Biobased Coatings (Bio-gebaseerde Coatings)

In order to meet changing consumer requirements in terms of origin and sustainability and European regulations, the coating industry and its users need to adapt. Although everyone in the value chain is convinced of the usefulness of bio-based coatings, their introduction is stagnating. European research and a survey of Flemish companies show that there are various reasons for this delayed breakthrough. However, there are immense opportunities to develop new bio-based coatings thanks to the increasing supply of new bio-based building blocks from (non-food) biomass. Some bio-based coatings have even better or wider application possibilities than fossil-based coatings.

Often, the way the coating is applied appears to have a greater impact on the proper functioning of the coating layer than its composition. Although there is a will among distributors and developers, there is insufficient know-how about the processing and application of bio-based coatings and the start-up to process new bio-based raw materials is complex, time consuming and expensive. Moreover, it is impossible to replace certain chemicals on a 'one-to-one' basis and the unfamiliarity with the composition of bio-coatings results in insufficient insight into the possibilities and bottlenecks during their development. Internationally, research focuses on the development of building blocks and not on the validation of bio-coating formulations and their application.

The application and performance of bio-based coatings has been demonstrated for different coating cases, including acrylates, epoxy, polyurethanes and PLA. Based on an overview of industrially available bio-based components, several binders, cross-linkers, diluents and additives were selected and concentration studies through gradual replacement of the fossil-based parts into bio-based parts were performed. The compositions have been tuned towards use on substrates such as wood, textiles, concrete, metal,… with specific requirements on functional properties such as abrasion resistance, weatherability, washability, corrosion resistance, hydrophobicity. In particular, the introduction of bio-based coatings was validated by the identification of application procedures and user conditions where bio-based coatings outperform the traditional fossil-based coatings in terms of hydrophobicity or lifetime. For acrylate coatings, a UV curing process has been evaluated where the better lubricating properties and hydrophobicity of bio-based acrylate monomers contribute to the higher abrasive wear resistance. In parallel, the better ductility and high elasticity of the bio-based acrylates results in better scratch resistance. For epoxy coatings, novel crosslinkers and diluents based on oil extracts were evaluated, which provide high crosslink density, hardness and hydrophobicity in parallel with better wear lifetime of the coating. The properties can be tuned depending on the concentration of diluents and crosslinkers, providing an operational set of parameters that is compatible with the thermal curing conditions. For polyurethane coatings, the alternatives with bio-based isocyanates, bio-based polyols and development of isocyanate-free dispersion coatings were evaluated. For 2K PU systems, the drop-in solution with a bio-based diisocyanate was optimized towards same pot-life, viscosity and drying times, where linear increase in hardness, wear and UV resistance of the bio-based component implies good compatibility and mixing properties. For dispersion systems, novel stabilization techniques have been developed resulting in the augmentation of coating performances mainly in textile applications. Finally, the emulsification and dispersion coatings of PLA were further developed towards final applications with appropriate additives to improve processibility and performance. The project demonstrated, in cooperation with a guidance group of 70 companies, that traditional coatings can be reformulated into bio-based alternatives and while adapting processing conditions, operational ranges with superior performance can be detected.