【作者】 汪玲；

【导师】 应继儒；

【作者基本信息】 湖北工业大学 ， 材料学， 2010， 硕士

【摘要】 研究注塑制品的多层结构、形成条件及其与材料性能之间的关系,对于高分子材料的设计和性能优化具有十分重要的意义。本文采用熔融共混制备了聚丙烯(PP)/乙烯-辛烯弹性体(POE)共混物,通过改变PP/POE共混体系的组分和在注塑过程中的加工参数,如保压压力、保压时间、冷却时间、注射速率和加工温度等,使熔体在不同的剪切场和温度场下冷却成型,以实现对共混物多层结构的有效控制。采用切片的方法研究共混物各层的取向、结晶以及对应的宏观力学性能,期望找出加工条件、共混物体系微结构以及性能之间的联系,实现注塑制品高性能化。多层结构形貌演变结构表明,在注射成型中各种加工条件的注塑制品表现出明显的多层结构,可以分成表皮层、过渡层、剪切层以及芯层。通过扫描电镜(SEM)表征发现表皮层不含POE粒子,芯层的POE含量最大。剪切层的分散相POE粒子取向最为强烈,而过渡层和芯层形变就小得多。还发现在平行流动方向上和垂直流动方向上,远浇口端的分散相颗粒尺寸大于近浇口端。从过渡层到芯层,我们观察到分散相尺寸的变化与加工条件密切相关,在较高的保压压力、短的冷却时间、高的注射速率、高的加工温度会导致分散相POE的颗粒尺寸减小,并且对近浇口端的影响大于远浇口端。通过X-射线衍射仪(WAXD)和差热扫描量热仪(DSC)表征得到多层结构中从表皮层到芯层,每一层的熔点都不一样,表皮层的熔点接近与纯PP,并且高于其他任何一层。由于表皮降温快,结晶度最小,而芯层的结晶度最大。此外DSC结果表明多层结构中过渡层和剪切层中含有p晶,剪切层中p晶衍射峰值特别高,而在芯层没有发现β晶的存在。力学性能研究结果表明相同加工条件下随着POE含量的增加,体系的冲击强度显著增加但是拉伸强度呈下降趋势,当POE含量超过25%时,共混体系出现脆韧转变。注射速度较低时,样品的缺口冲击强度最高；随着温度的降低,注射试样的拉伸强度呈升高趋势。本文采用切片的方法对各层动态力学性能(DMA)进行了研究,结果发现同一组分下加工温度对各层影响较大,加工温度越高,无论是表皮层还是芯层,储能模量都增加,而注射速率仅仅对表皮层的模量影响比较明显,并采用COX模型预测各层的模量与实验结果接近。更多还原

【Abstract】 Properties of multiphase polymeric materials are related to their microstructure greatly, and the formation of their microstructure depends on proeessing condition.It is very important for the structura design and modification of polymeric materials.In this dissertation, polypropylene (PP)/ethylene-octene elastomer (POE) blends were prepared in melting state, by changing the composition of PP/POE blends and different processing parameters,i.e. holding pressure、holding pressure time、cooling time、injection rate and injection temperature, to made meltting cooling molding at different shear field and temperature field,so that to control the multi-layer structure of blends effective.Using slice to research the orientation, crystallization and macroscopic mechanical properties of each layer. Expected to find out the relation of processing parameters, micro-structure of blends and performance,to achieve high performance injection molding products.The results show that, for the PP/POE blends, when the POE content of 50%, system form cocontious phase.During injection molding, PP/POE blends form the multi-layered structure under each processing parameters, i.e. skin, transition, shear and core layers.By SEM, there exist no POE phase in the skin layer, but the content of POE phase in the core layer is highest.In shear layer, POE particle orientation is strongest, and the phase size is large, thereby POE phases are elongated, broken and behave as flat ellipse ball.Moreover, both in parallel to the flow direction and the vertical flow direction, size of POE particle in G-G section is larger than N-N section. We observed the changes in dispersed phase size are closely related with the processing conditions, POE dispersed phase particle size decreases with high holding pressure,short cooling time, high injection rate, high injection tempereture,and the impact to N-N section is biger to G-G section.The results of WAXD and DSC show that, the melting point (Tm) of PP phase in injection molding product of each layer is different,in skin layer, is closed to that of pure PP, and higher than those at other layers. Due to the rapid cooling rate at skin, the melting peak of PP phase at skin layer is wide and its crystallinity is low. However, the crystallinity of PP phase at core is highest. Moreover, the results of DSC show that,there are some P crystals of PP in transition and shear layers, but noβcrystal of PP appears in core layer.The results of mechanical properties show that with increasing the POE content, the impact strength values of the PP/POE blends increase, but their tensile strength decrease. Their brittle-ductile transition (BDT) at ambient temperature appears when the POE content of more than 25%. The impact strength values is highest at low injection rate; as the temperature decreased, tensile strength of the sample is tended to increase.At the same processing temperature, the storage modulus (E’) of PP/POE blends at skin layer is higher than that at core layer. Under the same component, processing temperatures greater impact on the E’ values of each layer, with increasing the processing temperature, all E’ values at core and skin layer increase at the same time,the injection rate is only effect the E’ values of skin layer, and the modulu of layers is calculated by COX model,the ressult of predicted is close to the experimental data.更多还原