Studies on a Novel Accelerator System in the Vulcanisation of Polychloroprene Rubber

Abstract

Polychloroprene (CR) is a polar rubber and its compounding, curing etc. are somewhat different from other hydrocarbon rubbers. Thiourea derivatives are popular in neoprene compounding. For example ethylene thiourea (NA22) is a common ingredient of compounding of this rubber. Metal oxides are also an important part of the curing system in CR. Considering the carbon backbone structure with double bonds sulphur crosslinking is also sometimes followed. It is to be emphasised that the conventional accelerators used in CR vulcanisation especially NA22 is a toxic chemical and is reported to be carcinogenic. In our studies we tried sulphur vulcanisation of Neoprene-W along with MgO and amidinophenyl thiourea (APT) which is a non-toxic chemical used in the pharmaceutical industry. TMTD-NA22 combinations are used as controls. Investigations were carried out to find out the effect of this amidinothiourea derivative on filled CR systems also. Carbon black and precipitated silica were used as fillers. From our investigations it is found that experimental mixes containing TMTD-APT are effective in the vulcanisation of polychloroprene rubber. A nucleophilic reaction mechanism for the above vulcanisation reactions can also be envisaged. The cure characteristics and tensile and other physical properties evaluated are found to be better/comparable to the control systems in both gum and filled formulations studied. The percentage retention of tensile properties of the vulcanisates containing APT is also found to be satisfactory. Non-toxic nature of this amidinothiourea derivative will be an added advantage in this context.