Phase Structure's Evolution And Properties Of Polypropylene/ Metallocene-Ethylene Propylene Elastomer Blends

Polypropylene/ metallocene-ethylene propylene elastomer blends were prepared in a XXS-30 mixer and scanning electron microscope (SEM), small angle laser scattering (SALS), phase contrast microscope (PCM) and Fourier transformation were employed to describe the phase evolution and morphology development during the mixing. For SEM, particle diameter was calculated and further, a graph-estimation method was introduced to confirm the distribution of particle diameter to obey a log-normal distribution and subsequently, an effective structure parameter,σ, was computed to discuss the distribution width of particle size. For laser scattering, different parameters, e.g., gyration radius, correlation distance,mean chord length,integral constant and so on, were calculated based on Debye-Bueche scattering theory. Besides, effect of mixing time, blends composition, mixing temperature and rotor speed on each structure parameter was also investigated and the correlation distance of the blends, ac2, was studied by means of a mathematic model. For PCM and SEM images in Doi space, which correspond with light scattering images, were obtained by applying Fourier transformation to PCM and SEM images and then, corresponding scattering theory was apply to these Doi images to computed mean chord length l1 and fractal dimension Dc and discuss their dependence on blend composition, mixing time, mixing temperature and rotor speed. These results showed that, the change mainly occurs in the initial stage of the mixing and levers off due to the dynamic equilibrium between the breakup and coalescence of particles. The particle size is influenced by rotor speed and mixing temperature and there exists an optimal rotor speed and mixing temperature at which the phase morphology was more fine. Results by different methods were similar, showing that these methods were all effective to study the morphology development of PP/mEPE blends during the mixing.Besides the structure and morphology of PP/mEPE blends, the thermal property, rheological and dynamic mechanical property were also studied using different scanning calorimeter, rheometer and dynamic mechanical analyzer, respectively. The results showed that, the mEPE is a semi-crystalline copolymer of propylene and ethylene, which have two crystalline temperatures: one is of PP segment and the other is of PE segment. The crystallnity of PP/mEPE decreased with the content of PP. The result of rheology property by plate-plate rotating rheometer indicated that, with Han curve,the results showed that there is crystallization phase in mEPE below 160℃. The curves with different composition in PP/mEPE blends are not entirely coincidence, which notes that the blends microstructure dependents on experimental temperature, PP/mEPE is to some extend phase separation blends. The result of DMA showed that the glass temperature of PP approaches to that of mEPE, indicating that PP/mEPE is a part-compatible blend system, so, PP/mEPE is a part-compatible and some phase separation blend system.