Self-extinguishing epoxy nanocomposites containing industrial biowastes as sustainable flame-retardant additives

Polymers are essential in modern life, but their large-scale production from non-renewable sources contributes to raw material depletion and environmental pollution. The shift from a linear to a circular economy aims to address these issues by promoting sustainable practices. Recent research focuses on incorporating natural fillers and biowastes to improve flame retardancy and reduce resource depletion. This work demonstrates the suitability of humic acids, biochar derived from both spent coffee grounds and the hydrothermal liquefaction of sludge, for use as flame-retardant additives in epoxy resins. The results are discussed in relation to the composition and preparation procedure of the composite materials. Particularly, the modification of epoxy chains with a proper coupling agent guarantees the uniform distribution of the waste throughout the polymer matrix.