Effect of Surface Treatment of Glass Fibres on Adhesion to Phenolic Resin

Mixtures of epoxy emulsion and coupling agents. as well as coupling agent alone, were used to treat glass fibres to improve their adhesion to phenolic resin. The surface of the glass fibres was observed by scanning electron microscopy (SEM), and the chemical bonding of the treated glass fibres was analyzed by X-ray photoelectron spectroscopy (XPS). The improvement in the flexural and shear strength of glass fibre reinforced phenolic resins was investigated, and the fractured surfaces were observed by SEM. Experimental results demonstrated that the coupling agent could be formed either as a thin, uniform layer or as particles on the glass fibres. Mixtures of epoxy emulsion with zircoaluminate coupling agent were formed as a uniform layer, whereas mixtures of epoxy emulsion with titanate coupling agent were formed as particles. Analyzing the above results using XPS revealed that coupling agent and epoxy emulsion reacted with the glass fiber surface to form functional groups that react with phenolic resin. When the concentration of coupling agent was 0.2 wt.%, the effect of the glass fibre on the physical properties of phenolic resin composite was optimum. Among these coupling agents, the zircoaluminate coupling agent showed the best improvement, followed by silane and titanate coupling agents. After mixing it with epoxy emulsion, the flexural and shear strength were further increased. For instance, when using zircoaluminate coupling agent mixture, the shear strength of the composite was increased by 45% and the flexural strength by 43%.