Preparation and self-healing property of phenolic modified epoxy vitrimer
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摘要: 类玻璃体(Vitrimer)在保持交联的状态下还具有塑性变形能力，意味着传统的热固性树脂具有了二次热加工成型的能力，有效地减少废品率，从源头减少垃圾。利用Vitrimer具有的塑性变形能力也可以进行材料自修复而延长使用寿命，从而对环境保护、减排作出贡献。本文以异辛酸亚锡为催化剂、酚醛树脂为改性剂制备了环氧 Vitrimer 材料。研究结果表明：催化剂含量的增加会使体系固化更加完全，因此对材料弯曲强度有一定的改善，最高可达到 87.5 MPa。引入酚醛树脂后弯曲强度由改性前的 87.5 MPa 提高到 126.9 MPa，拉伸强度达 63.3 MPa。但酚醛树脂的加入量过高时，材料的交联密度有所降低，其力学性能在达到顶点后出现下降趋势。对酸酐固化的环氧 Vitrimer 体系松弛过程研究表明：增加催化剂含量和提高温度都可以降低材料的松弛时间，但是高温后固化会抑制松弛过程，影响自焊接强度。酚醛改性后材料的应力松弛明显快于纯酸酐固化的环氧试样。10mol%催化剂试样在180 ℃至190 ℃松弛速率产生一个突变，190 ℃明显加快，而酚醛的引入则可以将突变温度Ts提前到180 ℃。在无压力条件下，样品可以实现划痕的修复。在松弛的突变温度以上修复的试样剪切强度和划痕修复效果明显提高。相对未加酚醛样品，酚醛改性样品修复效果更好。催化剂对试样修复强度和修复速度有明显影响。
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关键词:
- 环氧类玻璃体(Vitrimer) /
- 自修复 /
- 松弛行为 /
- 酚醛 /
- 回收利用
Abstract: Vitrimer can undergo plastic deformation while maintaining a cross-linked state, which means that traditional thermosetting resins have the ability to undergo secondary thermal processing and molding, which will effectively reduce scrap rates and reduce waste from the beginning. The plastic deformation of vitrimer can also endow item self-healing ability and extended its service life, and so contribute to environmental protection and emission reduction. In the paper stannous iso-octanoate as a catalyst and phenolic resin as a modifier was used to prepare anhydride cured epoxy vitrimer materials. The research results indicate that the increase in catalyst content could make the system cure more completely, so there is a certain improvement in the bending strength of the material, up to 87.5 MPa. With introduction of phenolic resin, the bending strength increases from 87.5 MPa before modification to 126.9 MPa, and the tensile strength reaches 63.3 MPa. When the amount of phenolic resin added is too high, the crosslinking density of the material decreases, and the mechanical properties of the material show a downward trend. The study on the relaxation behavior of the epoxy vitrimer system cured with pure anhydride shows that increasing the catalyst content reduces the relaxation time of the materials, but the post curing reaction at high temperature could inhibit the relaxation process and suppress the self-welding strength. The stress relaxation of epoxy vitrimer material modified with phenolic resin is significantly faster than that of epoxy vitrimer system cured with pure anhydride. The relaxation of the samples with 10mol% catalyst shows a sudden change, and there is a significant acceleration when the temperature rises to 190 ℃, and the introduction of phenolic resin could advance the sudden change temperature Ts to 180 ℃. Under no pressure conditions, scratches are repaired. The tensile shear strength and scratches repair effect of the samples repaired above Ts are significantly improved. Compared to samples without phenolic resin, phenolic modified samples could be repaired better. Catalyst have a significant impact on the repair strength and repair speed of the samples.-
Key words:
- epoxy vitrimer /
- self-healing /
- mechanical relaxation behavior /
- phenolic resin /
- recycling
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图 1 试样制备过程示意图
MeTHPA—Methyl tetrahydrophthalic anhydride;
Figure 1. Diagram of preparation process of samples
图 2 10%固化剂含量的树脂液固化不同时间的FTIR全谱图(a)和局部放大对比(b)
Figure 2. FTIR spectra (a) and local enlarged spectra (b) of the resin mixture with 10% cure reagent cured for various times
图 3 SamCa系列试样(a)及SamPF系列试样(b)的DSC分析曲线
Figure 3. DSC curves of the SamCa vitrimer samples (a) and that SamPF samples (b)
图 4 不同酚醛树脂(PF)含量Vitrimer试样的可溶物溶出份数和溶胀比率
Figure 4. Percent of sol and swelling ratio of Vitrimer samples with various content of phenolic resin (PF)
图 5 固化后的SamCa试样和SamPF试样的弯曲强度
Figure 5. Bending strength of the cured SamCas and SamPFs samples
图 6 催化剂含量不同的SamCa系列样品在200℃下的应力松弛曲线
G/G0—Normalized shear modulus
Figure 6. Stress relaxation curves for SamCa series samples with various content of catalyst at 200℃
图 7 酚醛含量不同的SamPF系列试样210℃下的应力松弛曲线
Figure 7. Stress relaxation curves for SamPF series samples with various content of phenolic at 210℃
图 8 SamCa 10 (a)和SamPF 20试样(b)在不同温度下的应力松弛曲线及其松弛时间随温度的变化(c)
Figure 8. Relaxation curves vs. temperature for SamCa 10 (a) and SamPF 20 (b) and their relaxation time vs. temperature curves (c)
图 9 (a) SamCa试样的环氧基团残留量及不同温度下试样拉伸剪切强度随催化剂含量的变化；(b) SamPF系列试样在170℃下自焊接30 min的拉伸剪切强度及SamPF 20试样拉伸剪切强度随温度的相对变化
Figure 9. (a) Residue epoxy groups of SamCa samples and their tensile shear strength vs. content of catalyst at various temperature; (b) Tensile shear strength vs. content of phenolic resin for SamPF samples welded at 170℃ for 30 min and tensile shear strength vs. temperature for SamPF 20 sample
图 10 SamCa 10样品在200℃下试样后固化前后的自焊接强度(a)及试样弯曲疲劳损伤前后及修复后的弯曲强度(b)
Figure 10. Self-welding strength for SamCa 10 samples at 200℃ (a) and bending strength for the samples after and before bending fatigue damage and self-healing (b)
图 11 160℃ ((a), (b))和200℃ ((c), (d))温度下SamCa 10试样划痕修复前((a), (c))和修复后((b), (d))对比
Figure 11. Before ((a), (c)) and after ((b), (d)) healing of scratch for SamCa 10 sample at 160℃ ((a), (b)) and 200℃ ((c), (d))
图 12 SamPF 20酚醛改性试样分别在170℃((a), (b))和210℃ ((c), (d))温度下划痕修复前((a), (c))和修复后((b), (d))的对比
Figure 12. Before ((a), (c)) and after ((b), (d)) healing of scratch for SamPF 20 samples at 170℃ ((a), (b)) and 210℃ ((c), (d))
图 S6 不同催化剂含量（a）及不同含量酚醛树脂改性（b）vitrimer试样的DSC一次升温分析曲线
Figure S6. DSC first heating curves of the vitrimer samples with various content of catalyst (a) and that with various content of phenolic resin (b)
表 1 试样固化后环氧基团残余量
Table 1. Residue epoxy groups of the cured samples
Catalyst percent in SamCas/mol% Residual epoxy groups in SamCas/% Phenolic percent in SamPFs/wt% Residual epoxy groups in SamPFs/% 0 11.2 0 7.9 3 9.9 5 3.8 5 8.3 10 6.9 7 6.4 20 5.1 10 6.2 30 4.4 15 7.6 40 4.0 
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表 2 SamPF 系列试样的拉伸力学性能
Table 2. Tensile strength of the SamPF series samples
Phenolic content/wt% Tensile strength/
MPaElongation at break/% Modulus/
GPa0 54.4±5.5 4.5±0.4 1.1±0.12 5 58.5±4.3 5.7±0.9 1.2±0.03 10 62.3±1.1 6.1±0.3 1.1±0.06 20 63.3±0.6 6.0±0.5 1.3±0.27 30 63.0±1.3 6.2±0.7 1.2±0.22 40 59.3±3.3 6.1±0.4 1.1±0.12
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表 3 试样不同温度下多次焊接的热焊接强度
Table 3. Welding strength of the samples repeated welded under different temperature
Welding times 1 2 3 4 5 Tensile shear strength/MPa SamPF 20 170℃ 1.8 1.6 1.4 1.1 1.1 190℃ 2.0 1.6 1.2 1.4 1.3 210℃ 2.2 2.1 2.0 1.8 2.0 SameCa 10 180℃ 2.4 1.3 0.9 0.7 —
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