Overflow during Vulcanization. Its Dependence upon Inactive and Active Fillers, and Errors in Previous Calculations of the Specific Gravity of Vulcanizates Resulting from It

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Abstract 1. Raw rubber undergoes no change in volume during vulcanization. 2. Whenever it is vulcanized with sulfur there is an increase in volume. 3. Every inactive filler influences the overflow (increase in volume) in a characteristic way during vulcanization. 4. An increase in the proportion of a given inactive filler influences the overflow curve in a manner characteristic of the filler concerned. 5. Different inactive fillers influence the overflow in various ways. 6. Active fillers influence the overflow curve in a different manner from inactive fillers. 7. An increase in the proportion of a given active filler influences the overflow curve in a manner entirely characteristic of the filler concerned. 8. Different active fillers influence the overflow in quite different ways. 9. The specific gravity of a vulcanizate with sulfur is always less than the specific gravity of the corresponding unvulcanized mixture. 10. All calculations of specific gravity heretofore made in the rubber industry and theories related to them are incorrect because they are based on the false assumption that no increase in volume occurs during vulcanization. 11. Specific gravity determinations of mixtures must be based on overflow determinations.