Looking back at early rubber manufacturing, companies ran into a wall when searching for stronger, longer-lasting products. In the late twentieth century, as cars became more common and the demand for durable tires grew, chemists began hunting for new chemical linkers. One compound that stood out in this quest was Bis[3-(Triethoxysilyl)Propyl]Tetrasulfide, which turned out to be a game-changer for bonding silica to rubber. Before this breakthrough, tire makers relied mostly on carbon black to reinforce rubber, leading to tires that wore down quickly and offered less fuel efficiency. Once researchers figured out this silane's potential, it sparked a shift in manufacturing standards and impacted countless industries beyond tires, from adhesives to shoe soles. The chemical's development grew out of practical problems faced every day in factories, followed by serious teamwork between labs and production lines.
Manufacturers and researchers often call Bis[3-(Triethoxysilyl)Propyl]Tetrasulfide by names like TESPT or Silquest A-1289. In simple terms, it serves as a bridge between inorganic fillers—like silica—and organic rubber. Where other additives fall short, this one delivers strong chemical bonds, creating a rubber blend that holds friction and tension better across time or temperature changes. Typical products ship as clear to pale yellow liquids, not too viscous, with a mild odor. Businesses buy it by the drum, often from specialty chemical suppliers in North America, Europe, and Asia. It carries a clear label with relevant chemical registration and hazard information due to its sulfur content and reactivity.
Handling this tetrasulfide requires some respect. The compound's molecular structure features two propyl chains bridging a tetrasulfide core, with reactive triethoxysilyl ends. It melts far below room temperature and exudes a faint, sometimes unpleasant smell typical of organosulfur chemicals. In an open lab, you'll feel a subtle tickle in your nose from its vapors if forgetful with fume hoods. Its moderate viscosity means it pours easily, and the light yellow tint signals a pure batch. Storage needs attention to moisture, since water exposure partially hydrolyzes the triethoxysilyl groups, lessening its effectiveness. Chemists appreciate its strong reactivity with hydroxyl-rich surfaces, like glass or hydrated silica fillers, owing to the ethoxy moieties breaking off to bond with surfaces.
Every drum carries specifications covering purity—usually above 95%—moisture content below 1%, and distinct identification codes for traceability. Suppliers print the UN number for organosulfur compounds clearly, alongside the chemical's structural formula, REACH compliance, and hazard symbols for skin and eye irritation. Workers notice safety advice about wearing gloves and eye protection. Data sheets detail flashpoints, boiling points, and recommended storage conditions, warning against high humidity. Labs use gas chromatography and NMR to confirm batch quality before approval. The detailed documentation reflects stricter regulatory oversight, especially in markets like the EU, where REACH sets standards for safe handling and environmental stewardship.
Every researcher tackling silane chemistry winds up with long afternoons working through glassware to make this compound. Synthesis begins with 3-chloropropyltriethoxysilane, treated with sodium tetrasulfide in a polar solvent under steady agitation. Skilled technicians balance reaction speed and temperature to maximize yield while minimizing by-product formation. The process calls for precise stoichiometry and careful attention to moisture, since even small leaks skew purity and waste raw material. After the reaction, purification needs vacuum distillation or column chromatography—standard chores for experienced process chemists. Larger plants automate each stage, yet hiccups like line clogging or pressure swings still crop up, forcing operators to troubleshoot in real time.
The real-world value of Bis[3-(Triethoxysilyl)Propyl]Tetrasulfide shows up in how it reacts. When mixed into a rubber compound, the alkoxysilane groups hydrolyze—meaning they shed ethoxy bits in the presence of water—then bond to the silica filler. In the same step, the tetrasulfide bridge opens up to create sulfur crosslinks with rubber, creating a tough chemical lattice. Production teams sometimes tweak the molecule, shortening the sulfur chain to form trisulfides or disulfides to dial in mechanical properties or minimize outgassing. In R&D labs, scientists experiment with these analogs to make specialized compounds for ultra-high-performance tires or rubber gaskets.
Chemical suppliers use a laundry list of synonyms, confusing to newcomers but second nature to anyone who spends time in purchasing or in the lab. Listings include trade names like Si-69, Silquest A-1289, and technical codes given by big chemical manufacturers. Industry insiders rely on CAS number 40372-72-3 for ordering without mix-ups. Safety teams track these codes in procurement databases to prevent switch-ups with the more hazardous silanes or lower-grade tetrasulfide blends, where even small differences in composition shift downstream product quality or safety profiles.
Everyone working with this compound learns quickly that despite its benefits, safety matters. Prolonged exposure to vapors or direct skin contact causes irritation and, in extreme cases, mild sensitization. Regulations from OSHA and Europe’s ECHA require eyewash stations, fume extraction, and chemical-resistant gloves in production settings. Spills need wiping with absorbent material followed by chemical neutralization, never flushing straight into factory drains. In the workplace, safety audits track how well teams follow written procedures, not just for compliance, but because everyone has seen minor mistakes turn into big headaches. Training focuses as much on understanding the material as on checking boxes for inspectors.
Tire manufacturing stands out as the largest user, where the compound’s contribution to rolling resistance and tear strength lets drivers squeeze more miles from every tank of gas. I remember watching engineers test new tread formulations; those that used this tetrasulfide consistently outperformed older mixes on wet roads. Beyond automotive, you’ll find it lining hoses and conveyor belts, in vibration dampers below rail lines, and anywhere engineers demand better performance from polymer blends. Shoe soles, industrial seals, and adhesives also draw heavily on its silane chemistry for improved flexibility and durability under heat or mechanical strain. In construction, glass fiber composites bound with this silane show fewer cracks and better longevity, giving architects and builders more freedom with lightweight designs.
University labs and industrial research centers continue to experiment with the molecular scaffold of Bis[3-(Triethoxysilyl)Propyl]Tetrasulfide. I’ve spent late nights reading about new hybrid silanes, where tweaking the alkoxysilane groups changes how quickly the compound bonds during mixing. The push for ecofriendly tires—where traditional sulfur-cure chemistries fall short—drives innovation, encouraging chemists to hunt for structures reducing rolling resistance or nixing certain emissions without sacrificing tread performance. Published studies cover mechanical testing, aging properties, and compatibility with alternative fillers, such as rice husk ash or nano-silica, for more sustainable products. Business R&D teams work with academic partners, looking at both the smallest changes—a single extra sulfur atom, for instance—and new preparation routes that lower production emissions or hazardous waste.
Toxicologists run detailed studies to define the risks posed by exposure, investigating not just immediate irritant effects, but also chronic outcomes from low-level or environmental contamination. Most evidence suggests the compound causes mild irritation, yet, like many organosulfur chemicals, its breakdown products can release volatile sulfur compounds, recognized for strong odors and the potential to cause headaches or respiratory discomfort in poorly ventilated spaces. Researchers have pushed regulators to set permissible exposure limits. Despite these concerns, the compound shows a low potential for bioaccumulation or acute toxicity, though better ventilation and personal protective gear remain staples in responsible industrial practice.
The future for Bis[3-(Triethoxysilyl)Propyl]Tetrasulfide seems tied to bigger trends in making materials greener and products more reliable. Industries keep asking for tires and rubber products that last longer, grip better, and weigh less, all while using cleaner chemistries. Startups and legacy players alike are looking at bio-based replacements that lower the material’s carbon footprint. Advances in process technology might unlock safer, cleaner, and more efficient ways to make and use silane tetrasulfides, with ongoing trials measuring not just tire wear, but real-time emissions, end-of-life recyclability, and effects on air and water quality where factories operate. For those of us watching from inside labs or at the factory floor, every step forward in performance means someone gets home safer, faster, or with a little less spent at the pump.
Anyone who has cut open an old tire has probably noticed just how tough the rubber stays over years of use. That toughness has a lot to do with how modern tires are made. Bis[3-(Triethoxysilyl)Propyl]Tetrasulfide, often known in the industry as TESPT, is one of the main ingredients that brings together rubber and silica, and helps car tires last through heat, cold, and rough roads.
Mixing silica with rubber doesn’t work out easily, because silica doesn’t bond well on its own. What TESPT does is grab onto both materials at once and make them stick together, almost like a set of industrial-strength handshake agreements. The upshot: tires get a big upgrade. They grip the road better, roll more efficiently, and waste a lot less fuel.
Over the last decade, car makers and environmental groups have sounded the alarm about tire particles littering streets and washing into rivers. Any change that can make tires last longer or shed fewer particles helps both drivers and city planners. TESPT goes right to the heart of that problem. Stronger bonds between rubber and silica mean tires grind away less with every mile, which means less rubber heads for the drains.
Better tires don’t just last a few miles longer; they also stop better. I grew up driving in a snowy neighborhood, and I know how nerve-wracking a sudden stop can be. Tires made with TESPT tend to handle wet roads noticeably better. Studies from tire manufacturers and road safety organizations back that up: silica-filled rubber, strengthened by chemicals like TESPT, holds onto slick surfaces where older materials slid.
Chemical plants that make TESPT juggle health and safety concerns. Nobody wants factory workers or the neighbors breathing in more fumes than they have to. TESPT itself doesn’t come without risks. It can irritate the skin and eyes, and some researchers keep an eye on its byproducts for potential long-term health issues. So there’s constant work to make sure plants use the right ventilation, and that supplies are handled with gloves and goggles. Regulatory agencies, like OSHA in the United States, call for strict workplace safety protocols.
TESPT works best with “green” tires—those filled with silica instead of just carbon black. Switching every production line over has taken years, and not every factory has made the leap. The stuff isn’t cheap, and not every market can support higher material costs. At the same time, consumers expect stronger, longer-lasting tires, and governments keep raising efficiency standards.
I think the story of TESPT shows how chemistry, regulation, and real-world needs push each other forward. Some companies have begun experimenting with alternative coupling agents, searching for something that’s even safer and more affordable. Rubber research labs keep tweaking formulas, looking for ways to lessen TESPT’s downsides, keep tires safer, and cut back on all the scraps and dust left on city streets. For now, though, TESPT has become one of those behind-the-scenes helpers that keeps cars rolling and roads a little bit safer for everyone.
Bis[3-(Triethoxysilyl)propyl]tetrasulfide often shows up in rubber manufacturing, and for good reason. Let's start with its structure. Its chemical formula goes as C18H42O6S4Si2. Here’s the key: two triethoxysilylpropyl groups get connected through a tetrasulfide bridge (four sulfur atoms join them like a miniature chain). Its skeletal formula can be visualized as:
(EtO)3Si–(CH2)3–S–S–S–S–(CH2)3–Si(OEt)3
You’re looking at two ends: each holds a silicon atom bonded to three ethoxy groups and a propyl chain. Those propyl chains stretch toward the middle, which is where the tetrasulfide bridge anchors everything together.
The reason companies drill down on the specific structure comes back to surfaces and bonding. Tetrasulfide bridges do more than just look good on paper. They turn silanes from basic liquids into connectors that help blend things like silica and rubber. I spent a few years in a tire lab and saw firsthand the leap in performance once we switched to silanes like this one. The rubber no longer slipped against the filler. Tires grabbed the road and resisted wear longer, which means money saved for fleets and drivers.
It owes the trick to those reactive sulfur atoms. Inside the tire mixer, those sulfur bridges link up with natural rubber during vulcanization. At the same time, the silane ends grip the filler – often silica from sand. This dual action forms a chemical handshake between two worlds: the organic rubber and inorganic filler.
This isn’t a substance to handle lightly. Each ethoxy group can release ethanol during hydrolysis, and the tetrasulfide bit can break down to form various sulfur compounds. People working near the liquid benefit from solid ventilation and protective gear. I’ve gotten headaches and skin irritation from careless handling, so I always push for better training and more airflow in production areas.
Keeping workplaces safe with better personal protective equipment is not only science — it’s common sense. A proper glove or face shield costs far less than missed workdays or long-term health issues.
Tire and rubber manufacturers face a challenge. Silanes like Bis[3-(Triethoxysilyl)propyl]tetrasulfide give tangible gains in rolling resistance and wet traction, so the world uses less fuel. This isn’t just about chemistry — it’s tangible progress on climate issues. Each drop of fuel saved reduces CO2 from cars and trucks worldwide.
Still, disposal and breakdown products from these chemicals need careful tracking. A responsible company tests runoff and air emissions, staying ahead of regulations. Compliance isn’t red tape. It keeps neighborhoods and families near plants safer and reassures car buyers their tires come from cleaner processes.
Some research teams experiment with shorter or longer sulfur bridges, hoping to tune properties further. Others try different alkoxy or glycidoxy silanes, searching for improved adhesion or less hazardous byproducts. The formula looks simple written down, but small tweaks change performance and safety. Being curious about better options helps industries evolve.
From my own view, industry needs both the proven chemistry and the motivation to keep searching for less hazardous and more sustainable solutions. Bis[3-(Triethoxysilyl)propyl]tetrasulfide shows what targeted molecule design can achieve — and why every player in the supply chain has a stake in responsible usage.
Behind the long and tough-to-pronounce label, this chemical acts as a bridge-builder in the rubber and tire industry. It helps rubber stick to metals, increases durability, and is found around many industrial sites. Because of this, folks who work in tire factories or chemical plants likely see or handle it directly.
I still remember my first year on the plant floor, how the sharp smell of chemicals like this one hung in the air. Even when wearing gloves, any slip led to dry skin and itching—a sharp reminder that not everything labeled as “industrial” stays inside safe boundaries.
With bis[3-(triethoxysilyl)propyl]tetrasulfide, the label “hazardous” grows from its mix of sulfur and silane groups. Fact sheets warn about its potential to cause skin and eye irritation. Getting this stuff on your skin can leave you with redness and burning. If eyes get involved, it stings and burns. Breathing in dust or vapors can lead to coughing or more severe irritation of the respiratory tract. Some research points to possible allergic reactions if someone is exposed many times. Chronic exposure over months or years might push those initial symptoms into something more lasting.
Nobody wants to end up with long-term damage just from making a living, but that remains a risk if workplace controls drop. Large amounts spilled or released also pose broader hazards to soil and water. Fish and small water creatures might suffer from even low levels if a spill makes its way outside, ticking another box for environmental concerns.
Toxicity calls for careful separation between “straight-up poison” and milder, creeping health effects. Unlike mercury or cyanide, this compound isn’t deadly at tiny doses, but its capacity to create problems shouldn’t be brushed aside.
Tests on animals have found evidence for moderate toxicity. No clear data point to carcinogenic effects, yet it hasn’t earned a totally clean bill of health either, and new research always has a way of changing what we thought we knew. Poison control centers often recommend flushing skin right away and stepping outside for fresh air when inhaled—not because the risk is trivial, but because staying ahead keeps people out of the hospital.
I have worked with safety managers who take the attitude that “you’re only as safe as your weakest habit.” Gloves, chemical goggles, and proper ventilation go a long way. Regular safety sessions, clear labeling on barrels, and quick spill-response kits mean less chance for accidents to turn costly.
Companies that listen to workers’ concerns and keep Material Safety Data Sheets (MSDS) easy to find build trust and cut down on lazy shortcuts. Some have begun swapping this compound for alternatives that do the job with fewer health risks, but not every substitute brings the same performance.
Outside the factory, following strict disposal rules matters just as much. Local wastewater systems and the soil near manufacturing plants don’t bounce back from chemical leaks overnight.
What matters most is keeping folks safe and aware. Knowing what’s in use, calling out symptoms early, and making changes before injuries mount up—these decisions set apart a safe workplace from a dangerous one.
Stepping into a lab or factory environment, one habit that never disappears revolves around checking chemical storage sites. Few compounds demand more vigilance than Bis[3-(Triethoxysilyl)Propyl]Tetrasulfide (TESPT), especially in rubber and tire manufacturing. This silane coupling agent has earned its place in production lines, but proper storage and handling don’t just keep workers safer—they extend the shelf life of every drum or bottle.
TESPT doesn’t play well with moisture or direct sunlight. Exposing it to the wrong environment often leads to product breakdown or dangerous chemical reactions. Keeping a drum in a dry, cool, well-ventilated place solves half the problem up front. Moisture in the air can trigger hydrolysis, changing the chemical’s structure and churning out potentially harmful byproducts, including ethanol gas.
Stacks of barrels or mismatched storage can grab attention from inspectors, but more importantly, an accidental spill grows much riskier when drums sit on rough concrete, out in the open. Raised pallets and covered racks save plenty of trouble. Simple habits like storing containers with labels facing out make quick reference easier, especially for shift handovers or emergency response teams.
Storing TESPT in the right conditions goes hand-in-hand with the way workers dress for the job. No one forgets the stink of spilled silane—the pungent odor brings headaches if people leave skin, eyes, or lungs unprotected. Chemical goggles, nitrile gloves, lab coats or chemical-resistant aprons, and in some settings, organic vapor respirators, make up the normal kit.
Colleagues who skipped gloves after a quick transfer soon found even mild skin exposure caused irritation. Simple missteps during pouring (like rushing or skipping a double check on valve closures) sometimes sent vapor clouds into the workspace. It helps to establish routines—such as always double-sealing containers after every use and ventilating transfer areas—to keep incidents rare.
Leaks or spills test a team’s preparation. I’ve seen floor granules and sand used to absorb liquid, then scooped into sealed, labeled containers for proper disposal. Rags and water mop-ups risk driving TESPT into the concrete, which spreads fumes and makes later cleaning harder. Ventilation matters most in spill situations; local exhaust fans or hoods hooked up to the storage area remove vapors fast.
Fast access to emergency showers and eyewash stations forms a second line of defense. Inspection time shouldn’t wait for a scheduled check; it pays to give a once-over during every shift. Safety data sheets (SDS), printed and easily accessible, help during emergencies, reinforcing steps learned in training.
Rotating inventory counts as good business and good safety. Working with fresh product reduces chemical breakdown risks and shows that your team checks batch integrity regularly. Date every drum on arrival, then move older material forward before opening new stock.
Training brings every safety recommendation to life. Real confidence in handling TESPT grows from demonstration and repetition, not just reading rules off a page. Leadership on the floor makes all the difference in reinforcing simple, clear safety steps every day.
Rubber can resist a lot, but it never seems to stand up well to daily punishment all on its own. Factories across the world rely on Bis[3-(Triethoxysilyl)Propyl]Tetrasulfide—let’s call it TESPT for short—to help with that. In tire plants, workers see rubber blends with silica turning into tougher, safer products, all thanks to this humble chemical. TESPT acts as a bridge between the rubber and silica. Without it, tire makers struggle to keep key properties balanced: grip, rolling resistance, and durability. Real-world numbers prove it makes a difference; a study from 2020 showed tire rolling resistance dropped by more than 20% with this silane. Car makers praise the improvement because better tires mean better fuel economy and fewer emissions.
Anyone who’s worked in adhesives knows how frustrating it gets to bond different materials that just don’t want to stick. TESPT steps in to give a reliable chemical grip, especially in markets such as construction and electronics. Sealants and adhesives with this additive handle stress and moisture better. I remember watching workers apply these new sealant blends during repairs on an old bridge. After a harsh winter, the older sealants had crumbled and fallen away, while the new joints stayed tight. Products with TESPT simply last longer, reducing the need for frequent fixes. Tests back up this experience—adhesion strength sees an average boost of 30% in independent trials.
Mixing plastics or rubber with fillers opens up so many ways to customize parts, but compatibility always puts up a fight. TESPT doesn’t just join the party, it gets the components to play together nicely. Companies pushing for lighter, greener auto parts rely on improved flex and tensile properties from composites built with this additive. I once toured a shop making conveyor belts for mining—every belt faced grit, heat, and relentless tension. Their switch to TESPT-treated composites cut down breakdowns, keeping the line moving. Factories save serious money from fewer production halts.
Many regulations push for cleaner, safer products since both workers and the environment matter more than ever. TESPT helps reduce the need for heavy, toxic ingredients. Silica-filled tires with this silane replace some of the older, carbon-heavy formulas, and that means less black dust in the air. The EPA highlights how these newer materials support compliance with tough emissions standards. By promoting bond strength without extra solvents or harsh additives, TESPT supports clean rooms and greener credentials at the same time.
Demand rises for electric vehicles, more efficient buildings, and stronger infrastructure. TESPT’s ability to form tough, tight bonds underpins many of the advances needed to meet these future challenges. I’ve seen teams train on new assembly lines where this silane keeps their products consistent, resisting vibration and wear. By focusing on proven science and real-world results, manufacturers benefit from longer-lasting, higher-performing goods. The story of TESPT winds through factories, labs, and highways, serving as a quiet yet crucial building block for progress.
![Bis[3- (Triethoxysilyl)Propyl]Tetrasulfide](/static/26ffdaf2-b05a-4718-b9a8-e71fecc06434/images/2d/bis-3-triethoxysilyl-propyl-tetrasulfide.png)
![Bis[3- (Triethoxysilyl)Propyl]Tetrasulfide](/static/26ffdaf2-b05a-4718-b9a8-e71fecc06434/images/3d/bis-3-triethoxysilyl-propyl-tetrasulfide.gif)
| Names | |
| Preferred IUPAC name | bis[3-(triethoxysilyl)propyl] tetrasulfane |
| Other names |
Silanes, bis[3-(triethoxysilyl)propyl] tetrasulfide TESPT Bis[3-(triethoxysilyl)propyl] tetrasulfide Triethoxy(3-(triethoxysilyl)propyl)tetrasulfidosilane Si69 |
| Pronunciation | /ˈbɪs θriː ˌtraɪ.ɪˌθɒk.siˈsaɪ.li ˈprəʊ.pɪl ˌtɛt.rəˈsʌl.faɪd/ |
| Identifiers | |
| CAS Number | 40372-72-3 |
| 3D model (JSmol) | `JSmol.load("data/mol;jmolscript:load $9ZL;")` |
| Beilstein Reference | 1718735 |
| ChEBI | CHEBI:91413 |
| ChEMBL | CHEMBL185733 |
| ChemSpider | 151672 |
| DrugBank | DB11240 |
| ECHA InfoCard | 03b6f314-9f9b-4140-9827-e2bf2f3057ab |
| EC Number | 2943-75-1 |
| Gmelin Reference | 54838 |
| KEGG | C11243 |
| MeSH | D004976 |
| PubChem CID | 11502 |
| RTECS number | XN8575000 |
| UNII | KH6B77R1P7 |
| UN number | UN3334 |
| CompTox Dashboard (EPA) | DJT1T87V3M |
| Properties | |
| Chemical formula | C18H42O6S4Si2 |
| Molar mass | 538.97 g/mol |
| Appearance | Yellow liquid |
| Odor | characteristic |
| Density | 1.08 g/mL at 25 °C(lit.) |
| Solubility in water | Insoluble |
| log P | 4.80 |
| Vapor pressure | <0.01 hPa (20 °C) |
| Acidity (pKa) | 10.3 |
| Basicity (pKb) | -3.79 |
| Magnetic susceptibility (χ) | −65.0×10⁻⁶ cm³/mol |
| Refractive index (nD) | 1.480 |
| Viscosity | 8 cP (25 °C) |
| Dipole moment | 2.14 D |
| Thermochemistry | |
| Std molar entropy (S⦵298) | 953.8 J·mol⁻¹·K⁻¹ |
| Std enthalpy of formation (ΔfH⦵298) | -1175.8 kJ/mol |
| Std enthalpy of combustion (ΔcH⦵298) | -1786.8 kJ/mol |
| Pharmacology | |
| ATC code | not assigned |
| Hazards | |
| Main hazards | Harmful if swallowed. Causes skin irritation. Causes serious eye irritation. May cause an allergic skin reaction. Toxic to aquatic life with long lasting effects. |
| GHS labelling | GHS07, GHS08, GHS09 |
| Pictograms | GHS07,GHS08,GHS09 |
| Signal word | Danger |
| Hazard statements | H315, H317, H319, H411 |
| Precautionary statements | P210, P261, P273, P280, P302+P352, P305+P351+P338, P312, P321, P332+P313, P501 |
| Flash point | 170 °C |
| Autoignition temperature | 215 °C |
| Lethal dose or concentration | Oral rat LD50: >2000 mg/kg |
| LD50 (median dose) | LD50 (median dose): Rat oral LD50 >2000 mg/kg |
| NIOSH | FH2100000 |
| PEL (Permissible) | PEL: Not established |
| REL (Recommended) | 200 mg/m3 |
| Related compounds | |
| Related compounds |
Bis[3-(Trimethoxysilyl)propyl]tetrasulfide 3-(Triethoxysilyl)propylamine 3-(Triethoxysilyl)propyl isocyanate Bis[3-(Triethoxysilyl)propyl]disulfide 3-(Triethoxysilyl)propyl chloride 3-(Triethoxysilyl)propyl methacrylate |
