【作者】 朱琳；

【导师】 许鑫华；

【作者基本信息】 天津大学 ， 材料学， 2010， 博士

【摘要】 以聚丙烯为主的通用塑料高性能化是高分子材料科学与工程领域的研究热点和重点,聚烯烃与热塑性弹性体(如乙烯-1-辛烯共聚物等)共混是提高聚烯烃性能的一个重要途径。将等规聚丙烯(iPP)与乙烯-1-辛烯共聚物(PEOc)共混以改善聚丙烯的性能,而共混物形态是影响材料性能的关键因素之一,为获得高性能的聚丙烯共混物,必须对iPP/PEOc共混物在混合和成型过程中的形态演变规律进行研究,以达到对共混物形态的预测和控制。另外,iPP/PEOc共混体系的相结构形成与演变及其粘弹性流变性能、力学性能的研究,是高分子多尺度连贯研究的重要研究内容,为高分子多尺度连贯性理论研究提供实验依据。本论文使用密炼机在不同加工条件下制备了不同组成的iPP/PEOc共混物,利用动态小角激光背散射(SALS)在线采集与分析系统、扫描电子显微镜(SEM)、相差显微镜(PCM)以及SEM和PCM图样的傅立叶变换研究了iPP/PEOc共混体系熔体动态共混过程中相结构的形成及演变规律,以及研究了共混物熔体在密炼机内部自然降温过程中(凝固过程)和静态保温过程中的相形态变化。分析得到表征共混体系相结构的结构参数,讨论了各个结构参数随混炼时间,共混组成,混炼温度和速率,以及结构参数在密炼机内部自然降温过程中和静态保温过程中的变化规律。结果表明:共混过程中相形态变化主要发生在共混初期,后期处于颗粒破裂和聚结的动态平衡中;颗粒尺寸随着分散相含量的增加而增大;转速条件和温度条件会影响到平衡时分散相颗粒尺寸的大小,存在最佳转速和最佳温度;在密炼机内部静态保温过程中分散相的颗粒尺寸及其分布随保温时间的增加而增加,20min后基本趋于不变。研究了iPP/PEOc共混体系的粘弹流变性能及力学性能,通过结合本体系共混过程中介观及微观结构参数将共混体系的宏观性能联系起来。结果表明:iPP/PEOc共混体系在平常混炼过程中,即在190-250℃,iPP组分在10-95 wt%之间时,共混体系处于相分离状态;分散相间距τ值与材料的冲击性能存在对应关系,能很好的描述本体系的脆韧转变。随PEOc含量的增加,过渡层厚度d逐渐增大,相界面结合变好,进而材料的冲击强度增加。将上面对iPP/ PEOc共混物相形态的理论与实验结果应用于iPP合金纤维的制备,以此实验条件为基础制备了合金纤维。结果表明:iPP纤维表面光滑,对于iPP/ PEOc合金纤维,随着PEOc含量的增加,表面粗糙度明显增加,且在纤维中形成了很多PEOc的原位微纤。更多还原

【Abstract】 Performance enhancement of general-purpose plastics(mainly polypropylene) is one of the most important research focuses in the field of polymer materials science and engineering.Blending modification with thermoplastic elastomer is a major route to enhance the performance of polyolefin. Poly(ethylene- co-octene) copolymer (PEOc) was used to modify the performance of polypropylene (PP) in this thesis.The phase morphology is the most important factor to influence the properties of the blend.Therefore,the morphology development of PP/PEOc blends during the mixing and molding was investigated in this thesis. In addition, the phase morphology development, viscoelastic rheological and mechanical properties of the blends of iPP/PEOc as an important research issue of polymer multi-scale constituency research was studied.PEOc at various concentrations was mixed into iPP by an internal mixer (XXS-30) under different mixing conditions, and the formation and evolution of phase structure during molten and mixing process were studied using back small angle laser scattering (SALS), scanning electron microscope (SEM), phase contrast microscope (PCM) and the 2D Fourier transformation of SEM and PCM patterns. The phase morphology variants during solidification process under the natural cooling condition and during heat preservation under quiescent condition in internal mixer were also studied. The structure parameters were analyzed and calculated to characterize the phase structure. Besides, the influence of mixing time, blends composition, mixing temperature and rotor speed on each structure parameter and their variants during solidification process under the natural cooling condition and during heat preservation under quiescent condition in internal mixer were also investigated. The results showed that the variants of phase morphology mainly occurred in the initial stage of the mixing and levered off due to the dynamic equilibrium between the breakup and coalescence of particles. The particle size increased as the concentrations of dispersed phase increased. The particle size was influenced by rotor speed and mixing temperature and there existed an optimal rotor speed and mixing temperature at which the phase morphology was more fine. In addition, the visoelastic rheological and mechanical properties of iPP/PEOc blends were investigated, and the macroscopic properties were connected with meso- and microscopic structure parameters. The results showed that the blends with 10-95wt-% iPP exhibited phase-separated morphology at 190-250℃. We established a correlation between inter-dispersed phase distance and the brittle-tough transition for elastomer toughened polypropylene. The transition layer thickness d increased as the concentrations of dispersed phase increased, then the toughness of iPP/PEOc blends increased.Then, the alloy fibers were prepared by capillary rheometer. The results showed that the surface of iPP fiber was smooth. The surface roughness of the alloy fibers increased as the concentration of PEOc increased, and formed in-situ short fibers更多还原