Water resistant fibre/matrix interface in a degradable composite: Synergistic effects of heat treatment and polydopamine coating

Retaining a robust fibre-matrix interface in an aqueous environment has been an enduring challenge for fibrereinforced biocomposites. This study addresses the issue by applying a polydopamine coating as a coupling agent to annealed and non-annealed phosphate-based glass fibres. The presence of the polydopamine coating was confirmed using X-ray photoelectron spectroscopy and Raman techniques. The thickness of the coating increased with treatment time, forming a bimodal structure, and showed good correlation with the percentage of surface nitrogen observed via XPS. A 6 h coating period was selected to balance fibre strength improvements against degradation caused by the aqueous coating solution. In-situ polymerised polycaprolactone composites were produced using the fibres, resulting in improved retention of strength and modulus when the fibres were both annealed and coated. This is the first example of long-term retention of wet strength properties for phosphatebased glass fibre composites, falling within the target range for bone healing (6-12 weeks).