FT-IR microscopic studies on coupling agents: treated natural fibres

Natural fibres (sisal) were treated with various coupling agents such as or ganosilane, zirconate, titanate and N-substituted methacrylamide. The natur e of the adsorbed chemical species on the fibre surfaces was analysed by Fo urier transform infrared microscopy (FT-IR). The presence of precipitated o ligomers on the surface was confirmed by the appearance of hydrogen-bonded carbonyl group and unsaturation bands. The results showed an irregular phys isorption/chemisorption of coupling agents, their penetration beyond the su rface, and a decrease in the hydrophilicity of fibres. SEM and dynamic cont act angle studies on the fibres supported these findings. FT-IR microscopy in its reflectance mode was more effective in ascertaining the chemical nat ure and structure of adsorbed layers onto sisal fibre surfaces compared wit h DRIFT and transmission spectroscopy. The difference in the properties of untreated and chemically treated fibres has also been verified in the polym er composites. (C) 2000 Society of Chemical Industry.