Investigating the use of chitosan as a coupling agent to improve the interfacial properties of phosphate glass fibre/polycaprolactone composites

Chitosan (CS) was investigated to improve the interfacial properties of the phosphate glass fibre/polycaprolactone (PGF/PCL) composites. Dilute acetic acid was used as the solvent for CS and its influence on mechanical properties of the fibres was analysed via single fibre tensile testing. The interfacial shear stress (IFSS) was analysed using a fragmentation test and the interaction between the sizing agent and the glass surface was analysed by XPS. TGA and SEM were also used to indicate the sizing performance. A dip-coating process in the CS-acetic acid solution was observed to increase the IFSS by 56% with insignificant (p > 0.05) fibre strength loss compared to the pure PGF control. The enhancement of IFSS after sizing was suggested to be attributed to the interaction between the protonated amine groups of the CS and the phosphate structure of the PGF. Then the sized fibres were rinsed in the acetic acid solution (2% v/v) to remove the extra agent on the fibre surface and the IFSS consequently increased by 78% of the control, but with a significant (p < 0.001) strength loss of 20%. This increase in IFSS was suggested to be due to the improvement of the interphase and load transmission between the matrix and fibres.