Wax-treated hemp fabrics to reduce water absorption in PLA/PBSA laminated composites

Biocomposites with natural fibres have generated considerable interest thanks to their environmental sustainability. Nevertheless, their use in humid environments remains limited. This study investigates a blend of poly(lactic acid) (PLA) and poly(butylene succinate) (PBSA) reinforced with twill hemp fabric treated with an emulsion of waxes. The focus is to analyse the efficiency of the wax emulsion pre-treatment in decreasing the water uptake of these thermoplastic laminated composites. Two bio-based wax emulsions (from carnauba and sunflower) were used at 5, 10, and 15 wt%. Contact angle measurements on the fabrics were conducted using a Wilhelm balance setup to determine the wax treatments effectiveness. Tensile and contact angle tests demonstrated that the carnauba emulsion at 5 wt% exhibited an optimal compromise between mechanical properties and water repellence reaching a contact angle of 89.60°. The effect of the wax treatment on the final properties of the laminated composite system was evaluated through mechanical and thermal characterization. The effect of the wax treatment on the fibres adhesion with the polymeric matrix was also investigated by SEM analysis. The results demonstrated that the treatment did not cause a significant alteration in the structural integrity of the composites, contemporarily decreasing of 2% the water uptake.