Synthesis and characterization of modified novolac phenolic resin nanocomposites as metal coatings

Novolac phenol formaldehyde NPF resin/organobentonite clay nanocomposites were prepared and modified with epoxy and/or urethane resin via solution technique. The prepared samples at organoclay content 2 phr were characterized by transmission electron microscope TEM, X-ray diffraction (XRD), and Fourier transform infrared measurements (FTIR) in comparison with unmodified NPF resin. TEM showed that nanocomposites achieved good clay dispersion. X-ray diffraction analysis indicated that exfoliated structures were obtained. Furthermore, the FTIR investigation confirmed the incorporation of epoxy and/or toluene diisocynate in the modified structure. The influence of the nanoclay content (i.e., 0.5, 1.0, 1.5, 2.0, and 2.5) relative to the micrometer clay (i.e., 2, 4, 6, 8, 10, and 20) on the NPF resin was analyzed through mechanical properties (viz., adhesive, scratch hardness, impact resistance and elongation at break), thermal stability (TGA) and electrical volume resistivity. Epoxy modified NPF nanocomposites with 2 phr organoclay gave the optimum adhesion and scratch hardness values, thermal stability and electrical insulation resistance as compared with epoxy/urethane, urethane modified NPF, and unfilled NPF samples. The samples could be successfully evaluated as metal coatings.