Preparation and properties of micromodulation-based polypropylene/polybutylene terephthalate/carbon nanotube electromagnetic shielding materials
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摘要: 电子设备对外界环境造成的电磁污染已经成为继噪声污染、大气污染、水污染、固体废物污染之后的又一大公害，因此高性能电磁屏蔽材料的研制与开发已经成为现今材料科学研究的热点。本文通过调整聚丙烯(PP)、聚对苯二甲酸丁二酯(PBT)、碳纳米管(CNTs)在熔融共混过程中的共混方式，借助CNTs对PBT的定向迁移行为调控PP/PBT/CNTs共混物中聚合物相的相畴尺寸。通过形貌分析、动态流变和结晶行为测试，研究了复合材料微观形貌对其电磁屏蔽特性的影响。研究结果表明，相比于PP相，CNTs对PBT相的亲和作用更强，在四种共混方式中始终位于PBT相畴内；当采用PP/CNTs母料法制备PP/PBT/CNTs复合材料时，所得到的复合材料内部PBT的相畴尺寸更小，PP和PBT间的相容性更高，此时导电通路和界面面积都显著增加，复合材料内部形成了更加密集均匀的导电网络结构，因此所制备的聚合物基复合材料的电导率显著提升，达到29.60 s/m，电磁屏蔽效能在X波段(8.2-12.4 GHz)达到35.6 dB，远超过商业电磁屏蔽材料的需求。Abstract: The electromagnetic pollution caused by electronic equipment to the external environment has become another major public hazard after noise pollution, air pollution, water pollution and solid waste pollution, so the research and development of high-performance electromagnetic shielding materials has become a hot spot in materials science research. In this paper, the phase domain size of the polymer phases in the PP/PBT/CNTs blends was regulated by adjusting the blending methods of polypropylene (PP), polybutylene terephthalate (PBT) and carbon nanotubes (CNTs) during the melt blending process. The influence of the microscopic morphology of the composites on their electromagnetic shielding properties was studied by morphology analysis, dynamic rheology and crystallization behavior tests. The results show that compared with the PP phase, CNTs have a stronger affinity for the PBT phase, and are always located in the PBT phase domain among the four blending methods. When the PP/PBT/CNTs composites are prepared by PP/CNTs masterbatch method, the phase domain size of the PBT inside the obtained composites is smaller, the compatibility between PP and PBT is higher, the conductive path and interface area are significantly increased, and a denser and uniform conductive network structure is formed inside the composites, so the conductivity of the prepared polymer matrix composites is significantly improved, reaching 29.60 s/m, and the electromagnetic shielding efficiency is in the X-band (8.2-12.4 GHz) to 35.6 dB, far exceeding the demand for commercial electromagnetic shielding materials.
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Key words:
- Polymer /
- Carbon nanotubes /
- Blending method /
- Microscopic topography /
- Electromagnetic shielding
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图 1 PP-CNTs/PBT复合材料微观形貌照片及氧元素分布图
Figure 1. Microscopic morphology and oxygen distribution of PP-CNTs/PBT composites
图 2 不同共混方式所制备的复合材料的微观形貌照片
Figure 2. Microscopic morphology photographs of composites prepared by different blending methods
图 3 不同共混方式所制备的复合材料刻蚀PP相后的微观形貌照片
Figure 3. Microscopic morphology photos of composite materials after etching PP phase prepared by different blending methods
图 4 PP、PBT、PP-CNTs和PBT-CNTs的剪切黏度随剪切速率的变化曲线
Figure 4. The shear viscosity of PP, PBT, PP-CNTs and PBT-CNTs as a function of shear rate
图 5 不同共混方式所制备的复合材料的动态流变性能
Figure 5. Dynamic rheological properties of composites prepared by different blending methods
图 6 不同共混方式所制备复合材料的结晶曲线(a)和熔融曲线(b)
Figure 6. Crystallization curves (a)and melting curves(b)of composites prepared by different blending methods
图 9 聚合物相相畴尺度对复合材料电磁屏蔽性能影响机制示意图
Figure 9. Schematic diagram of the influence mechanism of polymer phase domain scale on the electromagnetic shielding performance of composite materials
图 10 不同共混方式所制备的复合材料拉伸强度柱状图
Figure 10. Histograms of the tensile strength of composites prepared by different blending methods
表 1 样品名称及共混方式
Table 1. Sample names and blending methods
Sample code Blending method PP/PBT/CNTs One-step method 12 min PP-PBT/CNTs ①PP+PBT 3 min ②PP-PBT+CNTs 12 min PP-CNTs/PBT ①PP+CNTs 12 min ②PP-CNTs+PBT 3 min PBT-CNTs/PP ① PBT+CNTs 12 min ②PBT-CNTs+PP 3 min Notes: PP—polypropylene; PBT—polybutylene terephthalate; CNTs—carbon nanotubes 
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表 2 各组分表面张力值
Table 2. Surface tension values of each component
Sample Surface tension/mJ·m−2 $\gamma $ ${\gamma ^d}$ ${\gamma ^p}$ PP 22.3 14.2 8.1 PBT 24.1 16.4 7.7 CNTs[27] 27.8 17.6 10.2 Notes: $\gamma $—Surface energy; ${\gamma ^d}$—Dispersive surface energy; ${\gamma ^p}$—Polar surface energy.
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