2-Benzothiazolesulfinicacid

Incorporation into the masterbatch stage of a truck radial tire compound proceeds via a two-roll mill at a nip setting calibrated to maintain a stock temperature below 110°C. The compound, based on 100 phr natural rubber (SIR20) with 50 phr N330 carbon black, receives 2‑benzothiazolesulfinic acid as a pre‑dispersed powder at 0.25–0.40 phr, co‑fed with zinc oxide and stearic acid. The sulfinic moiety functions as a radical trap that quenches thiol‑derived autoxidation species generated during the break‑down of polysulfidic crosslink precursors, delaying the onset of the scorch plateau without flattening the final torque rise. Processing on a 12‑speed calendering line producing 1.2 mm steel cord skim stock pushes the compound residence time at 95–105°C close to 12 minutes; the addition widens the Mooney scorch window (t5 at 127°C) from 18.2 min to 28.6 min while preserving the t90 cure time within ±8% of the reference. Regulatory compliance for export to EU‑27 retreading plants is documented under REACH Annex XVII (entry 50, PAH restriction, not applicable to the substance itself but to extender oils in the compound) and ISO/TS 16949 process control clauses requiring full traceability of curatives. The skim compound proceeds to a four‑zone curing press operating at 155°C with 22‑min cycle, converting green rubber into a fully vulcanized breaker‑belt composite. Terminal articles include 315/80R22.5 truck‑and‑bus radials and off‑the‑road (OTR) 23.5R25 loader tyres, both of which demand a process safety margin sufficient to survive compound flow interruptions on the building machine.

How does 2‑benzothiazolesulfinic acid reshape the vulcanization induction profile in peroxidic EPDM coolant hoses?

In a peroxide‑cured EPDM formulation for automotive coolant hoses—composed of 100 phr EPDM (ethylene 55 wt%, ENB 4.5%), 85 phr N550 carbon black, 55 phr paraffinic oil, 6.5 phr dicumyl peroxide (40% active on clay), and 1.2 phr triallyl cyanurate co‑agent—the introduction of 2‑benzothiazolesulfinic acid at 0.15–0.30 phr shifts the onset of the curing exotherm by modulating the homolytic cleavage equilibrium of the peroxide. The sulfinic hydrogen donates to peroxyl radicals, suppressing early crosslinking in the extruder head zone where the stock temperature rises to 118–122°C during the final screw stage of a 90 mm vented pin‑barrel extruder (L/D 16:1). Laboratory vulcanization is tracked with a moving‑die rheometer per ASTM D5289‑17 at 175°C: ML decreases by 4–7 dN·m versus the non‑sulfinic control, and scorch safety (ts2) extends from 0.48 min to 0.92 min at 175°C, a critical improvement for mandrel‑formed hoses that require a full 1‑min shape‑setting delay before the pressurised autoclave ramp. During continuous autoclave curing at 170°C under 5.0 bar nitrogen, the hose wall (ID 32 mm, wall 4.5 mm) achieves a uniform state of cure with less than 5% deviation in elongation at break (ISO 37:2024, dumbbell type 1) over a 200‑m batch. The finished hose, rated for –40°C to +135°C glycol‑water service, meets SAE J20 Class D requirements and is assembled into turbocharger coolant circuits on Euro‑VII heavy‑duty engines. Compound compliance with GB/T 18948‑2017 for total volatile condensables is verified, and the sulfinic grade is listed in the manufacturer’s Global Automotive Declarable Substance List (GADSL) under advisory category.

Laboratory tensile‑strength retention after air aging at 150°C for 168 h (ISO 188:2023) falls to 62% of the original value when the sulfinic acid exceeds 0.45 phr, indicating secondary chain scission catalyzed by acidic decomposition by‑products beyond that threshold. Conductive carbon‑black dispersion, assessed by ISO 11345:2022 (POM optical method) on microtomed cross‑sections, shows a modest agglomerate count increase from grade 7 to grade 6 at the 0.30‑phr loading; therefore, the dose window is capped at 0.25 phr on large‑diameter suction hoses requiring burst pressures above 4.8 MPa.

Acid copper plating brightener intermediate: cathode polarization and grain refinement

In PCB through‑hole plating lines built around a horizontal conveyorized acid copper electrolyte—operating at 25°C±0.8°C with a jet impingement current density of 3.2 A/dm²—2‑benzothiazolesulfinic acid serves as a precursor that, upon anodic oxidation or controlled hydrolysis, generates a mercaptobenzothiazole derivative acting as a leveling suppressor. The sodium salt, pre‑dissolved in deionized water at 4.0 g/L stock, is dosed into the make‑up tank at 8–22 mg/L based on continuous Hull‑cell monitoring (267 mL air‑agitated cell, 2 A for 5 min). Cathode polarization measured against a saturated calomel electrode shifts by –48 mV to –64 mV relative to a blank additive‑free electrolyte, suppressing dendritic growth on high‑aspect‑ratio 0.20 mm drilled holes and producing a uniform thickness distribution with ≤12% standard deviation along 18‑µm starting copper foil. The plating line must adhere to IPC‑6012E Class 3 annular ring requirements and pass thermal stress at 288°C for 10 s (IPC‑TM‑650 method 2.6.8) without barrel cracking. Compliance for North American electronics assembly additionally invokes UL 796F for flex‑rigid boards. Final products are multilayer PCBs (up to 16 layers) embedded in 5G base‑station power amplifiers and automotive ADAS camera modules, where void‑free copper deposition is mandatory for impedance control at 28 GHz. All electroplating chemical inventories are registered under the K‑REACH Existing Substance program and classified per UN GHS with aquatic chronic Category 3 labelling.

A comparative galvanostatic study conducted on a rotating disk electrode (2000 rpm, Pt ring‑disk assembly) quantified the shift in exchange current density i₀ from 0.48 mA/cm² (additive‑free) to 0.27 mA/cm² at 15 mg/L sulfinic acid, confirming strong adsorption on Cu(111) terrace sites. When the concentration exceeds 35 mg/L, the 10–90% rise time of the chronopotentiometric signal doubles, pointing to a limiting mass‑transport layer; thus the upper control limit is fixed at 28 mg/L on lines running 0.8‑mil blind vias with 1.2:1 aspect ratio.

When selectivity for copper against pyrite in alkaline flotation circuits becomes governed by sulfinic surface passivation

Porphyry copper operations processing 0.4–0.6% Cu feed with a pyrite content up to 12% employ 2‑benzothiazolesulfinic acid as a secondary collector injected into the first cleaner bank at 60–140 g/t of ore, co‑dosed with a polypropylene glycol methyl ether frother. Conditioning time in the attritioning tank is held at 8–10 min at natural pH 9.2–9.8, where the sulfinic functional group chemisorbs onto chalcopyrite surface iron sites, increasing contact angle measured by the captive‑bubble technique from 62° to 81° while leaving pyrite at 47°. Denver D‑12 batch flotation tests demonstrate a rougher‑scavenger copper recovery lift from 84.5% to 88.9% with a concentrate grade maintained at 24.8% Cu, while arsenic rejection, critical for ores carrying enargite, improves by 7 percentage points. The flotation tailing water reporting to the thickener must comply with Australia’s ANZECC 2000 guidelines for zinc and thiocyanate discharge, which restricts the sulfinic acid consumption to a maximum of 160 g/t when no dedicated polishing pond exists. Concentrate auto‑sampling follows ISO 12743:2021 procedures for mechanical sampling of copper concentrates, and final shipment is assayed against ASTM E255‑23 for copper determination. The sulfinic acid is shipped in 25‑kg fibre drums with UN‑approved inner liners meeting IMO 5.2 bulk cargo requirements. Destination smelters processing the blend into 99.99% LME‑grade copper cathode operate under Kazakhmys and Jinchuan tolling contracts that explicitly list permitted collector chemistries.

Latent epoxy imidazole replacement in QFN package underfill

A single‑component epoxy underfill formulated for 7×7 mm quad‑flat no‑lead packages mixes bisphenol‑F diglycidyl ether (epoxy equivalent weight 168 g/eq), 55 wt% spherical silica filler with a cut size of 0.5 µm, a dicyandiamide latent hardener at 6.0 phr, and 2‑benzothiazolesulfinic acid at 1.8–2.5 phr as a cure accelerator that lowers the onset of dicyandiamide dissolution and amine‑epoxy ring opening. Dynamic differential scanning calorimetry at 10°C/min ramping (ISO 11357‑1:2023) reveals a single exothermic peak with T_onset at 118°C and peak temperature reduced from 162°C (unaccelerated) to 138°C, with an enthalpy of reaction held at 310 J/g. Jet dispensing through a 25‑gauge needle at 60°C chip‑cap temperature requires a pot life at 25°C exceeding 24 h; the formulation retains a viscosity below 25 000 mPa·s (Brookfield CPE‑51, 10 rpm) after 26 h, confirmed by triplicate batch checks. Capillary underfill flow into a 25‑µm stand‑off gap completes within 4.8 s as monitored by a high‑speed camera, and after a 1‑h post‑mold cure at 150°C, the die‑shear strength meets MIL‑STD‑883K method 2019.9 with values consistently above 18 kgF for 5×5 mm die. Reliability testing comprises 1000 cycles of –55°C to +125°C thermal shock (JESD22‑A106B) with no delamination observable by scanning acoustic microscopy. The underfill conforms to UL 94 V‑0 at 0.8 mm thickness and is listed in the Qualcomm QCP‑21022 approved material index for flip‑chip packages. Over‑acceleration beyond 3.2 phr induces void formation in the filler‑resin interphase, evidenced by a 22% drop in the glass‑transition temperature measured by thermomechanical analysis (ISO 11359‑2:2021).

A high‑speed micro‑dispensing evaluation on a 300‑mm wafer‑level fan‑out line (Asymtek S‑930 with dynamic pinch) yielding 12 000 dots per hour registers a tail‑break deviation below 6% attributable to the controlled thixotropic index imparted by the sulfinic‑accelerated epoxy‑dicyandiamide cluster architecture. Wafer‑level underfill processed by compression molding with a 60‑s transfer cycle meets the IMDS (International Material Data System) reporting obligations for automotive‑grade semiconductors assembled under AEC‑Q100 Grade 1 qualification.

As an aqueous-phase flash rust inhibitor in solvent-free direct-to-metal primers

Waterborne styrene‑acrylic dispersions targeted for structural steel primer (solid content 48%, pH 8.2) incorporate the sodium salt of 2‑benzothiazolesulfinic acid at 0.20–0.50 wt% on total wet paint. The additive is introduced during the let‑down stage after the pigment grind consisting of 12% Barium metaborate and 6% zinc phosphate, held at 35–40°C under a dissolver disc at tip speed 5.2 m/s. Upon application by airless spray (pressure 180 bar, tip 0.019 in) onto grit‑blasted SA 2.5 (ISO 8501‑1:2007) hot‑rolled steel panels, flash rusting is evaluated after 24 h in a salt‑fog chamber (ISO 9227:2022, 5% NaCl, 35°C) prior to top‑coating. A digital image analysis calibrated per ASTM D610‑08 (2021) classifies surface rusting as 9‑R (less than 0.03% of surface area) at the 0.40% dose, compared to 3‑R for the control without sulfinic inhibitor. Electrochemical impedance spectroscopy at 0.01 Hz after 72 h immersion in 3.5% NaCl yields an impedance modulus |Z| of 2.8 × 10⁶ Ω·cm², indicating strong barrier preservation through the chelation of ferrous ions at the nascent corrosion microcells. The primer falls under EU Ecolabel 2014/312/EU for indoor paints and must comply with GB 30981‑2020 volatile organic compound limits applicable to industrial maintenance coatings (subcategory 412). Finished product is applied as a single‑coat DTM (direct‑to‑metal) system on offshore container frames and onshore wind‑turbine tower internals, where it achieves C4‑high durability classification under ISO 12944‑6:2018 when paired with an aliphatic polyurethane topcoat. A mandatory restriction is the incompatibility with zinc‑rich silicate shop primers: the sulfinic anion reduces the zinc dust cathodic protection efficiency, visible as a loss of open‑circuit potential below –860 mV vs. SCE, so a wash primer barrier must be applied in maintenance overcoating scenarios.