Microgel, a New Macromolecule. Relation to Sol and Gel as Structural Elements of Synthetic Rubber

Abstract

Abstract In connection with the rubber crisis of the war, useful fundamental controls and improvements of quality of synthetic rubber which would fit in with current engineering were urgently needed. Variations in the solubility of butadiene polymers and copolymers had been noted by many rubber researchers seemingly to reflect important and controllable variables in the polymerization process, such as “modification” and degree of conversion. Solubility also was thought by some workers to bear on processability. Agreement was neither definite nor general on these phenomena. Solubility behavior and gel fraction had been casually observed for thirty years in natural and synthetic rubbers studied in Europe. No record of engineering application was found. After the organization of the polymer research program in the Office of the Rubber Director, more intensive examination of the significance of sol-gel in controlling the uniformity of GR-S was begun. A proposal new to polymer technology was made, viz., that the gel fraction of synthetic rubber comprised a characteristic structure in the raw polymer which affected the physical properties and quality (as in tire performance) of the final vulcanizate.