What Is Accelerator TBBS (NS)?
Accelerator TBBS, also called NS or NZ, CAS 95-31-8, chemically N-tert-butyl-2-benzothiazolesulfenamide, is a sulfenamide (delayed-action) rubber accelerator. It is the most widely used accelerator in the tyre industry, prized for its combination of excellent scorch safety and a fast, efficient cure.
Like other sulfenamides, TBBS stays largely inactive at the temperatures used for mixing and shaping, then releases the active accelerator at cure temperature. That is what lets large tyre components be built and stored without premature vulcanisation, and then cured quickly and reliably. PolyBlueChem supplies Accelerator TBBS to a controlled specification with per-batch COA and SDS.
| CAS number | 95-31-8 |
| Chemical name | N-tert-Butyl-2-benzothiazolesulfenamide |
| Synonyms | Accelerator TBBS; NS; NZ; N-tert-butylbenzothiazole-2-sulfenamide |
| Molecular formula | C11H14N2S2 |
| Molecular weight | 238.4 g/mol |
| Type | Sulfenamide accelerator (delayed action) |
| Appearance | White or light yellow powder / granular |
Chemistry and Structure
Accelerator TBBS is a sulfenamide made from the benzothiazole nucleus (the same thiazole found in MBT/MBTS) linked through a sulfur atom to a nitrogen carrying a tert-butyl group. The structure explains the behaviour:
- The benzothiazole fragment is the active accelerator; when released it is essentially MBT.
- The sulfur-nitrogen bond provides the delayed action – stable at processing temperature, breaking at cure temperature.
- The tert-butylamine fragment released on decomposition acts as an activator.
The tert-butyl group makes TBBS a medium-to-strongly delayed sulfenamide, giving it slightly more scorch safety than CZ (CBS). It is derived from a primary amine, which is why it is generally regarded as a lower-nitrosamine option within the sulfenamide family.
How It Works: Delayed-Action Vulcanisation
- Processing (cool) – TBBS is stable and does not significantly accelerate cure, so the compound can be mixed, calendered, extruded and stored safely.
- Heating to cure temperature – the sulfur-nitrogen bond breaks, releasing the benzothiazole fragment (MBT) and tert-butylamine.
- Cure – the released thiazole, with the amine activator and the zinc oxide/stearic acid activator system, accelerates the reaction of sulfur with the polymer.
- Completion – crosslinks form quickly, giving the required physical properties.
TBBS is used in a sulfur cure system – it needs sulfur (crosslinker) and activators (zinc oxide and stearic acid), and is often combined with a secondary accelerator or retarder to tune scorch and cure.
How Accelerator TBBS Is Produced
TBBS is made by reacting 2-mercaptobenzothiazole (MBT) with tert-butylamine in the presence of an oxidising agent, forming the sulfur-nitrogen bond of the sulfenamide:
- MBT and tert-butylamine are combined.
- An oxidant couples the thiazole thiol to the amine, forming the sulfenamide.
- The product is filtered, washed and dried, then milled to powder or granulated.
Control targets the correct linkage and low residuals (MBT and amine), because these affect scorch, cure rate and odour.
Specifications and Quality Control
Accelerator TBBS is supplied as a white or light yellow powder/granular to the following specification:
| Parameter | Specification |
|---|---|
| Appearance | White or light yellow powder / granular |
| Initial melting point | 104 °C min |
| Heating loss | 0.50% max |
| Ash | 0.50% max |
| Sieve residue (150 µm) | 0.1% max |
| Parameter | What it controls |
|---|---|
| Initial melting point (104 °C min) | Purity and identity |
| Heating loss (0.50% max) | Moisture and volatiles |
| Ash (0.50% max) | Inorganic residues |
| Sieve residue (150 µm, 0.1% max) | Particle size / dispersion |
A specification sheet and a per-batch certificate of analysis (COA) are available on request.
Key Properties
| Property | Behaviour | Practical value |
|---|---|---|
| Type | Sulfenamide, delayed action | High scorch safety + fast cure |
| Form | Powder or granular | Easy to weigh and disperse; granular is low-dusting |
| Delay | Medium-high | Safe processing of large components |
| Cure | Fast, efficient | Good physical properties at low level |
| Activators | Needs ZnO + stearic acid (and sulfur) | Standard sulfur cure system |
Applications
| Industry / product | Function |
|---|---|
| Tyres | The principal accelerator for tread, carcass and sidewall compounds |
| Belts and hoses | Cure control for conveyor belting and hoses |
| Moulded goods | Seals, gaskets and mechanical parts |
| Light-coloured goods | Clean-curing, non-discolouring accelerator |
| General rubber | NR, SBR, BR and blends |
- Tyres – TBBS is the industry-standard sulfenamide for tyre compounds, valued for the scorch safety it gives large, slow-curing components.
- Technical rubber goods – belting, hoses, seals and mouldings, where processing safety and cure uniformity matter.
- Light-coloured compounds – TBBS cures cleanly without discolouration, so it suits non-black goods.
Accelerator TBBS vs Other Accelerators
| Accelerator | CAS | Class | Delay | Typical role |
|---|---|---|---|---|
| MBT | 149-30-4 | Thiazole | Low | General accelerator; intermediate |
| MBTS | 120-78-5 | Thiazole (disulfide) | Low-medium | General accelerator, good scorch |
| CZ (CBS) | 95-33-0 | Sulfenamide | Medium | Tyres and technical goods |
| TBBS (NS) | 95-31-8 | Sulfenamide | Medium-high | Tyres; the most common sulfenamide |
| DCBS | 4979-32-2 | Sulfenamide | High | Thick sections, long scorch |
Guidance: TBBS is the default tyre sulfenamide for its balance of scorch safety and cure speed; move to DCBS for very thick parts and the longest scorch; use CZ as a close alternative; use thiazoles (MBT/MBTS) where a faster, less delayed cure is acceptable.
Dosage and Cure Systems
| Cure system | Character | Accelerator use |
|---|---|---|
| Conventional (CV) | Higher sulfur, lower accelerator | Moderate sulfenamide |
| Semi-efficient (semi-EV) | Medium sulfur, higher accelerator | More sulfenamide, less sulfur |
| Efficient (EV) | Low sulfur, high accelerator | High sulfenamide, minimal sulfur |
The compound is balanced as a system – sulfur, zinc oxide, stearic acid, TBBS, and often a secondary accelerator or retarder – to achieve the required scorch safety, cure rate and crosslink density. Confirm the level by rheometer and physical tests.
Safety, Handling and Storage
- Skin sensitisation – TBBS is a potential skin sensitiser (H317); avoid skin contact and follow good industrial hygiene.
- Dust – avoid breathing the powder; use local extraction where large amounts are handled.
- Nitrosamine awareness – TBBS is derived from a primary amine (tert-butylamine), a lower-nitrosamine option within the sulfenamide family.
- Storage – keep sealed, cool and dry, away from acids and oxidisers.
Regulatory Status
| Use | Status (as commonly cited) |
|---|---|
| Rubber (industrial) | Governed by the buyer’s specification and article requirements |
| Food-contact / potable-water rubber | Only where the specific accelerator is permitted; confirm the applicable regulation |
Packaging, Logistics and Supply
| Item | Standard options |
|---|---|
| Packaging | 25 kg PP/PE bags or fibre drums |
| Documentation | Per-batch COA and SDS |
| Incoterms | FOB and CIF |
| Storage | Sealed, cool and dry |
Price tracks the MBT and tert-butylamine feedstock and the finishing quality; buying on committed tonnage gives the best terms.
TBBS in Tyre Compounds
TBBS is the workhorse accelerator of the tyre industry, and tyres show why. A tyre contains several rubber components – tread, carcass, sidewall, bead, innerliner – each with its own compound, but all built into one article and cured together. The accelerator must let each component be mixed, calendered or extruded, and assembled, and then cure all of them together in the mould.
| Component | Why TBBS fits |
|---|---|
| Tread | Fast, uniform cure with scorch safety for large treads |
| Carcass and body | Consistent cure through thick, multi-layer builds |
| Sidewall | Clean cure, good ageing performance with antioxidants |
| Bead and apex | Scorch safety for thick, slow-heating sections |
The scorch safety of a sulfenamide is especially valuable in tyres: the stock may be stored, re-worked and assembled over time, and premature cure at any of those stages would waste the component. TBBS widens that processing window while still curing quickly in the press.
Sulfenamide Accelerators Compared (TBBS, CZ, DCBS)
| Accelerator | Amine component | Delay | Best for |
|---|---|---|---|
| CZ (CBS) | Cyclohexylamine | Medium | General tyres and technical goods |
| TBBS (NS) | tert-Butylamine | Medium-high | Tyres; the most widely used sulfenamide |
| DCBS | Dicyclohexylamine | High | Thick sections, longest scorch safety |
The bulkier the amine, the more delayed the accelerator. TBBS sits towards the safer end of the common range: more delayed than CZ, less so than DCBS. A formulator picks within this family to match article thickness and processing temperature.
Scorch Safety and the Processing Window
- Scorch is premature vulcanisation – the compound starting to crosslink before it is shaped. It wastes stock and can block processing equipment.
- Processing window – the margin between the conditions a compound tolerates during processing and the point at which it starts to cure. TBBS widens this margin.
- Measurement – Mooney scorch and rheometer cure curves quantify scorch time and cure rate; the system is adjusted until both are acceptable.
- Levers – accelerator choice (TBBS/CZ/DCBS), a retarder such as PVI, sulfur level and processing temperature.
For large, thick or slow-curing components, the scorch safety of TBBS is often the decisive reason it is chosen over a faster thiazole accelerator.
Nitrosamine Awareness
| Amine type | Nitrosamine potential | Examples |
|---|---|---|
| Secondary amines | Higher concern | Morpholine-based accelerators |
| Primary amines | Lower concern | TBBS (tert-butylamine), CZ (cyclohexylamine) |
TBBS is derived from tert-butylamine (a primary amine), which is why it is generally regarded as a lower-nitrosamine option. For articles with strict nitrosamine limits, the accelerator is chosen as part of the whole cure system and checked against the applicable regulation.
Quality: Reading a TBBS Certificate of Analysis
| Parameter | What it tells you |
|---|---|
| Initial melting point (104 °C min) | Purity and identity; low values suggest residual MBT or impurities |
| Heating loss (0.50% max) | Moisture/volatiles; consistent values keep scorch behaviour consistent |
| Ash (0.50% max) | Inorganic residues |
| Sieve residue (150 µm, 0.1% max) | Dispersion; coarse material can cause cure defects |
Cure consistency depends on the accelerator being pure and evenly dispersed, so buying against a written specification and checking the batch COA keeps the compound – and the tyre – consistent.
Accelerator TBBS in Practice
TBBS is the default sulfenamide in many rubber plants because it works well across a wide range of compounds without demanding unusual conditions.
| Situation | Why TBBS fits |
|---|---|
| Large tyre components | Scorch safety over long build and storage times |
| Mixed production | Versatile, well-understood accelerator |
| Light-coloured compounds | Clean cure, no discolouration |
| Nitrosamine-conscious plants | Primary-amine derived (lower concern) |
In practice TBBS is set against the sulfur level, the zinc oxide/stearic acid activators and any secondary accelerator or retarder such as PVI. With a semi-EV or EV system, sulfur is reduced and the accelerator level raised to change the crosslink type and improve heat resistance. The formulator confirms the level on the rheometer and on physical tests (tensile, elongation, hardness, compression set, heat ageing) so that the cured article meets its specification and its service life.
Because TBBS is so widely used, it is also a benchmark: formulators compare alternatives (CZ, DCBS, thiazoles) against a TBBS system when they want a faster, slower, cheaper or more scorch-safe cure.
Frequently Asked Questions about Accelerator TBBS (NS)
What is Accelerator TBBS used for?
It is a sulfenamide (delayed-action) accelerator for sulfur vulcanisation, used above all in tyres and technical rubber goods.
What is the CAS number of TBBS?
95-31-8.
Is TBBS the same as NS?
Yes – TBBS, NS and NZ are names for the same accelerator, N-tert-butyl-2-benzothiazolesulfenamide.
Why is TBBS so widely used?
It gives an excellent balance of scorch safety and fast, efficient cure, which suits large tyre components.
Does it need sulfur and activators?
Yes – it works in a sulfur cure system with zinc oxide and stearic acid as activators.
How does TBBS differ from CZ?
Both are sulfenamide accelerators; TBBS is slightly more delayed and is the more common tyre accelerator, while CZ is a close alternative.
Is TBBS a skin sensitiser?
Yes – like most accelerators it is a potential skin sensitiser; avoid skin contact.
Related reading
- Accelerator TBBS (NS) in rubber vulcanization
- Rubber antioxidants and accelerators: selection guide
- Accelerator CZ (CBS): properties and applications
- Accelerator MBTS (DM): properties and applications
- Accelerator TBBS (NS, CAS 95-31-8) – product page
PolyBlueChem supplies Accelerator TBBS (NS, CAS 95-31-8) to a controlled specification, with per-batch COA and SDS, competitive pricing on bulk volumes and FOB/CIF delivery. Contact us with your application, tonnage and delivery port.