2-Benzothiazolesulfenamide, N-Tert-Butyl-
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HS Code |
761326 |
| Chemical Formula | C11H14N2S2 |
| Molecular Weight | 238.37 g/mol |
| Appearance | white to light yellow powder |
| Odor | characteristic odor |
| Melting Point | 105 - 110 °C |
| Solubility In Water | insoluble |
| Solubility In Organic Solvents | soluble in common organic solvents like benzene, toluene |
| Flash Point | 171 °C |
| Density | 1.26 - 1.32 g/cm³ |
| Stability | stable under normal conditions |
| Cas Number | 95 - 33 - 0 |
As an accredited 2-Benzothiazolesulfenamide, N-Tert-Butyl- 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 - Benzothiazolesulfenamide for chemical packaging. |
| Shipping | 2-Benzothiazolesulfenamide, N - Tert - Butyl - is typically shipped in sealed, corrosion - resistant containers. Special care is taken to prevent exposure to moisture and heat during transit due to its chemical properties. |
| Storage | 2 - Benzothiazolesulfenamide, N - Tert - Butyl - should be stored in a cool, dry, well - ventilated area. Keep it away from heat sources, open flames, and oxidizing agents. Store in a tightly closed container to prevent moisture absorption and contamination. Avoid storing near incompatible substances to ensure safety and maintain chemical integrity. |
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In the production of silica-filled passenger radial tread compounds, the incorporation of N-t-butyl-2-benzothiazolesulfenamide (TBBS) at 1.0–2.0 phr alongside sulfur (1.5–2.2 phr) and a secondary accelerator such as diphenylguanidine (DPG) at 1.5–2.5 phr establishes a cure system characterized by a delayed scorch time exceeding 8 minutes at 135°C under ASTM D2084-19a rotorless curemeter conditions. The compound passes through a tangential internal mixer with intermeshing rotor geometry (typical fill factor 0.70–0.75), undergoing a two-stage mixing sequence where TBBS is added in the second, non-productive stage at temperatures strictly maintained below 110°C to prevent premature thermal decomposition of the sulfenamide bond. Single-screw extruder feeding of the calender train for tread profile shaping operates at a barrel temperature profile of 70/80/90°C for the feed/compression/metering zones, with a screw L/D ratio of 6:1 to 10:1 on hot-feed extruders. The extrudate is then calendered onto the carcass plies before being applied to the green tire building drum. Industry compliance is driven by the End-of-Life Vehicle Directive (2000/53/EC) and REACH Annex XVII entry 50 regarding polycyclic aromatic hydrocarbons, as well as the tire label regulation (EU 2020/740) that directly governs rolling resistance coefficients. The terminal cured product takes the form of a 205/55 R16 91V summer touring tire tread, where the TBBS-sulfur network contributes to a tensile strength of ≥18 MPa and elongation at break of ≥450% post-aging 7 days at 70°C per ISO 37:2017 type 2 dumbbell testing. In heavy-duty radial truck tire belt skim compounds where brass-coated steel cord adhesion is the primary functional requirement, TBBS forms part of a dual accelerator system with a sulfenamide-to-thiuram ratio near 4:1 by weight. The specific role of TBBS in this configuration is to sustain the formation of the interfacial CuxS layer at the vulcanization temperature plateau of 150–160°C. A typical composition combines natural rubber (STR 20 grade) at 70 phr with high-cis polybutadiene (Nd-BR) at 30 phr, cobalt naphthenate as adhesion promoter (0.8–1.5 phr cobalt content), TBBS at 0.6–1.0 phr, and insoluble sulfur (IS-HD OT20) at 3.5–5.0 phr. Compound mixing is executed in an intermeshing internal mixer (e.g., PES3 or GK 320E) with a ram pressure of 0.6 MPa; carbon black (N326) dispersion is verified by optical microscopy per ISO 11345:2006 method C to maintain a dispersion rating above 8. The compound is then processed on a four-roll inverted-L calender where adhesion-critical compound is applied to brass-coated steel cord wires at 70–75°C roll temperature, with a cord tension control accuracy of ±2 N per cord. Wire pull-out adhesion following cure is measured per ASTM D2229-19 with a required minimum pull-out force of 400 N for a wire embedment length of 12.5 mm. Cured adhesion retention after steam aging ( 24 h, 95°C, 100% relative humidity) is typically specified above 75% of original values to pass the internal quality standards of major OEM tire manufacturers. The resulting skim stock is formed into the breaker belts and ply layers of a 315/80 R22.5 on/off-road truck tire carcass. In curing bladder press curing for large off-the-road tires with bead diameters exceeding 35 inches, the compound is injected into segmented mold cavities at 95–105 MPa injection pressure through a curing press with a clamp force capacity of 9,000 metric tons. Published data for this specific configuration is limited, yet process records from curing press manufacturers indicate that TBBS is pre-dispersed in a polymeric binder at a 75% active concentration and dosed at 0.8–1.2 phr total to manage the cure reversion resistance in natural rubber compounds containing 50–55 phr carbon black N220. Cure curves generated by moving die rheometer (MDR) at 150°C according to ASTM D5289-19a show a cure rate index (tc90 minus ts2) of 4.2–5.8 minutes. The relevance of TBBS in this application lies in its ability to maintain a plateau modulus within ±0.2 dNm of Mh for up to 30 minutes post-cure, critical in thick cross-sections where heat transfer lags create internal temperature gradients exceeding 20°C from the mold wall to the core. The final products are earthmover tires, size 40.00 R57, used on rigid dump trucks in open-pit mining operations. What Governs Fatigue Life in Automotive Suspension Bushings Subjected to Multiaxial Loading?For natural-rubber-based suspension bushings produced through transfer molding with a clamping tonnage of 200–300 tons and a platen temperature of 165°C, the TBBS loading is narrowed to 0.5–0.8 phr. This low concentration prevents over-cure and modulus drift during the cushion-shape bellow compression cycles. The compound is pre-formed into a cylindrical preform of 45–55 durometer hardness (Shore A), and the injection cylinder temperature is held at 80°C. The specific industry compliance standard is the SAE J200 standard classification system for rubber materials, where typical bushing compounds are coded as AA 606 or AA 706 depending on the hot-air aging requirement at 100°C for 70 hours. The dynamic endurance test is performed on an MTS servo-hydraulic test system at 5 Hz frequency, with a control waveform of ±15° torsional angle and ±3 mm radial deflection, run for 500,000 cycles. Crack initiation length is limited to 0.5 mm per OEM internal specification. The TBBS cure system is chosen over a conventional CBS system to achieve a lower residual free amine content in the cured matrix, which reduces the rate of stress relaxation by 12–18% at 70°C. The terminal product is a hydraulic-bushed lower control arm bushing for a mid-size SUV platform.
In continuous vulcanization of extruded closed-cell EPDM-based sponge profiles for automotive door seals, TBBS acts as a secondary accelerator in a complex ultra-fast curing package where the primary accelerator is zinc dibutyldithiocarbamate (ZDBC) and the blowing agent is azodicarbonamide (ADCA) at 3.5–5.0 phr. The TBBS is introduced at a restrained dosage of 0.2–0.4 phr. In a salt-bath continuous vulcanization line operating at 230°C with a residence time of 3–5 minutes, any excess TBBS above 0.5 phr causes pre-cure inside the die head where the metal temperature can be as high as 125°C due to shear heating in the L/D 16:1 cross-head extruder. The formulation must meet the requirements of ISO 1795:2017 for rubber bale sampling and preparation, but far more significantly, the volatile organic compound (VOC) and fogging characteristics are regulated under VDA 278 and DIN 75201-B, respectively. A typical sponge lip seal extrusion runs at a line speed of 15–25 m/min, with a final cell density of 15–25 cells/mm² as verified by SEM cross-section. DIN 22102 Abrasion-Resistant Grade Conveyor Belting and Encapsulated Cable CompoundsCover compounds for abrasive service conveyor belts are continuously produced on a multi-head drum curing press or a Rotocure continuous vulcanization unit. The process requirement for TBBS here is not merely scorch delay but the preservation of the molecular weight distribution during a 40-minute plateau cure at 153°C. A typical formulation for a DIN 22102 - W grade abrasion-resistant cover uses natural rubber (40 phr) blended with emulsion styrene-butadiene rubber (E-SBR 1502) at 60 phr, carbon black N234 at 50–55 phr, aromatic process oil at 5 phr, TBBS at 1.3–1.6 phr, and sulfur at 1.8–2.1 phr. The green compound is calendered into a 6 mm thick sheet on a three-roll calender and then fed onto a steel cord or EP fabric carcass. In-process testing uses a Mooney viscometer (ASTM D1646-19a) at 100°C targeting a Mooney viscosity ML(1+4) of 60–75 MU. The cured cover is tested for abrasion loss per DIN 53516 at ≤90 mm³. The belt is finally spliced into a continuous loop of 1,200 m length for a coal-handling terminal operating at a load capacity of 4,000 t/h. In the two-stage compression molding of rubber-bonded metal anti-vibration mounts for industrial power-generation units, TBBS at 1.0–1.3 phr is added in a masterbatch that is milled on an open two-roll mill with roller speed friction ratio set at 1:1.15 and narrowed to a nip gap of 2.5 mm. The process produces a sheet-form preform that is transferred to a multi-cavity compression mold. During molding at 150°C and 20 MPa pressure, the initial thermal expansion of the compound and the delayed onset of crosslinking, as governed by the sulfenamide-to-thiol transformation kinetics, provides a critical 45–60 second window for the compound to fully flow and bond to the phosphate-treated steel insert surface. Bond testing follows ASTM D429-14 Method B, requiring a 95% rubber retention failure pattern on the metal surface. The finishers operate within the quality framework of ISO 9001:2015 supplemented by the environmental testing procedures of ISO 14001:2015 for waste disposal of scrap rubber containing residual sulfenamide. The terminal product is a massive 800 kg marine engine mount used for stationary generator sets on offshore platforms, designed for a static load capacity of 45 kN and a dynamic stiffness of 6,500 N/mm at 15 Hz.
For multi-station rotary injection molding of closed-cell microcellular athletic footwear midsoles, the TBBS is integrated into an EVA/NR/IR ternary blend compound. The blend typically contains ethylene-vinyl acetate copolymer (vinyl acetate content 26–28%) at 60 phr, standard natural rubber at 25 phr, and synthetic polyisoprene at 15 phr. TBBS is dosed at 0.3–0.5 phr as part of a combined curing and blowing activation system where dicumyl peroxide (DCP) at 0.6 phr acts as the primary crosslinking agent; TBBS serves here as a co-agent that modifies the crosslink density profile in the rubber domains exclusively. The 24-station rotary injection machine operates with an injection temperature of 90°C and mold stations heated to 175°C, with a station dwell time of 6 minutes. The molded pre-foam slab then undergoes a secondary free expansion oven process at 80°C for 30 minutes to achieve final part dimensions. The finished midsole must pass the SATRA TM173 and TM174 test methods for flexing endurance and abrasion, as well as the restricted substance list of the Apparel and Footwear International RSL Management Group (AFIRM RSL, version 2024). The end product is a size US 10 running shoe midsole with a density of 0.22–0.25 g/cm³ and a rebound resilience of ≥55% as measured by a falling ball rebound tester per ISO 4662:2017. |
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The compound, systematically named N-tert-Butyl-2-benzothiazolesulfenamide (CAS 95-31-8), is manufactured as a light yellow to tan granular solid. Typical industrial-grade powder exhibits a melting range of 104–112 °C when determined by differential scanning calorimetry at 10 K/min under nitrogen. Volatile matter in commercial shipments is controlled to ≤0.5 % (loss on drying, 60 °C vacuum oven, 2 h), and methanol-insoluble residue remains ≤0.10 %. The density at 20 °C averages 1.28–1.32 g/cm³, with bulk density for free-flowing prills settling between 0.60–0.70 g/cm³. Ash values, determined per ASTM D4574-17, are maintained below 0.30 %. Residual free amine, primarily tert-butylamine, is limited to ≤0.50 %, as excess amine induces scorch sensitivity in high-silica passenger tire tread formulations.
Storage stability under controlled conditions (sealed, ≤30 °C, RH <60 %) extends beyond 24 months without measurable loss of activity. However, exposure to relative humidity above 75 % accelerates hydrolysis, generating 2-mercaptobenzothiazole (MBT) and tert-butylamine, which markedly shortens scorch delay. Warehouses handling this sulfenamide routinely employ dehumidified zones for opened containers; a maximum cumulative open-time of 36 hours at 25 °C/65 %RH is recommended before re-sealing with dry nitrogen purge.
While the product’s thermal stability is robust, its sensitivity to hydrolytic decomposition governs shelf-life. Primary degradation products—MBT and amine—function as cure activators that lower the onset temperature of crosslinking, effectively erasing the characteristic delayed-action behavior. Analytical monitoring by reverse-phase HPLC (C18 column, acetonitrile/water mobile phase, UV detection at 254 nm) tracks MBT content; an increase to 1.0 % correlates with a reduction in Mooney scorch time (MS t5 at 127 °C, ISO 3417:2008) of approximately 25 % relative to a fresh control. For critical extrusions such as EPDM automotive weatherseals, a holding inventory of pre-weighed accelerator in sealed aluminum-laminate bags is common practice, with remaining material returned to desiccated storage cages within 4 h of initial opening.
Production-scale evidence from Banbury mixing lines indicates that accidental moisture uptake reaching 0.3–0.5 % on the accelerator—detected by Karl Fischer coulometry on a grab sample—can shift the T10 cure time (ASTM D5289-17, moving die rheometer at 160 °C) forward by 1.3–1.8 minutes in a standard NR/BR truck tread masterbatch, narrowing the processing safety window for downstream extrusion and calendering operations.
| Parameter | Value | Method |
|---|---|---|
| Melting point | 106–110 °C | Capillary tube, pharmacopeia-type |
| Assay (HPLC purity) | ≥96.0 % | External standard, reverse-phase |
| Methanol insolubles | ≤0.10 % | Gravimetric after dissolution |
| Ash | ≤0.30 % | ASTM D4574-17 |
| Free tert-butylamine | ≤0.40 % | GC headspace, FID detection |
| Moisture (K.F.) | ≤0.30 % | Karl Fischer coulometric |
Addition of N-tert-butyl-2-benzothiazolesulfenamide at 0.5–2.0 phr in combination with elemental sulfur (1.5–3.0 phr) yields a pronounced induction period followed by rapid crosslink formation. The delayed onset arises from the steric hindrance of the tert-butyl group, which retards the sulfenamide-to-MBT decomposition step. Oscillating disc rheometer data at 150 °C (ASTM D2084) consistently show a ts2 (scorch time) that is 30–50 % longer than that of N-cyclohexyl-2-benzothiazolesulfenamide (CBS) at equal molar loading. This extra processing latitude becomes non-negotiable in thick-section compression moldings of natural rubber engine mounts, where premature scorch in the interior of the part—due to low thermal diffusivity—would produce flow lines and internal adhesion flaws.
The kinetic profile has been mapped using a model-free isoconversional approach from differential scanning calorimetry traces. The apparent activation energy for crosslinking in an NR formulation containing 0.8 phr TBBS and 2.0 phr sulfur falls in the range of 85–95 kJ/mol, roughly 8–12 kJ/mol higher than the corresponding CBS system. That translates to a temperature coefficient of cure (calculated per 10 °C increment) of approximately 1.85–1.95 versus 1.70–1.80 for CBS, meaning processing line temperature fluctuations near 140–150 °C provoke a sharper cure-rate response. On injection molding shop floors, this mandates tighter barrel temperature control (±3 °C instead of ±5 °C) to maintain consistent cavity filling before crosslink density begins to build.
When TBBS is compared with N,N-dicyclohexyl-2-benzothiazolesulfenamide (DCBS), the latter provides an even longer delay but at the expense of significantly slower cure rates and lower ultimate state of cure at moderate temperatures (140–150 °C). TBBS occupies an intermediate position, balancing scorch safety against productivity, which is why continuous vulcanization lines for EPDM-based automotive coolant hoses frequently select TBBS over DCBS to meet line speeds exceeding 30 m/min without generating high compression set values.
Synergistic accelerator combinations define modern low-sulfur and efficient-vulcanization (EV) cure systems. TBBS functions as a primary delayed-action sulfenamide, and its activity is modulated by secondary accelerators such as tetramethylthiuram disulfide (TMTD), diphenylguanidine (DPG), or zinc dibenzyldithiocarbamate (ZBEC). In a typical semi-EV system for a conveyor belt cover compound (SBR/NR blend, sulfur 1.2 phr, TBBS 1.0 phr), the addition of 0.15 phr TMTD shortens t90 by 1.5–2.0 min at 160 °C while simultaneously raising the crosslink density (MH-ML torque difference) by 8–12 %. The dynamic stiffness (E’ at 60 °C, 10 Hz, DMA strain 2 %) also increases, which must be accounted for in fatigue life predictions using the Gent tearing energy model.
The zinc oxide/stearic acid activator system requires careful stoichiometric alignment. Zinc oxide levels below 3 phr in a mix containing 1.5 phr TBBS lead to incomplete utilization of the sulfenamide; unreacted accelerator can bloom to the surface of thick NR isolation pads after 48–72 h of storage, creating a waxy film that compromises adhesion to metal inserts during subsequent vulcanization. Increasing ZnO to 5 phr and stearic acid to 2 phr fully solubilizes the accelerator-derived intermediates, eliminating bloom while maintaining a reversion-resistant crosslink network, as evidenced by a heating plateau on a rotorless curemeter where the torque reduction after 10 min at 180 °C is held below 12 % of the maximum torque.
Silica-reinforced passenger tire treads demand a delicate balance between filler dispersion, coupling agent reaction, and accelerator-driven vulcanization. TBBS, when used at 1.3–1.8 phr with sulfur at 1.4–1.8 phr in a highly silanized S-SBR/BR blend, gives a processing safety margin (Mooney scorch at 130 °C) of 18–24 min, sufficient for twin-screw extruder mixing (L/D ≥48) where localized temperature spikes near the throttle valve can approach 145 °C. Compared to CBS, TBBS reduces the tendency for filler–filler networking as measured by the Payne effect (ΔG' from 0.1 % to 10 % strain at 60 °C). A formulation based on CBS typically yields a ΔG' of 450–550 kPa, whereas the TBBS analogue, processed under identical mixing conditions, reduces ΔG' to 340–400 kPa, attributable to a more favorable coupling reaction window before crosslinking locks in the flocculated silica structure.
However, a known processing limitation emerges when TBBS is paired with certain grades of bifunctional mercaptosilanes (e.g., Si 69). The amine moiety released during TBBS decomposition can prematurely activate the silane–silica coupling at temperatures as low as 120 °C, leading to an increase in compound viscosity in the second mixing stage (drop door internal mixer, ram pressure 0.5 MPa). To mitigate this, some manufacturing protocols reverse the addition sequence—dumping the silane and silica in the first non-productive stage while withholding the TBBS until the final productive stage where the batch temperature is capped at 105 °C. This staging preserves the intended silanization efficiency and maintains extrudate surface smoothness (SIS roughness Ra <1.5 µm on a Göttfert rheometer capillary profile).
Indirect food contact articles governed by FDA 21 CFR 177.2600 (rubber articles intended for repeated use) present a substitution case where migration limits dictate accelerator choice. TBBS produces less-extractable nitrosamines than secondary amine-based thiuram or dithiocarbamate accelerators. In a white NBR and EPDM gasket formulation, substituting 0.8 phr CBS with an equimolar amount of TBBS reduces total N-nitrosamines in the aqueous simulant (distilled water, 40 °C, 24 h migration test) from 4.2 µg/dm² to below the detection limit of 1.0 µg/dm² (LC-MS/MS analysis per EN 12868:1999). This reduction aligns with the German BfR Recommendation XXI category 3 guidelines, allowing the manufacturer to avoid post-cure leaching steps that add 3–4 hours to production. The trade-off lies in a slight modulus decrease: the 100 % modulus measured per ISO 37:2017 drops by 0.2–0.4 MPa, necessitating a marginal increase in carbon black N990 loading to meet compression force specifications for sealing rings in espresso machine portafilters.
| Property | TBBS | CBS | DCBS | Test Method |
|---|---|---|---|---|
| Mooney scorch t5 at 127 °C, min | 22.5 | 15.8 | 28.7 | ISO 3417:2008 |
| Minimum torque ML, dNm | 1.8 | 1.7 | 1.9 | ASTM D5289-17 |
| t10 at 150 °C, min | 5.2 | 3.8 | 7.0 | ASTM D5289-17 |
| Cure rate index (CRI), min−1 | 8.5 | 12.7 | 6.2 | ASTM D5289-17 |
| Tensile strength, MPa | 22.4 | 23.1 | 21.0 | ISO 37:2017 |
| Elongation at break, % | 520 | 490 | 550 | ISO 37:2017 |
| Hot air aged tensile retention, % | 82 | 78 | 85 | ISO 188:2011, 70 h at 100 °C |
In automotive coolant hose applications, where a peroxide cure is sometimes considered a benchmark for heat resistance, TBBS-sulfur systems at a low free-sulfur content (0.3–0.5 phr) paired with a sulfur donor like dithiodimorpholine (DTDM) challenge peroxide longevity. An EPDM hose compound subjected to long-term thermal aging per ISO 188:2011 (1000 h at 135 °C) displays retained elongation above 250 %, meeting SAE J20 Class D-1 requirements, while peroxide-cured variants with identical black loading can fail below 200 % after the same exposure due to chain scission. The sulfenamide system, however, generates a characteristic sulfidic network with a higher proportion of di- and polysulfidic crosslinks (detected by thiol/amine chemical probe analysis), which imparts superior flex crack resistance but sacrifices some compression set performance—a trade-off managed by a post-cure annealing step (2 h at 150 °C) that drives crosslink shortening without inducing reversion.
Limitations of TBBS emerge clearly in very fast-cure injection molding of thin-wall seals where cycle time is the dominant cost driver. At cure temperatures of 190–200 °C, the benefit of delayed action shrinks, and the reversion resistance of a TBBS-sulfur network in NR dips below that of a CBS-accelerated system. For these edge cases, a switch to MBTS with a small addition of thiuram is often favored despite the less favorable nitrosamine profile. Published data for this specific configuration is limited to in-house factory trials rather than standardized multi-laboratory studies, so the efficiency crossover point must be determined empirically on the specific molding machine.
Processing with twin-screw continuous mixing equipment demands accelerator feeding consistency. Gravimetric feeders handling TBBS prills require vibration-resistant mounting and frequent calibration; a deviation of ±0.02 phr in the feeding of 1.0 phr TBBS into a 60 mm co-rotating twin-screw extruder producing carbon-black-loaded NR masterbatch has been observed to alter the die swell ratio by 0.04–0.06, leading to out-of-specification extrudate dimensions after curing. Such sensitivity reinforces the need for statistical process control (SPC) charts monitoring Mooney viscosity and curemeter t90 of the final compound on every 10th batch, with upper and lower control limits set at ±3σ of the nominal.
