Accelerators

Types of vulcanizing accelerators

Sulphenamides:

They offer high scorch safety and cure rate. The more basic is attached amine, more is scorch safety and higher cure rate.Perhaps the most widely used sulphenamide is N-Cyclohexyl-2-Benzothiazole Sulphenamide (CBS) due to balance between scorch safety and cure rate. TBBS is another one which is used for more scorch safety. It produces vulcanizte of high modulus.

Figure 01: TBBS

 Thiazoles:

The most common accelerator related to this group is MBT. Later came MBTS. MBT provides medium vulcanization rate and vulcanizate of relatively low modulus. It can do scorching mainly in NR, during processing of green compound. For scorch safety, small amount of MBTS is added as replacement with MBT. It is common to use secondary accelerator or booster with MBT.

Figure 02: MBT

Guanidines:

The main accelerator is DPG. It has low vulcanization rate and relatively safe in processing. Their main use is as secondary accelerator with sulphenamides.

Thiurams:

The major member is TMTD. They give high vulcanization rate but are seldom used as primary accelerators.