Tetramethylthiuram Disulfide (TMTD, CAS 137-26-8): Ultra-Accelerator and Sulfur Donor

Tetramethylthiuram disulfide (TMTD), also known as thiram, is a thiuram rubber chemical with two jobs: it is a very fast ultra-accelerator, and it is a sulfur donor for low-sulfur and sulfurless vulcanisation systems. That combination makes it central to modern EV (efficient vulcanisation) compounds. This article covers what TMTD is, its specification, how it is made, how it is used, and how to specify and buy it.

1. What TMTD is

Property	Value
Name	Tetramethylthiuram disulfide (TMTD)
CAS number	137-26-8
Formula / MW	C₆H₁₂N₂S₄ / 240.43 g/mol
Synonyms	TMTD, thiram, tetramethylthiuram disulphide, bis(dimethylthiocarbamoyl) disulfide
Appearance	White or light-grey powder or granules

It is the disulfide of dimethyldithiocarbamate: two dimethylthiocarbamoyl groups joined through a sulfur-sulfur bond. That disulfide bond is what lets TMTD act as a sulfur donor, and the thiuram structure is what makes it such a fast accelerator.

2. Specification (typical commercial grade)

Property	Specification
Appearance	White or light-grey powder or granules
Melting point	142 deg C min
Loss on heating	0.4% max
Ash	0.3% max
Residue on 150 um sieve	0% (fully passing)

Melting point reflects purity; loss on heating controls moisture; ash and sieve residue reflect the cleanliness of the powder. Confirm all of them on the batch COA.

3. How TMTD is made

The route runs through dimethyldithiocarbamate: dimethylamine reacts with carbon disulfide in the presence of alkali to give sodium dimethyldithiocarbamate, which is then oxidised (for example with hydrogen peroxide, chlorine or air) to couple two molecules into the disulfide. The product is filtered, washed and dried to the commercial specification.

4. TMTD as an accelerator

TMTD is a thiuram ultra-accelerator: it cures very quickly, and it is almost always used with another accelerator rather than alone. Typical uses:

Secondary accelerator with a thiazole (MBT, MBTS) or sulfenamide (CBS, TBBS) to raise cure rate and crosslink density.
Primary ultra-accelerator in latex and some room-temperature-cure systems.
Continuous vulcanisation (for example salt-bath and hot-air) where a fast cure is needed.

5. TMTD as a sulfur donor: EV and semi-EV systems

Where TMTD really earns its place is in efficient vulcanisation (EV). In a conventional system the compound contains 2-3 phr sulfur and a little accelerator. In an EV system the sulfur is cut to 0.3-0.5 phr (or removed entirely) and the accelerator level is raised, with a sulfur donor supplying the crosslinking sulfur. TMTD is one of the main sulfur donors.

System	Sulfur	Accelerator / donor	Result
Conventional	High (about 2 – 3 phr)	Low accelerator	Good fatigue, lower heat resistance
Semi-EV	Medium (about 1 – 1.7 phr)	Higher accelerator	Balance of fatigue and heat ageing
EV	Low or none (about 0 – 0.5 phr)	High accelerator + sulfur donor (e.g. TMTD)	Heat-resistant, low set, better ageing

EV compounds – with TMTD or another donor – are used where heat resistance and low compression set matter (for example engine mounts, hoses, seals and belt compounds).

6. TMTD in adhesives and latex

Rubber-to-metal bonding – TMTD is used in bonding systems and in some adhesive and rubber-to-substrate applications.
Latex compounds – as a fast accelerator in dipped and latex goods.
Room-temperature and low-temperature cure – where its ultra-fast action is useful.

7. Other industrial uses

Use	Note
Lubricant additive	Component in some lubricant and grease formulations
Industrial biocidal use	The same molecule (thiram) is a well-known biocide
Plant-protection (thiram)	As a pesticide it is restricted or not approved in several regions – confirm the market requirements

Because the molecule is also a plant-protection active ingredient, its non-rubber uses are more tightly regulated than its use as an industrial rubber chemical. If you are buying for rubber use, say so on the enquiry so the right documentation is supplied.

8. TMTD vs other accelerators

Accelerator	Type	Cure speed	Scorch	Role
TMTD	Thiuram	Very fast	Short	Ultra-accelerator and sulfur donor
TMTM	Thiuram monosulfide	Fast	Short	Accelerator (not a sulfur donor)
TETD	Thiuram disulfide	Fast	Short	Accelerator and sulfur donor
MBT / MBTS	Thiazole	Fast / moderate	Lower / better	Primary or co-accelerator
CBS / TBBS	Sulfenamide	Delayed then fast	High	Processing-safe accelerators for tyres

Thiurams are the fastest family and have the shortest scorch times; they are almost always blended with a thiazole or sulfenamide rather than used alone.

9. Typical dosage

Use	Typical dosage (starting point)
Secondary accelerator	About 0.2 – 1.0 phr
Sulfur donor in EV systems	About 1.0 – 3.0 phr
Latex / room-temperature cure	Set by the system

Dosage is formulation-specific; these are starting points for compound development, not a specification.

10. Safety and regulation

Skin and respiratory sensitizer. TMTD is classified as a skin sensitizer (and can sensitise the respiratory tract); repeated contact can cause allergic dermatitis. Use gloves, dust control and ventilation.
Harmful if swallowed and harmful in contact with skin; serious eye irritation. Follow the hazard labelling and the SDS.
Very toxic to aquatic life. Prevent release to water; handle waste and dustings properly.
Alcohol reaction. Exposure to TMTD can produce a disulfiram-like reaction with alcohol – warn workers and follow the SDS.
Regulatory status. As an industrial rubber chemical TMTD is widely used; as a plant-protection active ingredient (thiram) it is restricted or not approved in several regions. Confirm the requirements for your market and use.

11. Packaging, storage and supply

Item	Detail
Packaging	25 kg PP/PE bags, 1000 kg jumbo bags; palletised for container shipment
Storage	Sealed, cool and dry, away from oxidising agents, acids and foodstuffs
Documents	Per-batch COA and SDS; third-party inspection on request
Delivery	FOB or CIF to your port; quote by tonnage

Tell us the application (accelerator and/or sulfur donor), the tonnage and the delivery port for a quotation.

Frequently Asked Questions

What is TMTD used for?

As a very fast thiuram ultra-accelerator in rubber, and as a sulfur donor in low-sulfur and sulfurless (EV) vulcanisation systems. It is also used in latex, adhesives and some industrial applications.

Is TMTD a sulfur donor?

Yes. It is one of the main sulfur donors used in EV and semi-EV compounds to carry the crosslinking sulfur when elemental sulfur is reduced or removed.

What is the difference between TMTD and TMTM?

TMTD is the disulfide and acts as both accelerator and sulfur donor; TMTM is the monosulfide and acts as an accelerator but not as a sulfur donor.

What is the typical dosage of TMTD?

About 0.2-1.0 phr as a secondary accelerator, or about 1.0-3.0 phr as a sulfur donor in EV systems – always set by the formulation.

Is TMTD the same as thiram?

Yes – thiram is the common name for TMTD. As an industrial rubber chemical it is widely used; as a plant-protection product (thiram) it is restricted in several regions.

What are the main hazards of TMTD?

Skin and respiratory sensitisation, harm if swallowed or in contact with skin, eye irritation and very high aquatic toxicity. It can also cause a disulfiram-like reaction with alcohol. Follow the SDS.