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This work aimed to develop a novel epoxy-modified tung oil waterborne insulation varnish with blocked hexamethylene diisocyanate as a curing agent. The Diels-Alder reaction between tung oil and maleic anhydride, and the ring-opening esterification reaction of epoxy resin were confirmed. The conversion rate of epoxy was explored as a function of reaction time and temperature. The effects of epoxy resin content on the thermal stability, water absorption and insulation properties (insulation strength, volume resistivity, and surface resistivity) of films were investigated, and the resistances of films to salted water were evaluated. The increase in epoxy resin contents could improve the thermal stability and insulation properties of films, and decreased the water adsorption of films, but when the epoxy resin content reached 30% and above, the water solubility of resin became poor. After being immersed in 3.5 wt % NaCl solution, the electrical insulation strength of films were lower than that in dry state, and decreased as the immersed time prolonged. In particular, the electrical insulation strength loss of films increased significantly for epoxy resin content at 15% and below. Furthermore, the increase of epoxy resin content could improve the hardness and adhesion of films, but the flexibility of films became worse. On the basis of experimental, the epoxy resin content at 25% was appropriate to prepare waterborne epoxy-modified tung oil resin. The resulting varnish may have potential as an immersing insulation varnish for the spindle of electric motor. V C 2015Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42755.

An acrylate-modified tung-oil waterborne insulation varnish was synthesized from tung oil, maleic anhydride, and acrylates via a Diels-Alder reaction and free-radical polymerization, and the varnish could be solidified at a relatively low temperature with blocked hexamethylene diisocyanate as a curing agent. The resulting films were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. The insulation properties (electrical insulation strength, volume resistivity, and surface resistivity) of the varnish films were tested, and the resistances of films to salted water were evaluated. With an increase in the maleic anhydride content, the thermal stability of the film was improved, whereas the electrical insulation strength, volume resistivity, and surface resistivity decreased. The electrical insulation strength of the film after it was immersed in the NaCl solution was lower than that in dry state, and it decreased as the immersed time was prolonged. In particular, the electrical insulation strength loss of the film increased significantly at maleic anhydride contents beyond 25 wt %. Furthermore, the hardness of the film increased with increasing methyl methacrylate/N-butyl acrylate ratio, whereas the flexibility and adhesion of film decreased to a certain degree at the same time.

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The eco-friendly functionalized TiO2/polymer antifouling (AF) coating was successfully synthesized by dispersing TiO2 nanoparticles in waterborne epoxy-modified tung oil resin. The AF effectiveness of coating was evaluated toward Staphylococcus aureus ( S. aureus, ATCC6538), Escherichia coli ( E. coli, ATCC8739) and diatom ( Cyclotella sp., FACHB-1635). The nanoTiO2/polymer AF coating showed good antimicrobial activity both under the light and dark conditions by comparison with the pristine TiO2 nanoparticles and bulk polymer. Under light irradiation for 50 min, the AF coating showed only 8.4% and 8% survival rate for S. aureus and E. coli. In addition, The AF coatings exhibited favorable inhibition efficacy toward the growth and adhesion of Cyclotella sp., and the efficacy was enhanced with the increase of TiO2 content. It can be concluded that TiO2 nanoparticles endow the AF coatings with promoted fouling resistance properties.