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Bismuththiol (DMTD): an insider’s look at a quietly essential additive If you work in lubricants, metalworking fluids, or electronics protection, you’ve almost certainly crossed paths with cas 1072 71 5 — better known as DMTD. To be honest, it’s not the flashiest molecule on the datasheet, but it’s a workhorse: a sulfur-rich, heterocyclic corrosion inhibitor and EP/antiwear booster that quietly keeps copper bright and gear teeth safer under load. What it is and why it matters Bismuththiol is the trade name here, though the chemistry behind it is 2,5-Dimercapto-1,3,4-thiadiazole (DMTD). Synonyms: 1,3,4-thiadiazole-2,5-dithiol; DMTD. In practice, formulators value it for three things: passivating yellow metals, boosting extreme-pressure performance, and playing nicely (mostly) with ashless packages. Actually, it also helps tamp down catalytic oil degradation around copper coils and bearings — a small tweak with a big life-cycle impact, many customers say. Industry trends I keep hearing Shift toward lower-P, lower-S packages while still needing EP performance; DMTD remains in the toolbox because dose rates can be modest. Electronics cooling and EV driveline fluids: rising demand for robust copper protection without staining. Compliance-first sourcing (REACH/RoHS/ISO 9001), and yes, traceable QC data, not just “typical” numbers. Typical product specifications (Bismuththiol / DMTD) Name Bismuththiol (DMTD) CAS No. cas 1072 71 5 (also written as CAS 1072-71-5 ) Appearance Off‑white to light yellow crystalline powder Purity (HPLC) ≥98% typical (real-world batches may vary slightly) Melting point ≈170–178 °C Water (KF) ≤0.5% typical Solubility Low in water; soluble in polar aprotic solvents; dispersible in oils with proper diluents Packaging 25 kg fiber drum, inner PE liner Origin 2-7-523 Jidong Building Materials, Tangshan, Hebei 064000, China How it’s made and qualified (process flow) Materials: carbon disulfide, hydrazine/thiosemicarbazide, base, solvent. Method: cyclization to 1,3,4-thiadiazole core; thiol formation; controlled precipitation; washing; drying. QC: HPLC assay, FTIR identity, ICP metals (ASTM D5185-style), KF moisture, particle size where relevant. Performance tests: ASTM D130 (copper strip), D2783 (four-ball EP), D4172 (four-ball wear) [2–4]. Service life: sealed shelf life ≈ 24–36 months; in-oil performance depends on additive synergy and base oil. Where it’s used Industrial gear oils, hydraulic fluids (non-zinc and ZDDP-containing), metalworking fluids, greases, transformer and immersion-cooling fluids for electronics, and specialty anti-tarnish coatings for yellow metals. Advantages include strong copper passivation, EP uplift at modest treat, and compatibility with common antioxidant packages. Real-world snapshot (case study, summarized) In a mid-viscosity gear oil, adding 0.25–0.35 wt% DMTD reduced ASTM D130 from 3a to 1a and raised four-ball EP weld load by around 10–15% (formulation-dependent). Wear scar per ASTM D4172 improved slightly; color stability around copper coils noticeably better after 1000 h storage. That’s pretty typical of cas 1072 71 5 chemistry, although your mileage may vary. Vendor comparison (at-a-glance) Vendor Purity spec Customization Certs Lead time MOQ Moneidechem (Bismuththiol) ≥98% HPLC Particle size, oil-diluted forms, salts ISO 9001, REACH-ready, RoHS Around 7–14 days 25 kg Generic Trader (CN) 96–98% Limited Basic COA 10–20 days 25–50 kg EU Distributor ≥98% Pre-dissolved concentrates REACH, ISO Stock-dep. 5–25 kg Customization tips Ask for oil-diluted masterbatches to simplify dosing in cold rooms. Consider salts/derivatives for improved solubility where needed. Request full QC pack: HPLC chromatogram, FTIR, KF, metals, and an ASTM D130 screening on a standard base oil. In short, cas 1072 71 5 continues to earn its keep. The trick is pairing it with your antioxidant/antiwear system and validating via ASTM D130/D2783/D4172 so you don’t over- or under-treat. I guess that’s the fun part of formulation. Authoritative citations PubChem: 2,5-Dimercapto-1,3,4-thiadiazole (DMTD). https://pubchem.ncbi.nlm.nih.gov/compound/2_5-Dimercapto-1_3_4-thiadiazole ASTM D130 Copper Strip Corrosion (overview). Intertek. https://www.intertek.com/petroleum/testing/astm-d130/ ASTM D2783 Four-Ball EP Method (overview). Intertek. https://www.intertek.com/petroleum/testing/astm-d2783/ ASTM D4172 Four-Ball Wear (overview). Intertek. https://www.intertek.com/polymers/testlopedia/astm-d4172/