Study of the morphological hysteresis in immiscible polymer blends

Minale, Mario; Mewis, Jan; Moldenaers, Paula

doi:10.1002/aic.690440420

Cited by 69 publications

(51 citation statements)

References 22 publications

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“…Since in Fig. 4 the largest drop radii show the same trend as those obtained from rheology (although they are smaller), it follows that the rheological data mostly account for the relaxation times A narrowing of the hysteresis zone is observed, in accordance with Minale et al (1998). The data for increasing and decreasing shear rates almost coincide (within experimental error), i.e., the morphology seems to become independent of the flow history.…”

Section: Pb In Pdmssupporting

confidence: 73%

“…We use h cr = 2 * 10 −8 m (Eq. 5), which is larger than the one reported by Tufano et al (2008b) for the same blend, but in that work, with a concentration of 1%, h cr = 0.36 * 10 −8 m. Increasing h cr values with increasing concentration were also reported in Minale et al (1997Minale et al ( , 1998 and two possible explanations were given: (a) the influence of dust particles Fig. 4 Average radii obtained by using Eq.…”

Section: Pb In Pdmscontrasting

confidence: 42%

“…Since theories are derived for isolated pairs of droplets, while we are dealing with concentrated blends, some authors choose to use the h cr as an adjustable parameter. It then contains all the uncertainties and approximations of the model and, to a certain extent, it is a function of the concentration (Minale et al 1997(Minale et al , 1998. We will use a 5 * 10 −6 1 * 10 −8 0.8 * 10 −8 50 * 10 −6 2 * 10 −8 1.7 * 10 −8 150 * 10 −6 3 * 10 −8 2.5 * 10 −8 fixed value for each system based on Eq.…”

Section: Hysteresis Zonementioning

confidence: 99%

“…Elmendorp (1986) showed that the equilibrium between breakup and coalescence can be reached only for shear rates higher than the critical one, which is defined as the shear rate at which the theoretical limiting curves for breakup and coalescence cross. Grizzuti and Bifulco (1997), Vinckier et al (1998), and Minale et al (1997Minale et al ( , 1998 showed, by means of rheological experiments and optical microscopy (OM), that the steady-state morphology is reached only after a certain critical shearing time. However, Janssen and Meijer (1995) reported that flow conditions might exist in which more that one morphology is possible.…”

Section: Introductionmentioning

confidence: 99%

“…The final morphology was shown not only to depend on the characteristics of the blend components and history of flow but also on the initial conditions. The effects of viscosity ratio and concentration of the blend have been studied by Minale et al (1998) for the same model system. They showed that the hysteresis region shifts to smaller shear rates and narrows with increasing the concentration of the dispersed phase.…”

Section: Introductionmentioning

confidence: 99%

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Study of morphological hysteresis in partially immiscible polymers

et al. 2008

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The morphology evolution of two systems of partially immiscible polymers, differing in miscibility, is investigated by means of rheological experiments and optical microscopy. For each system, two concentrations, 10% and 20%, are used. For immiscible systems, a hysteresis zone, defined by coalescence and breakup, exists where the average drop radius is not a unique function of the shear rate. We investigate whether the findings also apply to partially immiscible polymers. The average radii at different shear rates, measured with rheology, are compared to model predictions. The hysteresis zone, if present, is indeed affected by the polymeric system, the concentration and the flow history applied. Coalescence evolution is measured for three different step-downs in shear rate. For both 10% systems, the resulting average radii show a rather high scattering and do not match the theoretical predictions. For the 20% concentrations, the average experimental drop sizes seem independent of the magnitude of the step-down, at least during a certain period of time. Thereafter, it experiences a sudden, in the time scale of the experiments unbounded, increase in size that is more pronounced for the higher step-downs. Deviations of the experimental data from theoretical predictions are attributed to the partially immiscible character of the systems, yielding enhanced coalescence which, in turn, can induce confinement effects.

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Section: Pb In Pdmssupporting

confidence: 73%

Section: Pb In Pdmscontrasting

confidence: 42%

Section: Hysteresis Zonementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Study of morphological hysteresis in partially immiscible polymers

et al. 2008

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Rheological Measurements

2013

Encyclopedia of Polymer Science and Technology

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Rheology is the science to study the flow and deformation of matter. It becomes an important field in material science and engineering, food, biotechnology, and so on. The objects in rheological study are not the ideal solid and ideal fluid, which can be described by the Hookean elastic model and the Newtonian viscous model, respectively. Instead, the rheological study often focuses on materials that can exhibit viscous, elastic, and plastic behavior under different flow conditions. They are often termed as complex fluids or soft matter, which include polymers, gels, suspensions, emulsions, biofluids, foods, inks (1). In contrast to hydrodynamics, which often accounts for the complex flow behavior of simple fluids, simple geometry is utilized in rheological measurements to understand the rather complicated relationship between the mechanical input and output of complex fluids. The real flow fields encountered in many applications (such as polymer extrusion, injection molding, blow molding, fiber spinning, inkjet printing, coating) are rather complicated (2). It becomes a problem whether the rheological measurements that performed under simple flow fields are useful in understanding the complicated flow behaviors of complex fluids. Fortunately, it has been proved in many examples that the properties determined from simple rheological measurements are sufficient to quantify the material parameters in various constitutive equations, which have been used widely and successfully to simulate the flow behaviors in polymer processing (3-11). The most frequently used simple flow fields are simple shear flow and simple extensional flow.The simplest geometry that defines the simple shear is two infinite parallel plates separated by a distance h. The liquid is set between two plates with one plate moving parallel to the other (Fig. 1). In reality, when the length L and the width B are much larger than the gap h, the flow in the center regime resembles the flow between two infinite plates. It means that the edge effects are ignored in most experimental shear geometries. In rheological measurements, the flow between two plates should be laminar. Moreover, it is usually assumed that the velocity across the gap satisfies a linear profile. As shown in Fig. 1, if the bottom plate is fixed and the upper plate moves horizontally with the velocity V, the fluid velocity varies linearly from 0 at the bottom plate to V at the upper plate if the no-slip boundary condition is satisfied. The linear velocity profile generates a constant velocity gradient, which is known as the shear rate. Then, the flow field between two parallel plates is homogeneous in the shear rate. The homogeneous assumption is nontrivial in the rheological tests since the actual velocity

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Morphology Development in Immiscible Polymer Blends

Cardinaels

Moldenaers

2016

Polymer Morphology

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Study of the morphological hysteresis in immiscible polymer blends

Cited by 69 publications

References 22 publications

Study of morphological hysteresis in partially immiscible polymers

Study of morphological hysteresis in partially immiscible polymers

Rheological Measurements

Morphology Development in Immiscible Polymer Blends

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