Study On Relationship Of Morphology And Dynamic Rheological Behavior For Multiphase Polypropylene System

The morphology of multiphase/multicomponent polymers not only has a pronounced influence on its rheological behavior, but also determinates its application properties to a great extent. The rheological properties of these systems are related to the phase morphology and interaction of the components, and can reflect sensitively the change of morphology. In this thesis, the relationship of morphology and rheological behavior for polypropylene (PP) systems including ethylene-propylene-diene terpolymer rubber (EPDM), ethylene-vinyl acetate copolymer (EVA) and ultra-fine full-vulcanized powdered rubber (UFPR) were studied.1. The existence of oxygen was unavoidable during the dynamic Theological tests performed at the molten state of polymer materials. The change of polymer structure due to oxidation would result in misunderstanding the nature of viscoelastic properties for these systems. The thermo-oxidation of virgin polymers was investigated by means of dynamic Theological tests. The results revealed that dynamic Theological functions such as dynamic storage modulus ( G'), dynamic loss modulus ( G" ) and dynamic loss tangent ( tanδ ) at low frequency ( ω ) region could sensitively reflect the change of structure of EPDM. On the basis of the difference of dynamic Theological properties between virgin and antioxidant-added EPDM, the rheological characteristic of EPDM subject to annealing was attributed to the formation of physical network induced by the thermo-oxidation of EPDM at molten state. The addition of antioxidant could inhibit the oxidation of virgin polymers in the period of test.2. The morphology of the four type of PP/EPDM, PP/EVA blends in whole composition were investigated by scanning electron microscopy ( SEM ) and solvent extraction. The morphology such as droplet and co-continuous structure were observed and phase inversion occurred with changing of blend composition. It is concluded that the blend composition determines the main phase morphology of blends under the same processing conditions. A dispersed morphology is formed when the blend composition is highly asymmetric and a co-continuous morphology is formed when the blend composition is symmetric or close to symmetric.3. The study on the dynamic rheological behavior at molten state for PP/EPDM, PP/EVA blends was conducted on an advanced rheometric expansion system (ARES). The rheological properties were correlated to blend morphology by using theoretical model. The effect of composition on the mechanical properties was also investigated. From the point of the rheology view, the blends studied in this thesis could be classified as two types. One consisted of solid particles suspended in a continuous phase (PP/EPDM 1 blend), similar to the suspension. The other is emulsion consisting of two immiscible polymer melts (PP/EPDM2, PP/EVA 1 and PP/EVA2 blends). For the former, the linear mixing rule for immiscible polymer blends cannot completely predict the rheological behavior even though the dynamic modulus of the blend lies between those of the components. This is one of the rheological characteristic of the particles filled polymer at the melts. Both Palierne's model and suspension model fail to describe the behavior of the blends with higher EPDM1 content in the low to region. For the later, the enhancement of the elasticity at low G is related to the dispersed particle's deformability and the Cole-Cole curve is more sensitive to capture the structure information. It is found both Palierne's model and modified C-S model could be applied to predict the linear viscoelastic behavior of PP/EPDM2, PP/EVA 1 and PP/EVA2 blends and the interfacial tension values could be obtained from these predictions. The relationship between, the ratio of dispersed phase and matrix, K, and the contribution of the interface relaxation to elasticity, AG', exhibits exponential decrease.4. A detailed rheological analysis and morphology characterization were performed for y-ray-irradiated blends of PP with EPDM. It is found that irradiation resulted in properties change of compo...