One of the emerging topics in modern polyurethane (PU) technology is the exploitation of monomers and macromers from renewable resources to improve the environmental sustainability while preserving their excellent technical performances. PU coatings are obtained by the stoichiometrically balanced mixture and crosslinking of polyols (polyether and frequently polyester oligomers) with polyisocyanates. Polyester (PE) polyols are the largest fraction in the composition of PU coating materials. They are made from aliphatic as well as aromatic diacids and hydroxy functional monomers. Within aromatic acids, 2,5-furandicarboxylic acid (FDCA) is a “new” bio-based building block with a unique structure that is attracting great interest. Most of the studies concerning FDCA-based PE are about thermoplastics, but there is a lack of information in the literature about polyester copolymers based on FDCA as precursors for PU coatings. Moreover, there is a lack of LCA studies on PE/FDCA productions where just a very few environmental burdens are included. Based on this, the main objective was the development and environmental study of a new class of polyester binder based on FDCA suitable as precursors of PU coating materials. This strategy for this new 100% bio-based structure initially involved the selection and copolymerization of four different monomers (available from modern biorefinery downstreams) such as glycerine, 1,3-propanediol, 2,5-furandicarboxylic acid and succinic acid. The selection of all monomers was according to their functional role and available data from literature for the environmental study. This new structure was benchmarked against 75% bio-based and fossil-based PE binders. Successively, the obtained polyesters were crosslinked with a conventional polyisocyanate to obtain the corresponding PU coatings. Their technological performances were evaluated, especially for FDCA-based PU coating. The results obtained in the technological evaluation showed a stiffer FDCA-based PU coating and a more hydrophilic character leading to a better adhesion compared to the other coatings. A possible application is in the field of coil coating and automotive as intermediate layers or primers where a high adhesion of the material and recoatability are required. In addition, the evaluation of the total impact of greenhouse gas emissions (GHG) and the total non-renewable energy use (NREU) of all the obtained PEs by the Life Cycle Assessment (LCA) were included on the basis of a cradle-to-gate approach with the idea to observe the total impact of our new developed materials, specially the FDCA production process starting from sugar beet (primary data) to obtain the new PE binder. This study focuses on the ‘Cumulative Energy Demand’ method, which covers the impact category of non-renewable energy use (NREU) including fossil and nuclear energy and the ‘Greenhouse Gas Protocol (GGP)’ method, which covers the impact category of GHG emissions. The results showed a very noteworthy reduction in terms of GHG emissions (-36% and -79%) and a noticeable reduction impact in terms of NREU (-38% and -60%) compared to 75% bio-based and fossil-based PE binders respectively. Moreover, a sensitivity analysis regarding sugar production from beet cultivation was developed through different LCA calculation allocations such as economic and energy and no remarkable differences were observed between them.
Keywords: life cycle assessment, 2,5-furandicarboxylic, bio-based monomers, bio-based polyester, polyurethane coating.
4a. Predictions and responses
