Preparation and properties of bamboo fibers reinforced soybean oil-based vitrimer composites
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摘要: 热固性复合材料拥有优异的力学性能、耐热性和耐化学性,但存在原料不可再生、使用后无法回收、纤维与树脂不易降解等问题。本文分别以微米级竹粉(BP)和厘米级竹纤维(BF)为增强体,以含动态硼酸酯的二硫醇固化环氧大豆油(ESOBV)为树脂基体,采用模压成型技术制备可循环回收的竹纤维增强大豆油基类玻璃高分子复合材料,同时表征了生物质复合材料的拉伸性能、动态力学性能、松弛行为、界面结合、可重塑回收性及可降解性。结果表明:纤维形态显著影响复合材料的力学性能,复合材料的拉伸强度和拉伸模量随着BP含量的增加而降低,但随着BF含量的增加而增加;因ESOBV基体中动态键的存在,复合材料高温下具有明显的应力松弛现象,其松弛时间随BP或BF含量的增加而增加;BP增强复合材料可在高温下进行回收重塑,重塑后复合材料的拉伸强度、拉伸模量和断裂伸长率分别达到原始材料的91.0%、96.3%和110.7%;在100°C、常压下,ESOBV基体中的硼酸酯基可与甘油分子发生交换反应,因此基体经甘油降解后可回收BF,且回收的纤维形态不受损坏。Abstract: Thermosetting composites have been widely applied in many fields due to their excellent mechanical properties, heat resistance, and chemical resistance. However, the drawbacks including non-renewable raw materials, non-recyclability after service, and non-degradability of fibers and resins largely limit their further application. In this work, two bamboo fibers, i.e., micrometer-scale bamboo powders (BP) and centimeter-scale bamboo fibers (BF) were respectively used as reinforcements for the resin matrix from epoxidized soybean oil (ESO), and meanwhile, a dithiol monomer containing dynamic borate esters was used as a curing agent. The recyclable bamboo fibers reinforced soybean oil-based vitrimer (ESOBV) biocomposites were prepared via a compression molding technique. The tensile properties, dynamic mechanical properties, stress relaxation, interfacial bonding, recyclability, and degradability of the composites were investigated. The results show that the tensile strength and tensile modulus of the composites decreased with the increase of BP content, while increased with the increase of BF content, indicating a significant effect of fiber morphology on the mechanical properties of the composites. Due to the presence of dynamic covalent bonds, the composites showed a stress relaxation behavior at high temperature, and their stress relaxation times increased with the fiber contents. The BP-reinforced composites can be remolded at high temperature, and the remolded composites have 91.0% tensile strength, 96.3% tensile modulus, and 110.7% elongation at break of the original composites. The dynamic borate esters in ESOBV can exchange with glycerol at 100℃ and atmospheric pressure, and thus the matrix can be degraded in glycerol to recover the fibers without any damage in morphology.
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Key words:
- borate esters /
- epoxidized soybean oil /
- vitrimer /
- biocomposite /
- recyclability
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图 1 (a) 微米级竹粉(BP)/环氧大豆油(ESO)和厘米级竹纤维(BF)/ESO复合材料的制备;(b) ESOBV网络通过硼酸酯交换反应进行拓扑重排
DMAP—4-dimethylaminopyridine; ESOBV—Soybean oil-based vitrimer; BDB—2, 2′-(1, 4-phenylene)-bis[4-mercaptan-1, 3, 2-dioxaborolane]
Figure 1. (a) Preparation of micrometer-scale bamboo powders (BP)/epoxidized soybean oil (ESO) and centimeter-scale bamboo fibers (BF)/ESO composites; (b) Network topology rearrangement of ESOBV resins via borate ester exchange reaction
表 1 ESOBV基复合材料的配方
Table 1. ESOBV-based composite formulations
Sample Mass fraction/% BP BF ESOBV DMAP ESOBV 0 0 100 2 BP/ESO-30 30 0 70 BP/ESO-40 40 0 60 BP/ESO-50 50 0 50 BF/ESO-30 0 30 70 BF/ESO-40 0 40 60 BF/ESO-50 0 50 50 -
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