Bio-sourced unsaturated polyesters for 3D-printing Claire Morand 1,2,3 , Coralie Jehanno 1,2 , Haritz Sardon 2 , Andrew Dove 3 1 Polykey Polymers, Joxe Mari Korta Center, Donostia-San Sebastián, Spain, 2 Polymat, University of the Basque Country ,Spain, 3 School of Chemistry, University of Birmingham, UK
In the past years, the replacement of petro-sourced chemicals for molecules from renewable sources has become an important topic for the chemical industry. Polyesters are the family of polymers the most studied from bio- sourced monomers. They are vastly employed in a broad range of applications. 1 A few processes have been developed for the synthesis of conventional polyesters, such as PET, PBT or PLA. 2 However, these methodologies still need improvements for being considered sustainable or to employ only bio-sourced synthons. Synthesised from the transformation of cellulose, maleic acid is one of the most promising bio-sourced monomers for the preparation of unsaturated polyesters. 3 Indeed, the available double bond allows to use them as photocurable resins. The low molecular weight diols used in combination in this study are also bio-based, obtained from cellulose or from plant oils. They are linear, branched, or vicinal (glycols). Low molecular weight polyesters are targeted, around 1000 – 2000 g.mol -1 , as resins of low viscosity are required for 3D-printing. To synthesise these polyesters, 5 fully bio-based organo-catalysts are screened, such as L-proline or betaine. Depending on the catalyst used or the diol used, the cis- / trans- content of the resulting polyester is changed. With the different catalysts, polyesters containing from 10 to 90% of trans- conformation can be obtained. With linear diols, polyesters with low trans- content are obtained, while with ramified and vicinal diols, high trans- content are obtained. More polyesters have trans- content, more they are visually viscous. Unsaturated polyesters can be used as photo sensitive resins for 3D-printing. The mechanical response under UV light of some polyester resins is investigated. The resins show different behaviours: more the resins have trans- content, more the storage modulus is high, they are more rigid. As the carbon chain length of a linear diol increases, the storage modulus decreases, the material is more elastic. However, resins of low viscosity are required for 3D-printingTo decrease the viscosity, the resins can be combined with several reactive diluents. References 1. Zhang, M. Song, Y. Xu, W. Wang, Z. Wang and L. Zhang, Progress in Polymer Science , 2021, 120 , 101430.- 2. G. Rosenboom, R. Langer and G. Traverso, Nat Rev Mater , 2022, 7 , 117–137. 3. Yu, Z. Wei, X. Leng and Y. Li, Polym. Chem. , 2018, 9 , 5426–5441.
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