Fireproofing flammable composites using mycelium: Investigating the effect of deacetylation on the thermal stability and fire reaction properties of mycelium

This paper presents research findings on the influence of alkaline deacetylation on the thermal stability and fire reaction properties of non-pathogenic Basidiomycota fungi (mycelium) grown in molasses. The relationship between deacetylation conditions, such as incubation time and NaOH concentration, and the thermal and fire reaction properties of mycelium was investigated. The degree of deacetylation was also examined for its influence on the high-temperature thermal stability of mycelium, such as char formation. The findings indicated that the high-temperature thermal stability increased as the degree of deacetylation increased due to the conversion of chitin into chitosan as well as the presence of char-promoting hydroxyl‑terminated polysaccharide moieties. The study further investigated the influence of hollow glass microspheres on the thermal properties and microscale combustion behaviour of unmodified and deacetylated mycelium. This study provides an in-depth analysis of the thermal degradation mechanisms that govern the thermal stability and char-forming ability of unmodified and deacetylated mycelium. Additionally, the link between the thermal stability and fire reaction properties of mycelium and its deacetylated derivatives was established. Finally, the effectiveness of unmodified and deacetylated mycelium mats for fireproofing flammable glass fibre-reinforced epoxy laminates exposed to a simulated moderate-intensity fire was evaluated.