【作者】 于秀艳；

【导师】 许鑫华；

【作者基本信息】 天津大学 ， 材料学， 2005， 硕士

【摘要】 通过实验测试和计算机模拟两方面对PP/POE共混体系的相结构及其演化规律进行了研究。在哈克流变仪的双螺杆挤出机上在3个取样点在线取样,通过扫描电镜对不同共混组成、剪切速率的相形态及其演变过程进行研究,并计算出分散相平均粒径及其分布。定义相应的标度函数,研究了不同加工条件下的分散相演变的自相似性,在无标度区域采用分形维数来表征分散相的分散程度。由于相差显微镜图像的傅立叶变换谱图与光散射图像有很好的对应关系,引入光散射的相结构参数Q、L₁、a_c　,表征不同共混条件下体系的相形态。采用小角X光散射研究不同共混组成下,体系的相界面情况和分散相形态。结果表明:随POE含量的增加,分散相POE颗粒的体积和数量都有所增加,分散相颗粒呈类似球状或椭球状分布在PP连续相中,相分散过程包括分散相颗粒的破碎和小颗粒碰撞归并两个动态过程。当剪切速率较小时,分散过程中以分散相颗粒的破碎为主,剪切速率较大时,分散初期很短的时间里,分散相在高剪切作用下,迅速破碎成较小颗粒,以后的阶段小颗粒高速运动碰撞归并成较大颗粒,直到平衡。采用介观动力学方法对PP/POE共混体系的相容性进行研究。采用珠子代替一个重复单元或分子片段,用由珠子组成的高斯链代替真实分子链,真实分子链的特性反映在珠子的性质上,例如:珠子的溶解度参数,珠子体积和自扩散系数等。模拟得到等密度图、自由能密度和有序度参数来表征共混体系的相容性。结果表明:体系在453K时,POE含量为10%和90%时为部分相容,其余组成为相分离。在温度升高的过程中,体系有相分离过渡到部分相容。更多还原

【Abstract】 Blending process of Polypropylene/Poly (ethylene-1-octene)was studied by both experiments and computer simulation. The formation and evolution on phase behavior and morphology of PP/POE blends was discussed in this paper.The morphology of blends was observed by Scanning Electron Microscopy (SEM) and size distribution of dispersed phase was calculated. A scale function was defined to investigate the dynamical self-similarity patterns. And the fractal dimensions D, which characterize the phase dispersion degree, were deduced. Because the power spectrum of 2DFT of an phase contrast image is equivalent to the scattering intensity, Some character parameters of SALS (Integral invariant,Q; Average chord length,L 1 ; Correlation distance a c ) were used to discussed the mechanism of the phase dispersed dynamics.The results demonstrate that dispersed phase dispersed in PP phase like sphere, and both the dispersed diameter and the quantity of sphere were increase with the increasing POE quality fraction. The mixing process of PP/POE blends can be divided into two processes: dispersed phase breaks up into smaller pellets and coalescence of dispersed phase. The conclusion about the mixing process was basically consistent with the analysis result by the SEM and PCM Fourier transition. The SEM result also show that evolvement process of the phase region size has the self-similarity and the fractal dimension D can be a good means to study the evolution law of phase dispersion dynamics.The phase separation of the PP/ POE blend system in mesoscopic region is simulated using MesoDyn. The thermodynamic forces are obtained by a mean-field density functional method, using a Gaussian chain as a molecular model. The results demonstrate that phase separation of the system did not take place in these systems which the weight fraction of POE are 10% and 90%, but the systems which quality fraction of POE are 20%~80% occur typical phase separation更多还原