This class of accelerators include commercially available and widely used accelerators such as MBT, MBTS and ZMBT (NaMBT the sodium salt of MBT also finds applications in few latex goods manufacture).
Thiazoles are medium-fast primary accelerators with only moderate processing safety. Thiazoles are most widely used accelerators in the rubber industry for the production of wide variety of goods such as cycle tyres and tubes, footwear, beltings, hoses and other moulded and extruded goods.
Thiazoles are activated by Zinc oxide / Stearic acid combination and produce flat cure with vulcanizates having very good reversion resistance.
Activity of Thiazole accelerators with respect to cure characteristics can be summarised as follows:
Scorch Safety Longer…. (MBT < MBTS < ZMBT)
Cure Rate Faster….. (ZMBT < MBTS < MBT)
Crosslink Density Higher at equal dosage….. (ZMBT < MBT < MBTS)
Thiazoles act as retarders of cure in rubber compounds accelerated using Thiurams (TMTD/TMTM)/Dithiocarbamates (ZDC, ZDBC) or ETU class accelerators as main accelerator and also reduce bloom of Thiurams and dithiocarbamates in EV cure systems.
All thiazole accelerators can be further boosted to increase speed of vulcanisation by using small quantities of basic accelerators such as DPG, DOTG, TMTM, TMTD, ZDC, etc
Thiazole accelerators can be retarded using small proportion of Pilgard PVI or other retarders like NDPA, pthalic anhydride, salicylic acid, etc.
Addition of extra Stearic acid or partial replacement by sulphenamide accelerator also control scorch to some extent.
Thiazoles are particularly preferred for rubber to metal bonding applications as amine-accelerators affect the rubber-metal bond strength.