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Recyclable thermoset hyperbranched polymers containing reversible hexahydro-s-triazine

Nature Sustainability volume 3, pages 29–34 (2020)Cite this article

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Abstract

Thermoset materials containing about 70 wt% epoxy resin are widely used in critical aerospace and wind power structures, generating enormous amounts of waste (such as offcuts and damaged, worn and disposed parts) that affect both the environment and the sustainable development of human society. Owing to their irreversible crosslinked networks, thermoset materials pose major challenges for rapid degradation and high-efficiency recycling. Here we report the synthesis of thermoset hyperbranched polymers (HER-HTn) containing a reversible heterocyclic structure (hexahydro-s-triazine) that can be degraded under relatively mild conditions. The cured HER-HTn exhibit excellent mechanical and thermal properties, as well as rapid degradability in more environmentally friendly phosphoric acid solutions. Controlled degradation experiments show that the cured HER-HTn can be completely digested at relatively low temperatures (90 °C) in a short period (2 h) to recover 2-aminobenzyl alcohol at a high recycling efficiency (85.1%). The recovered 2-aminobenzyl alcohol can then be used to produce the initial hexahydro-s-triazine monomer, which demonstrates the reversibility of the hexahydro-s-triazine structure and recoverability of the thermoset hyperbranched polymers. This investigation provides a method for the synthesis of a degradable thermoset matrix and the cyclic use of high-value materials in the thermoset and its composites.

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Fig. 1: Synthesis and recycling of thermoset hyperbranched polymers containing hexahydro-s-triazine.
Fig. 2: Thermal property curves of the cured HER-HTn under nitrogen.
Fig. 3: Degree of degradation and solution photographs of the cured HER-HT3 under different conditions.
Fig. 4: NMR, LC-MS and ESI-MS spectra.

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Data availability

The data that support the findings of this study are available from the corresponding author on request. Source data for Figs. 2 and 4 are provided with the paper.

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Acknowledgements

We acknowledge financial support from the National Natural Science Foundation of China (grant nos. 51573210 and 51873233), Hubei Province Natural Science Foundation (grant no. 2018CFA023) and Hubei Province Fund for Major Technological Innovation Projects (grant no. 2017AAA131).

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Author notes

  1. These authors contributed equally: Zejun Xu, Yeyun Liang.

Authors and Affiliations

  1. Key Laboratory of Catalysis and Energy Materials Chemistry of Ministry of Education & Hubei Key Laboratory of Catalysis and Materials Science, Hubei R&D Center of Hyperbranched Polymers Synthesis and Applications, South-Central University for Nationalities, Wuhan, China

    Zejun Xu, Yeyun Liang, Xu Ma, Chenglong Yu, Yimei Wang & Daohong Zhang

  2. Key Laboratory for Green Chemical Process of Ministry of Education, Wuhan Institute of Technology, Wuhan, China

    Sufang Chen

  3. CSIRO Manufacturing, Waurn Ponds, Victoria, Australia

    Menghe Miao

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  1. Zejun Xu
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Contributions

Z.X., D.Z. and M.M. conceived and designed the experiments. Y.L. and X.M. performed the experiments. Z.X., S.C. and C.Y. analysed the data. Y.W. contributed the materials and analysis tools. Z.X., D.Z. and M.M. wrote and revised the paper. All authors participated in discussions and reviewed the manuscript.

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Correspondence to Daohong Zhang.

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Supplementary Figs. 1–9, Tables 1–5, Notes 1–3, methods and references.

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Xu, Z., Liang, Y., Ma, X. et al. Recyclable thermoset hyperbranched polymers containing reversible hexahydro-s-triazine. Nat Sustain 3, 29–34 (2020). https://doi.org/10.1038/s41893-019-0444-6

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