Wettability of carbon nanotube fibers

Carbon nanotube (CNT) fibers are interesting alternatives to carbon fibers as fibrous reinforcement. However, good interfacial adhesion between the fibers and the matrix is difficult to control. Wetting of the fiber reinforcement with the matrix strongly determines the interfacial strength. Therefore, accurate characterization of the wettability of CNT fibers is one of the most important cornerstones to improve the interfacial adhesion. In this work, dynamic contact angle measurements were conducted on individual CNT fibers by using a modified tensiometric method based on the Wilhelmy method combined with a synchronized optical observation. The CNT fiber-liquid interactions were monitored in-situ, and accurate measurements of the contact angles were achieved. Contact angles on CNTs were estimated through a modified Cassie-Baxter model on the basis of the experimental contact angle values of CNT fibers. Subsequently, the non-polar and polar surface energy components of the CNTs were obtained. Then, the wetting parameters (work of adhesion, spreading coefficient and wetting tension) were predicted by using the surface energy values of both the CNTs and a series of polymers (PP, MAPP, PET, PVDF, and PVA). The results indicate that PVA is in terms of wetting the most suitable matrix for the preparation of CNT fiber polymer composites.

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