Effect of thermal degradation of glass fibre sizing on interfacial adhesion

In this paper, thermal analysis, spectroscopic, and micromechanical testing methods are used to characterise the thermal degradation of a range of commercial epoxy-compatible glass fibre sizings and the effect of sizing degradation on interfacial adhesion. Thermogravimetric data indicated that around 50% of the glass fibre sizing decomposed following 300°C heat treatment and was removed almost entirely following treatment at 500°C. Spectra of thermally degraded fibre surfaces showed good correlation with TGA data, in that the intensity of bands attributable to an epoxy resin film former decreased with increasing treatment temperature and were removed completely at temperatures of 300– 350°C. Recycled glass fibres recovered from end-of-life wind turbine blade material showed pristine fibre surfaces indicating good receptibility for downstream resizing processes. Reduced interfacial adhesion onset at 300–350°C and at treatment temperatures of 400°C and above was comparable to that of unsized fibres, suggesting that most of the sizing components which influence adhesion had been removed. Despite displaying interfacial adhesion properties comparable to that of unsized fibres, fibres heat treated at 400–500°C appeared to show residual oxidised sizing material that was not present in the fibres recovered from the fluidised bed.