Application and characterization of a novel PVDF-HFP/PVP polymer composite with MoO3 nanowires as a protective coating for wood

Abstract

The coatings on wood must sometimes give aesthetic and basic protection to wooden elements and prevent the development and transmission of microorganisms. Several polymers containing different nanoparticles have already been offered to day for this purpose. The research presents a novel poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)/polyvinylpyrrolidone (PVP) polymer composite with MoO3 nanowires with the ability to form coating films on wood. The films of the developed coating exhibit elastic behaviour, which depends on the coating film thickness [tested wet film thicknesses (90, 180 and 360) µm]. The coating showed the ability to interact well with the surface of common beech (Fagus sylvatica L.) wood, in terms of wetting (contact angles of 15.6°), fast spilling on the surface, good penetration of the coating in wood structure and formation of up to 40 µm-thick films with excellent pull-off adhesion strength (6 MPa). An increased roughness of wood coated with C + MoO3 was a consequence of wood etching by the dimethylformamide solvent present in the coating. Moreover, the presence of C + MoO3 on wood made it considerably more hydrophobic, with contact angle of water raising to 123° from initially 46° measured on uncoated wood. The irradiation of wood surfaces with ultra-violet light resulted in visible colour changes on both uncoated and coated wood. The wood coated with C + MoO3 has a good resistance to water, alcohol and dry heat (grade 3 to 4). The antimicrobial testing showed that the presence of MoO3 in the coating plays an important role in the resistance of the coated wood to blue-stain fungi and mould development. The developed PVDF-HFP/PVP/MoO3 coating has an excellent ability to interact with the wood surface and has the potential to be used as a protection for wood in sensitive environments.