The Study Of Phase Morphology Evolution And Properties In Polypropylene/ethylene 1-octene Copolymer Blends During Molten Mixing Process

Performance enhancement of general-purpose plastics(mainly polypropylene) is one of the most important research focuses in the field of polymer materials science and engineering.Blending modification with thermoplastic elastomer is a major route to enhance the performance of polyolefin. Poly(ethylene- co-octene) copolymer (PEOc) was used to modify the performance of polypropylene (PP) in this thesis.The phase morphology is the most important factor to influence the properties of the blend.Therefore,the morphology development of PP/PEOc blends during the mixing and molding was investigated in this thesis. In addition, the phase morphology development, viscoelastic rheological and mechanical properties of the blends of iPP/PEOc as an important research issue of polymer multi-scale constituency research was studied.PEOc at various concentrations was mixed into iPP by an internal mixer (XXS-30) under different mixing conditions, and the formation and evolution of phase structure during molten and mixing process were studied using back small angle laser scattering (SALS), scanning electron microscope (SEM), phase contrast microscope (PCM) and the 2D Fourier transformation of SEM and PCM patterns. The phase morphology variants during solidification process under the natural cooling condition and during heat preservation under quiescent condition in internal mixer were also studied. The structure parameters were analyzed and calculated to characterize the phase structure. Besides, the influence of mixing time, blends composition, mixing temperature and rotor speed on each structure parameter and their variants during solidification process under the natural cooling condition and during heat preservation under quiescent condition in internal mixer were also investigated. The results showed that the variants of phase morphology mainly occurred in the initial stage of the mixing and levered off due to the dynamic equilibrium between the breakup and coalescence of particles. The particle size increased as the concentrations of dispersed phase increased. The particle size was influenced by rotor speed and mixing temperature and there existed an optimal rotor speed and mixing temperature at which the phase morphology was more fine. In addition, the visoelastic rheological and mechanical properties of iPP/PEOc blends were investigated, and the macroscopic properties were connected with meso- and microscopic structure parameters. The results showed that the blends with 10-95wt-% iPP exhibited phase-separated morphology at 190-250℃. We established a correlation between inter-dispersed phase distance and the brittle-tough transition for elastomer toughened polypropylene. The transition layer thickness d increased as the concentrations of dispersed phase increased, then the toughness of iPP/PEOc blends increased.Then, the alloy fibers were prepared by capillary rheometer. The results showed that the surface of iPP fiber was smooth. The surface roughness of the alloy fibers increased as the concentration of PEOc increased, and formed in-situ short fibers...