Morphology development in immiscible polymer blends

This chapter discusses the morphology development of immiscible binary polymer blends. It first describes morphology development in droplet-matrix structures, the dynamics of fibrillar structures and cocontinuous structures. The chapter then considers binary immiscible polymer blends, such systems consist of either dispersed domains in a continuous phase or of two cocontinuous phases. Polymer blends are generally solid at room temperature but they constitute a very viscous emulsion during their processing in the melt. This allows for morphology development during blending and further processing, while the blends are subjected to flow. The chapter also focuses on the morphology development in shear flow, which is the main flow component in many processing, mixing and other operations that involve rotating or moving parts. The polymer blending is industrially used for quite a long time to develop polymeric materials with properties that are a synergistic combination of those of the components

Quantifying the errors due to overfilling for Newtonian fluids in rotational rheometry

The errors on rheological measurements due to overfilling of Newtonian fluids using parallel plate and cone-plate setups in rotational rheometry are quantified. Overfilled sample causes an additional drag force, thereby increasing the measured viscosity, especially when the sample wets the geometry rim. This can cause errors up to 30% in standard experimental setups such as parallel plates with a gap height of 1 mm. This viscosity error increases proportionally with the ratio of gap height to radius of the geometry. By developing a scaling relation that captures the main effects of the geometrical parameters on the viscosity error due to overfilling, a master curve was constructed for the viscosity error as a function of the amount of overfilling. Our systematic analysis of the viscosity error due to overfilling can be utilized to correct for this error during rheological measurements in which overfilling is known but unavoidable or desired.\u3cbr/\u3e\u3cbr/\u3eKeywords\u3cbr/\u3eOverfilling Edge effects Rotational rheometry Shear viscosit

Complexation of lysozyme with sodium caseinate and micellar casein in aqueous buffered solutions

We present an extended structural and morphological study of the complexation of lysozyme (Lys) with sodium caseinate (SC) and micellar casein (MC) by means of turbidity measurements, phase analysis, dynamic, static and electrophoretic light scattering, bright-field and confocal laser scanning (CLSM) microscopy, fluorescence anisotropy and circular dichroism measurements. The solution behavior, structure, effective charge and morphology of the formed complexes as well as the protein structure within the complexes are dependent on the state of the casein molecules (SC versus MC), pH, ionic strength, and the [Cat+]/[An−] charge ratio (ChR). Absorption measurements indicate complexation of Lys with caseins at a pH as high as 11.29 (I = 0.01). At ChR>1, i.e. in excess of lysozyme, CLSM clearly showed formation of complex Lys/SC particles with a neutral core and an exterior part consisting exclusively of hydrophilic Lys macromolecules, whereas in the case of Lys/MC particles a uniform distribution of both proteins was observed. Binding of Lys with SC or MC leads to disruption of the secondary structure of Lys. Binding isotherms from fluorescence anisotropy are well described by an independent binding site model

The effect of geometrical confinement on coalescence efficiency of droplet pairs in shear flow

Droplet coalescence is determined by the combined effect of the collision frequency and the coalescence efficiency of colliding droplets. In the present work, the effect of geometrical confinement on coalescence efficiency in shear flow is experimentally investigated by means of a counter rotating parallel plate device, equipped with a microscope. The model system consisted of Newtonian droplets in a Newtonian matrix. The ratio of droplet diameter to plate spacing (2R/H) is varied between 0.06 and 0.42, thus covering bulk as well as confined conditions. Droplet interactions are investigated for the complete range of offsets between the droplet centers in the velocity gradient direction. It is observed that due to confinement, coalescence is possible up to higher initial offsets. On the other hand, confinement also induces a lower boundary for the initial offset, below which the droplets reverse during their interaction, thus rendering coalescence impossible. Numerical simulations in 2D show that the latter phenomenon is caused by recirculation flows at the front and rear of confined droplet pairs. The lower boundary is independent of Ca, but increases with increasing confinement ratio 2R/H and droplet size. The overall coalescence efficiency is significantly larger in confined conditions as compared to bulk conditions