碳纤维增强含酯键环氧树脂基复合材料的化学降解与回收

张洋; 张隽爽; 马崇攀; 孙忠霄; 王宇

碳纤维增强含酯键环氧树脂基复合材料的化学降解与回收

张洋¹,
张隽爽¹,
马崇攀¹,
孙忠霄¹,
王宇^{1, 2, ,}

1.
北京化工大学　材料科学与工程学院, 北京 100029
2.
碳纤维及功能高分子教育部重点实验室, 北京 100029

基金项目: 国家自然科学基金(National Natural Science Foundation of China，52102033)；装备预研教育部联合基金(Joint Fund of Ministry of Education for Equipment Research，6141 A02033231)

详细信息

通讯作者:
王宇，博士，副教授，硕士生导师，研究方向为聚丙烯腈基碳纤维及其复合材料　E-mail：wangy@mail.buct.edu.cn

中图分类号: TQ342.31
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- 被引次数: 0
出版历程
- 收稿日期: 2022-10-05
- 修回日期: 2022-10-29
- 录用日期: 2022-11-06
- 网络出版日期: 2022-11-16

Chemical degradation and recovery of carbon fiber reinforced epoxy resin matrix composites containing ester bond

1.
School of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China
2.
Functional Polymer Key Laboratory of Ministry of Education, Beijing 100029, China

摘要

摘要: 随着环氧树脂基碳纤维复合材料的广泛应用，其废旧产品的回收是循环利用大背景下的重要问题。但由于具有三维网状交联结构的热固性环氧树脂无法重新熔融、溶解或成型，导致树脂基体和高附加值的碳纤维增强体均难于高效再利用。本文以含酯键的环氧树脂TDE85(4,5-环氧己烷-1,2-二甲酸二缩水甘油酯)和胺类固化剂DDS(4,4’-二氨基二苯砜)组成的含酯键环氧树脂基体作为代表，并以该树脂体系制备的碳纤维复合材料为研究对象，选用苯甲醇作为溶剂，NaOH提供碱性条件，ZnCl₂作为促进剂，在常压190℃条件下进行降解研究。该降解方法具有简单高效便于操作的特点，降解后体系分层，上层清液的苯甲醇含量高达99%，非常易于其回收再利用；碳纤维与树脂降解后的胶状物在下层，采用简单的溶剂(丙酮)和水进行清洗，即可分离出碳纤维，碳纤维的表面理化结构与原始碳纤维相近，碳纤维的强度保留率达97%，可实现几乎无损伤回收再利用。经过对胶状物质的表征，提出了含酯键环氧树脂基体可能的降解机制。在碳中和思想指导下，以期研究结果为碳纤维增强三维网状热固性树脂基复合材料的开发、应用和循环再利用开阔思路和提供数据。1碳纤维复合材料环氧树脂降解后所得碳纤维力学性能和表面理化结构与原始碳纤维对比表
Sample Tensile strength of monofilament/GPa Element content surface morphology
C/% O/% C/O
Initial carbon fibers 3.44±0.08 84.65 13.26 0.157
Recycled carbon fibers 3.34±0.10 84.51 13.36 0.158
- 碳纤维复合材料 /
- 降解回收 /
- 含酯键的环氧树脂 /
- 循环利用 /
- 碱性环境
Abstract: With the wide application of epoxy resin-based carbon fiber composites, the recycling of their waste products had become an important issue for low-carbon development. The resin degradation mechanism of epoxy resin-based carbon fiber composites containing ester bonds and the effect of degradation process on the structure and properties of recycled carbon fibers were studied by GC-MS, FTIR, XPS, SEM and other characterization methods. The results show that the optimal degradation time is 1 h under the conditions of benzyl alcohol dosage of 120 mL, W (NaOH)∶W (ZnCl₂)=1∶1 and degradation temperature of 190℃, and the optimal dosages of NaOH and resin are both 1 g. The degradation products are separated by standing stratification, and the content of benzyl alcohol in the supernatant is 99%. The degradation mechanism of the resin is as follows: Firstly, benzyl alcohol is ionized to generate benzyloxy group in an alkaline environment, and the benzyloxy groups attack ester bonds in the resin, and transesterification reaction occures to break the ester bond to achieve degradation. Benzyl alcohol ester and alcohol anion are produced by transesterification reaction. Next, the benzyl alcohol ester undergoes saponification reaction in alkaline environment to regenerate benzyl alcohol. The transesterification reaction and the saponification reaction are repeated until the final degradation is completed. The surface O/C and surface smoothness of the recycled carbon fibers and the original carbon fibers are at the same level, and the strength retention rate of the recycled carbon fibers reaches 97%.
- Carbon fiber composites /
- Chemical degradation /
- Epoxy resin containing ester bond /
- Recycling /
- Alkaline environment

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图 1 降解时间对环氧树脂基体降解率的影响

备注：苯甲醇120 mL、W(NaOH)和W(ZnCl₂)均1 g、碳纤维复合材料2 g

Figure 1. Effect of degradation time on degradation rate of epoxy resin matrix

Note：Benzyl alcohol 120 mL, W(NaOH) 1 g, W(ZnCl₂) 1 g, Composite materials 2 g

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图 2 NaOH加入量对环氧树脂基体降解率的影响备注：苯甲醇120 mL、W(NaOH)∶W(ZnCl₂)=1∶1、复合材料2 g

Figure 2. Effect of NaOH dosage on degradation rate of epoxy resin matrix Note：Benzyl alcohol 120 mL, W(NaOH)∶W(ZnCl₂) =1∶1, Composite materials 2 g

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图 3 回收所得上清液与纯苯甲醇的红外光谱

Figure 3. FTIR Spectra of recovered supernatant and pure benzyl alcohol

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图 4 降解后溶液下层的胶状产物的液质联用测试结果: (a)正离子 (b)负离子

Figure 4. Results of LC-MS of degraded and recovered colloid: (a)positive ion (b)negative ion

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图 5 降解回收胶体与纯环氧树脂的红外光谱

Figure 5. FTIR of degraded and recovered colloid and pure epoxy resin

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图 6 环氧树脂基体降解过程机制图

Figure 6. Schematic diagram of degradation process of epoxy resin matrix

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图 7 原始碳纤维和降解回收碳纤维的表面形貌对比图

Figure 7. Comparison diagram of surface morphology of original carbon fiber and degraded carbon fiber

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1 碳纤维复合材料环氧树脂降解后所得碳纤维力学性能和表面理化结构与原始碳纤维对比表

Sample	Tensile strength of monofilament/GPa	Element content			surface morphology
Sample	Tensile strength of monofilament/GPa	C/%	O/%	C/O	surface morphology
Initial carbon fibers	3.44±0.08	84.65	13.26	0.157
Recycled carbon fibers	3.34±0.10	84.51	13.36	0.158

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表 1 碳纤维复合材料降解1 h后上清液的GC-MS结果

Table 1. GC-MS results of supernatant after 1 h degradation of carbon fiber composite

Sequence number	Retention time/min	Components’ name	Molecular structure	Content/%
1	8.460	Benzaldehyde		0.101
2	9.842	Benzyl alcohol		99.878
Others				0.021

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表 2 降解前后碳纤维表面的元素含量

Table 2. Element content of carbon fiber surface before and after degradation

Sample	Degradation rate /%	C/%	O/%	C/O
Initial carbon fibers	/	84.65	13.26	0.157
Recycled carbon fibers(W(NaOH)：W(Resin)=1：1)	100	84.51	13.36	0.158
Recycled carbon fibers(W(NaOH)：W(Resin)=0.1：1)	75.7	80.4	17.34	0.216

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表 3 原始碳纤维和降解回收碳纤维的单丝拉伸强度对比

Table 3. Comparison of tensile strength of carbon fiber monofilament before and after degradation

Sample	Degradation rate/%	Tensile strength of monofilament/GPa
Initial carbon fibers	/	3.44±0.08
Recycled carbon fibers (W(NaOH):W(Resin)=1:1)	100%	3.34±0.10

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