【作者】 陈绪煌；

【导师】 盛京；

【作者基本信息】 天津大学 ， 材料学， 2007， 博士

【摘要】 采用密炼机制备了不同组成的聚丙烯/茂金属催化乙烯-丙烯共聚物(PP/mEPE)共混体系,用扫描电子显微镜(SEM)、小角激光散射(SALS)、相差显微镜(PCM)及SEM傅立叶变换研究共混体系共混过程中的相结构的形成及演变规律。运用粒径理论讨论了该共混体系扫描电子显微镜图样,采用对数正态分布的图估计理论证明分散相粒径的分布符合正态分布,进而求取了用以表征尺寸分布宽度的参数σ。根据Debye-Bueche光散射理论,利用光散射图像处理软件,得出表征合金体系相结构的结构参数:旋转半径Rg、分散相相关距离ac 2、平均弦长l、积分不变量Q、光强平面积分Js、分散相比表面积Ssp和不均匀性距离lc等。分析讨论了各个结构参数随混炼时间,共混组成,混炼温度,混炼的剪切速率的变化规律;并对体系的相关距离ac进行了模拟。采用傅立叶变换技术将空域范围内的相差显微镜及扫描电子显微镜图样转化到视频域内的傅立叶变化图样;并根据光散射理论分析了共混体系的平均弦长l1及分形维数Dc与共混物组成、共混时间、混炼温度、混炼的剪切速率的关系。结果表明,共混过程中相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;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;颗粒尺寸随着分散相含量的增加而增大。四种方法的研究结果是一致的,说明这四种方法均可以用来研究PP/mEPE共混体系的相结构的形成及演变规律。在研究了PP/mEPE共混体系的结构与形态的基础上,研究了体系的基本性能。用差示扫描量热仪(DSC)研究了mEPE与PP/mEPE的结晶性能。茂金属乙烯-丙烯共聚物是聚丙烯和乙烯的半结晶聚合物,具有等规立构化特性。具有两个结晶温度,其一为PP嵌段的结晶,另一为PE段的结晶。PP/mEPE共混体系中PP的结晶度随PP含量的增大而降低。用平板式旋转流变仪研究了mEPE与PP/mEPE的流变特性。用Han曲线研究表明,温度低于160℃,mEPE出现结晶相。PP/mEPE体系中,随着mEPE含量的增高,在不同温度下测得的曲线没有完全重合,表明共混体系的微结构在一定程度上依赖于实验测量的温度,共混体系出现部分相分离。用动态热机械分析仪(DMA)研究了PP/mEPE共混体系的动态力学性能。研究结果表明:PP与mEPE的Tg内移,说明PP与mEPE具有一定的相容性。总之,PP/mEPE共混体系是具有一定相容性的微相分离体系。更多还原

【Abstract】 Polypropylene/ metallocene-ethylene propylene elastomer blends were prepared in a XXS-30 mixer and scanning electron microscope (SEM), small angle laser scattering (SALS), phase contrast microscope (PCM) and Fourier transformation were employed to describe the phase evolution and morphology development during the mixing. For SEM, particle diameter was calculated and further, a graph-estimation method was introduced to confirm the distribution of particle diameter to obey a log-normal distribution and subsequently, an effective structure parameter,σ, was computed to discuss the distribution width of particle size. For laser scattering, different parameters, e.g., gyration radius, correlation distance,mean chord length,integral constant and so on, were calculated based on Debye-Bueche scattering theory. Besides, effect of mixing time, blends composition, mixing temperature and rotor speed on each structure parameter was also investigated and the correlation distance of the blends, ac2, was studied by means of a mathematic model. For PCM and SEM images in Doi space, which correspond with light scattering images, were obtained by applying Fourier transformation to PCM and SEM images and then, corresponding scattering theory was apply to these Doi images to computed mean chord length l1 and fractal dimension Dc and discuss their dependence on blend composition, mixing time, mixing temperature and rotor speed. These results showed that, the change mainly occurs in the initial stage of the mixing and levers off due to the dynamic equilibrium between the breakup and coalescence of particles. The particle size is influenced by rotor speed and mixing temperature and there exists an optimal rotor speed and mixing temperature at which the phase morphology was more fine. Results by different methods were similar, showing that these methods were all effective to study the morphology development of PP/mEPE blends during the mixing.Besides the structure and morphology of PP/mEPE blends, the thermal property, rheological and dynamic mechanical property were also studied using different scanning calorimeter, rheometer and dynamic mechanical analyzer, respectively. The results showed that, the mEPE is a semi-crystalline copolymer of propylene and ethylene, which have two crystalline temperatures: one is of PP segment and the other is of PE segment. The crystallnity of PP/mEPE decreased with the content of PP. The result of rheology property by plate-plate rotating rheometer indicated that, with Han curve,the results showed that there is crystallization phase in mEPE below 160℃. The curves with different composition in PP/mEPE blends are not entirely coincidence, which notes that the blends microstructure dependents on experimental temperature, PP/mEPE is to some extend phase separation blends. The result of DMA showed that the glass temperature of PP approaches to that of mEPE, indicating that PP/mEPE is a part-compatible blend system, so, PP/mEPE is a part-compatible and some phase separation blend system.更多还原