Rubber Antioxidants and Accelerators: Selection Guide

Nearly every rubber compound contains two families of additives: accelerators (which control the sulfur cure) and antioxidants/antiozonants (which protect the rubber from ageing). This guide is a single reference for the main additives in each family – what they do, how they differ, and how to choose. It links to the detailed article for each product.

The two jobs: cure and protection

Family	Job	Main types
Accelerators	Make sulfur vulcanisation fast and controllable	Thiazoles, sulfenamides, guanidines, thiurams
Antioxidants / antiozonants	Protect the rubber against heat, oxygen, ozone and fatigue ageing	Hindered phenolics, amines (quinoline, PPD)
Pre-vulcanisation inhibitors	Delay the onset of cure (scorch control)	PVI

Accelerators: the classes

Class	Examples	Character	Typical use
Thiazole	MBT, MBTS	General-purpose; fast; moderate scorch safety	General rubber goods, technical goods
Sulfenamide	CZ (CBS), TBBS (NS), DCBS	Delayed action; good scorch safety; fast cure	Tyres, technical goods, thick parts
Guanidine	DPG (D)	Fast; secondary accelerator/booster	Boosting thiazole/sulfenamide cures; latex
Thiuram	TMTD, TMTM	Ultra-fast; sulfur donors	EV systems, latex, low-temperature cure

Accelerators at a glance

Accelerator	CAS	Class	Delay / speed	Best for
MBTS (DM)	120-78-5	Thiazole	Medium; better scorch than MBT	General / secondary accelerator
CZ (CBS)	95-33-0	Sulfenamide	Delayed (medium)	General tyres and technical goods
TBBS (NS)	95-31-8	Sulfenamide	Delayed (medium-high)	Tyres; the most common sulfenamide
DCBS	4979-32-2	Sulfenamide	Delayed (high)	Thick sections; longest scorch safety
DPG (D)	102-06-7	Guanidine	Fast (booster)	Secondary accelerator; latex
MBT (M)	149-30-4	Thiazole	Fast; lower scorch safety	General accelerator; intermediate
TMTD	137-26-8	Thiuram	Ultra-fast; sulfur donor	EV systems, latex
PVI	17796-82-6	Pre-vulcanisation inhibitor	Retarder (delays onset)	Scorch control

Antioxidants and antiozonants at a glance

Antioxidant	CAS	Type	Staining	Best for
Antioxidant 2246	119-47-1	Hindered phenolic (bis)	Non-staining	Light-coloured rubber, latex, plastics
BHT (264)	128-37-0	Hindered phenolic (mono)	Non-staining	Plastics, oils, food; fast action
Antioxidant RD (TMQ)	26780-96-1	Amine (quinoline)	Staining	Tyres and dark goods; heat/fatigue
6PPD / 7PPD	793-24-8 / 3081-01-4	Amine (PPD)	Staining	Anti-ozonant / antiflex for tyres

How to choose an accelerator

Delayed (sulfenamide) or not? For tyres and large parts, a sulfenamide (CZ, TBBS, DCBS) gives scorch safety; for general goods, a thiazole (MBT, MBTS) is cheaper and faster.
How much scorch safety? CZ (medium) < TBBS (medium-high) < DCBS (high). Pick the least delay that solves the scorch problem.
Need more speed? Add a booster such as DPG (or a thiuram) to a thiazole/sulfenamide system.
Thick section? Use DCBS, and consider PVI for extra scorch safety.
Nitrosamine limits? Prefer primary-amine sulfenamides (CZ, TBBS) and thiazoles (MBT/MBTS); be careful with secondary-amine sulfenamides (DCBS) and thiurams/dithiocarbamates.
Latex? DPG and dithiocarbamates are common in latex compounds.

How to choose an antioxidant

Colour requirement? Non-staining (2246, BHT) for white/bright goods; staining amines (RD, 6PPD) for dark goods.
Heat and fatigue? Amine antioxidants (RD, 6PPD) give the strongest protection but stain.
Processing temperature? Higher-molecular-weight phenolics (2246) resist volatilisation better than BHT.
Oils, fats or food? BHT (E321 where permitted).
Full protection? Combine a primary antioxidant with a secondary (phosphite/thioester) and, in tyres, with an antiozonant.

Cure systems: conventional, semi-EV and EV

System	Sulfur	Accelerator	Character
Conventional (CV)	Higher	Lower	Good fatigue, lower heat resistance
Semi-efficient (semi-EV)	Medium	Higher	Balance of fatigue and heat resistance
Efficient (EV)	Low	High	Best heat resistance; lower fatigue

Accelerators and sulfur are chosen together to set the crosslink type and density, and therefore the balance of heat resistance, fatigue life and other properties.

Nitrosamine considerations

Accelerator class	Nitrosamine potential
Thiazoles (MBT, MBTS)	No amine-derived concern
Sulfenamides from primary amines (CZ, TBBS)	Lower
Sulfenamides from secondary amines (DCBS)	Higher
Thiurams / dithiocarbamates	Treated with caution

Where strict nitrosamine limits apply, accelerator choice is made together with the whole cure system, and a retarder such as PVI can supply extra scorch safety without relying on a secondary-amine accelerator.

Additive loading: a practical note

Additive	Typical order of loading
Accelerator (primary)	A few phr, set by the cure system
Secondary accelerator / booster (DPG)	Low – a fraction to a couple of phr
Antioxidant	A few phr, set by the ageing requirement
Antiozonant (6PPD/7PPD)	A few phr for tyres and dynamic goods
PVI	Low – tuned for scorch safety

All loadings are starting points only; the final levels are confirmed by cure testing (rheometer) and ageing/physical tests on the cured article.

Buying rubber additives

Buy against a specification and COA – purity, melting, heating loss, ash and sieve residue all affect cure and ageing.
Watch residual monomers/impurities – for accelerators, residual MBT and amine change cure activity; for antioxidants, free phenol and ash matter.
Match the form – powder vs granular; low-dust granules and fine powders each suit different handling.
Confirm grade and regulation – especially for food-contact or potable-water rubber.
Order on committed tonnage – rubber chemicals are specialty products; committed volumes give the best terms.

Rubber Antioxidants and Accelerators: Selection Guide