Abstract
In this work, surface free energies and mechanical properties of resol-type phenolic resin (RPR)/poly(vinyl alcohol) (PVA) blends were studied. The intermolecular interaction between RPR and PVA was confirmed by Fourier transform infrared (FT-IR) spectroscopy. Contact angle measurements were performed using a three-liquid acid-base method to determine the surface free energies of RPR/PVA blends. Interlaminar shear strength (ILSS) and critical stress intensity factor ( $K_{IC}$) tests were carried out to exploit the effect of surface free energies on the mechanical properties of blends under study. The morphologies of he fracture surface of RPR/PVA blends were investigated by scanning electron microscopy (SEM). FT-IR results showed the formation of hydrogen bonds in RPR/PVA blends. Surface free energy was a maximum value when PVA content was 5 vl% in RPR. Both nonpolar and polar components contributed to an increase in the surface free energy. ILSS and $K_{IC}$ increased with the addition of PVA, and then decreased when PVA content was higher than 5 vol%. Morphological results showed that the fracture surface area increased with the increase in PVA content, which was in good agreement with the mechanical properties of RPR/PVA blends.s.
