Acid-base characteristics of silane-treated E glass fiber surfaces

Acid-base properties of E glass fiber surfaces treated with various commercial organosilane coupling agents were studied with angle dependent X-ray photoelectron spectroscopy (XPS), electrolytic thermodesorption analysis of water (ETA), inverse gas chromatography (IGC) and programmed thermal desorption (PTD). XPS analysis indicates that γ-aminopropyltriethoxysilane and γ-chloropropyltrimethoxysilane show some preference for inverted surface orientation. Monolayer isotherms using Lewis acids and bases as probe adsorbates show silane deposition to attenuate acid-base interaction between probe molecules and weak and medium strength sites on the substrate. Moisture thermodesorption analysis shows that the sorptive capacity for physically bound water was attenuated by all the silane treatments. Desorption polytherms using acidic and basic probes demonstrate that γ-aminopropyltriethoxysilane imparts strongly acidic and basic chemisorptive characteristics to the glass surface. Methyltrimethoxysilane imparts acidic but not basic chemisorptive properties, while γ-chloropropyltrimethoxysilane mitigates the acid-base properties of bare glass without imparting additional chemisorptive character. Chemisorptive properties imparted by silane deposition are not thermally stable, and disappear upon ramping the system temperature to 300°C.