Crosslinking of natural and polybutadiene rubbers with thiuram sulfur donors in the presence of a thiuram monosulfide

Abstract

The influence of tetramethylthiuram monosulfide (TMTM) in the vulcanization process of natural rubber and butadiene rubber with dipentamethylene thiuram tetrasulfide (DPTT) was investigated. Vulcanization parameters as reaction rate and reversion varied when TMTM was added in NR-DPTT formulations. Crosslinking density and proportion of monosulfidic crosslinks increased with TMTM content increase. However, a drop in physical properties was observed at high TMTM content and at long times of curing well over t97. Formation of densely crosslinked areas due to polymerization reaction was postulated as the origin of these variations. In BR-DPTT compounds, torque and monosulfidic crosslink proportions increased when TMTM was added. Polymerization reaction takes place in BR systems too. However, in BR vulcanizates, C—C bonds decreased with TMTM proportion, whereas in NR vulcanizates increased.