MBT vs MBTS and CBS: Choosing a Thiazole Rubber Accelerator

MBT is the parent of the benzothiazole accelerators, and choosing between MBT, MBTS and the sulfenamides (CBS, TBBS) comes down to one trade-off: cure speed against processing safety. This page sets the four side by side so you can shortlist for a compound.

1. The family

Accelerator	CAS	Type	Derived from MBT?
MBT	149-30-4	Thiazole (thiol)	–
MBTS	120-78-5	Thiazole disulfide	Yes (oxidative coupling of MBT)
CBS	95-33-0	Sulfenamide	Yes (MBT + cyclohexylamine)
TBBS	95-31-8	Sulfenamide	Yes (MBT + tert-butylamine)

2. The trade-off in one table

Property	MBT	MBTS	CBS	TBBS
Cure speed	Fast (semi-ultra)	Moderate	Delayed, then fast	Delayed, then fast
Scorch safety	Lower	Better than MBT	High	High
Processing window	Short	Medium	Long	Long
Typical dosage	0.5 – 2.5 phr	0.8 – 2.0 phr	0.5 – 2.0 phr	0.5 – 2.0 phr
Typical use	Fast curing, co-accelerated compounds; intermediate	Compounds needing more scorch safety	Tyres and technical goods	Tyres and technical goods

3. Why the sulfenamides behave differently

The sulfenamides (CBS, TBBS) carry the accelerator group on a nitrogen that has to be released before the active species forms. That delay means the compound can be mixed, extruded and shaped without premature cure – then cures quickly once the temperature rises. MBT has no such delay, which is why it is fast but has a short scorch time.

4. Quick selection rules

Need processing safety (tyres, thick sections, long flow paths)? Use a sulfenamide (CBS, TBBS).
Need speed at low cost and can accept a short scorch time? Use MBT, usually with a co-accelerator.
MBT scorches too fast but a sulfenamide is too slow to start? MBTS sits in between.
Building an EV system? Pair the thiazole with a thiuram (TMTD) as sulfur donor.
Always confirm on the compound – cure rheometry (MDR/ODR) and scorch tests decide the final choice.

5. Co-acceleration in practice

System	Typical combination	Result
MBT + thiuram	MBT with TMTD	Fast cure, higher crosslink density; short scorch
MBT + guanidine	MBT with DPG or DOTG	Faster, harder cure; classic general-purpose system
Sulfenamide alone	CBS or TBBS with sulfur	Processing-safe, delayed cure; tyre practice

6. Cost and availability

MBT is the lowest-cost member of the family and the feedstock for the others, so its price and availability influence the whole group. MBTS and the sulfenamides carry the extra processing cost of their manufacture. Where cost matters and the process allows, MBT with a co-accelerator is often the economical route.

Frequently Asked Questions

Is MBT or MBTS better?

Neither is universally better: MBT cures faster but scorches sooner; MBTS is slower with better scorch safety. The choice depends on the compound and the process.

Why use CBS or TBBS instead of MBT?

For processing safety. The sulfenamides delay the onset of cure, which suits tyres and thick or complex sections where the compound must be shaped before it sets.

Can MBT and MBTS be used together?

Yes – blends are used to fine-tune cure rate and scorch safety. Confirm the combination on the compound.

Which is the intermediate for the others?

MBT. MBTS, CBS and TBBS are all made from MBT.