Wettability of natural fibres used as reinforcement for composites

Wetting parameters e.g. contact angles, work of adhesion, fibre surface energy and interfacial energy of different flax and glass fibres in different liquids were determined. A polypropylene film was also studied by the Wilhelmy technique. The surface of the fibres was analysed with scanning electron microscopy. Results pointed out that the flax fibres are partially wetted out by polar solvents. A baseline shift hysteresis was observed, possibly due to hydratation of the surface. The wettability of the glass fibres with a finish for thermosets is higher in polar solvents, compared with glass fibres used as reinforcement for thermoplastics. It is observed that the wettability is independent of the fibre diameter for the glass fibres with the same cross sectional shape. The difference in contact angle hysteresis between the fibres can be explained by the difference in presence of higher surface energy components. By comparing the wettability of the fibres and polypropylene, some fibres could be expected to have a better adhesion with polypropylene than the others.