Zinc borate has roots in the early rise of fire safety standards in manufacturing. Folks around the industrial boom learned fast that fires spared no one, so there was a mad dash to cook up chemicals that could slow the spread or outright smother flames in everyday goods. Enter zinc borate. Some records date its practical use back to the 1970s, when plastics became the backbone of consumer goods. Engineers started mixing zinc compounds with borates as regulatory codes kept tightening around household items, electrical parts, and much more. Back then, lab techs squinted over beakers, trying to find flame retardants that didn’t poison people or break the bank. Zinc borate landed as a promising candidate. It meshed well with other flame retardants, showing off a knack for synergy that made it tempting to industries hungry for safer materials.
Zinc Borate 2335 carries a chemical structure that fuses both zinc and boron, forming a durable white powder. It draws interest not just as an additive in flame-proofing but as a general stabilizer and corrosion-fighting agent in plastics, rubber, ceramics, and paints. Most folks describe the product as a fine, off-white or pure white powder, almost fluffy, that blends into other compounds during mixing or extrusion. Several grades float around but 2335 dominates because it nails that balance between price and function, especially when working with lower-melting polymers or seeking minimal water release in high-heat settings. Factories count on its persistence — it doesn’t degrade quickly under stress, so it keeps protecting materials throughout their lifespan.
Zinc Borate 2335 comes in as a compound with the formula 2ZnO·3B₂O₃·3.5H₂O. Water content sits at about 3.5 moles per formula, which decides much of the processing — too much and it steams off in the melt, too little and it might not activate well at the needed temperature. Its melting point clocks in above 980°C, meaning it doesn't step aside easily under most processing conditions. Solubility in water almost doesn’t register, making it stable in wet environments or humid conditions. You get a powder with good flow, moderate bulk density, and no remarkable odor — not particularly dusty unless handled poorly. Chemically, it doesn’t burn, nor does it light up under normal fire test conditions. That’s the main trick: zinc borate gives up water and forms glassy borate residues when flames hit, cutting down smoke and blocking oxygen.
Manufacturers ship it in bags or drums, typically holding 25kg or more, labeled with its composition, batch number, and proper hazard warnings. Usually, the label confirms less than 1% insoluble matter, low heavy metal content, a zinc content hovering around 37%-40%, and boron around 48%-50%. Moisture test results come printed right there, since those numbers decide whether a batch works better for polyvinyl chloride, polyethylene, or melamine-based systems. Anyone working in compliance pays attention to the CAS Number (138265-88-0), hazard statements, and the REACH status in Europe or TSCA status in the States. I’ve watched warehouse staff reject shipments for missing UN codes or faded expiration dates — no company wants a compliance audit over bad stickers.
The process starts in reactors where zinc oxide and boric acid meet at controlled ratios. Water, sometimes as steam, plays a role in guiding the hydrate formation. You don’t need alchemy, just solid handling of temperatures and reaction times. The mix slurries up, crystallizes, filters, then dries down to a powder. Some operators tweak pH with soda ash to reduce contaminants. Filtration snags any unreacted rough stuff, and careful drying holds onto water of hydration where it matters. Some forms come out more granular, some chalky-fine, depending on drying and grinding setups. At plant scale, the success of the batch hangs on keeping the zinc and borate balanced — run too long and you get lumps, miss the mark and you tank your yield.
Heat treats this compound differently compared to simpler oxides. It loses water slowly, not all at once. Introduce it to a resin or polymer, and the fire triggers a slow dehydration that leaves behind borate glass and zinc oxide. In plastics mixes, this helps tamp down both flame spread and smoke production. Additives like antimony trioxide, alumina trihydrate, or magnesium hydroxide show up in recipes to increase or shape the flame-retardant effects. Over the years, researchers have tweaked the basic molecule, coating it or grinding it finer to improve dispersion or compatibility with new, trickier plastic blends. This is where R&D dollars go: finding surface treatments or granulation methods that boost shelf life or compatibility for the next generation of polymer systems.
Chemists and buyers toss around names like Firebrake ZB, Zinc Borate Hydrate, Tribasic Zinc Borate, or just plain ZB2335. CAS registry tags (138265-88-0) keep records straight, but in everyday talk, someone might just refer to it as “the zinc borate fire retardant.” Different suppliers attach brand names, hoping to nudge their version to the top of a purchasing manager’s spreadsheet.
Any industrial chemical needs sturdy safety playbooks, and Zinc Borate 2335 is no exception. Most safety data sheets put it as low toxicity, stating no acute poisoning with standard workplace exposures, but nobody wants a cloud of dust floating through air ducts. Personal protective gear — dust masks, basic gloves — is the rule in any plant. I knew a plant operator who cut corners with ventilation, only to regret it after a surprise inspection landed a huge fine. Disposal usually goes by standard local environmental regs; zinc itself isn’t easy on aquatic environments, so runoff management matters. Safe handling means dry environments, sealed bags, and clean storage — nobody wants a hygroscopic mess or chemical degradation ruining a costly shipment.
This additive shows up in places that surprise people. Beyond PVC wire jacketing and carpet backing, it supports structural foams, electrical connectors, circuit boards, household appliance parts, and some intumescent paints. I’ve seen cable manufacturers lean on it for smoke suppression just as much as fire resistance — regulations in transport and building construction tighten every year and push companies to chase lower toxicity and tougher flame spread requirements. More exotic uses pop up in ceramics for corrosion resistance or as a flux. As plastic recycling grows, newer blends need compounds that survive reprocessing, and zinc borate ticks that box. I’ve heard engineers say sometimes it’s the only thing standing between a safe product launch and a recall disaster.
Universities have set up labs to chase better flame retardant formulas, especially as antimony-based flame retardants lose favor over health concerns. Zinc borate’s ability to play well with halogen-free mixes is a key driver for R&D now. In recent years, scientists have also taken aim at tailoring particle size and surface coatings, looking for ways to help the powder disperse more evenly or improve chemical bonding in new types of plastics. Teams study interactions in nano- and micro-scale blends, watching how the material behaves under repeated heating, fouling, or stress. An idea getting more attention is the potential use in 3D printing applications and emerging bio-polymers, where additive compatibility isn't a given, and every small improvement brings big returns in safety and recyclability.
Zinc borate generally carries a reputation for low toxicity, which compared to older flame retardants like polybrominated diphenyl ethers, makes it a safer bet for consumer goods. Several studies have looked at acute ingestion and skin exposure — test animals show little toxicity unless exposed to absurd amounts, and it doesn’t build up in animal tissues the way heavy metals do. The main worry comes from workplace air — chronic exposure to dust needs minimizing mostly out of prudence. Environmental studies point out that both boron and zinc aren’t great for water life if they leak into rivers, so larger users must watch wastewater carefully, ensuring filters and traps don’t fail silently. That said, regulatory agencies in both the US and Europe have mostly issued a green light for use in products that don’t regularly contact skin or food.
The business side of zinc borate looks sturdy, especially as green chemistry moves into the mainstream. Fire regulations have a way of growing stricter, not more relaxed, so industries look for substances that don’t force tradeoffs between safety and health. Demand grows in electronics, especially as lithium-ion batteries get added scrutiny for fires. Emerging markets in Asia want affordable flame retardants they can trust to pass both US and EU standards. With plastics recycling on the rise, compounds that endure multiple processing cycles without degrading or leaching toxic byproducts are attractive. The ongoing challenge sits with further reducing environmental impact: less dust in manufacturing, improved recovery from waste streams, and recipes that use less energy to process at scale. The R&D effort won’t slow soon. There’s too much riding on making homes safer, meeting regulations, and keeping costs within reach, so you can bet zinc borate 2335 will hold its place in the market — and scientists will keep asking if it can do even more, even better.
A lot of folks talk about flame retardants like they’re some mysterious additive that only chemists need to worry about. But for anyone who’s ever thrown out a burned toaster oven or worried about faulty Christmas lights, it’s easy to see why safer plastics matter. Zinc Borate 2335 doesn’t sound flashy, but it’s crucial for keeping plastics from going up in flames.
Walk down the electrical aisle at any home improvement store. Every power strip or extension cord in there likely holds some blend of zinc borate. The stuff goes straight into PVC and polyolefins, cutting the risk that one little spark will set the casing alight. It blocks the chemical process that feeds a fire, working alongside other ingredients like antimony trioxide and aluminum trihydrate. What I’ve seen in my own shop is this — sometimes, good wiring alone doesn’t save you if the plastic can’t hold up to a heat spike.
Anyone who’s watched a roofing crew in July heat knows how insulation can get tested. Zinc borate finds a home in foam boards and siding, especially for buildings under tough safety rules. By working inside things like polyurethane foams, it helps construction meet fire codes without sending anyone shopping for expensive specialty materials. For people renovating old homes, there’s less worry about what’s hiding behind drywall if the insulation has better resistance to heat and flames.
One overlooked spot where zinc borate comes into play is wood composites—those beams and boards built from pressed wood chips. They save money and protect forests, but make for a fire risk if left untreated. Adding zinc borate gives these materials a better shot at holding up during a fire, which matters a lot if you think about apartment dwellers or warehouse workers surrounded by engineered wood all day.
It isn’t all about stopping fires, either. My neighbor had issues with termites eating away his deck over the years. Treated wood can help, but many conventional additives will fade or wash out over time. Zinc borate lingers longer and handles moisture better, making it a good fit for wood trim, fencing, and even playground sets. The mold resistance also helps inside wall cavities where you don’t want anything growing.
I’ve seen home repairs where the real cost doesn’t come from flames but from rot and bugs. While nothing is bulletproof, adding zinc borate to wood reduces that slow, quiet damage you usually find after it’s too late.
Outside the obvious uses, rubber gaskets and industrial conveyor belts count on zinc borate to stay safe. Factories use these all the time, and one mishap on a line can shut down the whole operation. The additive shields rubber from both heat and fire, which keeps things running longer.
Paint manufacturers have also tapped into zinc borate for coatings. It keeps mold off basement walls and helps paints perform in tough spots like hospitals or kitchens. This helps extend maintenance cycles, keeping costs down for building owners.
Regulations keep tightening, especially with toxic additives falling out of favor in plastics and consumer goods. Zinc borate offers a blend of safer handling and solid performance, without driving costs up to impossible levels. Factories can use it with standard equipment, and the supply chain for zinc and boron hasn’t gone the way of rare earth elements.
Whether you’re rewiring a kitchen, patching a fence, or working in a factory, it pays to know what’s keeping things safer behind the scenes. In my view, zinc borate 2335 deserves more credit for the way it quietly holds up everything from electronics to buildings.
Zinc Borate 2335 brings together zinc oxide and boric acid in a unique mix you won't find in your average household supplies. It sports the formula 2ZnO·3B2O3·3.5H2O. In plain speak, each molecule features two parts zinc oxide, three parts boron oxide, and three and a half parts water. Industry folks point to this specific blend for the way it handles heat and fights off flames. It contains about 45% zinc oxide by weight. Boron makes up most of the rest, with water molecules helping it keep its structural integrity. If you're judging by elements alone, you're looking at roughly 37% boron oxide, 3.5% water, and the balance from zinc.
Now, not all fire-retardant additives hold their shape at high temperatures. Zinc Borate 2335 stays stable up to 290°C—hot enough for most industrial processes. Ramp it higher, and it slowly gives up its water. At around 400°C, it dehydrates completely and starts breaking down. But in the thick of a house fire or the heat of extrusion lines, this stability means it won’t vanish too early or too late.
People who’ve handled zinc borate always mention its texture—a fine, white, powdery feel, not unlike talc or baking flour. It doesn’t have much odor. It rarely clumps up unless it gets wet, so it pours and mixes without fuss. This simplicity helps a lot in real-world manufacturing: nobody loves additives that gum up machinery. The density sits around 2.8 g/cm³, so it won’t float but doesn’t sink like a rock either when mixed with plastic pellets or rubber granules.
This compound does not dissolve much in water. That small but important feature lets it stay in paints, electrical coatings, or polymer blends without leaching out. In my experience working with composite panels, the non-solubility made a difference. Panels kept their fire-resistance years after installation, showing how additives like this stick around for the long haul.
The real push for zinc borate 2335 comes down to fire safety. It doesn’t act alone—it usually shows up beside halogen-free solutions, antimony trioxide, or aluminum trihydrate. It slows down burning and reduces smoke, which matters to anyone who’s ever watched news stories about deadly apartment fires. By creating a glassy layer when exposed to flames, it blocks oxygen and keeps underlying materials from feeding a fire. That simple reaction has cut property loss and injury in plenty of markets.
Zinc borate also gets pulled in for its resistance to fungi and pests. Playground equipment, power cables, flooring—all benefit from these properties. I’ve worked with engineers who saw budget cuts in municipal projects because they didn’t have to replace termite-damaged boards every few years. Treatments that use zinc borate guard electrical parts from rodents and bugs, which can mean avoiding costly blackouts or repairs.
As promising as zinc borate 2335 sounds, no chemical is perfect. The powdery form, while easy to blend, still creates airborne dust during production. Some factories have upgraded their ventilation and dust control systems to deal with this. For workers and the environment, keeping dust exposure low remains a priority. Research into pelletized or coated forms has picked up speed, aiming to reduce powdery mess without losing fire-slowing power.
There’s also the steady march toward “greener” additives. Folks in the field keep pushing for safer, cleaner flame retardants. Zinc borate’s relatively low toxicity compared to alternatives is an edge, but environmentalists stay cautious. Long-term runoff and disposal issues sit on the radar for regulators, so labs keep experimenting with new blends and recycling programs.
Zinc borate 2335 wants to stick around in manufacturing circles. By blending solid heat management, chemical durability, and some unexpected perks like pest resistance, it fills a niche that’s tough to beat. With a little more ingenuity, handling and environmental impacts could get even better—leaving plenty of room for new ideas to shape its future uses.
Fire risks haunt a lot of everyday products. Just think about plugging in your toaster, phone charger, or leaving kids’ toys out in the sun. A small spark or a surge, and the wrong plastic can melt or combust before you have time to react. Flammable plastics fill homes and workplaces; anyone who’s smelled that toxic plastic smoke during a wiring mishap won’t soon forget it. Lives are safer when materials slow flames down or stop them from spreading altogether.
Manufacturers want plastics that hold their shape, last through rough use, and don’t feed a fire. Zinc borate—specifically the 2335 grade—shows up in the mix. It isn’t some celebrity additive, yet step inside most electronics, furniture, wire coatings, or automotive interiors, and you start to see its footprint. It offers a blend of zinc and boron, both known for helping slow or stop burning; that's much more than just throwing sand on a fire. I’ve seen engineers treat it almost like a kitchen spice: it works best blended with other ingredients, which means fewer chemistry headaches and a better shot at passing fire safety standards.
Most plastics, by themselves, will burn fiercely with enough heat. Add zinc borate 2335 in, and it starts to make the flames stumble. As the material heats up, this powder helps soak up heat energy. Then, it releases water vapor—the kind you see when a candle hisses as it goes out. That vapor cools the surface and can keep oxygen away from the burning plastic. In a way, it’s forming a low-key barrier, making it tougher for a fire to catch hold.
There’s more. Once a polymer starts to char, zinc borate gets to work forming a crusty, glass-like layer. This layer blocks off more heat and oxygen from getting deeper into the material. Burning slows. Flames find less fuel. The result: products like electrical casings, insulation foams, and cables are less likely to turn into a raging torch. I still remember one wire manufacturer telling me how early versions of their product failed until they started using zinc borate. Suddenly, their cables passed flame spread tests and got insurance approval.
Of course, zinc borate isn’t magic dust. It doesn’t act alone and can’t always keep every mix totally flameproof. Most industrial recipes use it together with other agents like alumina trihydrate or antimony trioxide. Sometimes, adding too much changes how the plastic bends or flexes. Some folks worry about cost, because safer materials usually aren’t the cheapest. Many companies still cut corners, so questionable products wind up on bargain shelves, especially in markets where rules aren’t enforced.
If you want the next generation of electronics and cars to be safer, there’s no avoiding basic science and good standards. Zinc borate 2335 gives us a pathway—less toxic than older flame retardants, and it helps keep smoke and toxic gases in check. The real trick comes from not treating flame retardancy as a last-minute fix: manufacturers need to design plastics with these risks in mind from the first drawing. Maybe policy-makers and safety testers can work closer with industries, inspect more on-site, or enforce stricter product labeling. That keeps both people and homes safer, and ensures substances like zinc borate 2335 play their key part out in the open.
Anyone who has spent weeks blending additives on a compounding line knows how stressful it gets when compatibility problems sneak up on you. Most of us want to believe new flame retardants play nicely with others. Plenty of sales sheets about Zinc Borate 2335 hint this is the case. Truth sits in the details, right on the shop floor or inside a blown-out UL burn test.
I've watched so many customers try to solve a flammability rating issue just by upping one component—typically antimony trioxide or a halogen donor—without considering side effects. More than once, Zinc Borate 2335 has helped fill the gap. It brings some smoke suppression, stands up to higher temperatures better than other borates, and can reduce the dosage of older, dirtier halogenated options. That’s attractive, especially with pushback from environmental regulations against brominated products.
I remember working on a PVC insulation recipe where melting zinc borate right next to antimony trioxide got us solid LOI values but, annoyingly, led to surface blooming. Not every product behaves itself when wet-blending. Zinc Borate 2335 usually coexists with both halogenated and non-halogenated systems, but process temperatures, dosing, and pH adjustments matter. Use it alongside decabromodiphenyl ether or other brominated compounds, and often it acts synergistically, boosting the char-forming action and giving a cleaner burn. If you drop it into an ATH-heavy (aluminum trihydrate) or magnesium hydroxide system, there’s a dance around water release—determine which additive breaks down first or you risk unwanted foam or weaker mechanical properties.
There’s a lot of appeal in blends aiming for greener labels—phosphates, expandable graphite, some of these new nitrogen-based flame retardants. Can Zinc Borate 2335 join them? Often yes, but sometimes no, mostly due to shifting viscosity or side reactions. I’ve seen unpredictable thickening or clumping if someone skips a pre-mix trial. In my own work with EVA copolymer and polyamide blends, zinc borate has helped spread the burden, sometimes letting us lower total additive loading and meet both flammability and cost targets.
Zinc Borate 2335 still hits some trouble spots. In compounds where acidic byproducts emerge, think certain polyesters under heat, it can react unfavorably. Experienced hands use buffering agents or tweak compounding order so the borate meets as few enemies as possible. In flexible PVC, migration can become a concern if not enough stabilizer is present, so it’s a careful balancing act. Another issue turns up in pigments: zinc borate struggles with titanium dioxide in high-load white systems, which can mean streaking or unexpected color shifts. Here, the solution lies in finer particle grading or masterbatching steps, which I’ve watched make all the difference in cosmetics of finished parts.
Books tell part of the story, but most practical know-how flows through production staff and bench chemists. I’ve learned the hard way that small bench trials rarely capture the headaches of scale-up—water release, gassing and filter plugging all multiply in a busy manufacturing plant. Keeping open lines with additive suppliers helps, as they often know about quirks and tweaks that haven’t made it into the technical data sheets.
Choosing which flame retardants to combine with Zinc Borate 2335 needs some experimentation and willingness to call in help before bigger issues emerge in the field or, worse, in testing labs. People who get the best out of additive combinations work closely with their materials, never just following recipes but tinkering, probing, and testing. That hands-on approach creates safer, more durable, and sometimes even cheaper products—without endless compatibility headaches down the road.
Anyone who has dealt with Zinc Borate 2335 knows this powder rarely sits in the spotlight, but it quietly supports fire-retardant coatings, plastics, and even ceramics. Mess up the storing or handling, and suddenly your entire production line encounters knots. In my own shop, keeping specialty powders viable isn’t just about shelf-life; it’s about protecting workers, preventing costly waste, and holding up the reputation of your end product.
Moisture in the air can ruin a lot of chemicals, but Zinc Borate 2335 clumps quickly once it draws water. A sealed, tight drum or bag holds the powder as fresh as possible. I’ve seen crews toss open sacks back on the shelf after a shift—by the next month, weak paper packaging starts ripping, leaving chalky lumps that screw up mixing ratios. If you work anywhere humid, you’ll want to get serious about climate control. Targeting less than 50% relative humidity gives you a fighting chance.
Most shops don’t run into wild temperature swings, but it pays to keep Zinc Borate out of freezing zones and extreme heat. The powder itself doesn’t burn or melt under regular conditions; problems start with condensation inside bags if you bounce between hot and cold environments. In my experience, a basic insulated storage area—think somewhere between 15°C and 25°C, or 59°F to 77°F—handles ordinary shifts just fine. You just don’t want sweat and frost forming inside your barrels.
Every plant has that guy who grabs a scoop off the floor for loading powders. Seems harmless, until you start finding grime, scrap, or other chemicals in your next batch. Zinc Borate has a knack for picking up stray particles. Only use clean, dry tools and work in an area you can sweep up fast. Even one gritty mishap can trigger defects that look like someone never mixed the product at all.
It sounds old-fashioned, but stacking heavy bags at the bottom of a pile crushes contents and leaves an uneven mess. All the labeling in the world doesn’t help if boxes end up shuffled. In my last job, we kept one row for new material, another for what needed use next. Train your staff to grab older stock first. Otherwise, you’ll pull out yellowed, lumpy powder a year later and wonder why the end results don’t match specs. Marking every drum with the arrival date avoids these headaches.
Powdered chemicals float in the air or drop onto floors. Zinc Borate isn’t considered highly toxic, but inhaling it or getting it on skin for a long time can bother some folks. I learned quick: mask up, ventilate your work zone, and use gloves. Vacuum any spills with a HEPA filter instead of sweeping, or you’ll raise more dust. Wash any exposed skin before grabbing your lunch. These everyday steps keep operations smooth and workers healthy.
Quality storage and handling don’t demand fancy interventions, just real habits: dry and cool spaces, sealed containers, rotation of stocks, and a little discipline cleaning up. Every time I see a cracked bag left in the wrong spot, I know there’ll be trouble down the line. Respecting those basics means less waste, higher performance, and a lot fewer production headaches.
| Names | |
| Preferred IUPAC name | zinc;diboran(2-);hydrate |
| Other names |
Firebrake 500 Firebrake ZB |
| Pronunciation | /ˈzɪŋk ˈbɔːr.eɪt tuː θriː θriː faɪv/ |
| Identifiers | |
| CAS Number | 1332-07-6 |
| Beilstein Reference | 1722906 |
| ChEBI | CHEBI:91514 |
| ChEMBL | CHEMBL1201733 |
| ChemSpider | 170363 |
| DrugBank | DB14582 |
| ECHA InfoCard | 100.027.923 |
| EC Number | EC 235-804-2 |
| Gmelin Reference | ZnB 4 |
| KEGG | C18637 |
| MeSH | Zinc Borate |
| PubChem CID | 16682986 |
| RTECS number | ZD0870000 |
| UNII | WI4N83Y6VU |
| UN number | UN3077 |
| Properties | |
| Chemical formula | 2ZnO·3B₂O₃·3.5H₂O |
| Molar mass | 306.23 g/mol |
| Appearance | White powder |
| Odor | Odorless |
| Density | 2.67 g/cm³ |
| Solubility in water | Insoluble in water |
| log P | 0.85 |
| Vapor pressure | <0.01 mm Hg (20°C) |
| Basicity (pKb) | 6.7 |
| Magnetic susceptibility (χ) | 0.0000061 cm³/mol |
| Refractive index (nD) | 1.58 |
| Thermochemistry | |
| Std molar entropy (S⦵298) | 86 J·mol⁻¹·K⁻¹ |
| Std enthalpy of formation (ΔfH⦵298) | -1016 kJ/mol |
| Pharmacology | |
| ATC code | V03AX |
| Hazards | |
| Main hazards | May cause respiratory irritation. Causes serious eye irritation. May cause damage to organs through prolonged or repeated exposure. |
| GHS labelling | GHS07, GHS09 |
| Pictograms | GHS07,GHS09 |
| Signal word | Warning |
| Hazard statements | H319: Causes serious eye irritation. |
| Precautionary statements | P261, P264, P271, P272, P302+P352, P305+P351+P338, P312, P332+P313, P362+P364 |
| Autoignition temperature | Above 450°C (842°F) |
| Lethal dose or concentration | LD50 (Oral, Rat): >10,000 mg/kg |
| LD50 (median dose) | > 10,000 mg/kg (rat, oral) |
| NIOSH | NA |
| PEL (Permissible) | 15 mg/m3 |
| REL (Recommended) | 7.0 |
| IDLH (Immediate danger) | Not listed |
| Related compounds | |
| Related compounds |
Boric acid Zinc oxide Barium borate Calcium borate Magnesium borate |
