Study of the interface in natural fibres reinforced poly(lactic acid) biocomposites modified by optimized organosilane treatments

•The effect of silane treatments in natural fibres reinforced composites is investigated.•Fibre/matrix interface is investigated by physico-chemical and mechanical cross-analyses.•Optimizing the treatment conditions improves significantly the mechanical properties.•Treated biocomposites show a cohesive interfacial failure.•Chemical coupling and mechanical interlocking mechanisms at the interface are proposed.

This study investigates the effect of optimized organosilane treatments on the surface properties of flax fibres and the resulting mechanical properties and interface modifications in flax fibres reinforced poly(lactic acid) (PLA) biocomposites. Optimizing the treatment conditions increases the hydrophobicity of the fibres, and improves significantly the mechanical properties of the biocomposites, while reducing largely the scattering. The origins of the reinforcement at the fibre/matrix interface are investigated at the macromolecular and the microstructural levels by physico-chemical and mechanical cross-analyses. It is shown that it results from both modified chemical coupling and mechanical interlocking at the fibre/matrix interface. Dynamic mechanical thermal analysis reveals a decrease in damping for treated biocomposites because of the formation of a layer of immobilized macromolecular chains resulting from strong interactions at the interface. In situ observations of crack propagation by scanning electron microscopy illustrate clearly that the treated biocomposites show a cohesive interfacial failure at much higher loads, highlighting the enhanced load transfer from the PLA to the flax fibres.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slide