Posted on 08/07/2022 in Fire Safety 2022
PIN FRs for bio-based insulation materials

Lily Deborde, LGCGM Rennes University France, summarised work on PIN flame retardant alternatives to boric acid and ammonium salts for hemp fibre thermal insulation products (blown insulation, panels). The objective is to use local bio-resources in materials to reduce the environmental impact of the construction industry. A current challenge is to limit the sanitary and environmental impacts of the treatment, while optimizing the technical performances (against fire and fungus). Non-halogenated solutions, for application by soaking in aqueous solution, have been identified which can reduce peak heat release rate by 50%, achieving SBI Euroclass C. Evaluation of an industrial scale application for this treatment is now underway.

Svetlana Petlitckaia, SPE Corsica University, presented tests of composite materials made of cork waste (first cut cork) and recycled PP polypropylene, from consumer end-of-life bottle caps, with the aim of developing insulation panels. Further work is needed to improve compatibility between the cork and the polymer (coupling agent) and to identify appropriate flame retardants.

Roland El Hage, LCPM Lebanese University, summarised trials treating miscanthus fibres with urea and with plant-derived phytic acid (as PIN flame retardants) to produce fire-resistant rigid insulation panels. Inclusion of 40% olive pomace (waste from olive oil pressing) was also tested. Miscanthus is a fast-growing plant, adapted to marginal land, and widely used for bioenergy. Miscanthus was steam-treated (c. 200°C) to produce homogenous fibres. Rigid panels were successfully produced without other binders (three-phase thermocompression), with lignin acting as a natural binder. Phytic acid and urea were grafted onto the fibres from aqueous solution by spraying, drying and cooking at 150°C. With final inclusion of 1% P and 1.25% N non-flammable panels were produced, with peak heat release rate <25% that of panels with non-FR fibres.

Karina Antoun, LERMAB Lorraine University and LCPM Lebanese University, presented a recently patented method for the treatment of lignocellulosic materials. The process uses urea and phytic acid as PIN flame retardants. The treated fibres or wood particles can be used for the production of non-flammable textiles or pressed wood panels.
Urea alone had little effect on fire performance, whereas phytic acid only reduced peak heat release rate to <25% compared to no FR, and urea plus phytic acid reduced nearly to 15%. The presence of urea is important for the protection of the fibres from acid release during the PIN FR cooking at 150°C. Panels produced from treated wood particles show that the application of phytic acid improves the mechanical performance of the wood panels.

Rodolphe Sonnier, Mines Alès, presented trials of alginate, a complex carbohydrate (in which β-D-mannonic acid and α-L-guluronic acids are linked), obtained from seaweed, as a possible substitute for oil-based FR foams. Today’s global alginate production is orders of magnitude lower than expanded polystyrene (EXP), but is high enough for industrial processing. The alginate was loaded with a metal salt and processed to beads and ultimately rigid foam panels at room temperature, without solvent. The panels showed considerably lower heat release, smoke and gas toxicity than EXP or polyurethane and were self-extinguishing, as a result of low heat release, water release from the alginate compounds and charring. Biobased treatments can resolve the issue that alginate is hydrophilic.

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