The growing concern over the transmission of pathogens, particularly in high-risk environments such as healthcare facilities and public spaces, necessitates the development of effective and sustainable antimicrobial solutions. Traditional coatings often rely on metals, which despite their efficacy, pose significant environmental and economic challenges. This study explores the potential of bio-based alkyd resins, supplemented with natural antimicrobial bioadditives, as an eco-friendly alternative to traditional antibacterial and antiviral coatings. Specifically, alkyd formulations incorporating thymol and soft resins extracted from hops were evaluated for antimicrobial and antiviral efficacy, following ISO standards (ISO 22196:2007 and ISO 21702:2019, respectively). The coating formulations showed significant activity against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus), and Influenza A (H3N2) virus, proving their potential for mitigating pathogen spread. These bio-based coatings not only reduce reliance on harmful chemicals but also align with circular economy principles by repurposing industrial by-products. This innovative approach represents a significant step toward greener antimicrobial technologies, with broad applications in healthcare, public infrastructure, and beyond, especially considering the rising zoonotic disease outbreaks.

Alkyd resins are still one of the most important classes of binders for paint systems. They are outstanding in terms of their versatility of formulations and applications, cost-effectiveness, and durability. Traditionally, they are synthesized using phthalic anhydride, polyalcohols with three or four functional groups (pentaerythritol, glycerol, and trimethylolpropane), and fatty acids or oils. In this study, new bio-alkyd resins were synthesized with the objective of increasing the bio-based content by substituting phthalic anhydride, thereby also enhancing the biodegradability of coatings. The newly synthesized alkyd resins, formulated with azelaic acid, were used to develop coatings incorporating additives while avoiding cobalt-based driers. Additional agents such as leveling, wetting, and anti-skinning agents, were also included. Paints were applied to wood substrates and dried at room temperature. The resulting films were characterized by pendulum hardness, transparency, and color by colorimetry, cross-cut test, contact angle, and gloss. Thermal properties were analyzed by Differential Scanning Calorimetry (DSC), and Total Organic Carbon (TOC) content and aerobic biodegradation were also evaluated. The resulting coating films exhibited good mechanical performance, with hardness values ranging from 132 to 148 Persoz oscillations and strong adhesion to wood substrates (smooth cross-cut edges, Class 0). Significant biodegradability (70% in less than 90 days) was demonstrated under composting conditions, which was considerably higher than that of a commercial reference alkyd coating (34.7%) under the same conditions. These findings suggest that the developed bio-alkyd coatings formulated with azelaic acid and DCO-FA without cobalt-based driers represent a promising alternative to conventional phthalic acid-based alkyds. These novel coatings move closer to fully bio-based formulations and offer enhanced biodegradability, making them a more sustainable option for coating applications.

Phosphorus-containing water-borne alkyd resins were prepared for use as flame-retardant transparent wood coatings. The synthesis process involved alcoholysis followed by esterification, incorporating the reactive flame-retardants polyethyl-phosphate glycol ester (Exolit OP550) and 2-hydroxyethyl methacrylate phosphate (Sartomer 9054). Additionally, different size ammonium polyphosphate additive flame-retardants (Exolit AP422 and Exolit AP423) were incorporated into the base alkyd resin. Chemical characterisation using techniques such as NMR and FTIR confirmed the successful synthesis and the effects of the flame-retardants on the esterification reactions were analysed. Samples containing Santomer 9054 and high amount of Exolit OP550 did not give rise to stable dispersions. SEC analysis revealed changes in molar mass distribution with the incorporation of flame-retardants. Dispersion and film characterisation included particle size measurements, contact angle measurements, and evaluation of thermal properties by DSC and TGA. Evaluation of the formulated films included assessments of fire performance by cone calorimetry, transparency, adhesion to wood substrates, gloss, hardness, and water sensitivity. Flame-retardants had significant effects on fire behaviour, thermal properties, and coating performance, with additive flame-retardants demonstrating higher efficacy than their reactive counterparts.