What Is Accelerator DCBS?
Accelerator DCBS, CAS 4979-32-2, chemically N,N-dicyclohexyl-2-benzothiazolesulfenamide, is a sulfenamide (delayed-action) rubber accelerator with the longest scorch safety of the common sulfenamides. Its two cyclohexyl groups make it strongly delayed, which is why it is chosen for thick sections and large articles where heat build-up during cure is slow and premature vulcanisation would be costly.
DCBS belongs to the same family as CZ (CBS) and TBBS (NS), but it sits at the “most delayed” end: it protects a compound through long mixing, shaping and storage times and then cures efficiently in the press. PolyBlueChem supplies Accelerator DCBS to a controlled specification with per-batch COA and SDS.
| CAS number | 4979-32-2 |
| Chemical name | N,N-Dicyclohexyl-2-benzothiazolesulfenamide |
| Synonyms | Accelerator DCBS; N,N-dicyclohexylbenzothiazole-2-sulfenamide; DCBS |
| Molecular formula | C19H26N2S2 |
| Molecular weight | 346.6 g/mol |
| Type | Sulfenamide accelerator (delayed action / long scorch) |
| Appearance | Cream-colored powder |
Chemistry and Structure
Accelerator DCBS is a sulfenamide: the benzothiazole nucleus (the thiazole found in MBT/MBTS) is linked through a sulfur atom to a nitrogen carrying two cyclohexyl groups (a dicyclohexylamine fragment).
- 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 two bulky cyclohexyl groups make DCBS much more strongly delayed than CZ or TBBS, giving the longest scorch safety.
Because it derives from a secondary amine (dicyclohexylamine), DCBS carries a higher nitrosamine consideration than the primary-amine sulfenamides (CZ, TBBS) – a factor to weigh where nitrosamine limits apply.
How It Works: Delayed-Action Vulcanisation
- Processing (cool) – DCBS is highly stable, so the compound can be mixed, extruded, calendered and stored for long periods without scorching.
- Heating to cure temperature – the sulfur-nitrogen bond breaks, releasing the benzothiazole fragment (MBT) and dicyclohexylamine.
- Cure – the released thiazole, with activators (zinc oxide, stearic acid) and sulfur, forms crosslinks.
- Completion – the crosslink density develops quickly once the compound is hot.
The very long delay is the whole point of DCBS: in a thick article, the outside reaches cure temperature long before the inside, so a compound that cured too fast would be scorched or uneven. DCBS keeps the whole article uncured until it is hot throughout, then cures it uniformly.
How Accelerator DCBS Is Produced
DCBS is made by reacting 2-mercaptobenzothiazole (MBT) with dicyclohexylamine in the presence of an oxidising agent, forming the sulfur-nitrogen bond of the sulfenamide:
- MBT and dicyclohexylamine are combined.
- An oxidant couples the thiazole thiol to the amine.
- The product is filtered, washed and dried, then milled to a powder.
Control targets the correct linkage and low residuals (MBT and amine), which affect scorch, cure rate and odour.
Specifications and Quality Control
Accelerator DCBS is supplied as a cream-colored powder to the following specification:
| Parameter | Specification |
|---|---|
| Appearance | Cream-colored powder |
| Initial melting point | 98 °C min |
| Heating loss | 0.40% max |
| Ash | 0.30% max |
| Sieve residue (150 µm) | 0.1% max |
| Parameter | What it controls |
|---|---|
| Initial melting point (98 °C min) | Purity and identity |
| Heating loss (0.40% max) | Moisture and volatiles |
| Ash (0.30% 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, strongly delayed | Longest scorch safety of common sulfenamides |
| Form | Powder | Easy to weigh and disperse |
| Delay | High | Safe processing of thick, slow-heating parts |
| Cure | Fast, efficient once hot | Uniform cure through thick sections |
| Activators | Needs ZnO + stearic acid (and sulfur) | Standard sulfur cure system |
Applications
| Industry / product | Function |
|---|---|
| Large tyres and solid tyres | Scorch safety for very thick components |
| Heavy belting and hoses | Uniform cure through thick sections |
| Thick mouldings | Prevention of scorch in slow-curing parts |
| High-temperature processing | Protection where a faster accelerator would scorch |
| General rubber | NR, SBR, BR and blends, activated with ZnO/stearic acid |
DCBS is the specialised choice for the hardest scorch problems: very thick parts, high processing temperatures, or compounds with highly active cure systems. Where those constraints are absent, a less delayed (and usually cheaper) sulfenamide such as TBBS or CZ is used.
Accelerator DCBS vs Other Accelerators
| Accelerator | CAS | Class | Delay | Typical role |
|---|---|---|---|---|
| CZ (CBS) | 95-33-0 | Sulfenamide | Medium | General tyres and technical goods |
| TBBS (NS) | 95-31-8 | Sulfenamide | Medium-high | Tyres; the most common sulfenamide |
| DCBS | 4979-32-2 | Sulfenamide | High (longest scorch) | Thick sections, long scorch safety |
| MBTS (DM) | 120-78-5 | Thiazole | Low-medium | General / secondary accelerator |
| PVI | 17796-82-6 | Pre-vulcanisation inhibitor | Retarder | Extends scorch of active systems |
Guidance: choose DCBS when scorch safety is the limiting problem (thick parts, high temperature, active cure); choose TBBS or CZ for the general case; combine with PVI as a retarder if even more scorch safety is needed. And note the nitrosamine consideration – DCBS is a secondary-amine sulfenamide, so where nitrosamine limits are strict a primary-amine sulfenamide (TBBS, CZ) or a different system may be preferred.
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 |
As with all sulfenamides, DCBS works in a sulfur cure system with zinc oxide and stearic acid activators, and the level is confirmed by rheometer cure curves and physical tests on the cured article.
Safety, Handling and Storage
- Skin sensitisation – like most accelerators, DCBS 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 – DCBS is a secondary-amine sulfenamide, so nitrosamine considerations are higher than for CZ/TBBS.
- 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 |
| Articles with nitrosamine limits | Consider a primary-amine sulfenamide (TBBS, CZ) or another system; 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 |
As a specialty rubber chemical, price tracks the MBT and dicyclohexylamine feedstock and the finishing quality. Buying on committed tonnage gives the best terms.
Scorch Safety: Why DCBS Exists
To understand DCBS, it helps to understand scorch. During processing, a compound must stay uncured through mixing, extrusion, calendering, cooling and storage. If it begins to crosslink (“scorches”), it becomes unusable and can damage equipment. The longer and hotter the processing, and the thicker the article, the greater the risk.
| Factor increasing scorch risk | How DCBS helps |
|---|---|
| Thick sections (slow heat transfer) | Keeps the whole article uncured until it is hot throughout |
| High processing temperature | Very stable at processing temperature |
| Active cure systems | Delays the onset of vulcanisation strongly |
| Long storage of stock | Resists premature cure during storage |
DCBS is therefore the accelerator of last resort for scorch-prone compounds: when TBBS or CZ would still scorch, DCBS keeps the compound safe and then cures it uniformly.
Quality: Reading a DCBS Certificate of Analysis
| Parameter | What it tells you |
|---|---|
| Initial melting point (98 °C min) | Purity and identity; residual MBT lowers it and raises activity |
| Heating loss (0.40% max) | Moisture/volatiles |
| Ash (0.30% max) | Inorganic residues |
| Sieve residue (150 µm, 0.1% max) | Dispersion; coarse material can cause cure defects |
Because DCBS is chosen specifically for scorch-critical compounds, batch-to-batch consistency in purity and dispersion is especially important: a more active than expected batch could scotch the very compound DCBS was chosen to protect.
DCBS in Thick Sections and Large Articles
DCBS comes into its own wherever heat takes a long time to reach the centre of the article.
| Article | Why DCBS fits |
|---|---|
| Large and solid tyres | Very thick rubber; a fast accelerator would scorch before the centre cured |
| Off-the-road tyres | Heavy sections and long cure cycles |
| Heavy conveyor belting | Thick, multi-ply construction |
| Large moulded parts | Slow, even heat penetration |
In a thick article the surface reaches cure temperature well before the core; if the compound cured as soon as it was hot, the outside would over-cure while the inside lagged. Because DCBS holds the compound uncured until it is hot throughout, the whole article cures evenly – the reason it is specified for the most demanding, slow-heating parts.
Combating Scorch: DCBS vs PVI
There are two ways to buy scorch safety: a more delayed accelerator, or a retarder (pre-vulcanisation inhibitor). They can also be combined.
| Approach | How it works | Trade-off |
|---|---|---|
| More delayed accelerator (DCBS) | Slower onset built into the accelerator itself | Cure may be slightly slower; higher nitrosamine consideration |
| Retarder (PVI) | Added to delay the cure of an existing system | Extra additive; delays cure, can be tuned |
| Both together | Maximum scorch safety where needed | Highest cost; used only for the hardest cases |
DCBS is the choice when scorch safety should come from the accelerator itself; PVI is the choice when a plant wants to keep its existing accelerator and simply add scorch protection. For the most scorch-prone compounds, DCBS plus a small amount of PVI can be used.
Nitrosamine and Accelerator Choice
| Accelerator | Amine source | Nitrosamine consideration |
|---|---|---|
| CZ (CBS) | Cyclohexylamine (primary) | Lower |
| TBBS (NS) | tert-Butylamine (primary) | Lower |
| DCBS | Dicyclohexylamine (secondary) | Higher |
For articles with strict nitrosamine limits, this is a real design factor: a plant may prefer a primary-amine sulfenamide even where DCBS would give the most scorch safety, and take the extra delay from a retarder instead. The choice is made with the whole cure system and checked against the applicable regulation.
Sulfenamide Accelerators: The Full Picture
The three common sulfenamides differ mainly in delay and amine source.
| Accelerator | Amine | Delay | Nitrosamine | Best for |
|---|---|---|---|---|
| CZ (CBS) | Cyclohexylamine | Medium | Lower | General tyres and goods |
| TBBS (NS) | tert-Butylamine | Medium-high | Lower | Tyres; most common |
| DCBS | Dicyclohexylamine | High | Higher | Thick sections; long scorch |
Read across: as delay increases (CZ -> TBBS -> DCBS), scorch safety improves but the nitrosamine consideration rises for DCBS. A formulator picks the minimum delay that solves the scorch problem, preferring a primary-amine sulfenamide where nitrosamine limits apply.
Frequently Asked Questions about Accelerator DCBS
What is Accelerator DCBS used for?
It is the most delayed common sulfenamide accelerator, used for thick sections and large articles where long scorch safety is essential.
What is the CAS number of DCBS?
4979-32-2.
How does DCBS differ from TBBS?
Both are sulfenamide accelerators; DCBS is more strongly delayed, giving longer scorch safety, and is derived from a secondary amine (higher nitrosamine consideration).
Does DCBS need sulfur and activators?
Yes – it works in a sulfur cure system with zinc oxide and stearic acid activators.
Is DCBS a skin sensitiser?
Yes – like most accelerators it is a potential skin sensitiser; avoid skin contact.
When should I use DCBS instead of TBBS?
When the compound is scorching or the article is very thick and slow-heating, so the longest practicable scorch safety is needed.
Related reading
- Accelerator DCBS in thick rubber sections
- Rubber antioxidants and accelerators: selection guide
- Accelerator TBBS (NS): properties and applications
- Santogard PVI (pre-vulcanization inhibitor): properties and applications
- Accelerator DCBS (CAS 4979-32-2) – product page
PolyBlueChem supplies Accelerator DCBS (CAS 4979-32-2) 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.