Interfacial properties of polyurethane/nano-SiO2 modified carbon fiber epoxy resin composites
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摘要: 聚合物与纤维之间的界面性能对提升复合材料力学性能尤为重要。本文采用异氰酸根(—NCO)封端的聚氨酯(PU)分子对纳米SiO2表面进行改性,同时采用KH550对碳纤维(CF)进行表面改性,利用—NH2与—NCO较高的反应活性,在CF和纳米SiO2粒子间通过PU分子链形成共价键连接。结果显示:PU极性分子链的引入,提高了CF的表面能,使其表面润湿性显著提高。相较于KH550直接接枝纳米粒子的碳纤维(CF-KH550-SiO2),通过PU分子链接枝纳米粒子的碳纤维(CF-KH550-PU-SiO2),其表面能提升23.0%,表面纳米SiO2粒子的接枝率和分散均匀性也明显提升。CF-KH550-PU-SiO2/环氧树脂(EP)的界面剪切强度(IFSS)和层间剪切强度(ILSS)相比未改性CF/EP分别提高72.9%和47.9%,相比CF-KH550-SiO2/EP分别提高17.3%和11.2%。
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关键词:
- 碳纤维增强环氧树脂复合材料 /
- 界面性能 /
- 纳米二氧化硅 /
- 聚氨酯 /
- 碳纤维表面改性
Abstract: The interfacial properties between polymer and fiber are particularly important for improving the mechanical properties of composites. In this paper, the surface of nano-SiO2 was modified by polyurethane (PU) capped by isocyanate (—NCO), and the surface of carbon fiber (CF) was modified by KH550. Because of the high reactivity of —NH2 and —NCO, the covalent bond was formed between CF and nano-SiO2 particles through PU molecular chain. The results showed that the introduction of PU polar molecular chain improved the surface energy and wettability of CF. Compared with the CF directly grafted with nano particles by KH550(CF-KH550-SiO2), the surface energy of the CF with nano particles linked by PU (CF-KH550-PU-SiO2) molecules increased by 23.0%, and the grafting rate and dispersion uniformity of surface nano SiO2 particles also improved significantly. Compared with the untreaed CF/epoxy resin (EP) composites, the interfacial strength (IFSS) and the interlaminar shear strength (ILSS) of CF-KH550-PU-SiO2/EP composites increased by 72.9% and 47.9% respectively. Compared with the CF-KH550-SiO2/EP composites, IFSS and ILSS of CF-KH550-PU-SiO2/EP composites increased by 17.3% and 11.2%, respectively.-
Key words:
- CF/EP composite /
- interface property /
- nano-SiO2 /
- polyurethane /
- surface modification of carbon fibers
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图 1 (a)纳米SiO2表面接枝聚氨酯(PU)反应过程;(b)碳纤维(CF)表面多层结构制备示意图
TEOS—Ethyl orthosilicate; HDI—Hexamethylene diisocyanate; PPG—Polypropylene glycol; DBTDL—Dibutyl tin dilaurate; KH550—3-aminopropyl triethoxysilane
Figure 1. (a) Reaction process of grafting polyurethane (PU) on nano-SiO2 surface; (b) Schematic illustration of multilayer structure grafted on carbon fiber (CF)
图 3 未改性纳米SiO2 (a)及PU-SiO2 (b)的TEM图像、两种粒子的动态光散射(DLS)粒径曲线(c)及未改性纳米SiO2和PU-SiO2的分散液(d)
$\overline{D} $—Average particle size of particles; PDI—Polydispersity index
Figure 3. TEM images of raw SiO2 (a) and PU-SiO2 (b), dynamic light scattering (DLS) curves of the synthesized SiO2 (c) and photograph of the particle disperdion (d)
表 1 测试液的极性分量$ {\gamma }_{{\rm{l}}}^{{\rm{p}}} $、色散分量$ {\gamma }_{{\rm{l}}}^{{\rm{d}}} $及表面能$ {\gamma }_{\rm{{l}}} $
Table 1. Polar component$ {\gamma }_{{\rm{l}}}^{{\rm{p}}} $, dispersive component $ {\gamma }_{{\rm{l}}}^{{\rm{d}}} $ and surface free energy $ {\gamma }_{{\rm{l}}} $ of the testing liquids
(mJ·m−2) Testing liquid $ {\gamma }_{{\rm{l}}}^{{\rm{p}}} $ $ {\gamma }_{{\rm{l}}}^{{\rm{d}}} $ $ {\gamma }_{{\rm{l}}} $ Water 51 21.8 72.8 CH₂I₂ 0 50.8 50.8 表 2 CF表面元素含量变化
Table 2. Changes in surface element content of CF
Sample Element/wt% C1s O1s N1s Si2p CF 81.33 16.01 2.33 0.33 CF-KH550 70.53 22.64 4.74 2.09 CF-KH550-SiO2 51.36 30.42 3.48 15.74 CF-KH550-PU-SiO2 29.09 42.80 6.43 21.68 -
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