Evaluation of Non- Nitrosamine Generating Accelerator Systems for the Vulcanization of Chlorobutyl Elastomer

 

Vulcanization of chlorobutyl rubber differs from that of general purpose rubber. Butyl Rubber has approximately 2% unsaturation in the backbone. The presence of chlorine in chlorobutyl rubber increases the chemical reactivity of the isoprenyl units located in the butyl backbone. The low number of unsaturated monomer units has traditionally necessitated use of ultra-fast accelerators such as tetramethyl thiuram disulfide (TMTD) or zinc dimethyl dithiocarbamate (ZMDC). Use of such accelerators can result in undesirable  formation of nitrosamines. Many countries have enforced stringent laws to regulate the use of nitrosamine generating accelerators in rubber compounds.

 There are a number of alternatives to nitrosamine generating thiuram and dithiocarbamate cure systems. Sterically hindered accelerators like tetra benzyl thiuram disulphide (TBzTD) and zinc dibenzyl dithiocarbamate (ZBEC) can be considered as an alternative. Alkylphenol disulfide based accelerators also enable attainment of favorable properties when used in chlorobutyl rubber compound. Use of alkylphenol disulfide accelerators in halobutyl rubber compounds can allow improvement in reversion resistance, adhesion to natural rubber tire casing compounds, and aged property retention.

 This review explores the use of non-nitrosamine generating accelerator system in chlorobutyl compounds. Using design of experiment approach, the doses of alkylphenol disulphide, dibenzothiazyl disulphide (MBTS) and diphenyl guanidine are also optimized in a chlorobutyl natural rubber blend compound.