Bio-based furan coatings: adhesion, mechanical and thermal properties

Abstract

In this study, preparation of polyfurfuryl alcohol (PFA) as a renewable binder resin with an origin in biomass conversion is reported for developing a heat-resistant coating. PFA resin was synthesized in the presence of maleic anhydride as a catalyst. Various techniques were used to characterize the synthesized PFA resin. In the second step, different coating samples were prepared using PFA resin. Flexibility, adhesion strength and thermal/curing behavior of the coating samples were investigated as a function of their compositions such as the resin, plasticizers and titanium dioxide (TiO2) contents. The coatings were cured optimally at 150 °C according to isothermal and non-isothermal DSC measurements. Leveling property of the coatings was significantly improved in the presence of TiO2 due to a corresponding increased viscosity of the compound. The adhesion strength of the coating was low due to the aromaticity of PFA chains, high cross-linking degree of the binder resin and the difference existing between thermal expansion coefficient of the coating and steel substrate. In the presence of dioctyl phthalate and long-oil alkyd resin as plasticizers, flexibility and adhesion strength of the coatings were significantly improved up to 15 mm and 2.7 MPa, respectively. High thermal stability of the coatings was supported by TGA findings but it was deteriorated in the presence of alkyd resin. Alkyd resin, a plasticizer, increased the extent of cross-linking due to the chain flexibility enhancement according to DSC and DMTA findings. Finally, a heat-resistant coating formulation containing 9.3 wt% long-oil alkyd resin and 9.3 wt% TiO2 was selected as a good candidate for heat-resistant coating development due to the highest thermal and mechanical properties shown.