Structure and Mechanical Properties of Multi-Walled Carbon Nanotubes-Filled Isotactic Polypropylene Composites Treated by Pressurization at Different Rates
Structure and Mechanical Properties of Multi-Walled Carbon Nanotubes-Filled Isotactic Polypropylene Composites Treated by Pressurization at Different Rates
复制标题
不同速率加压处理多壁碳纳米管填充等规聚丙烯复合材料的结构与力学性能
DOI：
10.3390/polym11081294
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发表时间：
2019-08-01
期刊：
影响因子：
5
通讯作者：
Shao, Chunguang
中科院分区：
文献类型：
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作者：
Li, Xiaoting;Jia, Wenxia;Shao, Chunguang
填充有1重量%的等规聚丙烯制备了多壁碳纳米管（iPP/MWCNTs），研究了在2.5 ~ 1.3 × 104 MPa/s压力范围内加压至2.0GPa时iPP/MWCNTs的结晶行为。采用广角X射线衍射、小角X射线散射、差示扫描量热、透射电子显微镜和原子力显微镜等技术对样品进行了表征。结果表明，加压法是制备中间相、γ相或它们的共混物的简单方法。两个阈值增压率标记为R1和R2被确定，而R1对应于介晶iPP形成的开始。当加压速率低于R1时，只有γ相生成，随着中间相的增加，中间相开始生成并与γ相共存，当加压速率低于R2时，只有中间相生成。当iPP/MWCNTs在γ相中结晶时，与纯iPP相比，MWCNTs的存在促进了γ相的成核，形成了片层较厚的γ晶体。如果iPP/MWCNTs在中间相固化，MWCNTs可以降低结节结构的生长速率，导致形成具有较小结节结构域（约9.4 nm）的中间相。力学性能测试结果表明，缓慢加压法制备的γ-iPP/MWCNTs复合材料具有较高的杨氏模量、屈服强度和断裂伸长率，而meso-iPP/MWCNTs复合材料由于存在球状形貌，具有良好的变形性能。从这个意义上说，加压法被证明是一种有效的方法来调节iPP/MWCNTs复合材料的结晶结构和性能。
Isotactic polypropylene filled with 1 wt.% multi-walled carbon nanotubes (iPP/MWCNTs) were prepared, and their crystallization behavior induced by pressurizing to 2.0 GPa with adjustable rates from 2.5 to 1.3 × 104MPa/s was studied. The obtained samples were characterized by combining wide angle X-ray diffraction, small angle X-ray scattering, differential scanning calorimetry, transmission electron microscopy and atomic force microscopy techniques. It was found that pressurization is a simple way to prepare iPP/MWCNTs composites in mesophase, γ-phase, or their blends. Two threshold pressurization rates marked asR1andR2were identified, whileR1corresponds to the onset of mesomorphic iPP formation. When the pressurization rate is lower thanR1only γ-phase generates, with its increasing mesophase begins to generate and coexist with γ-phase, and if it exceedsR2only mesophase can generate. When iPP/MWCNTs crystallized in γ-phase, compared with the neat iPP, the existence of MWCNTs can promote the nucleation of γ-phase, leading to the formation of γ-crystal with thicker lamellae. If iPP/MWCNTs solidified in mesophase, MWCNTs can decrease the growth rate of the nodular structure, leading to the formation of mesophase with smaller nodular domains (about 9.4 nm). Mechanical tests reveal that, γ-iPP/MWCNTs composites prepared by slow pressurization display high Young’s modulus, high yield strength and high elongation at break, and meso-iPP/MWCNTs samples have excellent deformability because of the existence of nodular morphology. In this sense, the pressurization method is proved to be an efficient approach to regulate the crystalline structure and the properties of iPP/MWCNTs composites.