Epoxy resin selection

Grant Agreement number: 101058371 Project acronym: ESTELLA Project title: Design of bio-based thermoset polymer with recycling capability by dynamic bonds for bio-composite manufacturing DELIVERABLE 2.4 Epoxy resin selection Contractual Date of Delivery: 31 October 2024 Actual Date of Delivery: 31 October 2024 Lead contractor for this deliverable: ICSO Author(s): Biernat (ICSO), Giorgio Tofani, Filipa A. Vicente (NIC), Ghazal Tavakoli Gheinani, Willem Vogelzang (WR), Maria Schonherr, Daniela Trambitas (FEY), (AND) Participants(s): ICSO, NIC, WR, FEY, AND WP contributing to the deliverable: WP2 Nature: Confidential Version V. 5 Grant Agreement 101058371 Project ESTELLA ESTELLA_D2.4_v5 - This is the property of ESTELLA Parties: shall not be distributed/reproduced without formal approval of ESTELLA General Assembly. The Community is not liable for any use that may be made of the information contained therein. Executive Summary The work described in this report focused on the selection of epoxy resin matrices developed within the ESTELLA project for upscaling, based on the mechanical and thermal properties of the products, as well as their recycling potential. Task 2.4 is described as follows: T2.4 Selection and production of the epoxy resins formulations [ICSO, NIC, WR] (M22-M29) In this task the results of the thermal and mechanical analyses of T2.2 and the recyclability results of T4.1 will be compiled in order to select those that meet the g and the recovery of 65% of matrices after recycling process). This will lead to the synthesis and production of two final selected epoxy resin formulations scaled up to produce enough material. For associative CAN systems, this will be 15kg per resin. Originally, this amount was estimated at 25-30kg of both the highperformance and the low performance resins. However, after producing the different associative epoxy resins and characterising them, it became clear that, with the properties obtained for the latter, there would be no suitable application within the project for the low performance resin. Therefore, scaling-up this resin would not be an efficient use of resources and time. Moreover, based on the best formulations developed so far within the project, it became evident that upscaling the process to produce 25-30kg of these resins would be challenging and time-consuming. At the same time, reducing this amount to 15kg will in no way hinder the successful completion of the project objectives, so the proposed amount of epoxy resin was reduced. In case the dissociative CAN system is selected, WR will scale up to 1kg, which allow for reprocessing/recycling activities. In the case of dissociative CANs, it was also noted that the most promising epoxy resin requires a complex procedure that prevents scaling up to 3-5kg, with 1 kg being sufficient for scaling up. Below are the main findings of the research on synthesis and recycling of associative and dissociative epoxy resins. Associative bio-based epoxy from lignin with CAN [NIC] Considering the development of associative bio-based epoxy from lignin with CANs, two distinct pathways were explored: i) reaction between lignin monomers (vanillin and syringaldehyde) and various diamines to create imine bonds (Schiff bases), ii) functionalization of higher molecular weight (MW) fractions of lignin derived from softwood Kraft lignin to create ester and ether bonds. Considering the project objective, only one epoxy resin fulfils two of the required requirements for Tgand elongation at break. In the recycling of lignin-based epoxy resin developed by NIC, no dissolution was observed using glycol as a solvent. The dissolution of this type of matrix were observed when cyrene and combination of Cyrene-water were used as solvent together with the presence Grant Agreement 101058371 Project ESTELLA ESTELLA_D2.4_v5 - This is the property of ESTELLA Parties: shall not be distributed/reproduced without formal approval of ESTELLA General Assembly. The Community is not liable for any use that may be made of the information contained therein. of acidic catalysts such as p-TSA catalyst and TAR. However, none of the different approaches allowed the complete dissolution of the bio-based epoxy resin. Associative fossil epoxy resins with CAN [ICSO] Epoxy vitrimers developed by ICSO were based on the low-molecular weight fossil epoxy resin, crosslinked with carboxylic acids and/or anhydrides in ring opening condensation reaction. Epoxidized plant oils were used as reactive diluents to modify properties of resin. The use of a mixture of crosslinking substances, specifically a combination of acid and anhydride allowed for the meeting of project requirements for glass transition temperature Tg, tensile strength and Young modulus. The elongation value was not achieved, as this would have to be at the expense of deterioration of the other parameters. Significant efforts were devoted to developing an efficient process for the chemical recycling of cured epoxy resins based on Epidian-6. The cured epoxy material was completely dissolved in propylene glycol. The dissolution process was carefully monitored to ensure complete depolymerization of the cross-linked resin without chemical degradation of the monomers. Dissociative recyclable resins [WR] WR developed synthesis of epoxy materials containing Diels-Alder bonds, using Diels-Alder mechanisms, focusing on the use of bio-based raw materials and recycling potential. The thermal behavior of the developed thermosets is a critical parameter for selecting the optimal formulation, given the intended applications of Estella materials. Amongst the materials developed by WR, some formulations exhibit glass transition temperatures (Tg) that are near the specified range for Estella materials. Also, three formulations possess a bio-based content exceeding or approaching 60%. Additionally, these three formulations have mechanical properties that meet the established criteria, further supporting their suitability for the target applications. However, rheological studies revealed that none of the formulations exhibited the necessary viscosity drop required for effective recycling or reprocessing. Furthermore, attempts by other partners to recycle formulation A, as one of the best performance formulations, through chemical or mechanical methods were unsuccessful. Conclusions After reviewing all the observations and results, and evaluating the feasibility of synthesizing these thermoset resins, it was concluded that none of WR's formulations will be selected for scale-up in this project. In evaluating the different formulations developed by NIC, specifically those using lignin monomers and lignin itself to prepare bio-based epoxy resins containing CANs, it was determined that the former did not meet the sustainability requirements. Among the four Grant Agreement 101058371 Project ESTELLA ESTELLA_D2.4_v5 - This is the property of ESTELLA Parties: shall not be distributed/reproduced without formal approval of ESTELLA General Assembly. The Community is not liable for any use that may be made of the information contained therein. formulations of the latter, only one showed potential; however, even this option did not fully meet all of ESTELLA's requirements. In contrast, the fossil-based epoxy resin materials being developed at ICSO demonstrated very good mechanical properties and recycling potential. As a result, the formulation developed at ICSO was selected as the final composition with the potential for larger-scale implementation. This D2.4 deliverable has met its objectives, with the exception of selecting the dissociative CAN system. It was concluded that the formulations developed by WR did not meet the project's requirements and would not be selected for scaleup. This decision was based on a comprehensive analysis of the data and alignment with the project objectives. Considering the properties of all the developed systems, it was decided to upscale only the fossil-based epoxy vitrimer. According to the amendment to the Grant Agreement, it was also deviation in time and plan of the Deliverable.