Surface modification of ramie fibers with silanized CNTs through a simple spray-coating method

Abstract

Preliminary studies performed have indicated that carbon nanotube (CNT) coating is an effective method to enhance the bonding between a natural fiber and a resin matrix. However, the reported coating process is complex, and the improvement of the bonding strength is limited owing to obvious CNT aggregation. This paper reports a simple spray-coating method with uniform distribution of CNTs coated on ramie fiber surfaces. The dispersion of CNTs in a suspension for spray-coating was found to play a key role in CNTs distribution on the fiber surface. Silylated CNTs can be stably and uniformly suspended in a water and alcohol solution with a polyvinylpyrrolidone dispersant. The suspension was sprayed onto ramie fabric by using a hand-spraying pot, and CNTs were distributed on the fiber surface uniformly, as indicated by scanning electron microscopy results. The agglomeration of CNTs on the fiber surface became increasingly evident with an increase in the number of spray layers (from one to six). The effects of CNT coating on the flexural properties of the related composite and bonding properties were studied. The CNT-coated ramie fiber reinforced epoxy plate was prepared by a vacuum assistant resin transfer molding method. The CNT coating increased the flexural strength and modulus of the composite by 38.4% and 36.8%, respectively. A microdebonding test showed that the CNT coating increased the interfacial shear strength between a single ramie fiber and the epoxy resin by 25.7%, which is believed to result from stronger mechanical interlocking and chemical bonding.