A Study On The Phase Morphology And Properties Of Polypropylene/Poly (Ethylene-1-octene) During Blending

Blending of Polypropylene/Poly(ethylene-1-octene) was studied. The formation and evolution on phase behavior and morphology of PP/POE blends during melton and mixing was discussed in this paper. The morphology of alloy was observed by Scanning Electron Microscopy (SEM) and size distribution of dispersed phase was calculated. A scale function was defined to investigate the dynamical self-similarity patterns during molten and mixing. And the fractal dimensions D, which characterize the phase dispersion degree, were deduced. Small-Angle Laser Scattering (SALS) method was used in on-line study during blending for structure analysis. Some character parameters of SALS (Integral invariant,Q ; Average chord length,L₁ ; Correlation distanceL₂ ; dispersed layer thickness,a_c ) were used to discussed the mechanism of the phase dispersed dynamics. The phase structure of blends has fractal characteristic, and also, the fractal theory can be used to discuss the mixing process. The fractal dimension D was introduced to describe the mixing process of polymer blends. Mechanical properties of PP/POE blends were tested with different mixing condition. The mechanism of POE toughened PP was renewedly explained. A new parameter obtained by SALS was introduced to estimate the brittle-tough transition. The phase contrast microscopy (PCM) patterns in real space were transformed into patterns in wave-number space by Fourier transformation. The evolution law of patterns during melt mixing or with composition fraction changing were discussed by Fourier analysis parameter, such as h^-1_m,ac2 and so on, when the mixing condition (mixing temperature, shear rate) were changed. The fractal dimension was characterized the phase dispersion degree. The results demonstrate that the mixing process of PP/POE blends can be divided into three regions according to their dynamic mechanism. The dispersed phase evolves with different dynamic self-similarity in the first region and the end region respectively. In the first region, the dispersed phase breaks up into smaller pellets. The average dispersed diameter in the end region almost doesn't change with the increase of mixing time, demonstrating the balance between the break-up and coalescence of dispersed phase. The second region is the transition region of the first and the end region. The conclusion about the mixing process of PP/POE blends can be divided into â…¢ regions was basically consistent with the analysis result by the SEM and PCM Fourier transition. The result also show that evolvement process of the phase region size has the self-similarity and the fractal dimension can be a good means to study the evolution law of phase dispersion dynamics. DpAs the concentration of POE was increased further to 20 wt% and more, the dispersed phase had transformed from a spherical like domain to a more elongated feature, and co-continuous phase morphology was more and more evident. The optimum percentage elongation at break and improved impact properties obtained for the blends having an POE concentration of 20 wt% or greater may arise as a consequence of the elongated (co-continues) phase morphology of the elastomeric POE being well dispersed in the PP matrix. Moreover, we established a correlation between inter-dispersed phase distance and the brittle-tough transition for elastomer toughened polypropylene. There is a critical value Ï„ c, Ï„ c≈0.43 μm . When Ï„ is smaller than Ï„ c, the blend will be tough; when greater, it will be brittle. The transition layer thickness can describe the compatibility of the system and has a correlation with the mechanical properties of blends. d...