静电纺纳米纤维诱导同质及非同质聚合物界面结晶行为研究

发布时间：2018-05-07 15:34

本文选题：电纺纤维 + 聚己内酯　；参考：《郑州大学》2017年硕士论文

【摘要】：在纤维状填料(如碳纤维、碳纳米管等)增强半结晶聚合物基复合材料中,填料与聚合物基体间的界面结晶一直是研究热点。通常,直径为微米级的纤维可作为一维异相成核点诱导聚合物基体结晶而形成横晶结构;纳米级纤维(如碳纳米管)则可诱导聚合物附生结晶形成杂化串晶结构。静电纺纳米纤维具有超高长径比和高比表面积等优异特性,在增强聚合物复合材料方面的应用也逐渐引起人们的关注。然而,关于电纺纤维/聚合物基复合材料界面结晶的研究报道目前比较少,其中的机理尚不明确。鉴于此,本文将逐步研究电纺聚己内酯(PCL)纤维、聚己内酯/聚左旋乳酸-聚己内酯共聚物(PCL/PLCL)复合纳米纤维及聚酰胺(PA66)纳米纤维在诱导同质或非同质结晶聚合物(PCL)在溶液或熔体体系中的结晶行为,进而探讨电纺纤维/聚合物复合材料的界面结晶形态及形成机理。结合扫描电镜、原子力显微镜、偏光显微镜、差示扫描量热仪、广角X射线衍射等表征手段对界面结晶的晶体形态与结构、结晶动力学、结晶行为等进行深入研究。主要工作内容如下:首先,制备不同平均直径的PCL电纺纤维,探讨其诱导同质PCL溶液体系的界面结晶。结果表明:PCL纤维作为一维成核点成功地诱导同质PCL在其表面附生结晶,并且界面晶体形态和结构对纤维的直径和结晶时间具有强烈的依赖性。当PCL纤维直径为几百纳米时,PCL片晶在纤维表面垂直于纤维轴向周期性排列,形成典型的杂化串晶结构;而当纤维直径增大到2μm以上时,PCL片晶则在纤维表面无规排列,形成片晶相互贯穿的多孔状界面晶体形态。PCL纤维诱导同质PCL界面结晶形态的不同归因于PCL纤维本身表层的结晶结构和片晶排列。其次,制备PCL/PLCL复合纳米纤维,进一步探讨其诱导PCL溶液体系的界面结晶以及复合纤维中PCL相对界面结晶的影响。结果表明,复合纤维中PCL的含量对复合纤维诱导界面晶体结构有着显著影响。当PCL含量低于30 wt%时,PCL/PLCL复合纤维不能诱导PCL在其表面附生结晶;当PCL含量高于50 wt%时,复合纤维才能诱导PCL在其表面外延生长形成杂化串晶。此外,当复合纤维中PLCL含量大于50 wt%时,复合纤维表面才会形成贯穿纤维并规整排列的PCL片晶微结构。结合PCL纤维及其复合纤维表面微观结构及诱导形成界面晶体形貌分析,我们发现,纤维表层的PCL晶片结构对后续诱导PCL分子链在纤维表面的附生结晶有着决定性作用。该结果进一步证明了PCL纤维在诱导同质的PCL溶液界面结晶中,晶格匹配具有主导性的作用。最后,探讨尼龙66(PA66)电纺纤维诱导非同质的PCL溶液及熔体体系的界面结晶行为。在溶液结晶中,PA66电纺纤维诱导PCL形成杂化串晶结构,其中PA66电纺纤维作为“shish”结构,而非同质的PCL片晶作为“kebab”结构垂直于纤维轴向周期性排列。更有意思的是,我们首次观察到,在PA66电纺纤维诱导PCL熔体结晶时,纤维表面形成了杂化串晶和横晶共存的多层次界面结晶结构。可能的形成机理是:由于PA66电纺纤维与PCL基体具有较强的氢键作用,结晶时界面处的PCL分子链首先被吸附到PA66纤维的表面形成PCL分子层,这些被吸附的PCL分子链进而诱导PCL附生结晶形成杂化串晶结构;随后杂化串晶中的PCL片晶前端支化而发散生长生成树枝状晶体并最终在杂化串晶外围演变成为横晶结构。
[Abstract]:The interfacial crystallization between the filler and the polymer matrix has always been a hot spot in the reinforced semicrystalline polymer matrix composites, such as carbon fibers, carbon nanotubes, etc., usually, the fiber with a diameter of micron can be used as a one-dimensional heterogeneous nucleation point to induce the crystalline structure of the polymer matrix and the nanoscale fibers (such as carbon nanotubes). It can induce polymer epiphytic crystallization to form hybrid crystal structure. Electrospun nanofibers have excellent properties such as ultra high length diameter ratio and high specific surface area. The application of polymer composites is also attracting more and more attention. However, the research on interfacial crystallization of electrospun fiber / polymer matrix composites has been reported to be compared to the present. Less, the mechanism is unclear. In view of this, this paper will gradually study the crystallization behavior of polycaprolactone (PCL) fibers, poly (hexyllactone) / poly (L-lactic acid) copolymer (PCL/PLCL) composite nanofibers and polyamide (PA66) nanofibers in the induction of homogenous or non homogenous crystalline polymers (PCL) in solution or melt system. The interfacial crystallization and formation mechanism of the electrospun fiber / polymer composites are discussed. The main work contents are the scanning electron microscopy, atomic force microscopy, polarizing microscope, differential scanning calorimetry, wide angle X ray diffraction and so on. The crystal morphology and structure of the interface crystals, crystallization kinetics and crystallization behavior are studied. As follows: first, the PCL electrospun fibers with different average diameters were prepared, and the interfacial crystallization of the homogenous PCL solution system was investigated. The results showed that PCL fibers successfully induced the epiphytic crystallization of homogenous PCL on its surface as one dimension nucleation point, and the crystal morphology and structure of the interface had a strong dependence on the diameter and crystallization time of the fibers. When PCL When the fiber diameter is hundreds of nanometers, the PCL crystal is vertically arranged in the axial periodic arrangement of the fiber on the fiber surface, forming a typical hybrid crystal structure, and when the fiber diameter increases to more than 2 m, the PCL slices are arranged on the surface of the fiber, forming the interpenetrating multi hole interface crystal form of the lamellar crystal, which induces the crystallization of the homogeneity of the PCL interface. The difference of morphology is attributed to the crystal structure and crystal arrangement of the surface of PCL fibers. Secondly, the preparation of PCL/PLCL composite nanofibers is made to further explore the effect of the interfacial crystallization of the PCL solution and the relative crystallization of PCL in the composite fibers. The results show that the content of PCL in the composite fibers is the crystal junction of the composite fiber induced interface. When the content of PCL is less than 30 wt%, the PCL/PLCL composite fiber can not induce the epiphytic crystallization of PCL on its surface. When the content of PCL is higher than 50 wt%, the composite fiber can induce the epitaxial growth of PCL on its surface to form a hybrids. In addition, when the PLCL content in the composite fiber is larger than 50 wt%, the surface of the composite fiber will form through fiber. It is found that the structure of the PCL chip on the surface of the fiber surface is decisive for the epiphytic crystallization of the PCL molecular chain on the surface of the fiber, which further proves that the PCL fiber is induced to be induced by the microstructure of the PCL fiber and its composite fiber on the surface microstructure and the induced formation of the interface crystal morphology. Lattice matching has a leading role in the crystallization of homogeneous PCL solution interface. Finally, the interfacial crystallization behavior of non homogenous PCL solution and melt system induced by nylon 66 (PA66) electrospun fibers is investigated. In solution crystallization, PA66 electrospun fibers induce PCL to form a hybrid series crystal structure, in which PA66 electrospun fibers are used as "shish" structures, but not the same. The qualitative PCL crystal is perpendicular to the fiber axial periodic arrangement as "kebab" structure. It is more interesting that, for the first time, we observed that when the PA66 electrospun fiber induced the crystallization of the PCL melt, the surface of the fiber formed a multilayered crystal structure with the coexistence of hybrids and transversal crystals. The possible formation mechanism was that the PA66 electrospun fiber and the PCL matrix were formed. With strong hydrogen bonding, the PCL molecular chain at the crystallization interface is first adsorbed to the surface of the PA66 fiber to form the PCL molecular layer, and these adsorbed PCL chains then induce the PCL epiphytic crystallization to form a hybrid series crystal structure, and then the front-end of the PCL lamellae in the hybrids is branched and grows to generate dendritic crystals and eventually is hybrid. The perimeter of the series of crystals evolves into a transgranular structure.

【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ340.1;TB332

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