PILCURE CBS
  • Overview
  • Compounding Information
  • Application
Chemical Name N-cyclohexyl-2-benzothiazolesulfenamide (CBS)
Chemical Structure
CAS Reg. No. 95-33-0
Mol. Wt. 264
Product Specification
Parameter Limits Test Method
Product form Pellets  (4mm ) Powder (OT) -
Color Off white - cream Off white - cream -
Assay (titration ) ,% (min) 96.0 95.0 D 4936
Melting Point, initial, °C (min) 97.0 96.0 D 1519
Melting point , final , °C 99-105 98-105 D 1519
Heat Loss, % (max) 0.3 0.3 D 4571
Methanol Insolubles , % (max) 0.4 0.4 D 4934
Free Amine, % (max) 0.5 0.5 D 4936
Ash, % (max) 0.3 0.3 D 4574
Paraffinic Oil (<0.2% PCAH), % Not applicable 1.0-2.0 NOCIL 02-3-343
Residue on 150 µm sieve, % (max) Not applicable 0.05 D 5461
Residue on 63 µm sieve, % (max) Not applicable 0.5 D 5461
Typical Data
Specific gravity at  25°C 1.27 D 1817
Bulk density , kg/m3 450 - 490 410 - 450 NOCIL G-44
Bulk density (Comp), kg/m3 480 - 520 540 - 580 NOCIL G-44
Product Information
Solubility Soluble in acetone, benzene, naptha, carbon tetrachloride & ethyl acetate. Partially soluble in ethyl / methyl alcohol. Insoluble in water.
Classification Fast - Delayed action accelerator.
Discoloration & Staining Non staining. At higher dosages slight discoloration.
FDA Approval Status Regulated for use in articles in contact with food under FDA 21 CFR 177.2600, and BgVV XXI, Category 4.
Toxicity Data
(Please refer to the latest
 Toxicological information.)
Practically non-harmful. (Oral LD50rat over 5000 mg/kg). Not a skin or eye irritant.
Handling & Personal Protection Ensure good ventilation and avoid creating dusty atmosphere. In case of eye or skin contacts wash out with clean water for 5 to 10 minutes.
Storage Always store in a cool (below 30ºC) & dry place in single stack pallets away from direct sun light or any other heat source to avoid compaction. Avoid exposure to acids, acidic materials / atmosphere & high humidity.
Packaging
Paper-Fabric Bag 20 kg
FIBC 500 kg
Storage Life 12 months when stored as stated above.
Color code Dark Green colored strip.

Pilcure CBS is a delayed action sulphenamide accelerator for NR, SBR, BR, NBR and other sulphur / sulphur donor cured diene rubbers. Pilcure CBS is supplied in dust free pellet form which offers advantages such as easy handling, accurate weighing on all types of weighing systems. Pilcure CBS pellets disperse easily in rubber compounds. Pilcure CBS is also available in oil treated powder form.

Normal dosages of Zinc oxide and Stearic acid are necessary for all sulfenamide accelerators. However, excess dosage of Stearic acid does not offer additional advantage as in case of thiazoles. The normal dosage of Pilcure CBS is in the range of 0.5-1.0 phr for conventional cure systems, 1.5-2.0 phr for Semi-EV cures and 3.0-5.0 phr for low sulphur EV cures. Pilcure CBS is used at 1.0 phr dosage as an effective retarder for sulphur-less cures based on thiuram accelerators.

Pilcure CBS is very active above curing temperature of approx. 140°C and hence offers very good scorch safety during rubber compound processing operations (e.g. extrusion, calendaring, etc.) and improves the storage life of processed rubber stocks as compared to thiazole accelerators. Pilcure CBS/other sulphenamides are preferred when higher loadings of tread grade furnace blacks, (which are basic in nature and generate substantial heat during processing of NR/BR/SBR based stocks) are used. However; prolonged / repeated rub-ber stock processing above 120°C should be avoided, particularly in the absence of appropriate dosage of Pilgard PVI), to minimize the risk of 'scorch'.

Pilcure CBS / other sulphenamide accelerators are usually incorporated in the rubber compound at the end of mixing cycle when the temperature is above the melting point of the accelerator to ensure proper dispersion. However; generation of excessive heat is avoided to prevent decomposition of sulphenamide accelerators. In case, the sulphenamide accelerators are to be added at a later stage; addition in the form of sulphenamide-rubber master batch (prepared above the melting point of sulphenamide accelerator) is recommended.

When used alone; Pilcure CBS exhibits faster cure rate (above 140°C), higher state of cure and moderate plateau effect as compared to thiazole accelerators. Vulcanizates based on Pilcure CBS / other sulphenamide accelerators have a typical 'amine' odor and exhibit higher stress-strain properties along with better resilience and Flex-Fatigue resistance as compared to thiazoles.

Pilcure CBS / other sulphenamide accelerators can be further activated by using small proportions of thiurams or dithiocarbamate accelerators with a compromise on processing safety, reversion resistance and ageing resistance. Use of DPG / DOTG is generally avoided as booster accelerators due to their tendency of imparting higher heat build-up properties to the rubber vulcanizates as compared to thiuram boosted cure systems.

Pilgard PVI is a very effective pre vulcanization (scorch) inhibitor for sulphenamide and activated sulphenamide cure systems without any compromise on the rate of cure. The improvement in scorch safety is directly proportional to the dosage of Pilgard PVI and hence the minimum dosage required for obtaining desired scorch safety can easily be determined. Use of excess dosage of Pilgard PVI is avoided as the same may cause undesired delay for the on-set of cure besides affecting the state of cure to some extent.

Pilcure CBS / other sulphenamide accelerators decompose rapidly in the presence of hot steam and hence preferred for the manufacture of open steam cured rubber products requiring faster on-set of cure for better shape retention. However; due to delayed on-set of cure in the absence of moisture, sulphenamide accelerators are not preferred for hot air cured products.

Pilcure CBS itself is non-staining. However, when higher dosages are used, slight yellowing effect may be observed on white / light colored rubber products on exposure to sunlight.

Pilcure CBS alone or in combination with small quantities of booster accelerator is widely Used in NR, SBR, NR/BR, SBR blend, NBR and other synthetic rubber based compounds used for the manufacture of auto tyres, cycle tyre/tubes, beltings (conveyor, transmission, V and fan belts), tyre retreading and repair materials, footwear, hoses, cables, injection molded products and various compression / transfer molded as well as extruded rubber goods.

TYPICAL DOSAGES OF PILCURE CBS
Product Rubber Accelerator /  Sulphur, phr
CBS MBTS TMTD TMTM PVI (CTP) S
Auto Tyres
Treads   Casing
NR
NR-BR
SBR-BR
NR-SBR
NR
NR-SBR
NR-BR
0.5-0.7
1.2
1.4
0.8
0.7-0.8
1.0
1.0-1.2
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
0-0.25
0-0.25
0-0.10
0-0.20
0-0.20
0-0.10
0.10-0.15
0.10-0.15
0.10-0.20
0.10-0.15
0.15-0.20
0.15-0.20
0.15-0.20
2.4*
1.5*
1.7*
2.0*
2.4*
2.2*
2.2*
Cycle Tyre
Treads
NR-RR
NR-SR
1.0
1.2
-
-
0.1-0.15
0.15-0.2
  -
-
0.1-0.2
0.1-0.2
2.4
2.0
Conveyor Belt Cover
General Purpose Heat Resistant
NR
NR-SBR
NR-SBR
0.7
1.2
1.5
0.2
-
-
  -
-
0.5
  -
-
-
0.15
0.15
0.25
2.4
1.75
0.50
Transmission Belts NR 0.8 - 0.1 - 0.15 3.0
V Belts
Base
Cushion
Friction
NR
NR
NR
0.6
0.75
0.7
0.2
0.1
-
-
-
-
-
-
-
0.2
0.15
0.10
3.0
2.4
2.75
Retreads (Truck Tyres)
Hot Cure Pre Cured
Cushion- Hot Cure
NR
NR-BR
NR-BR
NR
0.6
0.9
0.9
0.7
-
-
0.3
-
-
-
-
-
-
-
-
-
0.20
0.15
0.10
0.15
2.4*
1.7*
1.6
2.5*
Footwear
DV Soles
Molded Soles & Heels
NR-SBR
NR-SBR
1.0
1.0
0.3
-
0.1
0.2-0.3
-
-
0.10
0.10
2.0
2.2
Hoses
Tube   Cover
NR
NR-SR
NBR
NBR
NR
0.8-1.0
1.0-1.2
1.5
0.7
0.8
-
-
-
-
-
0.10
0.20
0.50
0.10
0.10
-
-
-
-
-
0.10
0.10
0.10
0.15
0.15
2.2
1.5
0.7
1.8
2.2
Cables NR 1.0 - 0.20 ZDC-0.2 0.15 1.2
Injection Moldings NR 0.6 - - - 0.30 2.4
Molded & Extruded Goods NR
NR-SeEV
NR-EV
SBR
SBR-SeEV
SBR-EV
NBR
NBR-SeEV
NBR-EV
0.7
1.5
3.0
1.0
2.0 1.5
1.0
1.0 2.0
-
-
-
-
- -
-
- -
0.15
0.50
-
0.20
0.50 3.0
0.15
1.0 3.0
-
-
-
-
- -
-
- -
0.10
0.10
-
0.10
0.10 0.20
0.10
- -
2.2
1.4
0.5
2.2
0.75 0.30
1.50
1.0 0.3
Note: * Insoluble Sulphur (100% active content basis)