Study Of Crystallization, Morphology, Rheology And Mechanical Properties Of Modification Polypropylene

Polypropylene (PP) is one of the most widely used polyolefm polymers, but it's application in some fields are limited due to its low fracture toughness at low temperature and a high notchsensitivity at room temperature. Compounding PP with a dispersed elastomeric phase [e.g., ethylene-propylene rubber(EPR), ethylene-propylene-diene rubber (EPDM)] is widely practiced, because the rubber can increase the overall toughness of the PP matrix. But the addition of elastomers often takes negative effects on some properties of PP, such as stiffness and hardness. Moreover, EPR or EPDM is elastic lump, it's processing technology when blending with PP, such as extrusion, injection molding, etc., is complicated.In this study, a series of the latest new product in new materials, such as PP-R, mPE, nano-SiO2 and nano-TiO2 are applied to modify PP. For optimizing blend composition, processes and understanding properties of the processed products, the crystallizatio. morphology. rheology and mechanical properties of the blends are investigated detailed.For PP/PP-R blends, the results indicates that: PP-R has good toughening effect on PP. With the addition of 30 wt.% PP-R, the notched impact strength increased about one times, while tensile strength of PP remained basically. PP/PP-R blends are pseudoplastic fluid. Melt viscosity of the melt promptly increased with increasing of the PP-R content. For the crystallization behavior, the results show that PP and PP-R are well miscible and co-crystallizable. Values of Avrami exponent indicate the crystallization nucleation of the blends is heterogeneous, the growth of spherulites is tri-dimensional and crystallization mechanism of PP is not affected by PP-R. The addition of less PP-R phase favors to increase the overall crystallization rate of PP. The maximum enhancing effect is found to occur at a PP-R content of 20wt.%, however, the total crystallinity of the blends is decreased. The POM results guide towards the conclusion that spherulites morphology and size is greatly affected by the PP-R, and the addition of PP-R results in the promptly decreased of the spherulites size and increased structural compactness of the blends. For PP/mPE blends, the results indicates that: mPE has good toughening effect on PP. When the mass fraction of mPE in the blend is up to 25%, the blend has better tensile strength, toughness and processability. For the crystallization behavior, the results showed that PP and mPE are partial miscibility, although the extent is very small, the crystallization____crystallization mechanism of PP is not affected by mPE. The addition of less mPE phase favors to increase the overall crystallization rate of PP, however, the total crystallinity of the blends is decreased. The morphology of the blends is also studied for the purpose of investigating the effect of mPE on the microstructure of the blends. The SEM observations indicate that mPE phase uniformly dispersed in the PP matrix, and the dimension of dispersed phase increases with the blend composition. When the content of mPE is up to 20~30wt.%, the "sea-island" structure is formed, these fracture surfaces are accompanied by extensive plastic deformation. The POM results guide towards the conclusion that spherulites morphology and size are greatly affected by the mPE, and the addition of mPE results in the promptly decreased of the spherulites size.HN For the PP/nano-Si02 and PP/nano-Ti02 composite materials, the results indicate that: The addition of nano-SiO2 or nano-Ti02 can increase mechanical properties of the PP; Melt viscosity of the materials is increased with increasing of the nano-SiO2 or nano-TiO2 content; The addition of nano-SiO2 increases the crystallization temperature and crystallization rate, the total crystallinity is also increased. Ultraviolet aging on the properties of PP/nano-TiO2 composite materials are studied. The results show that the resistance aging properties of composites material is greatly improved by addition of 4wt.% nano-TiO2.