Short-chain Polyols from Bio-Based Carboxylic Acids for High-Performance Polyurethane Coatings

Emerging bioengineering methods have created an opportunity to introduce a range of novel sustainable raw materials into industrial chemical processes. Among others, a multitude of bio-based acids can become available on the market on a commercial scale. These functional molecules can be useful as reagents for manufacturing sustainable high-performance materials. To this end, we evaluated a series of seven bio-based carboxylic acids as starting materials in the development of cross-linked 2K polyurethane (PU) coatings. By reacting the acids with propylene oxide (PO), seven short-chain polyols were synthesized. The synthesized polyols, consisting of mixtures of polyfunctional hydroxy-terminated products, were cross-linked with two isocyanate trimers (hexamethylene diisocyanate (HDI) trimer and isophorone diisocyanate (IPDI) trimer) to produce polyurethane coatings. The thermal, mechanical, and coating properties of PU films can be varied depending on the polyol and isocyanate used. Thus, coatings formulated using IPDI trimer were hard and brittle, whereas films made with the aliphatic HDI trimer offered a valuable combination of excellent hardness and extraordinary flexibility. Using polyols made from several isomeric carboxylic acids resulted in a significant variation of properties in the PU coatings. The results illustrate the applicability of novel bio-based acids as starting materials in the coatings industry and highlight the necessity to explore their potential application as components of sustainable materials.