Surface Activation and Characterization of Basalt Fiber by Plasma Treatment and Its Interfacial Adhesion with Epoxy

The weakness of the fiber-matrix interface restricts the practical application of basalt fiber (BF) as a reinforcing material. In order to improve the interfacial adhesion between the BF and epoxy matrix, surface activation of the BF was carried out using low-pressure O2 and H2-Ar plasma under various conditions. The interfacial shear strength (IFSS), evaluated by a micro-droplet de-bonding test, was adopted to demonstrate the bonding effects at the BF/epoxy interphase. Compared to bare BF, the IFSS between the modified fibers and epoxy matrix was efficiently improved with an increment of 38.4% and 14.4% for O2 plasma and H2-Ar plasma treatment, respectively. Scanning Electron Microscope (SEM) and Atomic Force Microscopy (AFM) analysis indicated that H2-Ar plasma-treated BF had a much rougher and more rugged surface than O2 plasma-treated samples. X-ray Photoelectron Spectroscopy (XPS) and surface energy results revealed that O2 plasma activation could effectively increase the content of oxygenous groups on the BF surface, thus resulting in a higher total surface energy value. Based on the results, O2 plasma modification at a power of 200 W and pressure of 80 Pa for 0.5 min was considered to be the most favorable condition for the surface activation of BF.