Development of thermoset epoxy resins with CAN

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 2.2 Development of thermoset epoxy resins with CAN Contractual Date of Delivery: 30/09/2024 Actual Date of Delivery: 30/09/2024 Lead contractor for this deliverable: NIC Author(s): Giorgio Tofani, Filipa A. Vicente, Damian Ghazal Tavakoli Gheinani, Willem Vogelzang Participants(s): WP contributing to the deliverable: WP2 Nature: Confidential Version V. 4 Grant Agreement 101058371 Project ESTELLA ESTELLA_D2.2_v4.docx 6 Executive Summary In the ESTELLA Project, Task 2.2 is described as follows: Subtask 2.2.1 Development of associative bio-based epoxy from lignin with CAN [NIC] Bio-based epoxy resin will be obtained using a lignin-based platform. NIC will develop a bio-based epoxy resin using a glycidylation process with low Mw lignin fractions that will be further upgraded using a CAN. NIC will follow the reactions and evaluate the dynamic bonds in the system with state-of the art analytics (insitu FTIR probe, SS-NMR, TGA, dynamic mechanical analysis (DMA), HPLC-CAD and GC-MS) enabling the finetuning of the reaction conditions. The obtained material will be tested in terms of mechanical, rheological, morphological, and physicochemical properties. CAN formation will be performed by carrying out the epoxy resin from the lignin-based platform curing itself through a dynamic transesterification reaction, thus leading to the creation of highly recyclable biobased cross-linked thermoset structure. After the evaluation of mechanical properties and recyclability, two epoxy resins will be chosen to evaluate for scalability in the T2.4. Considering this subtask, all experiments were performed at the National Institute of Chemistry (NIC) laboratories in Ljubljana, Slovenia, in the period M3-M28. 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. In the first pathway, the obtained Schiff bases were further reacted with epichlorohydrin to produce lignin monomer epoxides, which were subsequently mixed with a crosslinker to obtain the final epoxy resin. The difficulty with this approach was that the purification of these compounds required extensive use of liquid chromatography and high consumption of organic solvents, hindering its further application and scale-up. Consequently, this method was not further pursued for large-scale studies. In the second pathway, the lignin was solubilized and functionalized using succinic anhydride in the presence of THF and 1-methyl-imidazole as a catalyst. The functionalized lignin was then mixed with various greener epoxides (polypropylene diglycidyl ether, 1,4-butanediol diglycidyl ether, neopentyl diglycidyl ether, and polyethylene diglycidyl ether) than bisphenol A derivatives and cured to form the final epoxy resin. Tensile strength with each epoxide was measured in order to select the most promising epoxy resin. The epoxy resin prepared using 1,4-butanediol diglycidyl ether met the initial requirements, including a tensile strength greater than 40 MPa and a Young's Modulus over 1 GPa. Therefore, this method using 1,4-butanediol diglycidyl ether was chosen for scaling up, and preparation of epoxy resin samples to deliver to the partners. Grant Agreement 101058371 Project ESTELLA ESTELLA_D2.2_v4.docx 7 Subtask 2.2.2. Development of associative fossil epoxy resins with CAN [ICSO] Epoxy by (ICSO) will be based on crosslinked with carboxylic acids and/or anhydrides in ring opening condensation reaction. Epoxidized plant oils will be used as reactive diluents to modify properties of resin. Also, the addition of epoxidized plant oils will increase renewable content. Research works will focus on the product composition, especially selection of proper catalyst allowing for in terms of product mechanical properties and recyclability. Designed epoxy will be characterized by DSC, TGA, FT-IR, HPLC and high temperature gel chromatography. Basic mechanical parameters and rheological properties will be determined. After evaluation of mechanical properties and recyclability, 2 epoxy resins (one with Tg<60ºC and Tg>60ºC) will be chosen to evaluate for scalability in T2.4. Relatively to this subtask, all experiments were performed at the Instytut Ciezkiej Syntezy Organicznej Blachownia (ICSO) laboratories in - , in the period M3-M28. This subtask summarizes works on the development of associative fossil epoxy resins with CAN. Series of trals of epoxy resins crosslinked with carboxylic acids and/or anhydrides in ring opening condensation reaction were carried out. Epoxidized soybean oil, sorbitol and propylene glycol were used to modify properties and increase of renewable content of epoxy vitrimers. Research works were focus on: - choosing the right amount and combination of hardeners to get the best mechanical and thermal properties of the cured materials, - choosing the proper catalyst and its amount to speed up the curing reaction, - optimisation of temperature and time in the curing stage - maintain the right balance of hardness and flexibility of the products The best results were obtained with succinic anhydride and succinic acid as a hardeners, and epoxidized soybean oil as a reactive diluent. Obtained products, containing Covalent Adaptable Networks (CAN) were characterized by the highest glass transition temperature (76.1 °C) and a tensile strength of 49,8 MPa. Subtask 2.2.3 Development of dissociative recyclable resins [WR] Bio-based monomers for resins containing Diels-Alder active functional groups will be designed and synthesized. In total, a minimum of three different Diels-Alder pairs will be compared (of which at least furan-maleimide, the other two candidates can be chosen from, for example: cyclopentadienecyclopentadiene, furan-itaconimide, cyclopentadiene-benzoquinone). The resins will be developed on a lab scale (10-50 g resin). The remainder of the resin structure will be kept as constant as possible to allow comparison of the different Diels-Alder pairs. The effect of the chosen Diels-Alder pair on the resins properties (DSC, TGA and mechanical) and recyclability by a thermal stimulus will be studied. The most promising resin will be converted into a one- Grant Agreement 101058371 Project ESTELLA ESTELLA_D2.2_v4.docx 8 Considering this subtask, all experiments were performed at Wageningen Food and Biobased Research laboratories in Wageningen, The Netherlands, in the period M3-M28. The aim of the subtask 2.2.3 was to develop DA-containing dissociative recyclable resins with >60% biobased monomers and building blocks. Two different DA-containing hybrid systems have been studied in this work: i) hybrid epoxy/ DA system; and ii) hybrid aza-Michael/ DA system. The later approach has the potential of the full back-to-monomer recovery of the starting materials at higher temperatures. Different biobased resin components have been designed and synthesized in this subtask. The following research questions have been investigated: - Can BADGE which is a fossil-based and toxic commonly used epoxy derivative be replaced with biobased epoxy derivatives? - Does the position of DA bonds have an effect on the material properties and recycling behaviour? - Does the concentration of DA bonds have an effect on the material properties and recycling behaviour? - Does the crosslinking density have an effect on the material properties and recycling behaviour? Among all the DA-containing thermosets that have been prepared in this work, the best results in aspect of thermal and mechanical stability have been obtained using the following formulations: i) BADGE-FA-BMI-689; and ii) 50%BADGE-50%DFGE-BMI-1,3-BAC. These materials were used for further reversibility and recyclability studies in other tasks/ work-packages. This D2.2 deliverable has fully met its objectives. No deviations have been found in the deliverable or in the project progress in content, time or impacts, as set out in the Grant Agreement.