Fire-retardancy and mechanical performance of protein-based natural fibre-biopolymer composites

•Fully protein-based flame retardant biocomposites were developed.•Wool/gluten composite achieved self-extinguishment without flame-retardant treatment.•Interfacial adhesion between wool fibre and gluten enhanced composite strength.•Desirable manufacturing conditions for fire and mechanical properties were chosen. The aim of the present work was to comprehend the fire retardant and mechanical properties of protein based natural fibre and biopolymer composites. Wool fibre and wheat gluten as environmentally sustainable materials were selected as fibre reinforcement and polymer matrix, respectively. With the use of the Taguchi design-of-experiment tool, it was possible to identify the desired combinations of the selective factors: wool/plasticiser (glycerol) contents and processing temperature, to improve the composites properties. Pareto ANOVA indicated that the wool content was the most important factor (ca. 78%) to influence the peak heat release rate due to its charring competency. On the other hand, the content of plasticiser significantly affected the tensile strength of the composites. Of particular importance was that the addition of 30 wt% wool to the gluten polymer, having no flame retardant, was sufficient to achieve a self-extinguishing flame during the vertical burn test (V-1) and improve the composite's strength. [Display omitted]