Research Of The Multi-level Morphology Evolution And Properties Of PP/POE Blends Injection Molding Product

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.