From Borax to Bio‑Based: A Formulator’s History of Fire Retardant Coatings

If you are sizing up the fire retardant coatings market as a business opportunity, the single most useful thing you can study is not a market report. It is the formulation history. Every shift in this industry, every discontinuity that created an opening for a new supplier, was triggered by one of two forces: a chemistry that worked better, or a regulation that made the old chemistry unsellable. The companies that thrive are the ones that read those forces early.

What follows is a walk through that history, told from the formulation bench rather than the boardroom. We will look at what was actually in the can at each era, why it changed, and what the current research literature says is coming. Everything factual is referenced, because in an industry built on certification and trust, an unsourced claim is worth nothing.

01The salt age: alum, borax and theatre curtains

The first documented flame retardant formulation was a patent granted in England in 1735 to Obadiah Wyld, covering a treatment for textiles and wood based on alum, borax and ferrous sulfate^[1]. The logic was sound and still is: mineral salts do not burn, they absorb heat as they decompose, and they leave a glassy residue that shields the material below. In 1821, Gay-Lussac systematised the idea for French theatres, treating stage fabrics with a blend of ammonium phosphates, ammonium chloride and borax, work that historians of the field still cite as the conceptual starting point of flame retarded textiles^[2].

For more than a century the recipe barely moved. Fire protection of buildings meant mass: concrete encasement, gypsum plaster, brick. Coatings were decorative. The idea that a paint film a fraction of a millimetre thick could protect a steel column against a fully developed fire would have sounded absurd, because no one had yet found a chemistry that could turn a thin film into a thick insulator on demand.

02The halogen decades: effective, cheap, and eventually untouchable

The mid twentieth century brought synthetic polymers, and with them the first modern flame retardant additives. Brominated and chlorinated compounds, often paired with antimony trioxide as a synergist, worked in the gas phase: when heated they released halogen radicals that interrupted the chain reactions of combustion in the flame itself^[9]. They were efficient at low loadings, compatible with many binders, and cheap. By the 1960s and 1970s halogenated chemistry dominated flame retardancy across plastics, textiles, foams and coatings.

The cracks appeared early. In 1977, US regulators moved against Tris, a brominated phosphate used in children’s sleepwear, after it was found to be mutagenic; the episode made flame retardants a consumer safety story for the first time^[5]. The bigger reckoning came with the polybrominated diphenyl ethers (PBDEs). Evidence accumulated that they persisted in the environment, accumulated in people, and carried real toxicity concerns. The EU banned the penta and octa formulations in 2004, the sole US manufacturer stopped production at the end of that year, and in 2009 they were listed under the Stockholm Convention on persistent organic pollutants^[8][11].

One caution from this era matters for any founder today. A 2019 analysis in Environmental Science and Technology Letters, now one of the most cited papers in the field, asked whether the organophosphate esters that replaced PBDEs were simply a “regrettable substitution”, swapping one problematic chemistry for another before the health data were in^[10]. The lesson: in this market, a formulation is a regulatory position, not just a technical one.

04Regulation rewrote the recipe book

The 2004 to 2009 PBDE decisions did more than ban a few molecules. They changed the direction of formulation research worldwide, pushing the industry toward phosphorus, nitrogen and inorganic chemistries, and toward systems that work in the condensed phase (building protective char) rather than the gas phase^[8]. For coatings, that shift favoured technologies already in motion: intumescents, and heavily filled systems based on metal hydroxides.

The hydroxide story is worth understanding because it shows the trade-off logic of this industry. Aluminium trihydroxide (ATH), the world’s most widely used flame retardant by volume, decomposes endothermically from about 220 °C, releasing roughly 35% of its weight as water and leaving an alumina residue; magnesium hydroxide does the same job from about 330 °C^[19][23]. The chemistry is clean, cheap and halogen free. The catch is loading: these fillers often need to make up half or more of the formulation to perform, which constrains film properties. That tension, clean chemistry versus usable loading, is exactly where formulation skill converts into margin.

05The modern toolkit: waterborne binders, nano-synergists, thinner films

Today’s development work clusters around three fronts. The first is the carrier: water-based intumescents are the largest technology segment and are growing faster than solvent-borne systems as VOC rules tighten^[14][18]. The second is synergy. A landmark 2006 study by Wang, Han and Ke showed that nano-scale additives, including nano silica and layered double hydroxides, could strengthen the char, slow its oxidation, and improve both fire resistance and weathering of APP/PER/MEL coatings^[13]. Two decades on, nanoclays, expandable graphite, carbon nanotubes and graphene are standard tools for squeezing more performance out of the classic trio at lower film builds^[14][16].

The third front is durability, the field’s quiet weakness. Water immersion testing has shown that conventional acrylic APP/PER/MEL coatings can lose a third of their fire resistance after 500 hours of soaking, which is why microencapsulated APP, hydrophobic surface treatments and topcoat systems are now central to product development rather than afterthoughts^[14].

07What 290 years of reformulation tells a founder

The arc from Wyld’s borax bath to a graphene-dosed waterborne intumescent is not a story of chemistry replacing chemistry. It is a story of constraints changing: first the constraint was whether anything worked at all, then whether it was safe to live with, now whether it is sustainable to produce. Founders who understand which constraint is binding at any moment tend to build the right product. The literature says sustainability and durability are the binding constraints of this decade. History says that is exactly when new suppliers break in.