ESEM Study of Oil Wetting Behaviour of Polypropylene Fibres - Polypropylene (PP) fibres have been increasingly used in oil related areas, such as oil sorbents, oil coalescers, oil filters and oil separators. The wetting behaviour of the fibres by oil is of particular importance in these applications. The environmental scanning electron microscope (ESEM) technique was used in this study to investigate the oil wetting of polypropylene fibres. The wettability was investigated by contact angle measurements with oil. Oil drops were added onto fibres using a micro-injector. The contact angles were measured from ESEM micrographs using image analysis and theoretical approach. ESEM observation reveals the wetting of single fibres on a microscopic level.