Posted on 17/11/2022 in Fire Safety 2022
APP oyster shell bio-based flame retardant

Oyster shell powder reacted with ammonium polyphosphate reduced heat and smoke release of epoxy resin 70 – 80 %. Oyster shell powder (300 mesh) was ball milled with NaClO (0.3% w/w to oyster shell) for several hours, then added to APP (ammonium polyphosphate 2500 mesh) and further milled. Ratio of prepared oyster shell powder to APP was 1:1 to 1:10. The resulting APP-oyster shell material was tested as a flame retardant in DGEBA epoxy at 1 – 10 % loadings. In the epoxy samples, APP alone gave very considerable reductions in heat, smoke and carbon monoxide release. Peak heat release rate was somewhat lower with around 1:4 oyster shell:APP, compared to APP only, and peak smoke release rate was lowest with 1:1 oyster shell:APP. The improved fire performance and fire gas toxicity mitigation with the oyster shell material is considered by the authors to be due to increased char production, with a compact and continuous char including calcium as well as nitrogen, oxygen and phosphorus elements.

“Effect of functionalized oyster shell powder with ammonium polyphosphate on fire safety performance of epoxy resin”, J. Ren et al., Progress in Organic Coatings 172 (2022) 107054

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