Gel as a Definitive Property in GR-S Technology

Abstract

Abstract 1. Of the gel fraction that may occur in GR-S, only that portion which has low swelling volume in benzene—tight (B) gel—markedly affects processing behavior and quality of product. 2. As the proportion of tight (B) gel increases, mixing operations become more difficult, and the quality of the final vulcanizate is lowered; specifically, decreased tensile strength, increased modulus, and decreased cut-growth resistance result. Where maximum quality is desired, processing conditions which favor the formation of tight gel should be avoided. 3. Conversely, appreciable amounts of tight (B) gel aid the processing operations of calendering and extrusion by reducing shrinkage and roughness. Where ease of processing is paramount and quality defects can be tolerated, heat-plasticization cycles which favor gel formation may be used to advantage. 4. To account for the observed effects of tight gel, the theory is advanced that fillers cannot enter this gel portion. This explanation is supported by a limited am...