聚乙烯支化结构对无机填料在聚乙烯基体中分散性的影响

发布时间：2018-08-27 09:12

【摘要】：填料在复合材料中的分散情况很大程度上决定了复合材料成品的最终性能。本文选取两种微观结构不同的无机填料(滑石粉、碳酸钙)分别填充四种支化结构存在较大差异的聚乙烯(HDPE、LDPE、LLDPE以及mPE)制备填充复合材料,通过动态流变测试以及SEM观察等方法表征不同填料含量以及聚乙烯支化结构的差异对填料粒子在复合体系中分散性的影响;通过DSC测试研究不同复合材料的熔融及结晶行为,并通过力学性能测试分析了在填料不同的分散情况对材料力学性能的影响。研究结果如下:研究结果表明:较高填充量滑石粉的加入对HDPE、LLDPE及mPE三种体系的动态流变行为有较大的影响,其在小应变区域都呈现出明显的Payne效应,储能模量在低频区对频率变化十分敏感,表现出似固体行为,这表明三种高填充体系出现了滑石粉大量团聚的现象;对于长支链结构的LDPE复合体系,在小应变区域都没有出现Payne效应,低频区域也没有出现似固体行为,而剪切变稀行为在高频区域则更加明显。SEM观察发现,在HDPE、LLDPE及mPE三种基体中,滑石粉与基体间存在不同程度的空隙,滑石粉间的集聚现象较为明显;对于LDPE/Talc体系,断面十分光滑,没有凸出的滑石粉粒子,两相间没有任何空隙。根据DSC数据分析,低填充体系中,滑石粉加入,体系的结晶度和结晶速率都有所提升;对于PE/Talc复合材料,滑石粉含量的提升,对复合体系的结晶速率都有提升。根据力学性能分析,低填充复合材料的力学性能都所提升;而在高填充体系,对HDPE、LLDPE及mPE三种复合材料,由于滑石粉间严重的团聚行为,极大的降低了其力学性能。对于高填充LDPE/Talc复合材料中,其力学性能的损失相对较少。这得益于滑石粉在具有长支链结构的LDPE基体中良好的分散性。PE/CaCO3复合材料流变行为与PE/Talc复合材料基本类似,但当碳酸钙填充量为30 vol%时,LDPE/CaCO3体系也出现了明显的Payne效应和似固体行为,其复合材料的力学性能也有较大的损失。这可能是由于碳酸钙粒子更高的比表面积使得粒子间更易团聚导致的。未使用偶联剂改性填料填充体系的填料粒子存在更明显的Payne效应,从SEM微观形貌图也可以看出其更容易发生团聚行为,与基体的相容性也更差。
[Abstract]:The dispersion of fillers in the composites largely determines the final properties of the composites. In this paper, two inorganic fillers with different microstructure (talc powder and calcium carbonate) were used to prepare the filling composites, which were filled with polyethylene (HDPE,LDPE,LLDPE) and polyethylene (mPE) with different branched structure respectively. The effects of different filler content and polyethylene branching structure on the dispersion of filler particles in the composite system were characterized by means of dynamic rheological test and SEM observation, and the melting and crystallization behaviors of different composites were studied by DSC test. The effects of different dispersion of filler on mechanical properties of materials were analyzed by mechanical properties test. The results are as follows: the results show that the addition of high content talc powder has a great influence on the dynamic rheological behavior of HDPE,LLDPE and mPE systems, and the Payne effect is obvious in the small strain region. The energy storage modulus is very sensitive to the frequency change in the low frequency region, and shows solids like behavior, which indicates that the three kinds of high filling systems have the phenomenon of mass agglomeration of talcum powder, and for the LDPE composite system with long branched chain structure, the energy storage modulus is very sensitive to the frequency change in the low frequency region. There is no Payne effect in the small strain region, and no solids like behavior in the low frequency region, while the shear thinning behavior is more obvious in the high frequency region. It is found that in the three kinds of matrix, HDPE,LLDPE and mPE, the shear thinning behavior is more obvious. For the LDPE/Talc system, the section is very smooth, there is no protruding talc particles, and there is no void between the two phases. According to the analysis of DSC data, the crystallinity and crystallization rate of the low filling system increased with the addition of talcum powder, and the crystallization rate of the composite system increased with the increase of talcum powder content in the PE/Talc composite. According to the analysis of mechanical properties, the mechanical properties of low filling composites were all improved, while in high filling systems, the mechanical properties of HDPE,LLDPE and mPE composites were greatly reduced because of the serious agglomeration behavior between talc powder. For high filled LDPE/Talc composites, the loss of mechanical properties is relatively small. This is due to the good dispersion of talc powder in LDPE matrix with long branched structure. The rheological behavior of PE- / CaCO3 composites is similar to that of PE/Talc composites. However, when the content of calcium carbonate is 30 vol%, the Payne effect and solid-like behavior of LDPE / CaCO3 system are obvious, and the mechanical properties of the composites are also greatly lost. This may be due to the higher specific surface area of calcium carbonate particles, resulting in easier aggregation between particles. The Payne effect of the filler particles without coupling agent was more obvious, and the aggregation behavior and the compatibility with the matrix were also easy to occur from the SEM micrograph.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O632.12

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