2,2'-Dibenzothiazole Disulfide
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HS Code |
138369 |
| Chemical Formula | C14H8N2S4 |
| Molecular Weight | 356.54 g/mol |
| Appearance | Yellowish - brown powder |
| Odor | Characteristic |
| Melting Point | 165 - 170 °C |
| Solubility In Organic Solvents | Soluble in benzene, chloroform, carbon tetrachloride |
| Solubility In Water | Insoluble |
| Density | 1.52 - 1.58 g/cm³ |
| Stability | Stable under normal conditions |
| Cas Number | 120 - 78 - 5 |
As an accredited 2,2'-Dibenzothiazole Disulfide factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 25 - kg bags of 2,2'-Dibenzothiazole Disulfide, well - sealed for chemical protection. |
| Shipping | 2,2'-Dibenzothiazole Disulfide is shipped in sealed, corrosion - resistant containers. It's transported following strict chemical safety regulations, ensuring protection from moisture, heat, and physical damage during transit. |
| Storage | 2,2'-Dibenzothiazole Disulfide should be stored in a cool, dry, well - ventilated area. Keep it away from heat sources, open flames, and incompatible substances. Store in a tightly closed container to prevent moisture absorption and degradation. It is advisable to store it separately from oxidizing agents and strong acids to ensure safety and maintain its chemical integrity. |
In natural rubber-based heavy-duty tire tread compounds, the incorporation of 2,2'-dibenzothiazole disulfide at 1.2–1.8 phr directly modulates the induction period of accelerated sulfur vulcanization in a way that neither thiuram nor sulfenamide accelerators replicate identically. Processing on a F370 intermeshing tangential mixer with a net chamber volume of 370 L and a fill factor of 0.72 reveals that adding the MBTS powder in the second-stage masterbatch — after carbon black (N234, 50 phr) dispersion but before the curatives pass — minimizes zinc oxide (3.5 phr) agglomeration and preserves a Mooney scorch time (MS-t5, 121°C) of 28–34 minutes. This window becomes critically narrow when silane-terminated solution SBR partially replaces natural rubber to meet EU 2020/740 rolling resistance Class C or B thresholds: the silica-silane coupling reaction competes with zinc-accelerator complex formation, and a deviation of ±0.2 phr MBTS shifts the dynamic storage modulus (E′) at 60°C by up to 1.8 MPa, directly altering wet grip indicators per ASTM D6868-21. Downstream, the final cured tread, tested to ISO 4649:2017, delivers a relative volume loss of 115–140 mm³ for long-haul trailer tires (size 295/75R22.5). The vulcanization step in segmented mold presses at 155°C for 18–22 minutes requires precise cavity pressure profiling (±0.3 MPa) to prevent over-cure at the tread grooves while the undertread reaches 90% of state-of-cure, measured by offline moving-die rheometer (MDR) relative crosslink density analysis per ISO 6502-2:2018. Regulatory alignment with REACH Annex XVII Entry 50 (polycyclic aromatic hydrocarbons) for extender oils is mandatory; MBTS itself must be handled with local exhaust ventilation at ≥0.5 m/s capture velocity to maintain airborne dust below the 0.5 mg/m³ 8-hour time-weighted average when free-flowing powder grades are manually weighed. This compound design produces treads for steer-axle tires where the absence of amine-generated N-nitrosamines — a documented risk with certain secondary accelerators — becomes a specification clause in OEM approval protocols.When Does MBTS Replace Guanidine Secondary Accelerators in EPDM Automotive Weatherstrip Compounds?Extrusion of dense EPDM weatherstrip profiles for automotive door seals at line speeds of 15–25 m/min imposes contradictory requirements: the compound must resist scorching in the 90 mm cold-feed pin-barrel extruder (L/D 16:1) while curing rapidly in a 350–450°C hot air continuous vulcanization (CV) tunnel with a residence time of only 120–180 seconds. Substituting a portion of the primary sulfenamide accelerator with MBTS at 0.8–1.4 phr in conjunction with a sulfur donor (dithiodicaprolactam at 1.0 phr) and activated zinc oxide (4.0 phr) adjusts the vulcanization isotherm. The on-set of crosslinking shifts to a slightly higher temperature — the compound exhibits a 3–5°C elevation in the initial torque rise temperature during a 3°C/min temperature sweep on a sealed oscillating-die curemeter — while the total crosslink density (Mr value from equilibrium swelling in cyclohexane per ISO 1817:2022) remains within 3.8–4.4×10⁻⁵ mol/cm³. The critical processing limit is that MBTS disperses poorly in strictly amorphous EPDM below 70°C dump temperature; hence an upside-down mixing sequence in a 160L intermeshing mixer is implemented, where MBTS is added together with the carbon black (N550, 120 phr) and paraffinic oil (65 phr) to achieve a dispersion rating of A3 per ISO 11345:2023. Accelerator blooming is suppressed by keeping the fractional molar ratio of MBTS to elemental sulfur below 1:1.2. The final vulcanized profile must pass the compression set test at 70°C for 24 hours with a value ≤45% (method ASTM D395-18, Method B) and show no surface cracking after 200 hours of ozone exposure at 50 pphm, 40°C, and 20% elongation per ISO 1431-1:2022. End-use specification includes Volkswagen TL 52643 and GM GMW16767, with explicit restriction of N-nitrosamine content in the finished part to below 0.5 µg/kg as measured by chemiluminescence detection following dichloromethane extraction, a constraint that eliminates many thiuram-based systems and positions MBTS as a kinetically viable replacement in formulations where dithiocarbamates exceed migration thresholds.Steam Hose Inner Tube Processing: Defining the 0.9–1.3 phr Processing WindowManufacturing wrapped-cure steam hoses (SAT rating, working pressure 18 bar, 210°C superheated water intermittently) involves building the inner EPDM tube on a flexible mandrel before lead-jacketing and autoclave curing at 0.6 MPa steam pressure for 45–60 minutes. The inner tube compound, formulated with a medium-ENB EPDM, must exhibit sufficient green strength to resist mandrel collapse during braiding and yet flow adequately to fuse with the cover compound during the pressurization phase. MBTS is incorporated at 0.9–1.3 phr as the dominant delayed-action component alongside a minimal dose of a secondary dithiocarbamate (0.2 phr zinc dibutyldithiocarbamate) to establish a flat curing plateau on the rheometer curve at 160°C. A discrepancy of +0.3 phr MBTS outside this window reduces the torque difference (MH–ML) by 8–12% due to accelerator complexation with residual moisture from the carbon black (N660, 140 phr) moisture content exceeding 0.5 wt% — a condition detected only by Karl Fischer titration (ISO 15512:2019) on the pre-weighed batch. The vulcanizate is tested for adhesion to a polyester braid (1100 dtex/2) dipped in RFL (resorcinol-formaldehyde-latex) where pull-through force must exceed 3.5 N/mm (ISO 8033:2017); failure at the rubber-braid interface is systematically correlated with free MBTS concentration above 0.15 wt%, analyzed by HPLC-UV (254 nm) on acetone extracts. Per EN 854 and ISO 6134:2017 Type 2, burst pressure must exceed 60 bar at 23°C with no leakage at the end-fitting. The steam hose finds use as a cleaning line in dairy processing CIP systems, though FDA 21 CFR 177.2600 for food contact rubber is not claimed due to zinc migration and potential benzothiazole breakdown byproducts exceeding the specific migration limit of 0.5 mg/kg food simulant in 3% acetic acid.
Vertical Injection Molding of NBR Anti-Vibration Bushings: Gate-Freeze and Accelerator SelectionA 220-ton vertical hydraulic injection press with a 55 mm reciprocating screw processes NBR (ACN 34%, Mooney 45 MU) filled with 65 phr carbon black and 0.8 phr MBTS, injected through a cold-runner block maintained at 80°C into a multi-cavity mold heated uniformly to 175°C (±2°C inter-cavity). Gate-freeze time measured by a nozzle pressure decay of 10 MPa serves as the limiting process variable: the compound’s scorch time at 175°C by variable-temperature Mooney, which drops to 4.2–5.5 seconds, dictates that the injection stroke must complete within 3.2 seconds and the cavity filled before pressure builds to 80 MPa. MBTS contributes to a plateau modulus that minimizes overshoot in the damping coefficient at 15 Hz resonance, measured on a servo-hydraulic fatigue test stand per ISO 10846-2:2023. The cured bushing, after post-vulcanization in a hot air oven at 120°C for 4 hours to complete crosslinking of the residual MBTS-derived zinc mercaptobenzothiazole complexes, passes 3 million load cycles at ±5 kN with dynamic stiffness degradation limited to 12%, a criterion specified in SAE J1084. The final component is installed into the front subframe mount of a light-duty commercial vehicle where emissions compliance (China GB 18285-2018 / EU 2016/44/EU) requires the vulcanized rubber to emit no more than 50 µg/m³ total volatile organic compounds (TVOC) during the 24-hour chamber test at 65°C (VDA 278), a demanding constraint that disqualifies many secondary amine donors and reinforces MBTS use within a strictly zinc-activated network.Nitrile butadiene rubber roll coverings for hot-strip steel mill run-out tables constitute a highly abrasive service environment where the temperature of the strip reaches 550–700°C at the point of contact, requiring latent heat dissipation through a cooling water film applied simultaneously. A laboratory two-roll mill (Ø 200 mm × 450 mm) is used to incorporate MBTS at 0.7–1.2 phr into an NBR/carboxylated NBR (XNBR) blend (ratio 85/15) together with zinc oxide plus zinc methacrylate as a self-reinforcing filler. This formulation must avoid the generation of nitrosamines under high-temperature oxidative degradation during the grind-off process, a concern documented in TRGS 552 (German Hazardous Substances Ordinance) that restricts workplace concentrations of N-nitrosodiethylamine to 1 µg/m³; MBTS selection over thiuram donors therefore becomes a occupational hygiene protocol rather than a material performance choice. The compound is built onto a sandblasted steel core (HV 450) with a bonding agent based on a silane-cured epoxy primer, then wrapped and vulcanized in an autoclave at 148°C for 220 minutes to ensure a Shore D hardness of 40–45 at the surface. Service life checks at 500-hour intervals record weight loss according to ASTM G65-16 Procedure A; historical field data from a 60-inch continuous hot-dip galvanizing line roll show that MBTS-cured covers deliver a specific abrasion loss of 180–220 mg per 1000 cycles under 25 N load, a performance that competes with sulfur-donor EV systems but with fewer reversion artifacts.Dipped natural rubber latex examination gloves, produced on a continuous chain-driven former line at a line speed of 8–12 m/min, require a compounded latex bath with a shelf-life stability exceeding 72 hours at 25°C under gentle stirring. A prevulcanized latex system is prepared by heating field latex (60% DRC) with a dispersion containing 0.8 phr MBTS, 0.3 phr zinc diethyldithiocarbamate, 1.0 phr sulfur, and 0.5 phr zinc oxide at 70°C for 4 hours until the chloroform number reaches 3. The dispersion step uses a horizontal bead mill (chamber volume 2.0 L, zirconia beads 1.0–1.2 mm) run at 2500 rpm to reduce MBTS particle size to Dv90 ≤ 5 µm; incomplete milling results in sediment formation on the glove former tip, a defect that increases pinhole defects (AQL 1.5 per ISO 2859-1:1999) beyond the acceptable limit of 1.5%. The vulcanized film, after inline leaching in hot water (85°C) for 15 minutes to remove residual benzothiazole accelerator derivatives, is tested for protein content (≤50 µg/g by Modified Lowry per ASTM D5712-21) and tensile strength after aging at 70°C for 168 hours (≥21 MPa before and ≥18 MPa after aging per ASTM D3578-19). The manufacturer’s risk assessment under Annex I of EU 2017/745 (Medical Device Regulation) categorizes the migration of 2-mercaptobenzothiazole (2-MBT) — the principal decomposition species of MBTS — as a CMR Cat. 2 skin sensitizer, requiring lot-specific HPLC release tests with a reporting limit of 0.1 ppm in synthetic sweat simulant.
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In a high-cis polybutadiene / natural rubber (60/40) truck tire bead filler compound mixed on a 270‑L Banbury intermeshing mixer, the replacement of mercaptobenzothiazole (MBT) by 2,2'-dibenzothiazyl disulfide at 2.0 phr shifted the Mooney scorch time (t5, measured per ISO 289‑1:2014 at 120 °C) from 12–15 min to 38–42 min. This substantially widened the processing window for multi‑cavity injection transfer molding, where flow path lengths routinely exceed 500 mm and clamp tonnages of 800 t maintain cavity pressure above 15 MPa. The underlying cause is the homolytic cleavage of the disulfide bridge, which requires thermal activation energies of approximately 125–140 kJ·mol⁻¹ — a threshold that is not reached until the compound resident in the mold achieves 140–150 °C. Delayed release of the active mercaptobenzothiazole fragment prevents premature crosslinking during cavity fill and ensures near‑Newtonian flow in the gate region.
Table 1 captures the divergence in cure kinetics observed when 2.0 phr MBTS is compared with molar‑equivalent dosages of other common accelerators in a carbon‑black‑filled SBR 1502 formulation (SBR 1502 100, N330 50, ZnO 5, stearic acid 3, sulfur 2.5, all parts per hundred rubber). Curing characteristics were recorded on a moving‑die rheometer at 150 °C, arc 0.5°, frequency 1.67 Hz according to ASTM D5289‑17.
| Accelerator | Dose (phr) | ML (dN·m) | MH (dN·m) | t₂ (min) | t₉₀ (min) | CRI (min⁻¹) |
|---|---|---|---|---|---|---|
| MBTS | 2.0 | 1.8 | 15.2 | 6.8 | 16.5 | 10.3 |
| MBT | 1.5 | 2.0 | 16.5 | 3.2 | 9.8 | 15.2 |
| CBS | 1.2 | 1.9 | 16.0 | 4.5 | 12.3 | 12.8 |
| TBBS | 1.4 | 2.1 | 17.2 | 4.0 | 11.5 | 13.3 |
The cure rate index (CRI = 100/(t₉₀ – t₂)) confirms that MBTS gives the slowest onset and a lower post‑scorch curing velocity. However, the final torque difference (ΔS' = MH – ML) remains within 10 % of that produced by CBS or MBT, indicating that the crosslink density is not sacrificed if the cure cycle is extended to the corresponding t₉₀. The absence of any secondary amine structure in the MBTS molecule eliminates the risk of N‑nitrosamine formation — a critical advantage over sulfenamide accelerators such as CBS, where regulatory limits under REACH (Annex XVII, entry 43) constrain its use in consumer rubber goods.
When compounding natural‑rubber bridge bearings with section thicknesses above 100 mm, the slow heat transfer implicit in thick‑section vulcanization makes the extended t₉₀ of MBTS (16.5 min at 150 °C, scaling to over 40 min at 140 °C) an advantage rather than a drawback. Long‑plateau cure allows the inner core to reach the 130–135 °C activation threshold before the outer layers over‑cure, thereby minimizing modulus gradients across the part. Published data for this specific configuration is limited, but industrial production records from seismic‑isolation bearing manufacturers indicate that switching from TBBS to MBTS reduced edge‑reversion failures detected by ultrasonic scanning after ISO 22762‑3 aging cycles.
MBTS catalyzes sulfur vulcanization in EPDM only in the presence of adequate zinc‑oxide/stearic acid activator complexes. Processing trials on a 90‑mm pin‑barrel extruder feeding EPDM automotive weatherseal profiles demonstrated that at a ZnO level of 3.0 phr and stearic acid 1.2 phr (ratio 2.5:1), the rheometer t₉₀ at 170 °C shifted from 8.2 min to 11.7 min compared with the recommended 5.0 phr ZnO and 2.0 phr stearic acid. The torque increment ΔS' fell by 18 %, confirmed by lower 100 % modulus after hot‑air aging per ISO 188:2011. MBTS is therefore sensitive to sub‑stoichiometric co‑activator concentrations and should not be used in under‑activated halogenated‑butyl or EPDM formulations unless the ZnO level is verified by atomic absorption spectroscopy per ISO 6101‑2:2019 on the mixed batch. Incompatibility with highly acidic processing aids (pH 4) has been noted; the disulfide bridge can hydrolyze prematurely, generating free 2‑mercaptobenzothiazole that causes incipient scorch during silo storage at ambient temperatures above 35 °C.
Powdered MBTS (assay ≥ 96 % per GB/T 11407‑2013, melting point initial ≥ 170 °C, moisture ≤ 0.5 %) is increasingly supplanted by a masterbatch grade designated MBTS‑80 — an 80 % active concentration pre‑dispersed in an SBR or EPDM binder. The pre‑dispersion’s filter residue on a 100 µm mesh, measured per ASTM D1514‑15, is typically < 0.1 %, eliminating macro‑agglomerates that cause surface imperfections in extrusion‑vulcanization lines. In a 1.5 L laboratory intermeshing mixer (ram pressure 0.6 MPa), replacement of powder with MBTS‑80 reduced incorporation energy by 15–20 % and shortened drop temperature rise from 9 °C/min to 6 °C/min, as recorded by the mixer’s power‑integration control unit. This mitigates the risk of early‑stage heat‑hardening in fast‑batch production of brake diaphragm compounds. Industrial hygiene measurements using personal sampler cassettes (NIOSH 0500) confirm that MBTS‑80 maintains respirable dust levels below 0.5 mg·m⁻³, well within the OEL limit of 3 mg·m⁻³ for nuisance particulates.
If stored at relative humidity exceeding 60 %, MBTS‑80 absorbs moisture, leading to a 0.3–0.5 % weight increase and potential hydrolysis during mastication. Pre‑drying at 60 °C for 2 h in a forced‑air oven is required before feeding into a loss‑in‑weight gravimetric system. Shelf life from date of manufacture is certified at 12 months under 25 °C and dry‑bag storage, verified by rheometer cure‑curve stability as per ISO 6502‑3:2023.
In latex dipping applications for thin‑wall surgical gloves, MBTS is supplied as an aqueous dispersion with 50 % solids content. However, the compound pot‑life at pH 10.5 is constrained to 4–6 h at 30 °C because hydroxyl ions catalyze gradual ring‑opening and deactivation. Field experience on continuous chain‑type dipping machines shows that once the dispersion viscosity exhibits a shear‑rate‑dependent increase beyond 200 mPa·s at 100 s⁻¹ (Brookfield LV spindle), the surface film on the coagulant‑coated former becomes irregular, and pin‑hole rates in finished gloves rise above the 1.5 acceptable quality level (AQL) specified in ASTM D3577‑19. For conveyor belt cover compounds requiring high modulus and long fatigue life under cyclical loading, substituting 1.5 phr MBT with an equivalent molar MBTS dose shifts the post‑vulcanization network structure to predominantly di‑ and polysulfidic crosslinks with a lower proportion of accelerator‑terminated pendant groups. The result, verified by equilibrium swelling in toluene per ISO 1817:2022, is a 12–15 % increase in crosslink density and a reduction in compression set at 70 °C from 28 % to 21 % after 24 h aging. The slower cure rate is accommodated by increasing the cure‑meter residence time by 2 min on a rotocure line carrying 12 mm thick rubber sheet at 160 °C.
