Preparation and properties of graphene functionalized polyvinylidene fluoride dielectric composites
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摘要: 为获得高介电性能的复合材料,以聚偏氟乙烯(PVDF)为基体,首先以离子液体功能化改性的氧化石墨烯(GO-IL)为填料制备了不同GO-IL含量的GO-IL/PVDF二元介电复合材料,在此基础上引入羟基化钛酸钡(BT-OH)通过溶液共混制备了不同比例的BT-OH-GO-IL/PVDF三元介电复合材料。分别采用FTIR、FESEM、XRD、拉伸性能测试、电性能测试、DSC等方法系统研究了填料GO-IL和BT-OH的含量对所得复合材料的热性能、力学性能和电性能等的影响。FITR和XRD测试表明,IL成功接枝于GO上,GO-IL的加入促进了PVDF中β晶的生成。DSC测试进一步表明,GO-IL的加入提高了复合材料的结晶度,含2wt%GO和2wt%GO-IL的复合材料结晶度分别达到了35.3%和36.9%。电性能测试表明,GO-IL更容易在PVDF基中构成局部导电网络,促进电子位移极化,进而提高复合材料的介电常数。在GO-IL/PVDF复合材料中,当GO-IL填料含量为2wt%时,复合材料的介电常数达到了24.28,是纯PVDF的2.6倍。但当填料含量达8wt%时,复合材料的介电常数达到了78.46,同时介电损耗也大幅增大,达到了2.25。电阻相比于纯PVDF下降了1~2个数量级。三元复合材料中,当GO-IL含量为2wt%、BT-OH填料含量为20wt%时,复合材料的综合性能最好,介电常数达到了40.32,介电损耗为0.38。Abstract: In order to obtain the composites with high dielectric properties, polyvinylidene fluoride (PVDF) was used as matrix, graphene oxide modified by ionic liquid as filler (GO-IL) and GO-IL/PVDF binary dielectric compo-sites with different GO-IL contents were first prepared by solution blending method. And then, hydroxylated barium titanate (BT-OH)-GO-IL/PVDF ternary composites with different proportions were prepared by solution blending. The effects of GO-IL and BT-OH contents on the thermal, mechanical and electrical properties of the compo-sites were investigated by FTIR, FESEM, XRD, tensile, electrical and DSC tests. FTIR test shows that IL is successfully grafted on GO, and the addition of GO-IL promotes β-crystal formation of PVDF. DSC and XRD characterizations further improve that the addition of GO-IL promotes the growth of β-crystal. The crystallinity reaches 35.3% and 36.9% when the fillers are 2wt%GO and 2wt%GO-IL, respectively. Electrical test shows that GO-IL is easier to form local conductive networks in PVDF matrix, promoting the electronic displacement polarization and improving the dielectric constant of the composites. For GO-IL/PVDF composite, when the content of GO-IL filler is 2wt%, the dielectric constant of the composite reaches 24.28, which is 2.6 times of the pure PVDF. However, when the filler content reaches 8wt%, the dielectric constant of the composite reaches 78.46, and the dielectric loss also increases sharply, reaching 2.25. The resistance of the composite is 1-2 orders lower than that of the pure PVDF. When the content of GO-IL is 2wt% and the content of BT-OH filler is 20wt%, the composite shows the best comprehensive properties, the dielectric constant is 40.32 and the dielectric loss is 0.38.
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Key words:
- polyvinylidene fluorider /
- graphene oxide /
- ionic liquid /
- composite /
- dielectric property /
- barium titanate
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图 6 不同填料含量下BT-OH-GO-IL/PVDF复合材料的力学性能:(a) 拉伸强度;(b) 断裂伸长率;(c) 弹性模量;(d) BT-OH-GO-IL/PVDF复合材料的拉伸应力-应变曲线
Figure 6. Mechanical properties of BT-OH-GO-IL/PVDF composites with different filler contents: (a) Tensile strength; (b) Elongation at break; (c) Elastic modulus; (d) Stress-strain curves of BT-OH-GO-IL/PVDF
图 7 GO-IL/PVDF复合材料的介电性能曲线:(a) 频率为100 Hz时不同填料含量的介电常数和介电损耗;(b) 不同填料含量下GO-IL/PVDF复合材料的介电常数与频率的关系
Figure 7. Dielectric properties curves of the GO-IL/PVDF composites: (a) Dielectric constant and dielectric loss with different filler contents at 100 Hz; (b) Relationship between dielectric constant and frequency of GO-IL/PVDF composites with different filler contents
图 8 BT-OH-GO-IL/PVDF复合材料的介电性能曲线:(a) 频率为100 Hz时不同填料含量下复合材料的介电常数和介电损耗;(b) 不同填料含量下BT-OH-GO-IL/PVDF复合材料的介电常数与频率的关系
Figure 8. Dielectric properties curves of the BT-OH-GO-IL/PVDF composites: (a) Dielectric constant and dielectric loss with different filler contents at 100 Hz; (b) Relationship between dielectric constant and frequency of BT-OH-GO-IL/PVDF composites with different filler contents
表 1 不同填料含量下PVDF基复合材料的DSC测试结果
Table 1. DSC test results of PVDF composites with different filler contents
Sample Tcp/℃ ΔHc/(J·g−1) Tmp/℃ ΔHm/(J·g−1) Xc/% PVDF 123.90 36.59 159.6 29.76 28.50 2wt%GO/PVDF 136.26 41.92 167.5 37.64 35.30 2wt%GO-IL/PVDF 135.36 41.29 168.0 40.27 36.90 0.8wt%BT-OH-2wt%GO-IL/PVDF 139.45 37.22 168.0 36.04 33.10 20wt%BT-OH-2wt%GO-IL/PVDF 139.46 33.63 167.9 34.35 24.95 Notes: Tcp—Crystallizing point; ΔHc—Crystallization enthalpy; Tmp—Melting point; ΔHm—Melting enthalpy; Xc—Crystallinity. -
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