N-Tert-Butyl-2-Benzothiazole Sulfenamide
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HS Code |
336634 |
| Chemical Formula | C11H14N2S2 |
| Molecular Weight | 238.37 g/mol |
| Appearance | white to off - white powder |
| Odor | slight characteristic odor |
| Melting Point | 104 - 110 °C |
| Solubility In Water | practically insoluble |
| Solubility In Organic Solvents | soluble in acetone, benzene, chloroform |
| Density | 1.26 - 1.32 g/cm³ |
| Flash Point | 185 °C |
| Stability | stable under normal conditions |
| Cas Number | 95 - 33 - 0 |
As an accredited N-Tert-Butyl-2-Benzothiazole Sulfenamide factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 25 - kg bags of N - Tert - Butyl - 2 - Benzothiazole Sulfenamide, well - sealed for chemical safety. |
| Shipping | N - Tert - Butyl - 2 - Benzothiazole Sulfenamide is shipped in well - sealed containers. Precautions are taken to prevent moisture and contamination. It's transported following strict chemical shipping regulations to ensure safety during transit. |
| Storage | N - Tert - Butyl - 2 - Benzothiazole Sulfenamide should be stored in a cool, dry, well - ventilated area. Keep it away from heat sources, ignition sources, and direct sunlight. Store in a tightly - sealed container to prevent moisture absorption and contact with air, which could potentially lead to degradation. Avoid storing near reactive chemicals. |
How Production-Scale Twin-Screw Discharge Temperatures Define the Scorch Safety Window in Passenger Radial Tread CompoundsIn passenger car radial tire tread formulations utilizing emulsion-polymerized SBR (E-SBR) with high styrene content and N339 carbon black at loadings of 75–85 phr, the incorporation of N-Tert-Butyl-2-Benzothiazole Sulfenamide (TBBS) at 1.2–1.8 phr provides a commercially critical delay in the onset of vulcanization during the final mixing stages and subsequent extrusion. The primary processing hazard occurs when internal mixer dump temperatures, measured via embedded thermocouple probes, consistently exceed 150°C on a production-scale intermeshing twin-screw extruder with an L/D ratio of 48:1 feeding a roller-head die. At this thermal threshold, the sulfenamide undergoes homolytic scission of the S–N bond, releasing the 2-mercaptobenzothiazole (MBT) fragment and the tert-butyl amine moiety prematurely. The free MBT immediately forms a zinc-accelerator complex with zinc oxide present at 3.0–5.0 phr, initiating crosslink formation before the compound reaches the calendar or extrusion die. Plant-floor data indicate that a sustained dump temperature excursion of merely +7°C above the 155°C ceiling reduces Mooney scorch time (MS t5 at 135°C per ASTM D1646-19a) from a target of 18–22 minutes to 9–11 minutes, rendering the batch unsuitable for subsequent tire-building operations that require open-mill warm-up and component splicing. The curing isotherm at 160°C, characterized by a moving-die rheometer (MDR) per ASTM D5289-21, must deliver a t90 within 6–8 minutes to maintain press cycle economics while ensuring the t10 never falls below 2.5 minutes — a boundary that defines the limit of safe flow into the mold’s tread lug cavities. Failure to maintain this t10 threshold manifests as visible scorch particles in the extruded tread profile, detected via in-line laser profilometry as surface defects exceeding 0.3 mm in height, which translate into cured tire cross-sectional voids identified by shearography inspection. The finished tread compound, validated against ISO 23233:2016 for abrasion resistance using a LAT100 tester, requires a DIN abrasion loss below 120 mm³ under a 10 N contact load, a value directly influenced by the preservation of TBBS-derived crosslink homogeneity during the scorch-safe processing window.When Zinc Carboxylate Solubility Governs Steel Cord Adhesion in Heavy-Duty Conveyor Belt Friction CompoundsSteel cord conveyor belts operating in open-pit mining applications with rated tensile strengths exceeding ST 4500 N/mm depend on a cobalt-boron-modified NR/SBR skim compound where TBBS is the sole primary accelerator at 0.9–1.3 phr. The formulation’s distinguishing challenge arises from the competitive reaction between the resorcinol-formaldehyde-latex (RFL) dip curative migration and the formation of the CuxS interphase layer at the brass-plated cord surface. TBBS exhibits a measurable induction period during which soluble zinc carboxylate intermediates, generated from the reaction of zinc oxide with stearic acid at 1.0 phr, must diffuse across the vulcanization front boundary to catalyze the conversion of the cobalt naphthenate adhesion promoter into a coherent interfacial sulfide film. When the compound is calendered onto brass-coated cords at a line speed of 15–18 m/min and an idler roll temperature stabilized at 90 ± 3°C, premature crosslinking within the first 0.5 mm of the rubber matrix adjacent to the cord strand impedes this ionic mobility. Experimental peel adhesion results, tested per ISO 7623:2022 under both static and dynamic conditions following hot salt-water aging at 70°C for 168 hours, show a drop from an initial adhesion strength of 22–25 N/mm to below 12 N/mm when the TBBS dosage shifts upward by only 0.2 phr — a narrow operating window that leaves no margin for weigh-belt feeder error. The vulcanization curve measured at 148°C via an oscillating disc rheometer (ODR) at an arc of 1° must produce a cure rate index (CRI = 100/(t90 − t10)) between 6.0 and 7.5 min⁻¹; rates exceeding this range correlate with a brittle interfacial zone that fractures cohesively within the rubber bulk rather than exhibiting the desired mixed cohesive-adhesive failure mode. The final cured splice joint, microwave preheated to 90°C and pressed at 4.0 MPa for 45 minutes, must demonstrate less than 3% void content when examined by ultrasonic phased-array scanning per ISO 19285:2017.How Do TBBS/TMTD Synergistic Ratios Suppress Anaerobic Reversion in Large Natural Rubber Bridge Bearing Blocks?Seismic isolation bridge bearings cast from high-cis natural rubber (Mooney viscosity ML(1+4) 100°C of 75–85 MU) with dimensions exceeding 600 mm × 600 mm × 300 mm are cured in steam autoclaves at 140°C under 5.5 MPa external pressure for durations extending to 480 minutes. The time-temperature profile at the geometric center of the block, recorded via embedded thermocouple probes, lags the platen temperature by 60–80 minutes, exposing the innermost regions to prolonged thermal dwell while the exterior layers have already reached full cure. Unmodified TBBS-only curing systems at 2.0 phr with sulfur at 1.8–2.2 phr exhibit a marked modulus reversion plateau after 180 minutes at temperature, with the torque (MH) dropping 6–8% from the maximum plateau value on the rheometer curve — a signal of net polysulfidic crosslink degradation outpacing new crosslink formation. Co-addition of tetramethylthiuram disulfide (TMTD) at a controlled mass ratio of TBBS:TMTD = 4.0:1.0 to 4.5:1.0, with total accelerator loading kept within 2.0–2.4 phr, alters the cure profile to a marching curve that mitigates reversion by supplying MBT fragments continuously via TBBS thermal decomposition while the TMTD maintains a reserve of active sulfur-donating species. The crosslink density, quantified by equilibrium swelling in toluene using the Flory-Rehner equation per ISO 1817:2022, must remain above 4.8 × 10⁻⁵ mol/cm³ across the entire cross-section, verified by cutting a sacrificial block and sampling 25 mm cubes at 50 mm grid intervals. Mechanical testing per ISO 37:2017 on dumbbell specimens cut perpendicular to the lamination plane must yield elongation at break values in excess of 550% with no individual specimen falling below 500%; any single outlier below this threshold triggers a non-conformity report under ISO 22762-3:2020 for elastomeric seismic isolators.The introduction of TBBS into high-EDPM-vinyl-acetate-content compounds for continuous microwave vulcanization of automotive weatherstrip profiles requires detailed scrutiny of the activator adsorption envelope.Sponge-grade EPDM with an ethylene:propylene ratio of 55:45 and ethylidene norbornene (ENB) content of 7.5–8.5 wt%, blended with 15 phr of paraffinic process oil and fumed silica as a thixotropic modifier, is extruded through a pin-type cold-feed extruder with a barrel temperature profile ranging from 60°C to 75°C into a microwave hot-air tunnel. The TBBS, dispersed at 1.5 phr in a 75% active predispersed polymer-bound pastille form (to minimize airborne dust per REACH Annex XVII entry 45), is activated by a 2.45 GHz multi-mode cavity operating at 6–8 kW output across a 10 m resonant chamber. The critical rate-limiting step is not the primary accelerator chemistry but the desorption kinetics of the tert-butylamine cleavage product from the zinc oxide surface within the EPDM matrix, which exhibits lower zinc stearate solubility than natural rubber. Desorption lag leads to a surface tack deficiency of 15–20% (measured via a P.I.A. probe tack tester) on the sponge exterior skin when line speed is increased beyond 25 m/min — a defect that prevents adequate adhesion of the pressure-sensitive acrylic tape applied in the downstream flocking station. The cured density must achieve a specific gravity of 0.58–0.65 g/cm³ with a closed-cell structure exceeding 85% of total voids, verified by image analysis of a microtomed section under ×50 magnification, per the internal porosity classification defined in ASTM C1670-20 for cellular rubber.Pre-Sulfenamide Dispersion Requirements for Prevulcanized Natural Latex Dipped Goods Under Reduced Nitrosamine ConstraintsCentrifuged high-ammonia natural rubber latex with a dry rubber content adjusted to 45.0 ± 0.5% is compounded with an aqueous dispersion of TBBS prepared by ball-milling the dry powder with casein or polyvinyl alcohol as a protective colloid for 24–36 hours in a ceramic-lined mill. The median particle size of the resultant dispersion, measured by laser diffraction (Malvern Mastersizer), must be reduced to D50 < 5 µm to ensure uniform incorporation and avoid sedimentation during the lag period between compounding and dipping. Prevulcanization is conducted in a jacketed stainless-steel vessel at 60°C under constant low-shear agitation, with the TBBS added at 1.0–1.3 phr (dry weight basis) alongside zinc diethyldithiocarbamate (ZDEC) as a secondary accelerator at 0.3 phr. This binary accelerator system is specifically formulated to comply with the nitrosatable amine limits under EU Directive 93/11/EEC, as TBBS does not liberate secondary amines that form stable N-nitrosamines, unlike thiuram- and dithiocarbamate-dominant systems. The prevulcanization endpoint is monitored by chloroform number testing until a swollen gel state of 3–4 (moderately tacky, swollen but not dispersing) is reached, corresponding to a crosslink density sufficient for a film tensile strength of 22–25 MPa (tested per ASTM D3492-16 for thin-walled dipped goods) yet preserving the wet-gel green strength necessary for automated mold stripping without tearing. The post-cure leaching protocol cycles the finished gloves through hot water at 70°C for 60 minutes, extracting residual MBT to levels below the detection threshold of 10 µg/g as specified in the ASTM D6355-07 extraction test for Type IV allergy prevention.The recapping of off-the-road (OTR) tires with a service diameter exceeding 3.0 m introduces a low-temperature long-duration cure regime where the activity decay of TBBS in the cushion gum compound becomes the dominant variability source. The repair compound, a carbon-black-loaded NR/BR blend with 60 phr N220 carbon black, is formulated with TBBS at 0.8–1.0 phr and tertiary butyl peroxybenzoate at a controlled low addition to prevent the shift to a predominantly scorchy acidic environment during the autoclave cycle. Curing is carried out in a segmented mold within a large-capacity autoclave using saturated steam at 0.55 MPa and a corresponding temperature of 155°C for a total cycle time of 300–360 minutes. The low thermal diffusivity of the massive tire casing, combined with the insulating effect of the pre-existing cured tread base, creates a temperature ramp rate at the bonding interface that rarely exceeds 0.5°C/min through the critical activation zone of 110°C–135°C. Under this shallow thermal gradient, TBBS exhibits partial premature decomposition to MBT if the stock was compounded more than 72 hours prior and stored under ambient conditions of 30°C, 75% relative humidity — conditions commonly encountered in tropical mining site retread facilities. The bond integrity between the new tread rubber and the buffed casing, evaluated by a peel test at a 90° angle and a crosshead speed of 50 mm/min per ASTM D413-98(2022), must achieve a peel strength of 10 kN/m with mandatory rubber tear pattern across 100% of the peeled interface; any adhesive failure strip exceeding 5 mm in width is grounds for rejection of the entire retread batch under the guidelines of ISO 4224:2020 for assessing retreaded commercial vehicle tires. TBBS-Modified Chlorobutyl Stopper Formulations and Extractables Compliance For Aqueous Parenteral PackagingBromobutyl elastomer compounded for Type I pharmaceutical closures, as specified in USP
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| Property | Specification | Test Method |
|---|---|---|
| Assay (TBBS) | ≥97.0 % | HPLC, UV 280 nm |
| Free tert-butylamine | ≤0.50 % | Acid-base titration |
| Moisture content | ≤0.30 % | Karl Fischer (ISO 760) |
| Melting point | 104–108 °C | ASTM D1519 |
| Ash content | ≤0.30 % | ASTM D4570 |
| Sieve residue (150 µm) | ≤0.10 % | ASTM D4572 |
Moisture uptake during ocean freight or storage in unsealed containers above 65% relative humidity accelerates hydrolysis of the sulfenamide bond, releasing free tert-butylamine. A laboratory study simulating tropical warehouse conditions (30°C, 75% RH) showed a 0.15% increase in free amine content after 30 days, correlating with a 12% reduction in Mooney scorch t5. Processors receiving material with moisture exceeding 0.50% are advised to pre-dry at 50°C in a vacuum tray dryer for 4–6 hours before compounding.
In conventional high-sulfur (2.5 phr S) NR tire body ply compounds, replacing 0.3 phr diphenylguanidine (DPG) with 0.5 phr TBBS while keeping CBS at 0.8 phr yields a compound with reduced blooming and improved aged adhesion to brass-coated steel cord, as measured by pull-out force after humid aging (ISO 5603). However, this combination tends to produce a marching cure modulus in the absence of adequate sulfur reversion protection, leading to a 300% modulus increase of up to 15% over an additional 10 min at 160°C. Producers must confirm adequate reversion resistance by checking t90 plateau length on the MDR.
In a continuous vulcanization line for EPDM-based automotive weatherstrips, the use of TBBS at 1.5 phr with ZDBC at 0.8 phr delivers a Mooney scorch t5 of 28 min at 121°C, enabling safe processing through a 90-mm cold-feed extruder (L/D 16:1) with a screw temperature of 70°C. When the same accelerator system is used in a salt-bath continuous cure unit (LCM) operating at 210°C, the undercure risk demands a higher TBBS loading (2.2 phr) to achieve adequate hot tensile strength, which, in turn, reduces scorch safety to 21 min. Published data for this specific configuration is limited, and processors often validate t90 via online rheometer trials. Dense experimental profiles from a standard NR/BR truck tire tread base compound (NR 70/BR 30, N330 50 phr, ZnO 5, stearic acid 2, sulfur 2.0 phr, accelerator 1.0 phr) highlight the scorch-delay advantage and cure-rate trade-off of TBBS relative to other sulfenamides. Cure rheometry was conducted at 160°C per ASTM D5289; Mooney scorch at 121°C per ASTM D1646.| Accelerator | Mooney Scorch t5 (min) | MDR ts2 (min) | MDR t90 (min) | MH‑ML (dNm) | Reversion at 30 min (%) |
|---|---|---|---|---|---|
| CBS | 24.5 | 3.8 | 6.2 | 11.2 | 18 |
| TBBS | 32.1 | 5.1 | 8.1 | 12.4 | 12 |
| MBS | 28.7 | 4.4 | 7.0 | 11.8 | 16 |
| DCBS | 38.0 | 6.3 | 9.5 | 11.9 | 10 |
TBBS scorch t5 is 31% longer than CBS, permitting higher dump temperatures from an intermeshing internal mixer. In highly reinforcing silica compounds (BET 160 m²/g) containing bis(triethoxysilylpropyl) tetrasulfide (TESPT) at 8 phr, the amine released from silane-sulfenamide interaction partially neutralizes acidic silanol groups, accelerating the cure. A 270 L Pomini F270 mixer processing TBBS with silica/TESPT exhibited a Mooney scorch t5 of 18.5 min when the dump temperature exceeded 155°C, compared to 27 min at a dump temperature of 140°C. This narrowing of the processing window necessitates precise control of mixing energy input (specific energy ≤0.25 kWh/kg) and careful accelerator addition on a two-roll mill at a batch temperature below 90°C. In a high-speed pin-barrel extruder (cold-feed, 120 mm diameter, L/D 16:1) profiling tread compounds, TBBS at 1.2 phr combined with 0.2 phr TMTM generates a head pressure of 8–12 MPa and a scorch safety margin of 22 min at 110°C, sufficient for uninterrupted running for 6 hours. However, excessive shear in the die land can raise the compound temperature above 125°C, lowering Mooney scorch t5 to 12 min and risking scorch near the die exit. Processors install thermocouple-controlled cooling mandrels and maintain die temperature at 95°C to mitigate this risk.
TBBS releases N-nitrosodiisobutylamine during vulcanization and end-product service. Under EU Directive 2005/69/EC, rubber articles intended for prolonged skin contact or food contact must restrict N-nitrosamine migration. For tire manufacturing, German TRGS 552 mandates a workplace airborne nitrosamine concentration below 1 µg/m³. This drives compounders to employ TBBS in conjunction with nitrosamine scavengers such as 20% N-phenyl-N’-(1,3-dimethylbutyl)-p-phenylenediamine on a carrier. Further, TBBS supplied as an 80% pre-dispersion in a polymeric binder reduces dusting and inhalation exposure. Industrial hygiene monitoring using NIOSH 2522 confirms compliance with the occupational exposure limit.
In a BR/NR bus tire tread mixed in a 370 L intermeshing mixer, thermal decomposition of TBBS commences above 120°C, generating mercaptobenzothiazole (MBT) and isobutylene, which can cause porosity in thick sections. High-structure carbon black (N234, DBP absorption 120 mL/100g) adsorbs up to 5 wt% of the accelerator from the rubber matrix, effectively reducing the available curative. This competitive adsorption increases t90 by up to 30% when the black is added in the first mixing stage without a masterbatch step. In one production case, a single-stage mix for a solid tyre compound caused t90 to drift from 8.2 min to 11.0 min, requiring an offline press cycle adjustment of 2.5 min. A two-stage mixing protocol with accelerator addition in the second stage at a batch temperature below 100°C is mandatory to maintain predictable vulcanization kinetics. Furthermore, in tire curing bladder applications where resorcinol-formaldehyde/silica adhesion systems are employed, the acidic nature of the silica can protonate tert-butylamine, retarding sulfenamide cleavage and requiring an additional 10–15% TBBS dosage to achieve target modulus. Processors must verify Mooney scorch and MDR trace for each new formulation directly on factory-scale equipment.
