Back in the early days, industries relied on heavy halogenated compounds to slow down fires, which did the trick but left us with environmental headaches. DOPO-HQ, or 10-(2,5-dihydroxyphenyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, started gaining ground in the late 20th century as researchers recognized the toll that older flame retardants had taken on both people and the planet. The compound’s roots trace to academic labs, where scientists, tired of dangerous, persistent pollutants, started fiddling with phosphorus-based options. After a few rounds of chemical chess in the lab, DOPO-HQ took shape, boasting high thermal stability and low toxicity, catching the eye of everyone from electronics engineers to furniture makers.
This compound never struck me as just another powder or resin additive while working with plastic manufacturers. It’s a white or off-white solid, dissolves well in many organic solvents, and handles high heat without breaking a sweat. Unlike many other chemicals that spit out black smoke or toxic gases when fire strikes, DOPO-HQ sits tight, absorbing heat and forming a protective char that keeps flames in check. It fits right into epoxy, polyester, and polyurethane resins—the very backbone of circuit boards, building insulation, and car interiors. What always impressed me was its knack for blending performance with safety, sidestepping the mess of halogens that haunted my early years in the field.
Chemists peg the melting point of DOPO-HQ around 220°C, and it remains stable up to 320°C before decomposing. It's got a molecular weight of about 360 g/mol, showing respectable solubility in solvents like acetone and DMF, though less so in plain water. The hydroxyl groups on the phenyl ring open up doors for reactions with epoxy resins, forming chemical links that lock in the flame retardant properties. During production, you'd often see condensed DOPO with hydroquinone under mild acidic conditions, turning basic building blocks into a ready-to-use solution for bigger industrial processes.
In the warehouse or on a shipment manifest, you spot DOPO-HQ labeled with CAS number 99208-50-1. Most suppliers guarantee a purity of 98% or higher, with moisture limited to less than 0.5%. You’ll find instructions about storage—keep it cool and dry, away from sunlight and acids. Some standards highlight particle size, critical for resin blends, while others push for specific bulk density ranges to prevent dust issues in handling. Each batch I’ve worked with comes with a data sheet loaded with technical facts, guiding manufacturers on safe handling and performance expectations, so folks on the shop floor know exactly what they are getting.
Starting with hydroquinone and DOPO, you set up an acidic condensation. Odd smells fill the lab, yet the process itself stays straightforward—mix, heat, let react, then purify the product. Scaling up to industrial production, engineers keep a close watch on temperature and pH. Any slip, and impurities sneak in, raising questions about the safety and efficiency of the whole batch. We once had a situation where a change in reaction time shifted the color and flow properties, driving home how sensitive the process can be. Even minor tweaks in the washing or drying steps show up in bulk sample tests, forcing teams to think on their feet.
DOPO-HQ never stays static. Researchers in Asia and Europe keep altering the molecule, trying to add new functional groups and boost specific properties. Epoxy resin chemists pair it with isocyanates and anhydrides to tap into tougher fire resistance or improve mechanical strength in circuit boards. Trying new reactions, like grafting silane or boron moieties, brings mixed success—but it’s all part of a wider chase for safer and more efficient flame retardants. These modifications shape how DOPO-HQ interacts with plastics, adjusting everything from viscosity to the carbon footprint of the whole manufacturing cycle.
Depending on the manufacturer, DOPO-HQ shows up as “DOPO-HQ,” “phenylene-bis DOPO,” or “DHP-DOPO.” Big-name chemical supply houses sell it under branded labels, each touting purity tweaks or special blends for niche markets. Over the years, I've learned to watch for these names, since they influence purchasing specs and sometimes even regulatory paperwork. Nobody enjoys a situation where two different product names on paperwork spark confusion at customs or among project managers, so a firm grasp on synonyms saves headaches and keeps production lines moving.
Safety experts insist on proper gear—gloves, goggles, ventilation—during handling. Even though DOPO-HQ doesn’t rival older halogenated flame retardants for toxicity, dust can cause skin or respiratory irritation in busy factories. I’ve seen firsthand how quick spill cleanups and well-maintained equipment stop accidents before they start. Labels always warn against contact with strong oxidizers; fire marshals like to remind everyone that flame retardants can sometimes leave hot surfaces behind. Regular training and clear signage make a bigger difference than clever chemical engineering.
This compound found steady work in electronics, especially printed circuit boards, where fire-resistance isn’t just a bonus—it’s a requirement. People use it in construction, especially for insulation foams and molded plastics that line office towers and passenger trains. Automotive manufacturers have also picked up on DOPO-HQ, hoping its low-smoke, low-toxicity profile can help meet tough new safety standards. It’s turning up in coatings, adhesives, and paints—anywhere engineers worry about sparks or overheating. Demand keeps rising as industry pivots away from old-school, environmentally dicey chemicals.
Lately, a wave of research has focused on squeezing more performance out of DOPO-HQ while keeping health and safety at the forefront. New studies, many coming from China and Germany, probe how small structural changes to the DOPO-HQ backbone affect fire-resistance and compatibility with recycled plastics. Multinational grant-funded projects line up resources to assess how the compound breaks down in the environment. Collaborative efforts stand out—chemists, toxicologists, engineers all gather at conferences to compare notes about fire testing, processing conditions, or regulatory changes. The lessons they uncover drive home just how complicated real-world flame retardancy has gotten.
People want answers about health. Lab data show DOPO-HQ does not bioaccumulate or persist in wildlife for decades, unlike the chemicals it replaces. Rodent studies draw attention to potential long-term exposure effects, showing low acute toxicity but urging caution as more flame retardants enter homes and offices. Regulatory agencies in the EU and North America keep a sharp eye on new toxicity data, adding new restrictions or guidance as science delivers new evidence. Conversations in the field highlight the need for more independent research to track what happens after disposal, whether through recycling, incineration, or landfill.
Industry and the research community keep pushing for fire safety with a lighter environmental footprint. As regulations grow stricter and consumers demand greener materials, companies look for ways to boost DOPO-HQ’s effectiveness at lower concentrations, slash costs, and simplify blending with recycled materials. Scientists hope to design new derivatives that fight flames, last longer, and possibly break down faster if discarded. The race for better fire safety tools keeps labs buzzing—some driven by regulatory deadlines, others by fires that grab headlines and press public officials into action. The future for DOPO-HQ and similar compounds feels busy, with big expectations riding on cleaner chemistry and open collaboration between regulators, researchers, and everyone using plastics and textiles in their daily work.
Walk into any modern building, and you’ll notice how much attention goes into safety. Flame retardants like DOPO-HQ play a real part in that effort. Construction firms add this compound to materials such as insulation foam, electrical cables, and wall panels. Buildings now contain more plastics and polymers than ever. These items burn fast and hot, sometimes giving people little time to escape in a fire. By treating construction materials with DOPO-HQ, engineers help slow the spread of flames. It means more time for firefighters to respond, more time for people to get outside, and less property loss. Reports from the National Fire Protection Association point out that flame retardants have already lowered the number of fires in offices and apartment buildings. No one wants to think about disaster, but smarter material choices make a real difference.
From smartphones to washing machines, electronics fill daily life. These products often run for hours and sometimes overheat. Short circuits and power surges can spark fires in circuit boards, plastic cases, or connectors. To deal with this, manufacturers have chosen DOPO-HQ for its stable properties and ability to reduce flammability in plastics like epoxy resins. Gadgets rely on these kinds of additives for user safety. The days of melting chargers and overheated laptops have become a thing of the past for many thanks to safer flame retardant options. As devices keep shrinking and packing more power, the importance of non-toxic, efficient retardants only grows. Consumers expect products not just to work well, but also to keep families and homes safe.
Modern vehicles carry twice as much electronic wiring and soft trim as cars from a few decades ago. This evolution improves comfort and capability, but these materials often burn easily. Car makers have found that adding DOPO-HQ to plastic parts inside cars—such as dashboards, door panels, and wire coatings—helps keep fires from spreading after a crash or electrical fault. In trains and airplanes, flame retardant materials carry even stricter rules, since fires in transit quickly become life-threatening. Following tragic accidents in the past, regulators moved to require low-flammability interiors. DOPO-HQ fits into these efforts by offering an option that resists heat without leaking toxic smoke. From my time spent in the auto shop, I’ve seen the difference these treatments make. A fire-resistant dashboard could be the reason someone escapes after a roll-over or high-speed collision.
Many older flame retardants built up in the environment and sometimes found their way into food chains, creating health concerns for families. DOPO-HQ represents a shift away from the worst offenders. It has low toxicity and resists leaking into soil and water supplies. Manufacturers take this seriously—no one wants workers or children exposed to harmful residues. The move to safer options like DOPO-HQ ties back to real, lived experiences with pollution and product recalls. Regulators in countries like Germany and Japan have set new benchmarks. They look for better environmental outcomes, demanding proof of both performance in fire and minimal long-term risk.
No chemical solution covers every risk. New polymers and novel gadgets will test the limits of fire safety. But experience shows that moving toward options like DOPO-HQ, with lower toxicity and reliable fire resistance, opens the door for safer public spaces and homes. Product designers, builders, and watchdog groups now push for standards that put health and safety ahead of short-term savings. Continued funding for research has helped uncover safer mixtures and smarter ways to apply treatments. Scrutiny keeps moving forward as technology and risks evolve. Each big recall or new regulation often starts with people noticing a problem and pushing for a smarter way forward.
Anyone who has spent time tweaking polymer formulations knows that getting the dose right isn’t a minor detail. When you introduce DOPO-HQ—a popular phosphorus-based flame retardant—the numbers matter not only for performance but for processability, stability, and overall cost. For folks newer to this world, the “recommended dosage” can sound like an official figure. But the truth is, it’s mostly a starting point, and a lot depends on what you’re hoping to achieve.
Most technical documents and suppliers toss around a range from 5 to 20 percent by weight. Why so much wiggle room? It usually depends on the base resin, target flammability standards, and final application. Polycarbonate or epoxy resins, for example, often get formulated on the lower end if the baseline material already has decent flame resistance. Chasing a UL94 V-0 rating—or just peace of mind for lithium battery casings—might push the number toward the higher end.
Adding more DOPO-HQ cranks up flame retardancy, but there’s no free ride. High doses press on other properties. I’ve worked on batches where going above 15 percent started to affect transparency and made melt flow a real headache. Fill rates can also play tug-of-war with mechanical strength—load up too much, and you lose flex or impact toughness, which isn’t easy to fix after the fact. Most projects settle somewhere closer to 8-12 percent after a round or two of lab trials. That’s the sweet spot for a lot of medium-risk applications, balancing fire protection, processability, and reasonable pricing.
Today’s market wants more than just average safety. You see big pushes for electronics, transportation, and construction to hit higher fire performance without halogens. DOPO-HQ checks that box, but just bumping the dose isn't always enough. Lab work shows that after a certain level—usually around 20 percent—returns start dropping off. Some groups blend DOPO-HQ with other agents, like melamine polyphosphate or ATH, chasing synergies instead of brute force. It’s a game of tuning the mix rather than just pouring in more flame retardant.
The paperwork makes it sound easy, but upscaling from R&D to real plant runs brings headaches no datasheet mentions. DOPO-HQ doesn’t always behave as you’d hope in extrusion or injection molding. Caking during storage, inconsistent distribution, and reactions with hardeners or pigments all create hurdles. In my experience, dosing beyond 15 percent usually means you start dealing with compatibility aids or switching mixing speeds and temperatures—details most handbooks leave out.
Based on hands-on trials, I start at the low end—5 percent—run basic mechanical, fire, and processing checks, then climb by a couple points at a time. There’s no substitute for getting your hands dirty and logging results. Yes, standards and target rating drive the dance, but practical issues like screw torque, yellowing, and cycle times can push you to tweak the plan.
Teams run pilot batches to test different DOPO-HQ doses side by side, cutting down surprises later. Some shops have seen good results using masterbatch concentrates—pre-dispersed chunks of DOPO-HQ—making blending cleaner and more consistent. Careful choice of co-additives or surface modifiers can smooth out rough edges from overloading, helping you stay within process windows. There’s a lot to be said for regular talks with raw material suppliers, who tend to know which tweaks will spare you a few headaches down the line.
DOPO-HQ doesn’t come with a large reputation, but anyone working in a lab or plant sees it as more than just another niche flame retardant. The powder’s influence extends beyond a shelf in the chemical storeroom: mistakes in storing or handling this chemical can cost a whole load in lost time, damaged equipment, and worse, a health scare nobody wants on their hands.
I once watched a fresh shipment of DOPO-HQ lose value overnight because someone stashed it near a window—humidity found its way in, and by morning the product clumped together, almost stone-like. Moisture leads to loss of flow and sparks potential reactions. Anyone working with it soon learns the hard way that a cool, consistently dry area is non-negotiable. Factory basements, close to the boiler room, or next to open doors are the worst spots. For safety, air-tight containers made of materials that don’t react with phosphorus-based organics keep the powder in top condition. Desiccant packs around storage zones do a lot—think a silent insurance against atmospheric bad luck.
Messiness around this chemical is a recipe for trouble. DOPO-HQ sticks to surfaces, and any sign of a spill doesn’t just mean wasted material. If a batch lands on the floor, there’s a good chance someone will walk it down the hall before a broom even touches it; this brings contamination to places no one wants it. I always keep my area swept and my hands gloved—protective goggles should hang close by. Washing hands after handling isn’t just advice, it’s the first habit anyone should pick up on their first day.
It’s tempting to treat DOPO-HQ like salt or sugar—just grab a scoop when a recipe calls for it—but over time, degradation creeps in. While the product doesn’t break down overnight, thermal cycling from daily temperature swings and exposure to air during repeated scoop-outs will degrade performance. This material deserves a logbook entry for opening dates and batch numbers. Regular checks save headaches, because an expired lot in a new batch of flame retardant compounds spells delays, wasted resin, and angry calls from clients.
Anyone with enough years in the chemical world will nod at the mention of phosphorus fumes. Good airflow isn't a luxury, it’s protection. Dust generated from careless handling doesn’t just end up in your lungs—it’s a real fire risk. Flame retardant doesn’t mean flame-proof. Proper dust extractors, low-spark tools, and antistatic gear actually matter here, especially during weighing or mixing. I once saw a small pile go up after static from a plastic scoop built up. A metal scoop, properly earthed, left no room for doubt after that incident.
It’s always tempting to cut a corner for speed, but DOPO-HQ doesn’t forgive laziness or forgetfulness. Training everyone on site doesn’t just tick a compliance box—it slows everyone down long enough for mistakes to stay rare. Labeling each drum with clear instructions gives even new hires confidence. In a crunch, a simple poster by the door reminds everyone: respect the chemical, keep it dry, handle with care, and prioritize people over production quotas.
DOPO-HQ doesn’t demand a cleanroom or every gadget under the sun, just respect for the fundamentals and discipline in daily routines. Getting it right the first time, whether it’s in shipping or on a busy production line, makes for a safer workplace and a more reliable product at the end of the day—every time.
Plenty of companies and consumers have started paying attention to what goes into products, especially when the conversation turns to flame retardants. DOPO-HQ, a phosphine oxide-based compound, pops up in safety datasheets claiming to be “halogen-free.” For some, the absence of chlorine and bromine marks a clean bill of health, but I’ve been around enough plant labs and recycling yards to know chemistry rarely follows simple checkboxes.
Halogen-free sounds reassuring because halogenated flame retardants come with a nasty reputation—think persistent toxins, bioaccumulation, and scary headlines about polluted rivers. But “halogen-free” just means one subset of chemicals has been removed. It’s like saying a snack contains no peanuts but glossing over the sugar content. The important question isn’t just what’s missing, but what’s been used to replace it.
Swapping halogens for phosphorus-based compounds like DOPO-HQ can reduce the toxic smoke and nasty byproducts during a fire. That’s a step in the right direction—I’ve read studies where halogenated retardants unleash dioxins when burned, which linger in soil and water and build up inside fish. DOPO-HQ doesn’t release those same toxins if it goes up in smoke, so in that sense, it does less harm during disasters.
Still, labeling something “environmentally friendly” can be misleading. Every chemical leaves some kind of trail in its production and disposal. Manufacturing DOPO-HQ takes energy and creates waste streams of its own. Phosphorus, the core of this molecule, isn’t exactly infinite on this planet, and mining it can chew up landscapes and pollute water. The push to replace one bad actor with another sometimes misses the root cause, swapping out problems rather than addressing them directly. We’ve seen this switcheroo before with BPA-free plastics, which sometimes wind up no safer in the long run.
The rise of DOPO-HQ and similar flame retardants shows people want safer products without giving up fire resistance. That’s good news—nobody wants their electronics or building materials turning into torches. Yet just ticking the “halogen-free” box doesn’t solve every problem. Alternatives still need thorough life-cycle studies. How will DOPO-HQ behave in a landfill? Can it break down safely, or will pieces of it circulate in wildlife? From what I’ve seen in long-term environmental monitoring, chemicals can show up years after everyone thought they were safe and buried.
If we’re serious about environmental health, we can’t lean only on what’s trendy or sounds clean. Fire safety rules still demand robust flame retardants, and DOPO-HQ offers some improvements where halogens clearly fail. But there’s room to think bigger—engineers could design products and circuits that resist burning in the first place, rather than slathering on ever-evolving coats of chemicals. On the regulation side, governments could push for full disclosure of ingredients and encourage research into compostable, natural alternatives.
At home and at work, I’ve seen demand driving change. When buyers press for proof, and researchers dig beyond marketing slogans, companies start hunting down better answers. Maybe the future holds materials that are safe to touch, safe to burn, and gentle when they finally get thrown away. For now, moving beyond halogens is progress, but the real goal still lies further down the road.
People in my last lab job never stopped talking about fire safety. If you’ve spent enough time around plastics or circuit boards, you might have heard that same buzz. That’s where DOPO-HQ comes up. The chemical, properly called 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide, has a bit of a mouthful for a name, but that structure is what makes it work so well. You can crack open the textbooks and see a phenyl group—classic six-sided benzene ring, with two hydroxy groups parked at the 2 and 5 positions. It’s then hitched to a bulky DOPO moiety, the 9-oxa-10-phosphaphenanthrene-10-oxide unit. In chemistry land, that means phosphorus and oxygen sit at the party, ready to interrupt the chemical chain reactions that make flames spread. This combination sits at the center of why it gets tossed into resins and epoxy.
People ask about CAS numbers whenever a new chemical pops up in a process. That’s not just paperwork. The CAS number for DOPO-HQ is 72850-90-5. You punch in those digits, and a whole world of data unspools. Synthetic pathways, toxicity information, handling guides—every chemist I know keeps those digits in their back pocket. That number ends confusion. Chemical names can overlap, but that CAS gets you what you want on a supplier’s shelf. My own troubleshooting often involved hunting down the right structure, and CAS numbers made that headache a lot shorter.
I’ve watched the scramble as industries try to ditch old flame retardants that pollute water or mess with hormones in people and wildlife. Folks want safer, greener options, but nothing’s ever simple. DOPO-HQ stands out because its phosphorus-oxygen structure reacts in fires, meaning it can slow down or block flames before things get out of hand. Plus, having those hydroxy groups means DOPO-HQ bonds more tightly to polymers. No one wants flame retardants leaching out with every fingerprint or rinse, so that secure attachment helps keep it in place where it’s added.
Still, nothing’s perfect. There’s always a tug-of-war between safety, cost, and performance. In my own experience, stricter rules kick in every few years, and teams need to redesign plastics or circuit boards to meet the new limits. Every swap means more time wrestling costs, testing for toxicity, and sorting persistent breakdown products.
DOPO-HQ, with its balanced structure and clear CAS tag, gives people a bit of breathing room. Still, there’s room to grow. More groups are pushing for toxicology data that run longer and deeper. If companies and regulators cooperate, sharing results and tracking side effects, the industry won’t need to play catch-up every time standards jump higher.
Some labs are looking at tweaks—changing side groups or pairing phosphorus compounds with bio-based polymers. I sat through plenty of meetings, watching researchers compare notes on how these combos did in punishing fire tests. That’s where progress looks promising. Transparency and longer-term data sharing help weed out duds early, letting stronger, safer chemicals like DOPO-HQ shine where they work best.
| Names | |
| Preferred IUPAC name | 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide |
| Other names |
9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide-6-(4-hydroxyphenyl) DOPO-HQ DOPO-HQ Flame Retardant |
| Pronunciation | /ˈfleɪm rɪˈtɑːr.dənt ˌdiːˌəʊˌpiːˌəʊ ˌeɪtʃˈkjuː/ |
| Identifiers | |
| CAS Number | 63562-33-4 |
| Beilstein Reference | 3613967 |
| ChEBI | CHEBI:143611 |
| ChEMBL | CHEMBL2107818 |
| ChemSpider | 21370949 |
| DrugBank | DB11326 |
| ECHA InfoCard | 03c250af-1825-4300-9f28-03a062d7b644 |
| EC Number | 612-129-3 |
| Gmelin Reference | 108432 |
| KEGG | C11568 |
| MeSH | Phosphorus Compounds |
| PubChem CID | 17616920 |
| RTECS number | GV1925000 |
| UNII | 9A2T8V0FPF |
| UN number | NA Flamable |
| CompTox Dashboard (EPA) | DTXSID50878955 |
| Properties | |
| Chemical formula | C18H15O3P |
| Molar mass | 356.18 g/mol |
| Appearance | White powder |
| Odor | Odorless |
| Density | 1.20 g/cm³ |
| Solubility in water | Insoluble |
| log P | 3.3 |
| Vapor pressure | Negligible |
| Acidity (pKa) | 13.2 |
| Basicity (pKb) | 13.3 |
| Magnetic susceptibility (χ) | -84.2e-6 |
| Refractive index (nD) | 1.601 |
| Viscosity | 1200-1500 mPa·s (25°C) |
| Dipole moment | 3.54 D |
| Thermochemistry | |
| Std enthalpy of formation (ΔfH⦵298) | -115.8 kJ/mol |
| Std enthalpy of combustion (ΔcH⦵298) | -5421 kJ/mol |
| Pharmacology | |
| ATC code | TR0400000649 |
| Hazards | |
| Main hazards | Harmful if swallowed. Causes serious eye irritation. Causes skin irritation. May cause an allergic skin reaction. |
| GHS labelling | GHS07, GHS09 |
| Pictograms | GHS07,GHS09 |
| Signal word | Warning |
| Hazard statements | H319: Causes serious eye irritation. |
| Precautionary statements | P261, P264, P270, P272, P273, P280, P301+P312, P302+P352, P304+P340, P305+P351+P338, P308+P313, P312, P330, P332+P313, P337+P313, P362+P364, P403+P233, P405, P501 |
| NFPA 704 (fire diamond) | 1-1-0 |
| Flash point | > 230°C |
| Autoignition temperature | 550°C |
| Lethal dose or concentration | LD₅₀ (oral, rat) > 2000 mg/kg |
| LD50 (median dose) | > 3,434 mg/kg (Rat, Oral) |
| NIOSH | RGFT |
| PEL (Permissible) | PEL (Permissible Exposure Limit) for Flame Retardant DOPO-HQ: Not established |
| REL (Recommended) | 0.5-3.0 |
| Related compounds | |
| Related compounds |
DOPO DOPO-HQ-Ph DOPO-PEPA DOPO-BDE DOPO-NH2 |
