Enhancing flame-retardant and mechanical properties of epoxy composites through bio-based flame retardant treated cotton fabric reinforcement

Due to tightening fire safety regulations and environmental concerns, eco-friendly natural fiber-reinforced composites (NFRCs) are increasingly popular for their biodegradability, renewability, low cost, and high specific mechanical properties. However, ensuring fire safety in NFRCs is challenging, as conventional synthetic flame retardants can reduce mechanical properties due to particle agglomeration and poor compatibility with the matrix. Therefore, in this study, the flame-retardant epoxy composite (EP/FR) was fabricated by using cotton treated with novel dual complex solutions containing phytic acid, chitosan, and urea. Remarkably, applying just one bilayer of this treatment led to significant improvements in flame retardancy, as evidenced by a reduction of up to 44.8 % in the peak heat release rate and a 23.7 % decrease in total heat release during cone calorimeter testing. Additionally, the horizontal burning rate was reduced by up to 16.8 %. Analysis of solid residue after fire test and gas product liberated during pyrolysis demonstrated an intumescent mechanism of flame retardancy. Mechanical property studies showed better performance for EP/FR, with SEM of the fractured surface proving better interfacial adhesion between fiber and matrix because of the fiber treatment. Overall, this study offers a novel and greener approach to improving the flame-retardant and mechanical properties of NFRC, paving the way for more sustainable composite materials.