N-(1,1-Dimethylethyl)-Benzothiazolesulfenamid
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HS Code |
390956 |
| Chemical Formula | C11H14N2S2 |
| Molecular Weight | 238.37 g/mol |
| Appearance | Yellowish to light brown granules or powder |
| Odor | Characteristic odor |
| Solubility In Water | Insoluble |
| Solubility In Organic Solvents | Soluble in common organic solvents like benzene, toluene |
| Melting Point | 104 - 110 °C |
| Boiling Point | Decomposes before boiling |
| Flash Point | 177 °C |
| Stability | Stable under normal conditions, but may decompose on exposure to heat, light, or strong acids |
As an accredited N-(1,1-Dimethylethyl)-Benzothiazolesulfenamid factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 500g of N-(1,1 - Dimethylethyl) - Benzothiazolesulfenamid in sealed chemical - grade bags. |
| Shipping | N-(1,1 - Dimethylethyl)-Benzothiazolesulfenamid is shipped in well - sealed, corrosion - resistant containers. Compliance with chemical shipping regulations ensures safe transportation, avoiding exposure and environmental risks. |
| Storage | N-(1,1 - Dimethylethyl) - Benzothiazolesulfenamid should be stored in a cool, dry, well - ventilated area. Keep it away from heat sources, open flames, and incompatible substances like strong oxidizers. Store in tightly closed containers to prevent moisture absorption and degradation, ensuring its stability and safety during storage. |
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Within passenger car radial tire tread compounds, the dominance of TBBS over other sulfenamides is rooted in the need to balance high-temperature vulcanization kinetics during continuous tread extrusion and the demands of ISO 14001-managed production environments. The compound must conform to EU REACH Regulation (EC) No 1907/2006 Annex XVII entry 50 for PAH content (< 1 mg/kg for BaP) and to ASTM D2226-93(2022) classification for oil-extended natural rubbers. In a typical NR/SBR 1500 blend of 80/20 phr, TBBS is metered at 0.9 to 1.3 phr alongside 1.7 to 2.1 phr of polymeric sulfur (Crystex® OT 20) and 0.15 phr of diphenylguanidine (DPG) as a secondary kicker. Processing starts with a masterbatch in an intermeshing internal mixer (F370 with tangential rotor configuration, ram pressure 0.55 MPa, fill factor 0.74) where the rubber, carbon black N234, and ZnO/2.5 phr stearic acid are masticated to a dump temperature not exceeding 158 °C. The final curatives are incorporated on a downstream twin-roll mill with a friction ratio of 1:1.15 and a cooling water temperature of 28 °C to keep the stock below 102 °C, preserving the scorch induction period (ts2 at 135 °C via ASTM D5289 typically 8–12 min). The tread strip is shaped through a pin-barrel cold-feed extruder (L/D 16:1, 120 mm screw diameter) at a head pressure of 9–14 MPa and transferred to a flat-bed press or a continuous salt-bath curing line at 165 °C for 12–15 min. The finished product is a precured tread strip for pneumatic radial tires complying with ECE Regulation 30, optimized for wet grip and rolling resistance labeling under EU 1222/2009. Contamination with strongly alkaline amine-based processing aids must be avoided during the final mixing phase since even 0.05 phr of free TMQ can shorten the scorch delay by 2–3 min and trigger premature crosslinking in the extruder barrel. Can TBBS alone satisfy the cyclic fatigue demands of heavy-duty conveyor belt cover compounds?In rubber cover blends for DIN 22102-classified steel cord conveyor belts operating in iron ore terminals, the combination of high abrasion resistance and long-term dynamic flex cracking resistance is regulated by ISO 4649:2021 (relative volume loss < 100 mm³) and DIN 53516 for abrasion. The formulation typically incorporates NR/BR 70/30 with a sulfur loading of 1.9–2.3 phr and TBBS at 1.2 to 1.8 phr, where the higher end of the dosage is necessary to achieve a Shore A hardness of 68 ±3 without resorting to excessive carbon black loading that would impair elongation at break (> 400% per ISO 37:2017). TBBS is used exclusively as the primary accelerator; its delayed action permits safe processing during two-stage mixing in a GK400E intermeshing mixer—first stage dump temperature is held at 147 °C to disperse the silica/silane (12 phr ULTRASIL VN3 with 1.2 phr Si 69) for improved tear resistance. After cooling and resting for 8 h, the final curatives including TBBS and insoluble sulfur are blended on a tandem mill with a gap setting of 6 mm at 92 °C stock temperature. The cover compound is then calendered onto the carcass plies using a 4-roll Z-calender with roll camber compensation, and vulcanized in a Rotocure continuous drum press at 168 °C for 18 min. The end product is a Class D (heavy-duty) abrasion-resistant rubber cover layer for underground and overland steel cord conveyor belts, compliant with MSHA 30 CFR Part 18 for flame resistance where applicable and ISO 340:2020 for conveyor belt flammability. Transfer of any peroxide-cured compound residue into the sulfur-TBBS system must be prevented; even trace yields of dicumyl peroxide reduce the effective crosslink efficiency and generate volatile acetophenone that forms surface pinholes on the cover. For EPDM coolant hose extrusions intended for long-life thermal management circuits in Euro VI diesel engines, the selection of TBBS as the sole sulfenamide governs the compromise between cure speed and the prevention of premature scorch in the extruder head. The hose compound must meet VW TL 52361 for coolant resistance and GM6279M for ethylene glycol compatibility, with a maximum volume swell of +15% after 168 h at 125 °C in 50% coolant solution. The EPDM backbone (ethylene content 55%, ENB 4.2%) is loaded with 0.9 phr TBBS, 1.5 phr sulfur, and 0.4 phr ZDBC as a secondary accelerator to achieve a t90 of 4.5–5.5 min at 180 °C on an MDR per ASTM D5289. Dispersion of carbon black N550 (95 phr) and paraffinic oil (60 phr) is carried out in a tangential internal mixer with a ram pressure of 0.6 MPa and a discharge temperature of 138 °C; the batch is then sheeted out on a mill and allowed to cool to 35 °C before adding the curatives at a second stage. The hose is extruded through a crosshead die with a 0.5 mm wall thickness tolerance on a vacuum-extruder line (screw speed 28 rpm, barrel temperatures set in four zones from 50 to 85 °C), followed immediately by a UHF microwave tunnel (2.45 GHz, 8 kW) and hot air cure at 230 °C for 2.5 min. The final product is a smooth-bore, unreinforced EPDM coolant bypass hose meeting SAE J20 R1 and ASTM D380 Type EC classifications, used in commercial vehicle engine compartments. A reduction of the TBBS level below 0.7 phr in this compound results in an unacceptable t90 drift above 6.5 min and significantly lower tensile retention after heat aging for 1008 h at 125 °C. Bridge Bearing Elastomer Vulcanizates and the TBBS/CBS SynergyLaminated elastomeric bearings for seismic isolation of bridge structures must satisfy the stringent long-term creep and shear modulus requirements of EN 1337-3:2005 and AASHTO LRFD Bridge Construction Specifications (2017), with a design shear modulus G typically 0.8–1.2 MPa. The rubber compound is based on natural rubber (SIR 20) with a low-sulfur, high-acceleration cure system to maximize reversion resistance: sulfur is capped at 1.2 phr, TBBS is dosed at 0.7–1.0 phr in combination with CBS at 0.6 phr and PVI (cyclohexylthiophthalimide) at 0.2 phr as a prevulcanization inhibitor. Mixing is conducted in a GK190E intermeshing mixer with a dual-flight rotor, where the base elastomer and reinforcing carbon black N330 (45 phr) are discharged at 142 °C. The cooling batch is then passed through a pin-type cold-feed extruder (screw diameter 150 mm, L/D 12:1) to form thick slabs (25–60 mm) that are compression molded between steel laminates in large daylight presses (3000 t clamping force) at 148 °C for 75–120 min under a holding pressure of 18 MPa to ensure complete flow and bonding with the metal interlayer treated with Chemlok 205/220 primer. Process stability relies on maintaining a minimum Mooney scorch time (MS-t5 at 121 °C) of 22 minutes; TBBS combined with CBS provides the required processing safety while attaining a crosslink density (determined by equilibrium swelling in toluene per ISO 1817:2015) that yields a compression set after 22 h at 70 °C of < 18%. The finished product is a laminated elastomeric bearing pad with integrated steel reinforcing plates, certified under the CE marking scheme according to ETAG 013 guidelines for structural bearings.
When specifying dense EPDM weatherstrip profiles for automotive glazing that must pass the long-term compression set and appearance criteria of ASTM D2000 M4CA410 A14 B13 C12 F18 Z1 (where Z1 designates an OEM-specific fogging requirement per VDA 278), the accurate control of TBBS addition within 0.8–1.2 phr determines the cure lag and surface bloom tendency. The EPDM compound, filled with 110 phr of carbon black N550/N762 blend and 45 phr of paraffinic oil, is mixed in two stages: first in an interlocking internal mixer (HF M200, fill factor 0.68, ram pressure 0.5 MPa) to a dump temperature 132 °C; after slab cooling, TBBS is added alongside 1.6 phr sulfur and 0.5 phr MBT on a temperature-controlled open mill at 75 °C. The resulting compound, with a Mooney ML(1+4) at 100 °C of 55±5 MU, is profile-extruded using a vacuum vented cold-feed extruder (screw diameter 90 mm, L/D 16:1) through a precision die that forms the bulb and lip geometry, with minimised die swell controlled by the rapid crosslinking action triggered by TBBS once the compound enters the continuous heating system. The vulcanization is performed in a combined microwave-hot air tunnel with five magnetrons at 2.45 GHz and a hot air chamber set to 240 °C; line speed is adjusted to 22 m/min to achieve a Shore A hardness of 68±3. The final product is a finished dense EPDM glass run channel seal, supplied in coiled lengths and meeting GMW16534 material specification for UV and ozone resistance. Operating below 0.8 phr TBBS in this formulation consistently generates a faint surface bloom after 72 h of ambient storage due to incomplete solubilization of the residual sulfenamide, which violates the Class A surface requirement. When pre-cured tread stock for OTR retreading requires reversion resistanceIn the off-the-road (OTR) tire retreading industry, where precured tread strips are bonded to giant carcasses in giant autoclaves, the formulation must resist thermal reversion during the 6–10 h cure cycle at 132 °C under 0.7 MPa internal steam pressure. The compound, compliant with ISO 9001:2015 and Mine Safety and Health Administration (MSHA) 30 CFR §75.1731 for underground mine tires, employs NR/BR 85/15 phr with a sulfur level of 1.6 phr and TBBS at 1.0–1.4 phr supplemented by 0.3 phr of hexamethoxymethylmelamine (HMMM) as a post-vulcanization stabilizer to suppress crosslink shortening. The tread base compound is mixed in an F370 intermeshing mixer at a ram pressure of 0.62 MPa and a discharge temperature of 143 °C, then processed through a two-roll mill with stock cooling to 38 °C before adding the TBBS in a separate curative stage. The strip is preformed through a duplex cold-feed extruder with a roller head die (die width 350 mm, gauge 25 mm), then partially cured in a flat press at 148 °C for 25 min to a crosslink density targeting 65% of full cure, as determined by a moving die rheometer torque rise (MH–ML) per ASTM D5289. The pre-cured tread is subsequently applied to the buffed casing with a tie gum and cured in an autoclave at 125 °C for 8 h. The final product is a retreaded loader or haul truck tire (size 29.5R25 or larger) suitable for open-pit mining operations, with a guaranteed TKPH (ton-kilometre per hour) rating validated through ISO 10231:2003 endurance testing. Published data for the specific interaction of TBBS with HMMM in prolonged low-temperature cure regimes remains limited; industrial experience indicates that exceeding 1.6 phr TBBS without an adequate dosage of reversion inhibitor leads to a reduction in modulus and the formation of a sticky surface layer on the finished retread after the autoclave cycle. |
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The molecular architecture of TBBS imposes a distinct balance between processing safety and cure rate relative to other benzothiazole derivatives. While N-cyclohexyl-2-benzothiazolesulfenamide (CBS) contains a secondary cyclohexylamine moiety, the steric bulk of the tert-butyl group in TBBS elevates the onset temperature of accelerator decomposition. In a standard ASTM D2084-19a oscillating disc rheometer curve at 160 °C for a 100-phr NR/50-phr N330 carbon black compound with 2.5-phr sulfur, TBBS at 0.7 phr typically exhibits a scorch time (ts2) that is 15–25 % longer than an equimolar loading of CBS, while the cure rate index (CRI = 100/(t90 − ts2)) is 5–12 % lower. This characteristic makes TBBS the preferred choice for thick-section articles where heat transfer limitations demand a prolonged induction period to avert premature crosslinking in the core before the mould cavity is fully filled. By contrast, CBS is selected when a sharper cure rate is required for thin-walled extrusions. Compared to the non-sulfenamide disulfide accelerator MBTS (2,2'-dithiobis(benzothiazole)), TBBS provides a significantly more pronounced delayed-action profile: MBTS yields ts2 values 30–50 % shorter under identical test conditions, and the resulting network exhibits a lower crosslink density due to fewer accelerator-terminated pendant side groups being converted into elastically active network chains.
Internal mixer processing on intermeshing or tangential rotors (e.g., a 1.8 L Banbury-type or an intermeshing 4.5 L Farrel CoFlow) routinely subjects the compound to temperature excursions reaching 130–150 °C during the final pass. The thermal stability of TBBS under these conditions is quantified via a Mooney scorch test (ISO 289-1:2015) at 132 °C. A compound containing TBBS as the sole accelerator exhibits a minimum Mooney viscosity increase of 5 MU from the minimum at 15–25 min, whereas an analogous CBS formulation reaches the same viscosity increment 2–5 min earlier. Plant-floor data from continuous production of conveyor belt covers indicates that a compound discharged from a dump mill at 135 °C with TBBS retains a processing window of 8–12 min before scorch initiates, sufficient for calendering into a 3–5 mm carcass skim. When TBBS is partially replaced by a secondary accelerator such as diphenylguanidine (DPG) at a 0.1–0.3 phr level to boost cure rate without sacrificing safety, the synergistic effect shifts the scorch curve; the DPG/TBBS ratio must remain below 0.4 to prevent t5 at 135 °C from dropping below 10 min, a threshold identified from twin-screw extruder downtime logs in a Romanian technical rubber goods plant. These narrow windows underscore the cost of overzealous acceleration in large-scale multi-cavity compression moulding.
Substitution of CBS with TBBS in a typical silica-filled S-SBR/BR tread compound (e.g., 70 phr S-SBR, 30 phr high-cis BR, 80 phr highly dispersible silica, 6 phr silane TESPT) is not a straightforward one-to-one swap. Rheometer traces collected at 150 °C (ASTM D5289-19a) show that the maximum torque (MH) differential remains within 0.2 dN·m, confirming comparable final crosslink density. However, the tan δ at 60 °C measured by dynamic mechanical analysis (ISO 4664-1:2011, 10 Hz, tensile mode) indicates a 0.005–0.012 higher value for the TBBS variant, translating into a marginal increase in rolling resistance contribution. This is attributed to the different adsorption/desorption kinetics of the tert-butylamine fragment on the acidic silanol surface during the silanization phase. The mixing protocol must therefore be adjusted: to compensate, 0.5 phr additional TESPT or a small increase in silanization temperature from 145 °C to 150 °C during the second non-productive pass is recommended based on observations from a 320 L intermeshing mixer equipped with a ram pressure of 6.0 MPa. In the absence of this protocol modification, the laboratory abrasion resistance index (DIN 53516:2018, 10 N load) can drop by 3–7 %, a variance that becomes statistically significant over a fleet trial of 50,000 km.
| Property | TBBS | CBS | MBTS | Test Method |
|---|---|---|---|---|
| Scorch time ts2 at 150 °C (min) | 8.5–11.0 | 7.0–9.5 | 4.5–6.5 | ISO 3417:2008 |
| Optimum cure t90 at 150 °C (min) | 18–24 | 15–20 | 12–16 | ISO 3417:2008 |
| Tensile strength at break (MPa) | 24.5–27.0 | 24.0–27.5 | 22.0–25.0 | ISO 37:2017, Type 2 |
| Modulus at 300 % elongation (MPa) | 11.5–14.0 | 11.0–13.8 | 9.5–12.0 | ISO 37:2017 |
| Heat build-up ΔT (°C, Goodrich flexometer) | 24–28 | 23–27 | 30–35 | ASTM D623-07(2014) |
Comparative cure data were generated on a compound comprising 60 phr TSR 20 NR, 40 phr high-cis BR, 50 phr N330, 5 phr zinc oxide, 2 phr stearic acid, 2.25 phr sulfur, and accelerator at 1.2 phr. The ts2 values confirm the hierarchy of scorch delay, with TBBS offering the greatest safety. The divergence in heat build-up underscores the influence of network homogeneity: MBTS generates a broader distribution of sulfur rank crosslinks, leading to higher hysteresis during dynamic deformation.
Undispersed TBBS agglomerates act as local cure-rate disruptors, causing surface blemishing in extruded profiles and heterogeneous modulus in injection-moulded seals. For EPDM compounds destined for automotive weatherstrip (solid profile, 80 Shore A), a screen pressure rise test (ASTM D7611-20) using a 100 µm filter screen in a single-screw extruder at 70 °C barrel temperature is employed. Acceptable TBBS grades generate a pressure rise of less than 2.5 MPa over a 30 min run at 60 rpm screw speed; a rise exceeding 4.0 MPa triggers an automatic lot rejection. Such fines and oversized particles originate from crystallization irregularities during spray chilling. The particle size distribution after a 1.0 mm sieve cut typically specifies ≤2.0 % passing through a 63 µm screen and ≤5.0 % retained on a 2.0 mm screen, as confirmed by Alpine air jet sieving (ISO 4610:2001). Post-blending with a 3 phr paraffinic process oil in a tumble mixer for 15 min prior to weigh-feeder introduction reduces static agglomeration in plants operating at relative humidity below 30 %, a common condition in Middle Eastern mixing facilities where packaging integrity against moisture is critical.
Shelf life under unopened, factory-sealed conditions in a 25 kg PE-laminated paper bag is specified at 24 months from the date of manufacture when stored below 30 °C and 60 % relative humidity. However, opened bags exposed to cyclic warehouse temperatures between 10 °C and 35 °C exhibit a measurable decline in assay purity of 0.3–0.7 % over 6 months due to slow hydrolytic decomposition catalyzed by trace humidity, releasing 2-mercaptobenzothiazole (MBT). The presence of free MBT in excess of 2.0 % (HPLC) shortens the Mooney scorch time by 15–20 %, an effect documented in EPDM automotive hose compounds. In solid storage, bulk migration of TBBS to the bag surface is negligible below its melting point, but elevated storage temperatures above 40 °C can induce surface blooming, leading to dusting during manual addition. For automatic feeding systems using FIBC (500–1000 kg), the bulk density, typically 0.55–0.65 g/cm³, influences silo discharge flow patterns and must be cross-checked with the manufacturer’s Jenike shear cell data for mass flow design.
TBBS is listed under the European Chemicals Agency REACH regulation (EC No. 202-409-1) with a registered tonnage band above 1000 tonnes per annum and appears in multiple food contact material inventories but with strict specific migration limits. Under Commission Regulation (EU) 10/2011 on plastic materials and articles intended to come into contact with food, the specific migration limit (SML) for the sum of TBBS and its hydrolysis product MBT, expressed as MBT, is 0.5 mg/kg (Annex I, Table 1, FCM substance No. 964). The tert-butylamine moiety is regulated separately under the same framework with an SML of 0.05 mg/kg. For repeated-use rubber articles such as milking machine liners, FDA 21 CFR § 177.2600 permits the use of TBBS as an accelerator provided the finished article passes extraction tests with water and n-hexane under specified time and temperature conditions. These migration limits impose a practical ceiling on TBBS loading in rubber compounds formulated for potable water seals (e.g., BS EN 681-1 elastomeric seals for water supply) where residual amine odour and total organic carbon (TOC) leaching can become performance-critical during commissioning flushes.
| Parameter | Value | Test Standard |
|---|---|---|
| Assay (HPLC, area %) | ≥ 97.0 | ISO 13365:2011 |
| Melting point (°C) | 105–110 | ISO 3146:2000 (capillary) |
| Loss on drying (70 °C, vacuum, %) | ≤ 0.5 | ISO 21870:2004 |
| Ash content (%) | ≤ 0.3 | ISO 1125:2015 |
| Methanol insolubles (%) | ≤ 0.5 | Internal method |
| Bulk density (g/cm³) | 0.55–0.65 | ISO 60:1977 |
| Residue on 63 µm sieve (%) | ≤ 2.0 | ISO 4610:2001 |
The assay value is critical for calculating the effective accelerator molar concentration when formulating with a ternary cure system (sulfur/primary accelerator/secondary accelerator). A batch-to-batch purity variation of just 1.5 % can shift the ts2 at 160 °C by 0.4–1.0 min, sufficient to cause sporadic scorch rejects on a 12-cavity injection mould running EPDM lip seals with a cycle time of 75 s. Operators compensating by reducing barrel temperature to 78 °C from 82 °C often observe a viscosity rise that impairs mould filling at the farthest gate, illustrating the cascading process sensitivity.
When co-curing EPDM rubber with high-ethylene-content (70 wt%) grades, TBBS exhibits a cure activation energy (Ea) derived from the Arrhenius plot of rheometer data (multiple temperatures between 150–190 °C) in the range of 95–105 kJ/mol. This is approximately 8–12 kJ/mol higher than that of CBS in the same polymer matrix, requiring a corresponding increase in cure temperature of 4–7 °C to achieve an equivalent t90. In ultra-high-frequency (UHF) continuous vulcanization lines processing sponge or solid profiles at line speeds of 20–40 m/min, this translates to a need for a longer curing tube or a higher microwave power setting. TBBS crosslinks are predominantly monosulfidic after extended cure thanks to the rapid decomposition of polysulfidic crosslinks; the network matures to a stable plateau, as confirmed by equilibrium swelling in toluene (ISO 1817:2015) showing a crosslink density of approx. 1.2 × 10⁻⁴ mol/cm³ after t90 + 5 min at 180 °C. In contrast, under-cure by 10 % (at t81) results in compression set (ISO 815-1:2019, 70 h at 100 °C) exceeding 65 %—unacceptable for a VW TL 520 15 specification sealing profile—while the fully cured TBBS system achieves 35–40 %. This delineates the narrow processing window on UHF lines where dwell time fluctuates by ±3 s.
