Wetting behavior of elastomer-modified glass fibers

Interfacial properties of glass fibers coated by admicellar polymerization with a styrene-isoprene copolymer thin film have been investigated. Advanci ng and receding contact angles on single glass fibers as small as 6.2 mum i n diameter were measured at slow meniscus velocities (2.0 mum/s) by using t he Wilhelmy method with probe liquids of various hydrophobic/hydrophilic ch aracteristics. Distinctly different contact angles were obtained from the d ynamic wetting of fibers with different surface treatments. In water, the a verage advancing contact angle for admicellar-modified fibers was high (the ta (adv) approximate to 65-75 degrees), suggesting an increased hydrophobic ity as compared to that of the fully wettable desized fibers. Furthermore, it was found that both fibers with silane coupling agents and admicellar-co ated fibers are chemically heterogeneous on their surfaces. Contact line pi nning behavior induced by regions of different surface energy, as well as h igh hysteresis values, indicates that the ultrathin styrene-isoprene film i s not uniform throughout the. glass on a macroscopic length scale. However, when assessed with an epoxy resin (e.g. EPON 815C), the admicellar polymer ization treatment produced fibers with statistically identical wetting char acteristics to those of fibers containing a proprietary sizing. Good adhesi onal wetting of the elastomer-modified fibers by an epoxy resin may be indi cative of an adequate interaction between fiber and matrix in large-scale c omposite fabrication.