Green vulcanization of brominated Butyl rubber via primary amine cross-linking without ZnO or sulfur

The increasing demand for brominated butyl rubber (BIIR) has intensified the use of conventional ZnO/sulfur-based curing systems, raising significant environmental concerns. Herein, we present a sustainable, ZnO- and sulfur-free cross-linking strategy enabled by a primary amine, octadecylamine (ODA), which serves as an efficient cross-linker for BIIR. Upon thermal activation at 160 °C, ODA reacts with the benzylic bromide groups of BIIR via dual nucleophilic substitution, forming stable covalent networks. The cross-link density and resultant mechanical properties exhibit a positive correlation with ODA loading, reaching an optimum at 3 phr. In contrast, octadecyltrimethylammonium bromide (OTAB) and diethylamine hydrochloride—lacking N–H protons—show negligible reactivity, highlighting the essential role of the primary amine functionality in the cross-linking mechanism. This work establishes a quantitative structure–efficiency relationship for amine-based cross-linkers, providing both experimental validation and mechanistic insight for the rational design of environmentally benign vulcanization processes in halogenated elastomers.