Rubber accelerators: types, speed and how to choose
Buyer guide · Riddhi Polymers · Updated 2026-09-29
Short answer: Accelerators control how fast and how safely a sulphur-cured compound vulcanises. Sulfenamides (CBS, TBBS) give delayed action and good scorch safety and are the workhorses of tyres and moulded goods; thiazoles (MBT, MBTS) are medium-speed primaries; thiurams (TMTD, TMTM) and dithiocarbamates (ZDBC, ZDMC) are ultra-fast and are mostly used as secondary boosters or in low-temperature and latex cures; DPG is a secondary accelerator, especially in silica compounds.
The main accelerator classes
| Class | Examples | Cure speed | Scorch safety | Typical use |
|---|---|---|---|---|
| Sulfenamides | CBS, TBBS, MBS, DCBS | Fast (delayed action) | Good to very good | Primary accelerator in tyres, belts, moulded goods |
| Thiazoles | MBT, MBTS, ZMBT | Medium | Moderate (MBTS better than MBT) | Primary in general goods; with secondaries in NR/SBR |
| Thiurams | TMTD, TMTM, TBzTD, DPTT | Very fast | Low | Secondary booster; sulphur donor (TMTD) for heat-resistant EV cures |
| Dithiocarbamates | ZDBC, ZDEC, ZDMC | Ultra-fast | Low | Latex, low-temperature cures, EPDM boosters |
| Guanidines | DPG | Slow on its own | Moderate | Secondary with thiazoles/sulfenamides; silica compounds |
Primary and secondary accelerators
Most compounds use a primary accelerator for the main cure and a small amount of a secondary to speed it up or raise crosslink density. A common pattern is a sulfenamide primary (for example 1–1.5 PHR TBBS or CBS) with a small thiuram or DPG secondary. Zinc oxide and stearic acid are needed as activators in almost every sulphur cure.
How to choose
- Need processing safety (thick moulded parts, multi-stage mixing): a sulfenamide such as TBBS or CBS.
- Need faster cure at low temperature or latex goods: a dithiocarbamate or thiuram.
- Need better heat ageing: an efficient (EV) or semi-EV system, with lower sulphur and a sulphur donor such as TMTD or DTDM.
- EPDM compounds: usually a blend of thiazole, thiuram and dithiocarbamate, because EPDM cures slowly with sulphur.
- Silica-filled compounds: add DPG as a secondary to offset cure retardation by silica.
Dosages and combinations depend on the polymer, fillers and cure temperature; treat these as starting points and confirm with rheometer trials.
Frequently asked questions
What is the difference between CBS and TBBS?
Both are sulfenamide accelerators with delayed action. TBBS generally gives slightly longer scorch safety and is widely used in tyre compounds; CBS is slightly faster and very common in general rubber goods.
Why use a secondary accelerator?
A small amount of a fast secondary such as a thiuram, dithiocarbamate or DPG speeds up the primary accelerator and increases crosslink density, shortening cure time.
Which accelerators are used for EPDM?
EPDM is usually cured with a combination of a thiazole (such as MBTS), a thiuram (such as TMTD) and a dithiocarbamate (such as ZDBC), or with peroxides for better heat resistance.
Related products and industries
- Rubber chemicals supplier in Chennai
- Zinc oxide and rubber activators
- Raw materials for automotive rubber parts
Need help choosing a grade?
Riddhi Polymers has supplied rubber raw materials to 400+ manufacturers across South India since 2009. Tell us your application and we will suggest grades to trial. Request a quote, call +91 98418 19109 or email sales@riddhipolymers.com.
