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Photographs of (a)VHP samples and (b)VMP samples after 24 h of immersion in different solvents and (c) Swelling Ratio of the VMP and VHP bio-based imine epoxy vitrimers in different solvents

Photographs of (a)VHP samples and (b)VMP samples after 24 h of immersion in different solvents and (c) Swelling Ratio of the VMP and VHP bio-based imine epoxy vitrimers in different solvents

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Traditional epoxy resin materials are widely used in coatings, composite materials, electronic packaging materials, etc. They are usually made of unsustainable fossil resources and cannot be recycled under mild conditions. Degradable thermosetting resins with dynamic covalent structure provide a potential solution to this conflict. In this paper, u...

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... 93 In a similar study, two different imine exchange based vitrimers were synthesized using vanillin/1,6-hexylenediamine (VHP) and vanillin/m-xylylenediamine (VMP) curing agents. 94 The tan d result shows that the T g of VHP and VMP bio-based imine epoxy vitrimers are 83°C and 96°C, respectively, whereas the storage modulus values are 2600 MPa and 2650 MPa, respectively. This could be attributed to the higher rigidity chain structure for VMP vitrimer ( Fig. 12a and b). ...
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To achieve sustainable development goals, approaches towards the preparation of recyclable and healable polymeric materials is highly attractive. Self-healing polymers and thermosets based on bond-exchangeable dynamic covalent bonds, so called "vitrimers" could be a great effort in this direction. In order to match the industrial importance, enhancement of mechanical strength without sacrificing the bond exchange capability is a challenging issue, however, such concerns can be overcome through the developments of fiber-reinforced vitrimer composites. This article covers the outstanding features of fiber-reinforced vitrimer composites, including their reprocessing, recycling and self-healing properties, together with practical applications and future perspectives of this unique class of materials.
... [14] The second group includes the development of novel thermoset materials that are easy to reprocess, repair, and degrade. Dynamic covalent bonds such as Diels-Alder (DA) adducts, [15,16] disulfides, [17][18][19][20] imines, [21,22] hydroxyl-esters [23][24][25] etc. have been introduced into the cross-linking network of novel thermoset materials. They can decompose or react reversibly under heating or other external stimuli (heat, light, mechanical force, p H , solvent, etc.). ...
... The same researchers also synthesized and compared two reversible imine bond-containing curing agents using sustainable vanillin, aromatic diamine, and aliphatic diamine as precursors, and then combined them with DGEBA. [22] Both thermosets have remarkable heat and chemical stability. Simultaneously, mechanical attributes such as stress, strain, and modulus were equivalent to or better than those of the standard DGEBA epoxy resin. ...
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... recyclability after degradation in acidic solution. The developed vitrimer was then used as matrix to prepare CF-based composites [119] . The easy degradation of the matrix in acidic conditions allows recovering the CF mat with fully preserved properties. ...
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Epoxy resins possess poor flame retardancy and have difficulty in both recycling and reprocess ability which largely limit their application. Herein, two vanillin-based epoxy monomers, shorted as VAD-EP and VDP-EP, containing both imine bonds and inherently fire retarding phosphorus elements, were synthesized via in situ condensation reaction with DDM and addition reaction with DOPO, followed by the epoxidation by epichlorohydrin. Epoxy vitrimer materials were then cured by D230 diamine hardener by adjusting the proportion of VAD-EP and VDP-EP monomer. When the mass ratio of VAD-EP and VDP-EP was 8:2, A8P2-D230 reached the fire retarding UL-94 V0 rating and LOI value of 27.0% with only 0.66% of phosphorus content, this behavior was ascribed to condensed phase and free radical scavenging mechanisms. When the mass ratio was 7:3, the tensile strength and elastic modulus of the A7P3-D230 epoxy were 75.5 MPa and 2.5 GPa, respectively, i.e. 48.6% and 18.8% higher than A10P0-D230 sample. Meanwhile, the material showed high stress relaxation rate, due to the presence of dynamic imine bonds in the topological crosslinking network. As a consequence, the epoxy vitrimer exhibited excellent self-healing capability, reprocessability and degradation behaviors. The biobased epoxy vitrimer was then used to prepare the carbon fibers (CFs) reinforced epoxy composites, results showed that CFs can be completely recycled. Interestingly, the recycled CFs maintain unchanged chemical structure, mechanical properties and morphology as the original CFs.