crosslink density over a wide temperature range. The proportionality constants can be used as convenient measures of the extensibility and in material evaluated on a constant modulus basis.