超声作用对聚丙烯及其复合材料结构与性能影响的研究

发布时间：2018-06-29 14:27

本文选题：超声作用 + PP降解　；参考：《华东理工大学》2016年博士论文

【摘要】：聚合物共混改性是聚合物高性能化的主要途径之一,而熔融共混作为一种简单易行的共混改性方法,得到了广泛的应用。如何通过熔融共混强化改性剂在聚合物基体中的分散,提高基体树脂的性能是目前共混改性领域关注的重点和热点之一。作者通过在熔融共混中引入超声作用,借助于超声分散作用,改善了助剂在聚合物基体中的分散效果,达到提高共混物性能的目的。作者采用自制的超声实验装置,对超声作用下聚丙烯(PP)的降解行为及其结晶性能进行了研究。通过对特性黏度与分子量及其分布的测试,建立了超声降解动力学模型,研究了超声频率、功率、作用时间、作用距离及熔体温度对PP降解的影响,并提出了超声降解的机理。借助于广角X射线衍射(XRD)、示差扫描量热分析(DSC)及偏光显微镜等手段,对超声作用下PP结晶行为进行了深入的研究,揭示了超声作用对PP结晶行为的影响规律。通过对样品流变性能和力学性能的表征,研究了超声作用对PP流变特性和机械性能的影响。作者针对超声作用下氢化苯乙烯-丁二烯-苯乙烯嵌段共聚物(SEBS)在PP中的分散行为开展了研究。通过扫描电镜分析(SEM)和理论推导,建立了超声分散破碎动力学模型,并研究了影响分散相粒子超声破碎的因素。借助于红外光谱分析(IR)和动态力学分析(DMA),对超声作用下PP与SEBS原位增容效应进行了研究。通过对样品流变性能和力学性能的表征,研究了超声作用对PP/SEBS共混物流变特性和机械性能的影响。作者采用超声辅助双转子连续混炼的方法,制备PP/SEBS/有机蒙脱土(OMMT)三元纳米复合材料。通过小角XRD、透射电镜分析(TEM)和SEM等表征方法,研究了超声作用和相容剂马来酸酐接枝聚丙烯(PP-g-A)对复合材料微观分散形态的影响。借助于广角XRD分析,研究了超声混炼作用下复合材料的结晶性能。通过对样品流变性能和力学性能的表征,研究了超声作用和PP-g-MA对复合材料流变特性和机械性能的影响。研究工作得出以下几点创新性结论：(1)在超声样品中观察到空化泡,并提出空化作用是造成超声作用下PP降解的主要原因之一。空化作用越强,PP的降解程度越高。随着超声功率和超声作用时间的增加,超声空化作用增强,PP的降解程度增大。但是,随着超声功率和作用时间的进一步增加,PP的降解程度减小,其分子量和特性黏度最终趋于一个极限值。此外,在20KHz(低频率)的超声作用下,PP熔体中的空化效应最明显,在此频率下的降解行为也最显著。(2)适当强度的超声作用可诱导β晶型PP的形成,但超声强度过高会导致PP的大幅降解而不利于β-PP的结晶。(3)建立了聚合物两相共混物中分散相颗粒的超声破碎动力学模型及破碎速率动力学模型提出增大超声功率、降低超声频率和降低熔体温度均可提高分散相颗粒的破碎程度,并且距离超声源较近处,分散相颗粒的破碎程度较高。(4)在超声作用下PP与SEBS会发生共聚反应而使其相容性得到提高,适当提高超声强度会促进反应过程的进行,但是过高的超声强度会因为聚合物的大幅降解而不利于增容过程。(5)首次采用超声辅助双转子连续混炼方法制备PP/SEBS/OMMT (95/15/5)三元纳米复合材料。经历超声辅助共混的复合材料的冲击强度较纯PP提高了80.9%,较未经超声辅助混炼的复合材料提高了7.9%,达到49.2J/m；添加15ph的PP-g-MA并经历超声辅助共混的复合材料的拉伸模量较纯PP提高了24.8%,较未经超声辅助混炼的复合材料提高了84.8%,达到913.6MPa。
[Abstract]:Polymer blending modification is one of the main ways of high performance of polymer, and melt blending, as a simple and easy method of blending modification, has been widely used. How to strengthen the dispersion of the modifier in the polymer matrix by melt blending and improve the properties of the matrix resin is the focus and heat in the field of blending modification at present. One of the points. Through the introduction of ultrasound in melt blending, the author improves the dispersing effect of the additives in the polymer matrix by ultrasonic dispersion and improves the properties of the blends. The author studied the degradation behavior and crystallization properties of polypropylene (PP) under ultrasonic action by using the self-made ultrasonic apparatus. After testing the viscosity and molecular weight and its distribution, a kinetic model of ultrasonic degradation was established. The effects of ultrasonic frequency, power, action time, action distance and melt temperature on the degradation of PP were studied, and the mechanism of ultrasonic degradation was put forward. By means of wide angle X ray diffraction (XRD), differential scanning calorimetry (DSC) and polarizing microscope, etc. The crystallization behavior of PP under ultrasonic action was deeply studied. The influence of ultrasonic action on the crystallization behavior of PP was revealed. The effects of ultrasonic action on the rheological properties and mechanical properties of PP were investigated by the characterization of the rheological and mechanical properties of the samples. The dispersion behavior of the segment copolymer (SEBS) in PP was studied. By scanning electron microscopy (SEM) and theoretical deduction, the ultrasonic dispersion fragmentation kinetic model was established and the factors affecting the ultrasonic fragmentation of the dispersed phase particles were studied. With the aid of infrared spectroscopy (IR) and dynamic mechanical analysis (DMA), the in situ Compatibilization of PP and SEBS under ultrasonic action was carried out. Effects were studied. Through the characterization of the rheological and mechanical properties of the samples, the effects of ultrasound on the rheological properties and mechanical properties of PP/SEBS blends were studied. The author uses the ultrasonic assisted double rotor continuous mixing method to prepare the PP/SEBS/ organic montmorillonite (OMMT) three element nanocomposite. Through the small angle XRD, transmission electron microscope The influence of ultrasonic action and compatibilizer maleic anhydride grafted polypropylene (PP-g-A) on the microdispersion of the composites was studied by means of (TEM) and SEM characterization methods. The crystallization properties of the composites were studied with the aid of wide angle XRD analysis. The ultrasonic effect was studied by the characterization of the rheological and mechanical properties of the samples. The effects of PP-g-MA on the rheological properties and mechanical properties of the composites are obtained. The following innovative conclusions are obtained: (1) the cavitation bubbles are observed in the ultrasonic samples, and the cavitation effect is one of the main reasons for the degradation of PP under ultrasonic action. The stronger the cavitation effect, the higher the degradation degree of PP. With the increase of time, the effect of ultrasonic cavitation increased and the degree of degradation of PP increased. However, with the further increase of the ultrasonic power and time, the degradation degree of PP decreased, and the molecular weight and characteristic viscosity eventually tended to a limit value. In addition, the cavitation effect in the PP melt was the most obvious under the 20KHz (low frequency) supersonic effect, and the frequency of this frequency was the most obvious. The degradation behavior is also the most significant. (2) the proper intensity of ultrasound can induce the formation of beta crystalline PP, but the high ultrasonic intensity will lead to the degradation of PP and the crystallization of beta -PP. (3) the ultrasonic fragmentation kinetics model of dispersed phase particles in the polymer blends and the kinetic model of breaking rate have been established to increase the ultrasonic power. The fragmentation degree of dispersed phase particles can be increased by reducing the ultrasonic frequency and reducing the melt temperature, and the fragmentation degree of the dispersed phase particles is higher than the ultrasonic source. (4) the compatibility of PP and SEBS will be enhanced under ultrasonic action, and the proper enhancement of ultrasonic intensity will promote the process of reaction. The high ultrasonic intensity will not benefit the compatibilization process because of the large degradation of the polymer. (5) the ultrasonic assisted double rotor continuous mixing method is used for the first time to prepare PP/SEBS/OMMT (95/15/5) three element nanocomposites. The impact strength of the composite with ultrasonic assisted blending is 80.9% higher than that of the pure PP. The material increased by 7.9% to 49.2J/m, and the tensile modulus of the composite added with 15ph PP-g-MA and through the ultrasonic assisted blending was 24.8% higher than that of pure PP, and the composite improved by 84.8% to 913.6MPa. without the ultrasonic assisted mixing.
【学位授予单位】：华东理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TQ325.14;TB33

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