Tetramethyl thiuram monosulphide

Organic phosphates Tetramethyl thiuram monosulphide and disulphide... 

Name Tetramethyl thiuram monosulphide Common Abbreviation TMTM... 

With the sulphur-modified polymers cure may be brought about by zinc oxide and magnesium oxide in combination either alone or together with an accelerator such as ethylene thiourea. In the case of the homopolymers it has been common practice to support the zinc oxide/magnesium oxide/ethylene thiourea system with a further component. This component consists of a sulphide or a blend of sulphides of the type more commonly used as accelerators for the diene hydrocarbon polymers. These include mercaptobenzothiazole disulphide (MBTS), diorthotolyl guanidine (DOTG) and tetramethyl thiuram monosulphide (TMTM). In the polychloroprene homopolymers these materials appear to act as retarders of cure at processing temperatures but are accelerators at vulcanization temperatures. Their mechanism does not appear to have been fully elucidated. 

When EPDMs first appeared, there was difficulty in finding a good crosslinking system based on sulphur and accelerators. It was sufficient to adopt those already in use for butyl rubber as suggested by the low unsaturation level of the two families of elastomers. The commonest system was, and still is, based on mercaptobenzthiazole (0 5 phr) tetramethyl thiuram monosulphide (1-5 phr), sulphur (T5 phr) plus zinc oxide (5 phr) and stearic acid (1 phr). 

In sulphur cured rubbers, accelerators are generally used to reduce the dependency on sulphur in order to achieve more efficient vulcanisation, to improve heat and flex resistance due to the presence of more monosulphidic crosslinks, and to increase the cure rate of the rubber and improve production capacity. Two accelerators which have been shown to enhance bondability of rubbers are 2-mercaptobenzothiazole (MBT) and mercaptobenzothiazole disulphide (MBTS). An accelerator which is known to negatively impact on adhesion is tetramethyl thiuram disulphide (TMTD). 

The use of sulphur donors in place of elemental sulphur has been practised since the early 1920s when it was found that the accelerators tetramethyl thiuram disulphide and tetraethyl thiuram disulphide in conjunction with zinc oxide gave vulcanizates with improved ageing properties when compared with conventional accelerated sulphur systems. For many years it was believed that vulcanization was brought about by the abstraction of one sulphur atom from the disulphide to yield the corresponding monosulphide... 

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