Abstract
New epoxy resins containing degradable acetal linkages were synthesized by the addition reaction of bisphenol-A (BA) and epoxy-functionalized vinyl ethers containing hydrophilic oxyethylene chains, 2-(vinyloxy)ethyl glycidyl ether (VEGE) and 2-[2-(vinyloxy)ethoxy]ethyl glycidyl ether (VEEGE). Carbon fibers were applied with the obtained degradable epoxy resin-based sizing agents (designated as BA-VEGE and BA-VEEGE) in ordinary (1.4 ~ 2.2 wt%) or excess (6.4 ~ 13.4 wt%) amounts. Interfacial adhesion between the carbon fibers applied with the degradable epoxy resin-based sizing agents and matrix resins (bisphenol-A-type epoxy resin) was evaluated by the microdroplet method. Carbon fibers with both degradable epoxy resins as a sizing agent showed improved adhesive properties compared with the desized carbon fibers. Using the degradable sizing agent-applied carbon fibers, carbon fiber-reinforced plastics (CFRPs) were prepared by laminating prepreg sheets and heating them under pressure. The tensile properties of the CFRPs with [0]50 lay-up did not depend on the structure of the sizing agents, but the tensile strength decreased as the amount of sizing agent used increased. On the other hand, the tensile properties of the CFRPs with [0/90]12S lay-up were not dependent on the structure or volume of sizing agents used. The impact toughness of the CFRPs was evaluated by the charpy impact test. When an ordinary volume of sizing agent was applied, the CFRPs with degradable epoxy resin-based sizing agents exhibited higher levels of impact strength than the commercial sizing agent-based CFRPs. However, applying an excessive volume of sizing agent to carbon fibers led to a decline in impact strength. The degradation reaction was conducted under acidic conditions by the treatment of HCl at room temperature or 70 °C. CFRPs with degradable epoxy resins as sizing agents in ordinary volumes were barely decomposed due to insufficient degradable regions in the CFRP components. However, the CFRPs applied with excess degradable sizing agents decomposed and carbon fibers were recovered.
Similar content being viewed by others
Log in or create a free account to read this content
Gain free access to this article, as well as selected content from this journal and more on nature.com
or
References
Nakanishi Y, Ikuta N. Interphase of FRP and its chemical. Control J Soc Mat Sci Jpn. 1996;45:1307.
Tsujioka N, Maekawa Z, Hamada H, Hojo M. Effect of surface oxidation and sizing treatment of carbon fiber on interfacial adhesion. J Soc Mat Sci, Jpn. 1997;46:163.
Cao X, Wen YF, Zhang SC, Yang YG. A heat resistant emulsifying sizing agent for carbon fibers. New Carbon Mater. 2006;21:337.
Zhang RL, Huang YD, Liu L, Tang YR, Su D, Xu LW. Effect of emulsifier content of sizing agent on the surface of carbon fibres and interface of its composites. Appl Surf Sci. 2011;257:3519.
Zhang RL, Huang YD, Liu L, Tang YR, Su D, Xu LW. Effect of the molecular weight of sizing agent on the surface of carbon fibres and interface of its composites. Appl Surf Sci. 2011;257:1840.
Guo H, Huang Y, Liu L, Shi X. Effect of epoxy coatings on carbon fibers during manufacture of carbon fiber reinforced resin matrix composites. Mater Des. 2010;31:1186.
Yamaguchi K, Kitano A. Development in composites technology for reduction of environmental load II: recycle method for CFRP. J Soc Mat Sci Jpn. 2008;57:747.
Pickering SJ. Recycling technologies for thermoset composite materials-current status, Compos. Part A Appl Sci Manuf. 2006;37:1206.
Okajima I, Hiramatsu M, Shimamura Y, Awaya T, Sako T. Chemical recycling of carbon fiber reinforced plastic using supercritical methanol. J Supercrit Fluids. 2014;91:68.
Liu Y, Liu J, Jiang Z, Tao T. Chemical recycling of carbon fibre reinforced epoxy resin composites in subcritical water: Synergistic effect of phenol and KOH on the decomposition efficiency. Polym Degrad Stabil. 2012;97:217.
Bai Y, Wang Z, Feng L. Chemical recycling of carbon fibers reinforced epoxy resin composites in oxygen in supercritical water. Mater Des. 2010;31:999.
Luzuriaga ARD, Martin R, Markaide N, Rekondo A, Cabañero G, Rodríguez J, et al. Epoxy resin with exchange disulfide crosslinks to obtain reprocessable, repairable and recyclable fiber-reinforced thermoset composite. Mater Horiz. 2016;3:241.
Luzuriaga ARD, Matxian JM, Ruipérez F, Martin R, Asua JM, Cabañero G, et al. Transient mechanochromism in epoxy vitrimer composites containing aromatic disulfide crosslinks. J Mater Chem C. 2016;4:6220.
Yuan Y, Sun Y, Yan S, Zhao J, Liu S, Zhang M, et al. Multiply fully recyclable carbon fibre reinforced heat-resistant covalent thermosetting advanced composites. Nat Commun. 2017;8:14657.
Wang Y, Cui X, Ge H, Yang Y, Wang Y, Zhang C, et al. Chemical recycling of carbon fiber reinforced epoxy resin composites via selective cleavage of the carbon-nitrogen bond. ACS Sustain Chem Eng. 2015;3:3332.
Deng T, Liu Y, Cui X, Yang Y, Jia S, Wang Y, et al. Cleavage of C-N bonds in carbon fiber/epoxy resin composites. Green Chem. 2015;17:2141.
Hashimoto T, Meiji H, Urushisaki M, Sakaguchi T, Kawabe K, Tsuchida C, et al. Degradable and chemically recyclable epoxy resins containing acetal linkages: synthesis, properties, and application for carbon fiber-reinforced plastics. J Polym Sci Part A Polym Chem. 2012;50:3674.
Yamaguchi A, Hashimoto T, Kakichi Y, Urushisaki M, Sakaguchi T, Kawabe K, et al. Recyclable carbon fiber-reinforced plastics (CFRP) containing degradable acetal linkages: synthesis, properties, and chemical recycling. J Polym Sci Part A Polym Chem. 2015;53:1052.
Yamaguchi A, Hashimoto T, Kakichi Y, Urushisaki M, Sakaguchi T, Kawabe K, et al. Recyclable, adhesive, acetal-linkage-containing epoxy resins: measuring the adhesive properties with carbon fibers. Kobunshi Ronbunshu. 2016;73:244.
Kakichi K, Hashimoto T, Yamaguchi A, Urushisaki M, Sakaguchi T, Kawabe K, et al. Development of acetal linkage-containing matrix epoxy resins with high toughness and degradability for chemically recyclable CFRP. Kobunshi Ronbunshu. 2017;74:208.
Kakichi K, Yamaguchi A, Hashimoto T, Urushisaki M, Sakaguchi T, Kawabe K, et al. Development of recyclable carbon fiber-reinforced plastics (CFRPs) with controlled degradability and stability using acetal linkage-containing epoxy resins. Polym J. 2017;49:851.
Kawabe K. New spreading technology for carbon fiber tow and its application to composite materials. Sen’i Gakkaishi. 2008;64:262.
Acknowledgements
We are grateful to Nicca Chemical Co., Ltd., Fukui, Japan for allowing us to use its sizing agent-applying apparatus. We also thank Nippon Carbide Industries, Tokyo, Japan for donating 2-hydroxyethyl vinyl ether and diethylene glycol monovinyl ether.
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
Conflict of interest
The authors declare that they have no conflict of interest.
Additional information
Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
About this article
Cite this article
Aoki, R., Yamaguchi, A., Hashimoto, T. et al. Preparation of carbon fibers coated with epoxy sizing agents containing degradable acetal linkages and synthesis of carbon fiber-reinforced plastics (CFRPs) for chemical recycling. Polym J 51, 909–920 (2019). https://doi.org/10.1038/s41428-019-0202-7
Received:
Revised:
Accepted:
Published:
Issue date:
DOI: https://doi.org/10.1038/s41428-019-0202-7
