【作者】 江霄汉；

【导师】 肖茹；

【作者基本信息】 东华大学 ， 材料物理与化学， 2011， 硕士

【摘要】 多组分聚合物的性能不仅取决于化学结构,而且在很大程度上取决于材料的形态结构。而多组分聚合物形态结构及其形成机理取决于组分比、界面张力、粘弹特性、加工条件等因素。因此,研究多相多组分聚合物形态及其演化具有理论与实际价值。本文运用扫描电子显微镜(SEM)、小角X射线散射仪(SAXS)等手段,对等规聚丙烯／醋酸丁酸纤维素酯(iPP/CAB)体系形态结构及其分散相演化机理进行研究,建立了iPP分散相形态结构演化的模型；同时分析了材料粘度特性、温度场、加工设备、组分比等因素对iPP/CAB体系形态结构的影响。通过在双螺杆挤出机螺杆不同位置取样淬冷的方式观察分散相形态演化的过程,发现了两种形态演化方式。一种是长条拉伸型,即分散相液滴在共混熔融软化阶段被拉伸成细长的长条状结构,然后由于界面扰动长条状结构破裂成一系列微小颗粒,最后这些微小颗粒在挤出口附近发生凝聚并且形成了纤维。另一种是层状铺展型,即分散相液滴在共混熔融软化阶段铺展成了层状结构,之后层状结构逐渐变薄,其表面生成了大量孔洞,孔洞大到一定程度后层状结构破裂,形成大量的球状、椭球状微小颗粒和带状结构,最终在剪切流场的作用下分散相形成了纤维状结构。根据剪切场中分散相液滴形变破裂理论,对共混熔融软化阶段分散相液滴的两种形变方式进行分析,并计算了长条状结构的扰动破裂时间和椭球状结构的回缩时间。研究发现,分散相尺寸变化主要集中在共混熔融软化阶段,长条状分散相结构形成之后在很短时间内即破裂成为椭球状、哑铃状等结构,椭球状结构回缩成球状结构的时间也非常短。最后结合实验现象以及理论分析绘制了熔融共混过程中分散相形态结构演化示意图。研究了粘度比、加工设备、温度场和组分比对iPP/CAB体系形态结构的影响。不同粘度比条件下分散相形态演化方式不同：粘度比较大的体系为长条拉伸型,所制备分散相尺寸较大、尺寸分布较宽；粘度比较小的体系为层状铺展型,所制备分散相尺寸较小、尺寸分布较窄。加工设备的混合能力对分散相的形态尺寸有重要影响：双螺杆挤出机和微型共混挤出机对物料的剪切作用充分,所制备分散相尺寸较小,单螺杆挤出机对物料剪切作用不够充分,所制备分散相尺寸较大。在不同温度场,分散相形态尺寸不同：共混样品放置于150℃硅油时,随时间增加分散相尺寸增大,两相间距变大；而共混样品放置于140℃烘箱时,随时间增加分散相尺寸缓慢增大,两相间距基本不变。最后利用SAXS研究了组分比对共混体系形态结构的影响,发现随分散相组分比增加,其相关距离和平均弦长均不断变大,这表明分散相尺寸随组分比增大而增大。更多还原

【Abstract】 The properties of multicomponent polymers not only depend on the chemical structure but also the morphology of system. While, the morphology of multicomponent system can be affected by the blend ratio, interface tension, viscoelasticity ratio, processing parameters and so on. So it is valuable both in theory and practical to study the phase evolution mechanisation of the multicomponent polymers.In this paper, the process of phase evolution of isotactic polypropylene/cellulose acetate butyrate (iPP/CAB) system was analyzed by scanning electron microscopy (SEM) and small angle X-ray scattering(SAXS), then the theory model of which was simulated. What is more, the influence of the material viscoelasticity, the temperature field, blending machine and the blend ratio on the phase development was also discussed.To study the process of phase evolution of iPP/CAB system, the samples were taken out at different positions of the twin-screw extruder. Two kinds of morphology evolution mechanization were found. (1) The separated phase droplet is drawn into cylinder at the initial stage of compounding, then the cylinder breaks into small particles, at last the small particles change into long fibers. (2) The separated phase is stretched into a sheet at the initial stage of compounding, then the sheet would break up into small particles, at last the small particles change into long fibers. According to the theory of droplet deformation and breakup, the process of phase development was analyzed. The time of the separated phase evolution was calculated, and the process of ellipsoid separated phase changes into sphere was also simulated. It was found that the separated phase’s morphology and size changes greatly at the initial stage of compounding. At last, the sketch map of the separated phase morphology evolution was given.The influence of the viscoelasticity ratio, temperature field, blending machine and blend ratio on the phase development was also studied. It was found that the process of phase development was not the same for systems different in viscoelasticity ratio:for the systems with larger viscoelasticity ratio, the separated phase droplets would change into long strips at the initial stage, and the final size of separated phase is large; for the systems with small viscoelasticity ratio, the separated phase droplets would change into thin sheets at the initial stage, and the final size of separated phase is small. The blending machines have significant effects on the separated phase size:the size of separated phase made by twin screw extruder is smaller than that made by a single screw extruder and a mini extruder. The separated phase would form different morphology and have different size distribution at different temperature field:when the blends specimen was placed in a silicone oil both at 150℃, the size of separated phase would increase greatly and the distance between two phases become larger; when the blends specimen was placed in the air oven at 140℃, the size of separated phase would increase slowly and the distance between two phases would not change. At last, the influence of blend ratio on the phase morphology and size was studied by SAXS. It was found that the correlation distance and average chord lengths of separated phase would increase with the increasing of blend ratio, which means the size of separated phase would increase with the increasing of blend ratio.更多还原