2,2'-Disulfanediylbis(1,3-Benzothiazole)
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HS Code |
114992 |
| Chemical Formula | C14H8N2S4 |
| Molar Mass | 332.49 g/mol |
| Appearance | Yellow - orange powder |
| Odor | Characteristic sulfur - containing odor |
| Melting Point | 175 - 181 °C |
| Solubility In Water | Insoluble |
| Solubility In Organic Solvents | Soluble in many organic solvents like benzene, toluene |
| Density | Approx. 1.52 g/cm³ |
| Stability | Stable under normal conditions, but may decompose on heating |
| Cas Number | 120 - 78 - 5 |
| Purity | Typically available in high purity grades (e.g., 98%+) |
As an accredited 2,2'-Disulfanediylbis(1,3-Benzothiazole) factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 1 kg of 2,2'-Disulfanediylbis(1,3 - Benzothiazole) in sealed, chemical - resistant packaging. |
| Shipping | 2,2'-Disulfanediylbis(1,3 - Benzothiazole) is shipped in well - sealed containers, following strict chemical transportation regulations. Special care is taken to prevent exposure to moisture, heat, and incompatible substances during transit. |
| Storage | 2,2'-Disulfanediylbis(1,3 - benzothiazole) should be stored in a cool, dry, well - ventilated area. Keep it away from sources of heat, ignition, and direct sunlight. Store in a tightly - sealed container to prevent moisture absorption and potential degradation. Avoid contact with incompatible substances like strong oxidizing agents. |
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The Banbury type F270 internal mixer discharges the masterbatch at 140–155 °C, at which point 2,2′-disulfanediylbis(1,3-benzothiazole) (MBTS) is introduced alongside 1.0–2.5 phr sulfur and a sulfenamide co-accelerator to assemble a typical semi-EV cure system for passenger radial tread compounds. On a twin-roll mill with a friction ratio of 1.20:1, the batch receives MBTS predominantly in the form of oil-coated pastilles to suppress airborne dust generation during open-mill handling — a practice mandated under the EU REACH Annex XVII restricted substances management framework. The target formulation contains MBTS at 0.8–1.2 phr in NR/BR blends with 55–65 phr carbon black N234, balanced to extend Mooney scorch time (MS-t5 at 127 °C) above 18 minutes while preserving a t90 cure time below 8 minutes at 160 °C per ASTM D5289-17. The mixing sequence must keep undispersed MBTS agglomerates below 10 µm diameter as confirmed by reflected-light microscopy on cryo-faced microtome sections; larger domains nucleate crystalline bloom on the green tire carcass within 6 hours of extrusion when ambient relative humidity exceeds 75 %. Extruded tread profiles are built onto the belt and carcass plies via a TBM-type single-stage building machine, and the green tire is cured in a BOM-type press at 165 °C under 22 bar internal steam pressure. The ultimate product — a 205/55R16 summer tire marked with a UTQG treadwear rating of 380–500 — must satisfy the tensile and tear requirements of ASTM D3191-19 for carbon black-filled SBR/NR compounds while passing an eight-week tropical warehouse aging simulation with a Shore A hardness drift limited to ±2 points. How does MBTS govern cure reversion stability in EPDM-based turbocharger charge-air duct compounds?Continuous extrusion of peroxide- and sulfur-cured EPDM charge-air hoses operating at a service temperature of 160–190 °C demands extremely flat cure torque plateaus. In these formulations MBTS is used not as a primary accelerator but as a sulfur-scavenging cure-control additive at 0.3–0.6 phr, specifically to suppress the irreversible network breakdown that appears following the maximum torque (MH) plateau in moving-die rheometer traces recorded per ISO 6502. The feedstock is compounded on a twin-screw extruder with an L/D ratio of 48:1 and high-dispersion mixing elements, where MBTS is injected as a pre-weighed EPDM-bound granulate (75 % polymer, 25 % MBTS) into zone 6 at 90 °C. The compound must pass the continuous compression set test described in ASTM D395-18 Method B ( 25 % compression, 150 °C, 168 hours) with a permanent set below 30 %. After microwave and hot-air continuous vulcanization at line speeds of 18–25 m/min, the duct is tested for burst pressure at 3.0 bar at 180 °C in accordance with SAE J20 Class D specifications. Equipment experience on a Troester multi-function line indicates that a deviation of MBTS addition exceeding ±0.05 phr from the target shifts the autoclave post-cure time required to remove residual sulfidic volatiles by over 60 minutes, a throughput-critical variable. Final part compliance includes OEM-specific fogging resistance (DIN 75201 method B, 100 °C, reflectometric value > 90 %) and long-term heat aging to ISO 188 at 175 °C for 1000 hours with elongation retention > 60 %. Steel-cable conveyor belt cover stocks and the MBTS–DTDM synergistic plateauCover compounds for ST-6300 grade steel-reinforced conveyor belts represent one of the few industrial rubber applications where MBTS is deliberately paired with dithiodimorpholine (DTDM) at a near-equimolar ratio to generate a flat sulfuric crosslink network that resists the abrasive gouging of +200 mm hard-rock lumps. The base formulation blends natural rubber with 20–30 phr butadiene rubber and contains MBTS at 1.2–1.8 phr together with DTDM at 1.0–1.5 phr and elemental sulfur at 0.3–0.6 phr. Mixing is carried out on an intermeshing tangential rotor internal mixer with a net chamber volume of 270 L and a ram pressure of 0.6 MPa; the MBTS/DTDM combination is added at the second-stage pass at 95–105 °C to prevent pre-scorch that would otherwise manifest as a visible grain surface on the calender-off gauge. Calendering on a four-roll Z-type configuration produces a 12 mm gauge cover sheet that must meet DIN 22131-1:2017 tensile strength of at least 24 MPa and elongation at break > 450 % before vulcanization. During continuous rotary press curing at 150 °C and a line pressure of 8 MPa, the MBTS component controls the reversion time to exceed 45 minutes as measured by the torque decay to 90 % of MH at 150 °C. The finished belt sections are subjected to DIN ISO 4649 abrasion testing with a loss not exceeding 90 mm³ and to the TECROM full-scale drum friction test per EN 14973, where the cover must sustain 25 000 cycles with a surface temperature rise limited to 140 °C before dynamic inspection. Polyether-polyol-based microcellular polyurethane foam midsoles demand entirely different acceleration chemistry, yet a specialized subset of the footwear supply chain exploits MBTS as a “delayed bloom” co-curative in molded rubber/EVA foam hybrid sheet stocks. Here MBTS is pre-dispersed into an ethylene vinyl acetate copolymer masterbatch at 0.4–0.7 phr alongside dicumyl peroxide and azodicarbonamide blowing agents, the key requirement being that MBTS must not interfere with the peroxide decomposition kinetics measured by differential scanning calorimetry at a heating rate of 10 °C/min — the peroxide exotherm must remain within 175–185 °C to match the gas evolution onset of 1.4–1.8 cm³/g. The hybrid sheet is expanded in a hydraulic three-platen press at 165 °C under a programmed decompression profile, followed by crosslinking through the MBTS-releasing dithiocarbamyl radicals that form in situ once free sulfur is liberated from the carrier during decompression. Compliance with the restricted substance list of the Apparel and Footwear International RSL Management Group (AFIRM) requires that the MBTS-derived N,N′-dithiobis(benzothiazole) and its decomposition fragment 2-mercaptobenzothiazole remain below 8 ppm as free thiazole in the finished foam as determined by GC-MS headspace analysis at 120 °C. The molded midsole must meet ASTM F1976-20 for impact attenuation (–50 g at –5 J energy), a property that is sensitive to the MBTS level because over-acceleration hardens cell walls beyond Shore A 48, causing premature foam collapse under repetitive compression set testing at 50 °C. When compression set performance at -40 °C forces an MBTS-modulated sulfur donor cure in nitrile sealing elementsCold-flexibly compounded NBR sealing rings for hydraulic aircraft actuators (Skydrol-resistant type) rely on an MBTS/TMTD/ZDC ternary accelerator system in which MBTS provides the necessary scorch delay during injection molding of complex lip geometries. The dosage is tightly bracketed at 0.6–0.9 phr, and each lot must equal a reference standard via extractable thiazole titration because even 0.05 phr excess liberates sufficient 2-mercaptobenzothiazole to etch the cadmium-plated bond surface of the metal insert, a process confirmed by SEM-EDX detection of Cd-thiolate crystals after 500-hour salt spray exposure per ISO 9227 NSS. Injection molding occurs on a 300-ton clamping-force machine with a cylinder temperature profile of 80–95–105 °C and an injection pressure of 120 MPa through a cold-runner system feeding eight cavities. The cure time is set at 180 seconds at 175 °C based on the torque increase to 95 % MH on an RPA 2000 instrument. Low-temperature compression set according to ASTM D1229-19 ( 25 % deflection, –40 °C, 22 hours) must not exceed 40 %, a criterion that governs the ratio of MBTS to TMTD: greater MBTS shares push the crosslink structure towards polysulfidic bridges that exhibit superior recoverable elasticity at sub-ambient temperatures. The cured seal is then assembled into the actuator housing and subjected to the full 3000-psi impulse test sequence of SAE AS6043, where the primary failure mode traced to MBTS variance is cold-leakage bypass at the heel radius after 8 000 cycles.
In ethylene-propylene rubber joint rings for district heating networks continuously operating at 130 °C, MBTS is deployed in a pure seal-centric role where the primary specification originates from EN 681-1:1998 (elastomeric seals for pipe joints carrying hot water). The mixing procedure is defined by a single-stage upside-down cycle on a 45 L intermeshing mixer, with MBTS loaded at 0.5 phr onto the carbon black/carbon nanotube hybrid filler matrix right from the start, an deviation from the standard late-addition rule that is justified because the high shear of the EPDM phase (> 1 200 kJ/m³ specific energy) requires the MBTS to act as a processing stabilizer preventing viscosity increase from premature oxidative crosslinking. The outflow compound is directly shaped into profiled strips on a roller-head extruder with a gear pump, then transferred to a 350-ton compression press where it cures under a 200-second dwell at 180 °C. Routine quality control audits at the press-side deploy a Rapra-Scan moving-die rheometer to ensure the S′ @ MH value lies within the 5.8–6.2 dNm band. The EN 681-1 stress relaxation test ( 25 % compression, 125 °C, 168 hours) tolerates a sealing force decay no greater than 22 %, a figure that accelerates exponentially when MBTS drops below 0.35 phr due to a surge in unbound curatives that produce extractable thiuram residues depositing in the counterface groove. After on-site installation validation per AGFW FW 505, the gaskets achieve a verified service life of 30 years in continuous 120 °C hot water — a data point derived from Arrhenius extrapolation based on oxygen induction time analysis per ISO 11357-6 at six temperature offsets.
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2,2'-Disulfanediylbis(1,3-benzothiazole), registered under CAS 120-78-5 and commonly designated as MBTS, is supplied as a pale-yellow to cream-coloured free-flowing powder with a melting range of 165–175 °C as determined by capillary method. The thiuram-free disulfide architecture confers an activation energy for sulfur crosslinking approximately 15–20 kJ/mol higher than that of the parent mercaptan, enabling a measurable processing safety window that has been exploited in high-volume natural rubber and diene elastomer compounding since the 1940s. Industrial specifications typically require assay ≥ 96.0% (titrimetric), loss on drying ≤ 0.5% at 70 °C under vacuum, and residue on a 63 µm sieve ≤ 0.1%, with oil-coated variants incorporating 1.5–2.5 wt% of a paraffinic process oil to suppress airborne dust during automated weigh-batching in tangential internal mixers operating at fill factors between 0.70 and 0.85.
The critical structural distinction—the elimination of the thiol proton through oxidative coupling to the disulfide bridge—shifts the onset of zinc-mediated accelerator complex formation to higher temperatures. Under Mooney scorch conditions defined by ASTM D1646, a natural rubber compound containing 1.0 phr MBTS and 2.5 phr sulfur registers a t5 at 121 °C of 18–22 min, whereas an equimolar loading of 2-mercaptobenzothiazole (MBT) typically reduces t5 to 8–12 min at identical sulfur levels. In continuous vulcanization tunnels processing EPDM profiles at line speeds of 15–25 m/min, this thermal lag permits full shape retention during hot-air preheating before the scorch boundary is approached, reducing dimensional waste rates below 0.3% of linear metre output. The phenomenon is exploited most aggressively in injection-moulded NR/BR engine mounts where barrel temperatures of 90–100 °C and injection pressures of 80–120 MPa must coexist with gate vestige dimensions ≤ 0.05 mm; MBTS at 0.8–1.2 phr combined with a sulfenamide primary accelerator maintains a compound viscosity below 55 MU for in-mold residence cycles exceeding 40 s, which is unattainable with straight MBT systems that exhibit pronounced crosslink density gradients near the gate due to premature zinc-thiolate formation in the nozzle.
Moving-die rheometer data acquired per ISO 6502-2 at 160 °C and 0.5° arc reveal that MBTS exhibits a pronounced dependence on elemental sulfur loading: the cure rate index (CRI = 100/(t90 − ts2)) climbs nonlinearly from 3.2 min⁻¹ at 1.5 phr sulfur to 8.1 min⁻¹ at 3.5 phr sulfur in a carbon black–filled SBR/BR blend, while the minimum torque (ML) remains confined within 1.7–2.1 dNm across the entire range. This contrasts with the behaviour of N-cyclohexyl-2-benzothiazolesulfenamide (CBS), where the same sulfur gradient produces a CRI shift of only 2.8 to 5.4 min⁻¹. The disulfide bridge undergoes homolytic scission at service-relevant temperatures, generating thiyl radicals that abstract hydrogen from polyisoprene backbones; when the sulfur rank in the crosslink precursor exceeds 4, the resulting polysulfidic bridges are longer than those formed by CBS at equivalent total-sulfur stoichiometry, giving the vulcanizate a lower crosslink density at full cure (νe ≈ 1.2 × 10⁻⁴ mol/cm³ vs. 1.6 × 10⁻⁴ mol/cm³) but a markedly higher elongation at break—typically 520–570% for unfilled NR—measured according to ISO 37:2017 Type 2 dumbbells. This property set makes MBTS the preferred primary accelerator in fabric-reinforced conveyor belt carcasses where dynamic flexing at 120 cycles/min under 15 kN/m pretension demands retained elongation above 400% after 10⁶ De Mattia flex cycles per ASTM D430-B.
Large-scale compounding on intermeshing twin-screw extruders with L/D ratios of 48:1 and screw diameters above 90 mm generates stock temperature excursions that approach the melting onset of MBTS, necessitating a pre-dispersion step when masterbatch discharge temperatures exceed 135 °C. Full-scale production records from an NR/BR tread line running at 4.5 t/h confirm that direct addition of MBTS powder into the hopper at dump temperatures of 148–152 °C results in a bimodal aggregate size distribution measured by optical microscopy on pressed films, with 15–22% of particles retaining diameters > 45 µm despite shear rates above 250 s⁻¹. This poor macrodispersion correlates with tensile strength reduction of 1.5–2.3 MPa in the final tread compound relative to identical formulations where MBTS is introduced as a 75% active content predispersion in EPDM binder via a side feeder at barrel 6. The stoichiometric incompatibility with primary amine curatives is similarly process-critical: any residual hexamethylenetetramine (HEXA) from a preceding novolac-cured compound batch must be purged below 0.05 wt% of chamber volume, as the amine groups catalyse disulfide disproportionation during the first 30 s of mastication, dropping the effective MBTS assay by 4–7% and accelerating scorch by 2.5–4.0 min on the subsequent Mooney curve.
Industrial grades differentiate themselves by residual free MBT content, a direct consequence of the oxidative coupling step during synthesis. Standard MBTS powder carries a free MBT fraction of 0.8–1.5 wt%; a low-MBT variant with free mercaptan restricted to ≤ 0.3 wt% is specified for low-protein latex dipping applications where extractable thiols above 50 µg/dm² on the cured film surface can trigger Type IV contact dermatitis under ISO 10993-10 sensitization assessment. The low-MBT grade additionally exhibits a delay in the torque increase on the MDR trace of 35–50 s at 150 °C, which becomes exploitable in thick-section NR bridge bearings where the cure time must be extended to 45–60 min to ensure a centre-to-surface temperature differential not exceeding 8 °C.
When benchmarked against the thiazole-sulfenamide accelerator class, MBTS occupies a distinct cost-performance node. The table that follows summarises characteristic cure parameters and physical property indicators for a reference NR compound (100 phr SMR CV60, 50 phr N330 carbon black, 2.5 phr sulfur, 5 phr zinc oxide, 2 phr stearic acid, accelerator loading equimolar to 1.2 mmol/100 g rubber).
| Parameter | MBTS | MBT | CBS | TBBS |
|---|---|---|---|---|
| Accelerator loading (phr, equimolar) | 1.0 | 0.8 | 1.3 | 1.4 |
| Mooney scorch t5 at 121 °C (min), ASTM D1646 | 19.5 | 9.8 | 28.2 | 32.7 |
| MDR ts2 at 160 °C (min), ISO 6502-2 | 2.8 | 1.6 | 4.5 | 5.2 |
| Cure rate index (min⁻¹) | 7.2 | 11.4 | 4.9 | 4.1 |
| Tensile strength (MPa), ISO 37:2017 | 25.8 | 23.3 | 27.4 | 28.1 |
| Elongation at break (%) | 545 | 475 | 510 | 500 |
| Relative material cost per active molar equivalent | 1.0× | 0.75× | 1.55× | 1.80× |
The data demonstrate that MBTS provides a scorch safety improvement of roughly 2× over MBT while preserving 65% of the rapid cure advantage, making it the rational choice when the balance of cycle-time compression and flow-safety margin tilts toward the latter. CBS and N-tert-butyl-2-benzothiazolesulfenamide (TBBS) extend scorch delay further but at cure rates that require elevated accelerator loadings or secondary dithiocarbamate activators, increasing formulation cost and raising the risk of blooming when the total benzothiazole moiety in the compound exceeds 3.5 phr—a limitation documented in ISO 13775-1:2015 hose testing where surface deposit mass must stay below 1.2 mg/cm² after 72 h at 70 °C.
In efficient vulcanization (EV) networks where sulfur content is constrained to 0.3–0.8 phr to generate predominantly monosulfidic bridges, MBTS cannot function as the sole accelerator because the low sulfur rank suppresses the thiol-disulfide exchange equilibrium required for active sulfurating agent regeneration. Instead, MBTS is co-vulcanized at 0.5–1.0 phr with tetramethylthiuram disulfide (TMTD) at 2.0–2.5 phr, producing an ambivalent donor-acceptor couple that sustains a cure rate index of 6.5–8.0 min⁻¹ at 170 °C while restricting total crosslink density to 5.8 × 10⁻⁵ mol/cm³—sufficient for resilience values above 80% rebound per DIN 53512. This combination underpins the curing of ethylene-propylene-diene seals specified under EN 681-1 for potable water contact, where the disulfide architecture contributes to a total organic carbon leachate figure below 0.25 mg/dm², a threshold not reliably met by formulations employing N-ethyl-N-phenyl dithiocarbamate accelerators. Heat ageing resistance at 125 °C for 168 h according to ISO 188:2023 retains above 70% of original tensile properties, consistent with the greater thermal lability of polysulfidic bonds that would otherwise be present at the same accelerator dosage in a semi-EV system.
Exposure of MBTS to atmospheric moisture during warehouse storage for periods exceeding 6 months in climates where the dew point routinely exceeds 22 °C produces a measurable drift in the free MBT fraction due to slow hydrolytic scission of the disulfide bond. Accelerated ageing studies at 40 °C and 90% relative humidity per ICH Q1A guidelines show a 0.2–0.4 wt% increase in free MBT per quarter, accompanied by a 2–3 °C depression in melting range onset. This drift, while analytically subtle, is sufficient to advance the Mooney scorch t5 by 1.5–2.0 min, a shift that must be compensated by adjusting the secondary retarder dosage—commonly N-(cyclohexylthio)phthalimide (CTP) at 0.1–0.3 phr—in any campaign processing material drawn from the tail end of the lot’s shelf life. Inventory management protocols at tier-one automotive seal production sites therefore specify a “first-expiry, first-out” sequence with the maximum allowable retest interval capped at 12 months from the date of packing in sealed, PE-lined multiwall paper bags stacked not more than 5 pallet positions high.
