A facile salt-templating route to design polyvinyl butyral based coatings for birch wood surfaces

The need for wood surface protection in building and outdoor applications has intensified the search for innovative strategies in developing coating technologies. This research aimed to design a novel porous coating based on polyvinyl butyral (PVB) to ensure birch wood surface protection using a dip-coating procedure and a salt-templating methodology to achieve a porous structure. Firstly, the optimization of porosity has been achieved by using different NaCl crystal sizes. Sodium chloride, used as a porogen, was ground using mechanical milling for different times (0–12 h). Analyses of morphology, roughness, pore size, and water contact angle were carried out to select the optimal milling time. Then, by setting it equal to 2 h, which provided a mean pore size of PVB coating of 5 μm, carvacrol was loaded into the coating to further improve its properties, setting its concentration from 0 % to 30 % w/w. Barrier properties to water vapour of PVB-based coatings evidenced a slight improvement in sorption and a lessening of water cluster phenomena occurrence after the coating. The presence of the coating ensured an improvement in solar reflectance from 63 % for pristine wood to 78 % after the coating. Besides, carvacrol ensured a noticeable antimicrobial activity in inhibiting S. aureus growth at low concentrations and E. coli at the highest concentration tested (30 %) (2 log reduction in population density for both bacteria). These outcomes prove the potential use of PVB-based porous coating as protection of birch wood surface for outdoor applications and construction.