📅 April 2026 · ⏱ 8 min read · BSiO₂ Pty Ltd
Geosynthetics are synthetic polymer materials used across civil engineering, construction, infrastructure, and environmental containment. The family includes geotextiles (permeable fabric used for soil separation, filtration, and drainage), geomembranes (impermeable liners for landfills, mining, water containment), geogrids, geocells, and geocomposites.
They are predominantly manufactured from polypropylene (65% of the market) and polyester, with some polyethylene — all of which are inherently flammable organic polymers. In applications such as road tunnels, rail infrastructure, underground structures, and high-rise construction, these materials must meet strict fire performance standards. Until now, this has been achieved primarily through halogenated flame retardants — brominated and chlorinated chemicals that are effective but increasingly banned due to their persistence in the environment and toxicity to human health.
Mandatory FR geotextile lining
Fire safety code compliance
Building code FR requirements
Two major regulatory actions have fundamentally disrupted the geosynthetics flame retardant supply chain in Europe since late 2025:
The European Commission formally adopted amendments to the EU Persistent Organic Pollutants Regulation, tightening concentration limits for polybrominated diphenyl ethers (PBDEs) — the most widely used conventional flame retardants in polymer manufacturing — from 500 mg/kg to 10 mg/kg in all polymer articles. This 50-fold tightening is effective immediately and covers all geosynthetic products sold into European markets. PBDEs are persistent in the environment and have been found to bioaccumulate in human tissue, prompting the Stockholm Convention phase-out beginning in 2009 — now reflected in binding EU product law.
The European Chemicals Agency published an updated universal PFAS restriction proposal in August 2025, following evaluation of more than 5,600 scientific responses. PFAS-based flame retardant coatings applied to polymer articles including geosynthetics are within scope. The ECHA committees are targeting final opinions in early 2026, with implementation to follow. The direction of travel is unambiguous — PFAS-based systems face the same trajectory as PBDEs.
Together these two regulatory actions are creating an urgent need across the European geosynthetics industry for halogen-free, PFAS-free flame retardant solutions that achieve the necessary fire performance without the environmental and health penalties of conventional systems. BSiO₂ Natural Silica is positioned to be part of that solution.
Unlike halogenated flame retardants that work by releasing halogen radicals to interrupt combustion chemistry, amorphous diatomaceous earth works through entirely physical mechanisms — no toxic decomposition products, no persistent organic compounds, no bioaccumulation. There are five distinct mechanisms operating simultaneously:
DE has a thermal conductivity of just 0.04–0.06 W/m·K — comparable to mineral wool — due to its 83–85% porous diatom frustule structure. Incorporated into a polymer matrix, DE particles create millions of trapped air pockets that dramatically slow heat transfer to the polymer substrate, delaying ignition and slowing flame spread.
The amorphous silica lattice of diatom frustules contains bound water molecules that are released endothermically under fire conditions. This water vapour absorbs heat from the combustion zone and cools the polymer surface — the same mechanism used by aluminium trihydrate (ATH), the most widely used halogen-free flame retardant globally, but at far lower density than ATH.
At elevated temperatures, the amorphous SiO₂ content of DE contributes to the formation of a glassy, vitreous char layer on the polymer surface. This char layer physically blocks oxygen from reaching the burning polymer substrate — interrupting the combustion feedback cycle. Published research confirms that silicon compounds combined with other halogen-free systems significantly reduce peak heat release rate and smoke production.
Published research on DE-modified silicone rubber composites (2022) demonstrated that incorporating DE at 10 phr achieved a Limiting Oxygen Index (LOI) of 24.8% — above the critical 21% threshold at which a material self-extinguishes in air. Untreated polypropylene typically has an LOI of 16–18%. This improvement is achieved without a single halogen atom.
BSiO₂ Natural Silica has a melting point of 1,700°C and is classified as non-combustible — confirmed by its ICSC safety data. It remains structurally intact at temperatures far exceeding any polymer fire scenario. Where conventional flame retardants decompose and may release toxic gases during fire events, DE simply remains — inert, stable, and still performing.
DE does not need to work alone. Published research demonstrates strong synergistic effects between amorphous silica and other halogen-free flame retardant systems — including ammonium polyphosphate (APP), aluminium hydroxide (ATH), and intumescent systems. A combined DE + APP system in polypropylene showed LOI improvement from 19.6% to 23.3% at combined loading rates that would be commercially practical for geosynthetic manufacturing.
Not all diatomaceous earth is equal for flame retardant applications. The properties that determine performance are precisely those that BSiO₂ Natural Silica from the Mt Garnet deposit in Far North Queensland excels in — and importantly, all three have been independently certified by Australian laboratories:
| Property | BSiO₂ Value | Why It Matters for Flame Retardancy |
|---|---|---|
| Amorphous silica content | 80.2% (Agon Environmental, Oct 2025) | Amorphous SiO₂ forms protective glassy char more readily than crystalline quartz. Higher amorphous content means better char formation and oxygen barrier performance |
| Crystalline quartz | <0.5% — Not Detected (Simtars, Dec 2025) | Crystalline quartz does not contribute to char formation. Near-zero crystalline quartz means the entire mineral fraction is electrochemically active in fire suppression |
| Specific surface area | 494.4 m²/kg (HRL Technology, Dec 2025) | Enormous surface area maximises interfacial contact with the polymer matrix — better dispersion, better thermal barrier distribution, and more effective endothermic cooling surface |
| Calcination status | Non-calcined — frustule structure intact | Heat treatment destroys the porous diatom frustule architecture that creates the thermal barrier. Non-calcined DE preserves the millions of micro air pockets that slow heat transfer |
| Melting point | 1,700°C | Completely non-combustible at any temperature encountered in polymer fire scenarios. Where halogenated FRs decompose and release toxic gases, BSiO₂ remains inert and stable |
| Halogens / VOCs / heavy metals | Zero detected | Fully compliant with EU 2025/1482, PFAS restrictions, RoHS, and all current and anticipated European chemical regulations for polymer additives |
The fireproof performance of diatomaceous earth is not theoretical. DE has been used for decades as the primary thermal insulating material inside fireproof safes, filing cabinets, and fireproof doors — materials specifically designed to protect their contents even when external temperatures reach 1,500°C. The same properties that keep documents safe inside a safe during a building fire are now being applied to protect polymer geosynthetics from ignition in tunnels, underground structures, and buildings.
This is not an emerging or experimental application — DE's fire resistance is a well-established industrial reality. What is new is the application of this understanding to the geosynthetics polymer composite sector, driven by the regulatory pressure that is now removing halogenated alternatives from the market.
Tunnel drainage and lining geotextiles must meet EN 13501-1 Euroclass B or C fire performance in European infrastructure. TenCate Geosynthetics has already supplied fire-retardant polypropylene non-wovens for tunnel projects including the Pelješac bridge access tunnels in Croatia. With PBDEs now restricted to 10 mg/kg, the systems used in those products need to be reformulated. BSiO₂ DE offers a direct non-halogenated replacement pathway.
Cut-and-cover construction, underground car parks, basement retention systems, and subway infrastructure all use geotextiles and geomembranes that must comply with local building fire codes. Halogen-free fire retardant compliance is increasingly mandatory in these applications in both European and Australian markets.
Major road and rail projects increasingly specify fire-retardant geosynthetics for embankment, drainage, and reinforcement applications where fire risk is present — particularly near fuel pipelines, electrical infrastructure, and populated corridors.
Geomembranes used in mining heap leach pads, tailings dams, and chemical containment facilities often face fire risk from chemical reactions, equipment, or bushfire conditions. Halogen-free fire-resistant geomembranes are increasingly specified in Australian mining projects.
Geosynthetic drainage layers, root barriers, and waterproofing membranes used in green roof construction on multi-storey buildings must comply with building fire codes. European building regulations are progressively tightening FR requirements for these applications.
The following companies are the world's leading geosynthetics manufacturers and are each actively seeking halogen-free flame retardant solutions to comply with the new EU regulatory environment. BSiO₂ has reached out to each of these companies to discuss the potential of Natural Silica as a flame retardant additive or filler in their polymer formulations:
| Company | Country | Key Products | Contact |
|---|---|---|---|
| HUESKER Group | Germany | Woven and non-woven geotextiles, geocomposites, geogrids | huesker.com |
| NAUE GmbH & Co. KG | Germany | Geotextiles, geomembranes, geocomposites, tunnel applications | naue.com |
| TenCate Geosynthetics | Netherlands | FR polypropylene non-wovens, Mirafi range, tunnel geotextiles | tencategeo.com |
| Solmax | Canada / Europe | HDPE geomembranes, non-woven geotextiles, GCLs | solmax.com |
| AGRU Group | Austria | Geomembranes, pipe systems, specialist liners | agru.at |
| Freudenberg Group | Germany | Non-woven geotextiles, filtration, specialist geosynthetics | freudenberg-pm.com |
| Global Synthetics | Australia | Australian distributor — geotextiles, geomembranes, geogrids | globalsynth.com.au |
Certified sample quantities for R&D and formulation trials — at no charge
Full laboratory certification documentation (Simtars, Agon Environmental, HRL Technology Group)
Safety Data Sheet (SDS) and complete product technical data
Four current grades — 400 Micron, Minus 2 mm, 2–4 mm, 4–8 mm
Micronised grades to D50 5 micron — in development for polymer additive applications
Wholesale supply in 1 tonne FIBC bulka bags with freight to Brisbane, Townsville, and Darwin ports
Australia's only certified domestic producer — sovereign supply chain, no import risk
Collaborative R&D approach — we are seeking long-term supply partnerships, not one-off sales
For geosynthetics manufacturers considering BSiO₂ Natural Silica as a flame retardant additive, the development pathway is straightforward and well-understood within the polymer compounding industry:
Request certified samples from BSiO₂. Characterise particle size distribution, surface area, and purity — our laboratory certificates provide a head start on this process.
Incorporate DE at 5–15 wt% into your target polymer system (polypropylene, polyester, or PE). Test with and without synergistic halogen-free co-additives (APP, ATH) to optimise flame retardant performance at minimum loading.
Test against your relevant standard — EN 13501-1 (Euroclass), UL-94 (V-0 or V-2), or NFPA 701 depending on application. Measure LOI, peak heat release rate (cone calorimeter), smoke density, and toxic gas evolution.
Assess the effect of DE loading on tensile strength, elongation, and other mechanical properties critical to geosynthetic performance. BSiO₂'s high surface area and fine particle size generally improve mechanical compatibility versus coarser fillers.
If trial results confirm flame retardant performance meets your requirements — discuss a longer-term supply arrangement with BSiO₂. We are investing in micronising equipment specifically to serve this market.
Development of a novel DE-based halogen-free flame retardant system for geosynthetic polymer applications is eligible for the Australian R&D Tax Incentive — a 43.5% refundable tax offset on eligible R&D expenditure. Australian manufacturers or research partners engaging BSiO₂ in collaborative formulation trials may be able to structure this work as eligible R&D activity. Contact AusIndustry at business.gov.au for details.
BSiO₂ Pty Ltd is a family-owned Australian company — Richard and Marlene West — operating a deposit of biogenic amorphous silica near Mt Garnet in Far North Queensland that has been stewarded for 25 years. We are Australia's only known domestic producer of certified, non-calcined food-safe diatomaceous earth, with three independent Australian laboratory certifications confirming the exceptional quality of our deposit.
Our product is being actively researched across a remarkably diverse range of applications — silicon fertiliser for Queensland crops (150 commercial farm trials by the Russian Academy of Sciences confirmed yield increases of up to 28%), battery anode materials for electric vehicles (University of California research), marine antifouling coatings, thermal insulating paints, and now geosynthetic flame retardants. The common thread in every application is the unique three-dimensional porous diatom frustule architecture that no synthetic material can replicate — and that BSiO₂'s non-calcined process preserves intact.
Are you a geosynthetics manufacturer seeking a halogen-free, PFAS-free flame retardant alternative? We would be pleased to provide certified product samples, full laboratory documentation, and a technical discussion about your specific application requirements.
Request Samples & Data SheetContact Richard West to discuss your specific flame retardant application requirements. Certified samples available at no charge for qualifying R&D programs.
