Water-based acrylic coatings are nowadays the standard for exterior wood coatings due to their low cost, good mechanical resistance and good adhesion on most wood substrates. However, these coatings are alsosensitive to UV light and temperature. A new alternative for the wood industry is the water-based polyvinylidene fluoride (PVDF)-acrylic coatings. These coatings are known for their good chemical resistance and weatherability.
Previous works has shown that PVDF-acrylic coatings (70% of PVDF) present a better weatherability and color retention than pure acrylic coatings. Still, the permeability and the mechanical resistance have to be optimized. To do so, the PVDF concentration could be lowered. It could improve the flexibility and elasticity of the coatings and they could be more affordable for the wood industry.
In this project, clear PVDF-acrylic coatings containing respectively 50, 60 and 70% of PVDF were prepared. The Young’s modulus as well as the water vapor transmission rate were measured. From these tests, the optimal PVDF concentration was selected. Accelerated weathering tests were then performed to compare the performance of these coatings with water-based acrylic coatings. The results obtained have shown that lowering the PVDF concentration affects the weatherability of the coatings. In fact, a concentration of 55% in PVDF was found to be less efficient in terms of weathering than a concentration of 70%.