Summary of the activity report

During the first stage of the EPOCEL project, the parameters for the development of bio-epoxy matrix systems were identified and optimized. First, the protocol for obtaining epoxidized linseed oil (ELO) starting from commercial linseed oil was defined. The process employed for the obtaining of ELO based on the use of peracetic acid generated in situ, led to a high reaction yield of 96%. The results of the structural analyzes, FTIR and NMR, confirmed the efficiency of the linseed oil epoxidation reaction. Citric acid (CA) was tested as a crosslinking agent for epoxy ELO-based networks and its effectiveness was compared to that of a synthetic crosslinking agent (D). Another direction investigated in this stage was the selection of the best activator of the crosslinking reaction between water (W) and tetrahydrofuran (THF). Based on protocols developed during this stage, an optimal temperature program was developed for the crosslinking of the proposed epoxy systems. The results of the structural and thermal analyzes demonstrated the efficacy of the CA natural compound as a crosslinking agent for all studied bio-epoxy systems. Moreover, yields of up to 99% were obtained depending on the temperature and time of the crosslinking reaction. The preliminary results show that the bio-epoxy matrix systems proposed for the development of a high-performance bionanocomposite for electronics are promising due to their high reactivity, similar to commercial synthetic epoxy resins.

PHASE II

Title: Setting up the preliminary conditions for synthesis of epoxy system and preliminary compatibility tests (II); Structure and composition analysis; Designing and characterization of bionanocomposites

Period: 01.01.2021 – 31.12.2021

Summary of the activity report

The general objective of the second stage of the EPOCEL project was obtaining and characterization of bionanocomposites as a basis for the elaboration of the EPOCEL experimental model. Thus, following the experimental works, the materials that will constitute the bio-epoxy system were selected and characterized. Among the studied systems, the ELO/CA/THF sample showed the best thermal stability as compared to the commercial crosslinking system. Thus, THF can be considered as an effective activating agent for the ELO/CA bio-epoxy system. It showed a crosslinking density value

two times higher than that of the ELO/CA/W system and six times higher than that of the commercial system. In addition to the improved thermal and

mechanical characteristics, the biodegradability test indicated that the bio-epoxy systems crosslinked with CA have the ability to degrade in the environment as compare to the commercial epoxy system.

Another research direction was the surface modification of nanocellulose (NC) for improving its compatibility with the epoxy system. In this regard, organosilane coupling agents, mono-, di- and tricarboxylic acids as well as vanillin, a compound with mixed functions, containing aldehyde, hydroxyl and ether groups were tested as modifiers of nanocellulose. NC surface’s modification with silane and vanillin coupling agents has led to a significant increase in thermal stability. Afterwards, bionanocomposites from functionalized NC and bio-epoxy resin systems were obtained and optimized considering different concentrations of functionalized NC (0.25, 0.5 and 1%). TGA and DMA analyses indicated that an efficient crosslinking of the bio-epoxy system took place with the increase of functionalized-NC concentration. Moreover, a good correlation between the storage modulus and the calculated crosslinking density was observed. Following the research works carried out, the planned objectives of this second stage of EPOCEL project were thus achieved: the methodology for crosslinking the epoxy system and for dispersing NC; methodology for obtaining functionalized NC; methods for obtaining bionanocomposites.

Also, a part of the obtained results were disseminated by publishing an article (IF>4), sending an article for publication (IF>5) and by participating in 4 international and one national conferences (4 oral presentations and 1 poster presentation).

DISSEMINATION

PAPERS

1. Popa, M.S.; Frone, A.N.; Radu, I.C.; Stanescu, P.O.; Truşcă, R.; Rădiţoiu, V.; Nicolae, C.A.; Gabor, A.R.; Panaitescu, D.M. Microfibrillated Cellulose Grafted with Metacrylic Acid as a Modifier in Poly(3-hydroxybutyrate). Polymers 2021, 13, 3970. https://doi.org/10.3390/polym13223970 (IF=4.329)
2. Madalina Ioana Necolau, Celina Maria Damian, Brindusa Balanuca, Sustainable strategy to obtain epoxy-based materials with competitive thermo-mechanical properties. Submitted to Industrial Crops & Products Journal (IF=5.645)

CONFERENCES

1. Mădălina Ioana Necolau, Brȋnduşa Bălănucă, Celina Maria Damian, Horia Iovu, Bio-based Epoxy Networks – Comparative Study of Different Curing Systems, 2nd Bucharest Polymer Conference, 10-11 June 2021 – Young Scientist Science Presentation
2. Mădălina Ioana Necolau, Brȋnduşa Bălănucă, Celina Maria Damian, Horia Iovu, Sustainable approach to fabricate epoxy/nanocellulose composites and their properties, 7th Young Polymer Scientists Conference and Short Course, 27 – 28 September -Poster presentation
3. Mădălina Ioana Necolau, Brȋnduşa Bălănucă, Celina Maria Damian, Horia Iovu, Novel composite materials based on epoxidized vegetable oil and nanocellulose, 5th Virtual Edition of Polymers, Plastics and Composites, 15 November -Oral presentation
4. Marius-Stelian Popa*, Celina Maria Damian, Brîndușa Bãlãnucã, Denis Mihaela Panaitescu, Raluca Augusta Gabor, Cristian Andi Nicolae, Valentin Radiţoiu, Monica Florentina Raduly, Adriana Nicoleta Frone*, Effect of Nanocellulose Type on the Properties of a Bio‐Based Epoxy System, PRIOCHEM 17th Edition, 27-29 October 2021, Bucharest, Romania – Oral presentation
5. Marius-Stelian Popa*, Stefania Bădilă, Elena-Ruxandra Radu, Denis Mihaela Panaitescu, Raluca Augusta Gabor, Cristian Andi Nicolae, Adriana Nicoleta Frone*Novel bio‐based epoxy from epoxidized vegetable oils, 7th Portuguese Young Chemists Meeting, 19 – 21 May, Bragança, Portugalia – Oral presentation.

Phase III

Title: Elaboration of the EPOCEL experimental model; Validation of the selected EPOCEL models – TRL 4

Period: 31.12.2022 – 27.10.2022

Summary of the activity report

           The last stage of the EPOCEL project had as its general objective the elaboration of the EPOCEL model and its validation. Thus, first, we established the technology for obtaining the ELO/NCs bio-nanocomposites which constitute the proposed EPOCEL model. The technology proposed for the development of the EPOCEL model is eco-friendly, through the fact that it uses materials derived from renewable resources, and it is easily scalable at an industrial level. The laboratory validation of the EPOCEL model (TRL4) was performed after a complex analysis of the thermal (TGA, DSC), structural and surface (FTIR, XPS, XRD, contact angle), mechanical (DMA, nanoindentation), morphological (AFM, SEM), and dielectric (dielectric spectroscopy) properties of the resulting materials. Thus, following the carried out tests, it was demonstrated that the proposed EPOCEL model presents all the requirements imposed by the field of electronics, its main field of application, by exhibiting improved mechanical properties, simultaneously with an adaptable flexibility, a maintained hydrophobic character (as a result of the use of functionalized NC), and the characteristics of a good dielectric

material in a wide range of frequencies. The overall results confirm the achievement of Technology Readiness Level 4 (TRL4) – the technological maturity

level targeted within the project: the proposed technology was validated at a laboratory scale and the developed EPOCEL model presented the expected

performances. The EPOCEL experimental model developed within this project proved to be promising in applications from the field of flexible electronics,

especially in the manufacturing of soft, flexible, or extensible electronic systems for biomedical applications, robotics, wearable electronic devices, or

even smart textiles. A part of the obtained results was disseminated by publishing an article (IF>4), sending an article for publication (IF>9) and by participating at 3 international scientific conferences (an oral presentation and 2 poster presentations).

DISSEMINATION

PAPERS

1. Necolau, M.I.; Damian, C.M.; Olaret, E.; Iovu, H.; Balanuca, B. Comparative Thermo-Mechanical Properties of Sustainable Epoxy Polymer Networks Derived from Linseed Oil. Polymers 2022, 14, 4212. https://doi.org/10.3390/ polym14194212 (IF=4.967)
2. Necolau, M.I.; Balanuca, B.; Frone, A.N.; Damian, C.M. Tailoring an effective interface between nanocellulose and epoxidized linseed oil network through functionalization. Submitted to ACS Sustainable Chemistry &Engineering (IF=9.224)

CONFERENCES

1. Cătălina Diana Uşurelu, Denis Mihaela Panaitescu, Raluca Augusta Gabor, Cristian Andi Nicolae, Monica Florentina Raduly, Celina Maria Damian, Adriana Nicoleta Frone, Bio-Based Epoxy Composites Containing Surface-Modified Cellulose Fibers. 20^th International Balkan Workshop on Applied Physics and Materials Science, 12-15 July 2022, Constanţa, România – Poster presentation;
2. Mădălina Ioana Necolau, Celina Maria Damian, Brȋnduşa Bălănucă, Adriana Nicoleta Frone, Horia Iovu, Epoxy sustainable nanocomposites reinforced with functionalized nanocellulose for electronic coatings. Polymers 2022 – New Trends in Polymer Science: Health of the Planet, Health of the People, 24-28 May 2022, Torino, Italia – Oral presentation;
3. Mădălina Ioana Necolau, Celina Maria Damian, Brȋnduşa Bălănucă, Horia Iovu, Sustainable Epoxy Nanocomposites Reinforced with Functional Nanocellulose Structures, 22^nd Romanian International Conference on Chemistry and Chemical Engineering (RICCCE 22), 7-9 September 2022, Sinaia, România – Poster presentation.

Brief presentation of the results obtained within the project “Bionanocomposites based on epoxy-cellulose

with balanced thermo-mechanical properties” – EPOCEL

               As a result of the EPOCEL project implementation, new bionanocomposites, in the form of experimental models, were developed through the superior valorization of raw materials derived from renewable resources and from agro-food waste: linseed oil, citric acid, nanocellulose from plum seed shells. The obtained EPOCEL experimental model showed an adaptable flexibility simultaneously with an improved mechanical behavior which makes it promising for applications in the field of flexible electronics such as soft, flexible, or extensible electronic systems for biomedical applications, robotics, portable electronic devices, or even smart textiles.