Modification of industrial E-glass fibres by long-chain alcohol adsorption

Long chain alcohols (1-dodecanol, 1-tetradecanol, 1-octadecanol) have been reacted at 130°C with E-glass plates, fibres and powders to modify the solid surface in order to enhance their bonding as reinforcing materials in polymer matrices. Silane-coupling agents are generally used for such modification processes but long chain alcohols may offer a cheaper alternative. Alcohols are known to bond to silica surfaces but less information is available for glass surfaces. In this investigation three techniques - contact angle, diffuse reflectance Fourier transform infrared spectroscopy (DRIFT) and X-ray photoelectron spectroscopy (XPS) - are used to study alcohol-modified glass surfaces. It is found that alcohols adhere to the glass surface even after several organic solvent (hexane or cyclohexane) extraction processes, maintaining a high advancing water contact angle of 85-97°. These contact angle values correspond to those typical for exposed methylene groups as in a polyethylene-like surface or a surface with multilayered 'islands', i.e. incomplete coverage of the glass surface. Infrared DRIFT spectra from the methylene groups give 1-5 times monolayer coverage. Despite uncertainties in the quantification method multilayers in adsorbed regions are indicated. XPS analysis shows a silica-rich surface with loss of Na, B, Fe, Mg and K from the glass and fibre surfaces during manufacture compared with bulk E-glass. Angle-resolved XPS does not suggest a highly ordered monolayer adsorption of the alcohol molecules on the glass plates but, instead, disordered multilayers. The adsorbed alcohol is apparently stable giving altered hydrophobicity, albeit without complete monolayer coverage.