拉伸场下粒子/多相聚合物复合体系的结构形成机理及流变行为的研究

The introduction of inorganic nanoparticles into polymer blends is a low-cost way to produce multiphase materials with high performance and multiple functionalization. The key problem in this area is to reveal the critical role of nanoparticles in the morphology formation and final properties of polymer blends subjected to complex processing flow. However, most of the present research focuses on the morphology evolution and rheology of polymer blends in simple shear flow. The purpose of this research aims to visually probe the effects of nanoparticles on the dynamics of morphology evolution in polymer blends in elongational flow, such as phase deformation, orientation, relaxation, coalescence and breakup, through the combination of hot stretching stage and the on-line techniques (small angle light scattering and microscopy). Additionally, by the combination of extensional rheology, transmission electron microscopy and scanning electron microscopy, how the changes of the interfacial properties and component viscoelasticity induced by the differences in the surface chemistry, size and concentration of nanoparticles affects the morphology evolution and elongational rheology properties of blends will be systematically investigated. Finally, the results observed by the direct morphological evolution will be characteristically related with the elongational rheological response. The implementation of this project will provide new insights to comprehensively and thoroughly understand the role of nanoparticles in the morphology formation mechanism in the melt processing and final properties of polymer blends, especially in the processing methods based on the extensional flow.

聚合物共混物与无机纳米粒子的复合能以较低的成本实现材料的高性能化与功能化，该领域的核心问题在于揭示纳米粒子对多相体系在加工流场下结构形成机理及最终性能的影响规律。针对已有研究大多局限于剪切流场的现状，本项目拟将拉伸热台与小角激光光散射、光学显微技术等在线可视化手段相结合，揭示纳米粒子对共混物在拉伸场下的结构变形、取向、松弛、凝聚和破碎等微观动力学的影响。将拉伸流变技术与TEM、SEM等离线表征方法相结合，探讨纳米粒子的表面性质、尺寸及含量等因素对体系界面性质、组分拉伸流变性质等参数的改变对拉伸形态演变的作用机理，力求建立体系实时结构演变与拉伸流变行为的特征关联。本项目的顺利开展可为更加全面、深入地理解纳米粒子对多相聚合物体系在熔体成型（尤其是以拉伸流动为主的加工方法）中的结构-性能调控机制提供重要的理论指导。

采用纳米粒子填充不相容聚合物共混物是实现材料高性能化和功能化的经济有效的途径之一，其在加工流场中形成的微观形态结构是决定材料最终性能的关键因素。目前已有的研究绝大多数集中在剪切流场下相形态结构调控的研究，本项目揭示了拉伸流场下纳米粒子对共混物复合体系形态结构演化规律及其拉伸流变行为的影响。通过纳米粒子填充不相容共混物模型体系的构建，系统的研究了不同表面性质（亲水性、疏水性以及疏水程度等）和形状特性（球状、棒状等）的纳米粒子在PP/PS、PA6/PS等不相容共混物组分和界面处的选择性分布等对剪切和拉伸流场下形态结构变形、取向、凝聚等演变过程及其流变响应的影响。发现了剪切流场下纳米粒子的表面性质、纳米粒子填充量与共混物中分散相的含量的比值是影响共混物形态结构演变的关键因素。而在拉伸流场下，分布在界面处的疏水纳米粒子能够有效地促进不相容共混物中分散相产生变形。进一步，发现疏水程度较高的纳米粒子在较低含量时能使不相容共混物的形态结构产生显著变形，但是在较高含量下却抑制了其变形。而疏水程度较低的纳米粒子促进不相容共混物变形的能力随着填充含量的增加而增大。此外，我们还发现纳米粒子填充体系的拉伸流变行为还与纳米粒子的形状特性有关。与球形的纳米粒子填充体系在拉伸时呈现拉伸变稀现象不同的是，棒状的碳纳米管可使共混体系在拉伸时产生拉伸硬化现象。本项目从微观角度对含纳米粒子的多组分共混复合物加工成型中的形态结构演化规律及其拉伸流变响应进行了基础研究，所得结论及认识对深入理解共混体系在熔融加工成型（尤其是以拉伸流动为主的加工方法）中的结构调控提供理论指导和实验依据。本项目共发表SCI论文8篇、申请专利1项（授权），培养研究生4人。