1166: Sustainable two-step functionalization of carbon fibers with polyethyleneimine and investigation of curing kinetics in composites

Francesca Cicogna^a*, Edoardo Albertini^a, Serena Coiai^a, Roberto Spiniello^a, Stefano Legnaioli^a, Werner Oberhauser^b, Laura Capozzoli^b, Elisa Passaglia^a

^a National Research Council-Institute of Chemistry of OrganoMetallic Compounds (CNR-ICCOM), SS Pisa, Via Moruzzi 1, 56124 Pisa, Italy

^b National Research Council-Institute of Chemistry of OrganoMetallic Compounds (CNR-ICCOM), Via Madonna del Piano 10, 50019 Sesto Fiorentino, Firenze, Italy

To increase the interfacial shear stress, adhesion, and bonding between carbon fibers (CFs) and polymer matrices in carbon fiber-reinforced polymer (CFRP) composites, various strategies have been explored to reduce the hydrophobicity of CFs by increasing their surface area and enhancing their chemical reactivity¹. Both dry methods, such as plasma and high-energy irradiation, and wet methods, including sizing, electrochemical treatments, and acid treatment, have been used to modify the surface of CFs^1,2. In this study, we combined dry oxidative plasma treatment of CFs with a subsequent wet functionalization with branched polyethyleneimine (b-PEI). Plasma-activated fibers were suspended in a water b-PEI solution, allowing modulation of the grafted b-PEI amount by adjusting plasma treatment parameters, b-PEI concentration, and reaction time. Functionalized CFs were analyzed through infrared and Raman spectroscopies, scanning electron microscopy, and thermogravimetric analyses. Notably, our functionalization process is cost-effective and offers a sustainable and environmentally friendly alternative to traditional industrial methods, as it does not utilize hazardous reactants or solvents. Finally, we applied the non-isothermal method to study the curing kinetics of an epoxy/anhydride system in the presence of 20 wt.% of commercial CFs or CFs modified with b-PEI at two different concentrations, highlighting the role of grafted b-PEI in the curing process⁴.

ACKNOWLEDGMENTS

The work was partially funded in the context of Project MISE / INVITALIA Proposal for an Industrial Development Contract (according to Article 9 9 of the Degree of the Minister of Economic Development of 09.12.2014), Managing Entity: INVITALIA S.p.A., Code no. CDS000750; Contract n. LDO/DGE/A/0046328/20. Project title: Ampliamento e Potenziamento dello Stabilimento di Foggia Leonardo Divisione Aerostrutture (LAMPO).

Bibliography

1) Zheng H, Zhang W, Li B, et al. Recent advances of interphases in carbon fiber-reinforced polymer composites: A review. Compos B Eng. 2022;233.

2) Ansari MS, Zafar S, Pathak H. A comprehensive review of surface modification techniques for carbon fibers for enhanced performance of resulting composites. Results Surf.  Interfaces. 2023;12:100141

3) Sharma M, Gao S, Mäder E, Sharma H, Wei LY, Bijwe J. Carbon fiber surfaces and composite interphases. Compos Sci Technol. 2014;102:35-50.

4) Albertini E, Coiai S, Spiniello R, Legnaioli, Oberhauser W, Capozzoli L, Cicogna F, Passaglia E.  Sustainable two-step functionalization of carbon fibers (CFs) with polyethyleneimine and investigation of curing kinetics in composite materials. Polymer Composites 2025;1–19.