Flame-retardant, recyclable, and hydrothermally degradable epoxy resins and their degradation products for high-strength adhesives
Yue-Rong Zhang, Zhen Qin, Song Gu, Jia-Xin Zhao, Xian-Yue Xiang, Chuan Liu, Yu-Zhong Wang, Li Chen()
The Collaborative Innovation Center for Eco-Friendly and Fire-Safety Polymeric Materials (Ministry of Education), National Engineering Laboratory of Eco-Friendly Polymeric Materials (Sichuan), State Key Laboratory of Polymer Materials Engineering, College of Chemistry, Sichuan University, Chengdu 610064, China
To date, sustainable thermosetting polymers and their composites have emerged to address recyclability issues. However, achieving mild degradation of these polymers compromises their comprehensive properties such as flame retardancy and glass transition temperature (Tg). Moreover, the reuse of degradation products after recycling for upcycling remains a significant challenge. This study introduces phosphorus-containing anhydride into tetraglycidyl methylene diphenylamine via a facile anhydride-epoxy curing equilibrium with triethanolamine as a transesterification modifier to successfully prepare flame-retardant, malleable, reprocessable, and easily hydrothermally degradable epoxy vitrimers and recyclable carbon fiber-reinforced epoxy composites (CFRECs). The composite exhibited excellent flame retardancy and a high Tg of 192 °C, while the presence of stoichiometric primary hydroxyl groups along the ester-bonding crosslinks enabled environmentally friendly degradation (in H2O) at 200 °C without any external catalyst. Under mild degradation conditions, the fibers of the composite material were successfully recycled without being damaged, and the degradation products were reused to create a recyclable adhesive with a peel strength of 3.5 MPa. This work presents a method to produce flame retardants and sustainable CFRECs for maximizing the value of degradation products, offering a new upcycling method for high-end applications.
E H Discekici , A H St Amant , S N Nguyen , I H Lee , C J Hawker , J Read de Alaniz . Endo and exo Diels-Alder adducts: temperature-tunable building blocks for selective chemical functionalization. Journal of the American Chemical Society, 2018, 140: 5009–5013 https://doi.org/10.1021/jacs.8b01544
2
K Yu , Q Shi , M L Dunn , T J Wang , H J Qi . Carbon fiber reinforced thermoset composite with near 100% recyclability. Advanced Functional Materials, 2016, 26(33): 6098–6106 https://doi.org/10.1002/adfm.201602056
3
I Vollmer , M J F Jenks , M C P Roelands , R J White , T van Harmelen , P de Wild , G P van der Laan , F Meirer , J T F Keurentjes , B M Weckhuysen . Beyond mechanical recycling: giving new life to plastic waste. Angewandte Chemie International Edition, 2020, 59(36): 15402–15423 https://doi.org/10.1002/anie.201915651
4
A Chao , I Negulescu , D H Zhang . Dynamic covalent polymer networks based on degenerative lmine bond exchange: tuning the malleability and self-healing properties by solvent. Macromolecules, 2016, 49(17): 6277–6284 https://doi.org/10.1021/acs.macromol.6b01443
5
W Denissen , J M Winne , F E Du Prez . Vitrimers: permanent organic networks with glass-like fluidity. Chemical Science, 2016, 7(1): 30–38 https://doi.org/10.1039/C5SC02223A
6
D Montarnal , M Capelot , F Tournilhac , L Leibler . Silica-like malleable materials from permanent organic networks. Science, 2011, 334(6058): 965–968 https://doi.org/10.1126/science.1212648
7
Y Z Xu , S L Dai , L W Bi , J X Jiang , H B Zhang , Y X Chen . Catalyst-free self-healing bio-based vitrimer for a recyclable, reprocessable, and self-adhered carbon fiber reinforced composite. Chemical Engineering Journal, 2022, 429: 132518 https://doi.org/10.1016/j.cej.2021.132518
8
M Capelot , M M Unterlass , F Tournilhac , L Leibler . Catalytic control of the vitrimer glass transition. ACS Macro Letters, 2012, 1(7): 789–792 https://doi.org/10.1021/mz300239f
9
Y H Jin , Z P Lei , P Taynton , S F Huang , W Zhang . Malleable and recyclable thermosets: the next generation of plastics. Matter, 2019, 1(6): 1456–1493 https://doi.org/10.1016/j.matt.2019.09.004
10
C J Kloxin , C N Bowman . Covalent adaptable networks: smart, reconfigurable and responsive network systems. Chemical Society Reviews, 2013, 42(17): 7161–7173 https://doi.org/10.1039/C3CS60046G
11
X M Ding , L Chen , Y J Xu , X H Shi , X Luo , X Song , Y Z Wang . Robust epoxy vitrimer with simultaneous ultrahigh impact property, fire safety, and multipath recyclability via rigid-flexible imine networks. ACS Sustainable Chemistry & Engineering, 2023, 11(39): 14445–14456 https://doi.org/10.1021/acssuschemeng.3c03189
12
M Podgórski , B D Fairbanks , B E Kirkpatrick , M McBride , A Martinez , A Dobson , N J Bongiardina , C N Bowman . Covalent adaptable networks: toward stimuli-responsive dynamic thermosets through continuous development and improvements in covalent adaptable networks. Advanced Materials, 2020, 32(20): 2070158 https://doi.org/10.1002/adma.202070158
13
Y Y Liu , G L Liu , Y D Li , Y X Weng , J B Zeng . Biobased high-performance epoxy vitrimer with UV shielding for recyclable carbon fiber reinforced composites. ACS Sustainable Chemistry & Engineering, 2021, 9(12): 4638–4647 https://doi.org/10.1021/acssuschemeng.1c00231
14
T Liu , C Hao , L W Wang , Y Z Li , W C Liu , J N Xin , J W Zhang . Eugenol-derived biobased epoxy: shape memory, repairing, and recyclability. Macromolecules, 2017, 50(21): 8588–8597 https://doi.org/10.1021/acs.macromol.7b01889
15
T Liu , S Zhang , C Hao , C Verdi , W C Liu , H Liu , J W Zhang . Glycerol induced catalyst-free curing of epoxy and vitrimer preparation. Macromolecular Rapid Communications, 2019, 40(7): 1800889 https://doi.org/10.1002/marc.201800889
16
T Liu , B M Zhao , J W Zhang . Recent development of repairable, malleable and recyclable thermosetting polymers through dynamic transesterification. Polymer, 2020, 194: 122392 https://doi.org/10.1016/j.polymer.2020.122392
S Gu , Y F Xiao , S H Tan , B W Liu , D M Guo , Y Z Wang , L Chen . Neighboring molecular engineering in Diels-Alder chemistry enabling easily recyclable carbon fiber reinforced composites. Angewandte Chemie International Edition, 2023, 62(51): e202312638 https://doi.org/10.1002/anie.202312638
19
J H Chen , B W Liu , J H Lu , P Lu , Y L Tang , L Chen , Y Z Wang . Catalyst-free dynamic transesterification towards a high-performance and fire-safe epoxy vitrimer and its carbon fiber composite. Green Chemistry, 2022, 24(18): 6980–6988 https://doi.org/10.1039/D2GC01405J
20
J H Chen , Y R Zhang , Y Z Wang , L Chen . Reprocessable, malleable and intrinsically fire-safe epoxy resin with catalyst-free mixed carboxylate/phosphonate transesterification. Polymer, 2023, 281: 126083 https://doi.org/10.1016/j.polymer.2023.126083
21
X M Feng , J Z Fan , A Li , G Q Li . Multireusable thermoset with anomalous flame-triggered shape memory effect. ACS Applied Materials & Interfaces, 2019, 11(17): 16075–16086 https://doi.org/10.1021/acsami.9b03092
22
Q R Ren , S Gu , J H Liu , Y Z Wang , L Chen . Catalyst-free reprocessable, degradable and intrinsically flame-retardant epoxy vitrimer for carbon fiber reinforced composites. Polymer Degradation & Stability, 2023, 211: 110315 https://doi.org/10.1016/j.polymdegradstab.2023.110315
23
Y R Zhang , S Gu , Y Z Wang , L Chen . Intrinsically flame-retardant epoxy vitrimers with catalyst-free multi-reprocessability towards sustainable carbon fiber composites. Sustainable Materials and Technologies, 2024, 40: e00883 https://doi.org/10.1016/j.susmat.2024.e00883
24
J H Chen , J H Lu , X L Pu , L Chen , Y Z Wang . Recyclable, malleable and intrinsically flame-retardant epoxy resin with catalytic transesterification. Chemosphere, 2022, 294: 133778 https://doi.org/10.1016/j.chemosphere.2022.133778
25
C M Hamel , X Kuang , K J Chen , H J Qi . Reaction-diffusion model for thermosetting polymer dissolution through exchange reactions assisted by small-molecule solvents. Macromolecules, 2019, 52(10): 3636–3645 https://doi.org/10.1021/acs.macromol.9b00540
26
X Kuang , Y Y Zhou , Q Shi , T J Wang , H J Qi . Recycling of epoxy thermoset and composites via good solvent assisted and small molecules participated exchange reactions. ACS Sustainable Chemistry & Engineering, 2018, 6(7): 9189–9197 https://doi.org/10.1021/acssuschemeng.8b01538
27
Z H Liu , Z Z Fang , N Zheng , K X Yang , Z Sun , S J Li , W Li , J J Wu , T Xie . Chemical upcycling of commodity thermoset polyurethane foams towards high-performance 3D photo-printing resins. Nature Chemistry, 2023, 15(12): 1773–1779 https://doi.org/10.1038/s41557-023-01308-9
28
T Liu , X L Guo , W C Liu , C Hao , L W Wang , W C Hiscox , C Y Liu , C Jin , J Xin , J W Zhang . Selective cleavage of ester linkages of anhydride-cured epoxy using a benign method and reuse of the decomposed polymer in new epoxy preparation. Green Chemistry, 2017, 19(18): 4364–4372 https://doi.org/10.1039/C7GC01737E
29
S Gu , S D Xu , J H Lu , X L Pu , Q R Ren , Y F Xiao , Y Z Wang , L Chen . Phosphonate-influenced Diels-Alder chemistry toward multi-path recyclable, fire safe thermoset and its carbon fiber composites. EcoMat, 2023, 5(9): e12388 https://doi.org/10.1002/eom2.12388
30
C N Ye , V S D Voet , R Folkersma , K Loos . Robust superamphiphilic membrane with a closed-loop life cycle. Advanced Materials, 2021, 33(15): 2008460 https://doi.org/10.1002/adma.202008460
31
W Denissen , M Droesbeke , R Nicolaÿ , L Leibler , J M Winne , Prez F E Du . Chemical control of the viscoelastic properties of vinylogous urethane vitrimers. Nature Communications, 2017, 8(1): 14857 https://doi.org/10.1038/ncomms14857
32
Z Y Ma , Y Wang , J Zhu , J R Yu , Z M Hu . Bio-based epoxy vitrimers: reprocessibility, controllable shape memory, and degradability. Journal of Polymer Science. Part A, Polymer Chemistry, 2017, 55(10): 1790–1799 https://doi.org/10.1002/pola.28544
33
M Delahaye , J M Winne , F E Du Prez . Internal catalysis in covalent adaptable networks: phthalate monoester transesterification as a versatile dynamic cross-linking chemistry. Journal of the American Chemical Society, 2019, 141(38): 15277–15287 https://doi.org/10.1021/jacs.9b07269
34
C Hao , T Liu , W C Liu , M E Fei , L Shao , W B Kuang , K L Simmons , J W Zhang . Recyclable CFRPs with extremely high Tg: hydrothermal recyclability in pure water and upcycling of the recyclates for new composite preparation. Journal of Materials Chemistry. A, Materials for Energy and Sustainability, 2022, 10(29): 15623–15633 https://doi.org/10.1039/D2TA03161B
35
C Hao , T Liu , S Zhang , W C Liu , Y F Shan , J W Zhang . Triethanolamine-mediated covalent adaptable epoxy network: excellent mechanical properties, fast repairing, and easy recycling. Macromolecules, 2020, 53(8): 3110–3118 https://doi.org/10.1021/acs.macromol.9b02243
36
F Van Lijsebetten , Y Spiesschaert , J M Winne , F E Du Prez . Reprocessing of covalent adaptable polyamide networks through internal catalysis and ring-size effects. Journal of the American Chemical Society, 2021, 143(38): 15834–15844 https://doi.org/10.1021/jacs.1c07360
37
J H Zhang , X Q Mi , S Y Chen , Z J Xu , D H Zhang , M H Miao , J S Wang . A bio-based hyperbranched flame retardant for epoxy resins. Chemical Engineering Journal, 2020, 381: 122719 https://doi.org/10.1016/j.cej.2019.122719
38
X F Liu , B W Liu , X Luo , D M Guo , H Y Zhong , L Chen , Y Z Wang . A novel phosphorus-containing semi-aromatic polyester toward flame retardancy and enhanced mechanical properties of epoxy resin. Chemical Engineering Journal, 2020, 380: 122471 https://doi.org/10.1016/j.cej.2019.122471
39
A L Zhang , J Z Zhang , L N Liu , J F Dai , X Y Lu , S Q Huo , M Hong , X H Liu , M Lynch , X S Zeng . et al.. Engineering phosphorus-containing lignin for epoxy biocomposites with enhanced thermal stability, fire retardancy and mechanical properties. Journal of Materials Science and Technology, 2023, 167: 82–93 https://doi.org/10.1016/j.jmst.2023.06.004
40
Z C Bai , T Huang , J H Shen , D Xie , J J Xu , J H Zhu , F Q Chen , W B Zhang , J F Dai , P A Song . Molecularly engineered polyphosphazene-derived for advanced polylactide biocomposites with robust toughness, flame retardancy, and UV resistance. Chemical Engineering Journal, 2024, 482: 148964 https://doi.org/10.1016/j.cej.2024.148964
41
S Q Huo , T Sai , S Y Ran , Z H Guo , Z P Fang , P A Song , H Wang . A hyperbranched P/N/B-containing oligomer as multifunctional flame retardant for epoxy resins. Composites. Part B, Engineering, 2022, 234: 109701 https://doi.org/10.1016/j.compositesb.2022.109701
42
S Q Huo , P A Song , B Yu , S Y Ran , V S Chevali , L Liu , Z P Fang , H Wang . Phosphorus-containing flame retardant epoxy thermosets: recent advances and future perspectives. Progress in Polymer Science, 2021, 114: 101366 https://doi.org/10.1016/j.progpolymsci.2021.101366
43
M M Velencoso , A Battig , J C Markwart , B Schartel , F R Wurm . Molecular firefighting-how modern phosphorus chemistry can help solve the challenge of flame retardancy. Angewandte Chemie International Edition, 2018, 57(33): 10450–10467 https://doi.org/10.1002/anie.201711735
44
L Zhang , Z Li , Q Q Bi , L Y Jiang , X D Zhang , E Tang , X M Cao , H F Li , J Hobson , D Y Wang . Strong yet tough epoxy with superior fire suppression enabled by bio-based phosphaphenanthrene towards in-situ formed Diels-Alder network. Composites. Part B, Engineering, 2023, 251: 110490 https://doi.org/10.1016/j.compositesb.2022.110490
45
Q ChenS Q HuoY X LuM M DingJ B FengG B HuangH XuZ Q SunZ Z WangP A Song. Heterostructured graphene@silica@iron phenylphosphinate for fire-retardant, strong, thermally conductive yet electrically insulated epoxy nanocomposites. Small, March 1, 2024, 2310724
46
S B Nie , Z Q Zhao , Y X Xu , W He , W L Zhai , J N Yang . A strategy to synthesize phosphorus-containing nickel phyllosilicate whiskers to enhance the flame retardancy of epoxy composites with excellent mechanical and dry-friction properties. Frontiers of Chemical Science and Engineering, 2024, 18(3): 28–35 https://doi.org/10.1007/s11705-024-2391-7
47
S B Nie , W He , Y X Xu , W L Zhai , H Zhang , J N Yang . Molybdenum disulfide@nickel phyllosilicate hybrid for improving the flame retardancy and wear resistance of epoxy composites. Frontiers of Chemical Science and Engineering, 2023, 17(12): 2114–2126 https://doi.org/10.1007/s11705-023-2357-1
48
X M Ding , L Chen , X Luo , F M He , Y F Xiao , Y Z Wang . Biomass-derived dynamic covalent epoxy thermoset with robust mechanical properties and facile malleability. Chinese Chemical Letters, 2022, 33(6): 3245–3248 https://doi.org/10.1016/j.cclet.2021.10.079
49
L Shao , Y C Chang , B M Zhao , X Y Yan , B J Bliss , M E Fei , C H Yu , J W Zhang . Bona fide upcycling strategy of anhydride cured epoxy and reutilization of decomposed dual monomers into multipurpose applications. Chemical Engineering Journal, 2023, 464: 142735 https://doi.org/10.1016/j.cej.2023.142735
50
P Y Li , S Q Ma , B B Wang , X W Xu , H Z Feng , Z Yu , T Yu , Y L Liu , J Zhu . Degradable benzyl cyclic acetal epoxy monomers with low viscosity: synthesis, structure-property relationships, application in recyclable carbon fiber composite. Composites Science and Technology, 2022, 219: 109243 https://doi.org/10.1016/j.compscitech.2021.109243
