Yun‐yan Li

Study on Phase Morphology of PP/PS Blends by Phase Contrast Micrographs

The relation of the phase morphology of polypropylene/polystyrene (PP/PS) blends and their composition and mixing temperature was investigated using digital image analysis. The characteristic length L and the mean square radius of gyration were defined to discuss the phase morphology of the immiscible system. A fractal dimension, D f , was introduced to describe the distribution of sizes of domains of the dispersed phase. To study the distribution uniformity of these domains, another fractal dimension, D c , was defined. The results showed that these fractal dimensions were effective parameters to describe the evolution of the phase morphology.

Study on the mechanism of the formation and evolution of phase structure in PP/PcBR blends

Phase dispersion theory was proposed to study the dynamic process of polymer blending with the help of mineral processing theory. Two constants, dispersion coefficient n and process coefficient b, were calculated for the early dispersion stage to describe the varying velocity of the dispersed phase dimension. In this dispersion theory, the phase dimension of binary blends of polypropylene with poly(cis‐butadiene) rubber linearly increased with blending time in the early stage on a double logarithmic scale, which suggested that phase dispersion theory was applicable to the study of polymer blending dynamics. In this study, the influence of the processing conditions, that is, composition, temperature, and shear rate, on the two constants of n and b was also studied. The results showed that n and b decreased with increasing dispersed phase, and reached a minimum when the shear rate was 60 rpm. The dispersion coefficient n first decreased with increasing temperature, reached a minimum when the temperature was 200°C, and then increased with a further increase in temperature, but there was no apparent influence of temperature on the process coefficient b. The coinfluence of blending temperature and shear rate on the dispersion coefficient n showed that the smaller the content of the dispersed phase, the more sensitive the decreasing rate of phase dimension was to the temperature and shear rate.

Study on Phase Formation and Evolution of High Impact Polystyrene with Poly(Cis‐Butadiene) Rubber Blends

Phase formation and evolution of high‐impact polystyrene with poly(cis‐butadiene) rubber blends was studied. The characteristic length, L, was defined to describe the size of particles, and the graph‐estimation method was introduced to determine the width of the distribution of L. Based on the method, the distribution of L proved to be a log‐normal distribution and the distribution width of L was calculated. The phase structure was also discussed in the wave‐number space. The correlation distance, a c , was defined and computed, applying light‐scattering theory to power spectrum images obtained by 2‐dimensional Fourier transformation (2DFT). The change of a c was in accord with that of L, which meant 2DFT was valid to study the phase structure. A fractal dimension, D c , was introduced to describe the uniformity of the spatial distribution. The result showed that D c was an effective parameter to study the distribution of particles of the dispersed phase.

Morphology Development in Multi‐Component Polymer Blends: I Composition Effect on Phase Morphology in PP/PET Polymer Blends

The relationship of the phase morphology of polypropylene/polyethylene‐terephthalate (PP/PET) blends and their corresponding compatibilized blends with composition was investigated using digital image analysis. A diameter, d g , was defined and calculated to discuss the phase morphology of this polymer blend system. A figure‐estimation method was introduced to determine the width of the distribution of d g . Based on the method, it is proven that the distribution of d g obeys a log‐normal distribution and consequently, the distribution width, σ was calculated. Further, a fractal dimension, D f , was introduced to describe the distribution of main sizes of the particles of the dispersed phase. The results showed that, while d g increased with the concentration of the dispersed phase, σ and D f show different dependence relations on composition;σ increases monotonously but D f shows a maximum at a PET content of 30%, indicating that, even though the whole size distribution is much broader, the distribution of the main body of size becomes more uniform when the content of PET is less than 30%.

Role of Styrene‐Ethylene/Propylene Block Copolymer in Controlling Morphology Development of PP/PS Blends during Mixing

The role of styrene‐ethylene/propylene (SEP) diblock copolymer in controlling morphology development of polypropylene/polystyrene (PP/PS) blends was studied by means of small angle laser scattering (SALS) and scanning electron microscopy (SEM). According to SALS, a certain amount of SEP was located at the phase boundary, forming a relatively thick transition layer penetrating into the homopolymers. The thickness of the transition layer was quantified in terms of Debye–Bueche light scattering theory. For PP/PS (1/99) and PP/PS (20/80) blends, the incorporation of SEP into PP/PS blends resulted in a decrease in domain size following an emulsification curve as well as a uniform size distribution, and consequently, a fine dispersion of PP domains in the PS matrix. However, for PP/PS (45/55) blends, the addition of SEP results in a nonmonotonous change in domain size. The morphology fluctuation of the fracture surfaces was analyzed using an integral constant Q based on Debye–Bueche light scattering theories. Variation of Q as a function of the concentration of SEP showed that, due to the penetrating transition layer, adhesion between phases was improved, making it possible for applied stress to transfer between phases and leading to a more uniform stress distribution when blends were broken; accordingly, a more complicated morphology fluctuation of the fracture surfaces appeared.