Full definition
A class of chemical curing agents used as alternatives to sulfur for cross-linking rubber, producing thermally stable carbon-carbon (C-C) bonds rather than the sulfur bridges formed in sulfur vulcanization. C-C bonds are shorter and stronger than polysulfidic bonds, resulting in: better heat resistance (higher reversion temperature), superior compression set, better electrical insulation (no sulfur bloom), and non-staining/non-discoloring vulcanizates. Common peroxides: DCP (dicumyl peroxide — most widely used, 40-45% active, decomposes at 150-170°C), DBPH (di-tert-butyl peroxide — higher decomposition temperature for continuous vulcanization), and BIPB (2,5-dimethyl-2,5-di(tert-butylperoxy)hexane — for EPDM and silicone). Essential for: fully saturated rubbers (EPDM, silicone VMQ, HNBR, fluoroelastomer) that have no double bonds for sulfur to attack, and for applications requiring non-blooming, non-staining, low-odor vulcanizates (food-grade, medical, electrical). Limitations: lower tear and fatigue resistance than sulfur cure, oxygen inhibition during cure (requires positive pressure or inert atmosphere), and sensitivity to certain co-agents and antioxidants. Dosage: typically 1-5 phr. Often used with co-agents (TAC, TAIC, TMPTMA) to increase cross-link density and efficiency.