Effect of surface functionalization on the surface and interfacial properties of thermoplastic-coated carbon fibers in poly (ether ether ketone) matrix composites
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摘要: 本文利用混酸氧化以及乙二胺接枝的方法得到羟基和氨基官能化碳纤维(CF-OH以及CF-NH2),之后进行磺化聚醚醚酮上浆处理,制备了热塑性上浆剂涂层改性的官能化碳纤维(CF-OH-SPEEK以及CF-NH2-SPEEK),并研究表面官能化对热塑性涂层改性碳纤维表面以及复合材料界面性质的影响。结果表明,经过表面官能化处理后,碳纤维的表面官能团含量以及表面润湿能力得到了明显的提高。核磁氢谱分析显示,官能化引入的—OH、—NH2等基团能与磺化聚醚醚酮发生化学反应,提高碳纤维和上浆涂层之间的结合能力。因此,与磺化聚醚醚酮直接涂层改性的退浆碳纤维(desized-SPEEK)相比,CF-OH-SPEEK以及CF-NH2-SPEEK与聚醚醚酮复合时界面剪切强度分别提高了6.2%和14.0%,证明表面官能化处理有利于提高热塑性涂层改性的碳纤维复合材料的界面结合能力。Abstract: Hydroxyl- and amino- functionalized carbon fibers (CF-OH and CF-NH2) were prepared by surface oxidation with mixed acid and grafting with ethylenediamine, respectively. The functionalized CFs were sized with a sulfonated poly (ether ether ketone) (SPEEK) sizing agent to prepare CF-OH-SPEEK and CF-NH2-SPEEK. The effect of surface functionalization on the surface properties of CFs and the interfacial properties in PEEK maxtrix composites were investigated. Results show that the numbers of surface functional groups and wettability of CFs increase significantly after surface functionalization. There are chemical reactions between CFs and the sizing agent, which improve the interfacial adhesion between CFs and the sizing agent. The interfacial shear strengths of CF-OH-SPEEK and CF-NH2-SPEEK reinforced PEEK matrix composites are increased by 6.2 and 14.0%, respectively, as compared with that with CFs desized and sized with SPEEK. The surface functionalization is beneficial to improve the interfacial adhesion of thermoplastic-coated CF/PEEK composites.
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Table 1. The surface energy and its components of test liquids
Test Liquids γp (mN/m) γd (mN/m) γ (mN/m) DI 51 21.8 72.8 CH2I2 0 50.8 50.8 Table 2. Surface roughness of CFs
CF Types Sa(nm) Desized CF 5.6±1.1 Desized−SPEEK 12.7±2.3 CF−OH 23.4±3.2 CF−OH−SPEEK 18.3±2.9 CF−NH2 27.2±4.8 CF−NH2−SPEEK 21.7±3.6 Table 3. Surface elemental compositions of CFs
CF Types Elemental compositions (%) O/C (%) C N O S Si Desized 83.70 0.85 12.70 − 2.75 15.17 Desized−SPEEK 82.46 − 15.73 0.53 1.28 19.08 CF−OH 73.95 − 23.98 − 2.07 32.43 CF−OH−SPEEK 75.29 − 22.97 0.64 1.10 30.51 CF−NH2 73.69 4.08 20.73 − 1.50 28.13 CF−NH2−SPEEK 75.07 3.21 19.67 0.69 1.36 26.20 Table 4. The fitting results of C1s curves
CF Types Peak assignment (%) Surface
functional
group (%)C—C C—N C—O C—S C=O O—C=O Desized 77.90 2.56 16.36 − − 3.18 22.10 Desized−SPEEK 72.90 − 17.70 2.43 3.38 3.59 27.10 CF−OH 67.06 − 20.89 − 4.89 7.16 32.94 CF−OH−SPEEK 68.12 − 21.12 2.50 4.25 4.01 31.88 CF−NH2 66.78 9.00 16.54 − 4.09 3.59 33.22 CF−NH2−SPEEK 67.20 7.18 16.94 2.46 4.15 2.07 32.80 Table 5. The dynamic contact angles and surface free energy results of CFs
CF Types Contact angle (°) γp(mN/m) γd(mN/m) γ(mN/m) DI CH2I2 Desized 72.99 52.81 8.12 32.69 40.81 Desized-SPEEK 59.28 36.66 12.26 41.25 53.51 CF-OH 48.82 24.31 16.00 46.39 62.39 CF-OH-SPEEK 52.74 29.22 14.59 44.54 59.13 CF-NH2 48.11 23.62 16.29 46.63 62.92 CF-NH2-SPEEK 51.15 27.15 15.14 45.36 60.50 Table 6. The results of tensile strength and Weibull modulus
CF Types Tensile strength(GPa) Weibull modulus, m Desized CF 4.68 9.97 Desized−SPEEK 4.79 10.02 CF−OH 4.36 7.64 CF−OH−SPEEK 4.52 7.94 CF−NH2 4.37 6.79 CF−NH2−SPEEK 4.46 7.46 -
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