Surface free energy of basalt and glass fibers by contact angle method

The surface free energies and their dispersion/polar components of basalt and glass fiber were investigated using dynamic contact angle analysis. According to Fowkes' and Good's theory, by making use of the contact angle values for monofiber surfaces and standard liquids with known values of surface energy, surface free energy values as well as their components of both fibers were evaluated. It was found that the surface free energy of sized basalt fiber was higher than sized S-2 glass fiber while the polar component of both fibers tended to decrease without sizing; the liquid polarity also influenced the quantity of polar interactions as well as the quantity of dispersion interactions. These results indicate that sizing on the fiber improves wettability and interface adhesion between fibers and resin in fiber reinforced composites.