Thiuram class includes accelerators such as TMTM, TMTD, TETD, TBzTD and DPTT.
Thiurams are ultra-fast accelerators for NR, SBR, BR, NBR and other highly unsaturated rubbers and the most preferred primary accelerator for sulfur cured low-unsaturation content rubbers like butyl (IIR) and EPDM.
Thiurams are widely used as secondary accelerator generally at 0.05 - 0.4 phr with thiazole / sulfenamide
class accelerators to achieve faster curing rate, higher crosslink density with a compromise on scorch safety
and vulcanizate exhibit lower heat build up compared to DPG/DOTG activated sulphenamide cures.
Thiurams exhibit longer processing safety compared to dithiocarbamate accelerators. Thiurams, when used as vulcanising agents (2.5 - 3.0 phr) in the absence of sulfur; the vulcanizates attain high degree of state of cure exhibiting high tensile strength, high modulus, lower elongation at break, higher rebound resilience at elevated temperatures and lower tear resistance.
Thiurams are also used along with Guanidine in Polychloroprene compounds to achieve good processing
In combination with Dithiocarbamates and Xanthates, Thiurams have retarding effect without changing the rate of vulcanisation.
Thiuram accelerators do not discolour the vulcanizates & the products are tasteless.
Activity of various thiuram accelerators with respect to cure characteristics can be summarised as follows :
1. Scorch Safety Longer (TMTD < TETD << TMTM)
2. Cure Rate Faster (TMTM = TETD = TMTD)
3. Crosslink density at equal dosage Higher (TMTM = TETD = TMTD)