Influence of poly(vinyl alcohol) molecular weight on drop coalescence and breakage rate

Bąk, A.; Podgórska, W.

doi:10.1016/j.cherd.2015.10.027

Cited by 11 publications

(9 citation statements)

References 67 publications

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“…The exact value of this exponent is predicted by the multifractal breakage model. As was shown in previous papers, the multifractal breakage model not only predicts this exponent, but it also predicts transient drop size distributions very well [2,28,43], both for short agitation times, when the most probable stresses determine the drop size, and for long agitation times, when droplets of a diameter, d, are not disrupted by stresses, ( ) Figure 4b shows the Sauter diameter predicted for the Rushton turbine by Coulaloglou and Tavlarides' model [9], which does not take into account local intermittency. In this case, the slope of the line is close to -0.4.…”

Section: Resultssupporting

confidence: 76%

“…A multifractal model allows the probability of stresses characterized by different multifractal exponents, α, for a given average energy dissipation rate calculated for a given zone to be predicted. Such a model gives excellent results in predicting drop size evolution as was shown in previous papers [30,33,43]. The details of the flow pattern were not used.…”

Section: Geometry and Cfd Modelmentioning

confidence: 97%

“…This extra stress is due to the difference between the dynamic interfacial tension of the fresh surface (exposed during drop deformation under the action of pressure fluctuations), σ t→0 , and static interfacial tension, σ [28]. This extra stress is observed when surfactant can be easily removed from the surface [28,33], but is not observed when surface active additive is strongly grafted to the surface [43]. The multifractal exponent characterizing the weakest eddies that can disperse the drop covered with surfactant, which can be removed from the surface during its deformation, is given by [28]:…”

Section: Breakage and Coalescence Modelsmentioning

confidence: 99%

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The Influence of Internal Intermittency, Large Scale Inhomogeneity, and Impeller Type on Drop Size Distribution in Turbulent Liquid-Liquid Dispersions

Podgórska

2019

Entropy

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The influence of the impeller type on drop size distribution (DSD) in turbulent liquid-liquid dispersion is considered in this paper. The effects of the application of two impellers, high power number, high shear impeller (six blade Rushton turbine, RT) and three blade low power number, and a high efficiency impeller (HE3) are compared. Large-scale and fine-scale inhomogeneity are taken into account. The flow field and the properties of the turbulence (energy dissipation rate and integral scale of turbulence) in the agitated vessel are determined using the k-ε model. The intermittency of turbulence is taken into account in droplet breakage and coalescence models by using multifractal formalism. The solution of the population balance equation for lean dispersions (when the only breakage takes place) with a dispersed phase of low viscosity (pure system or system containing surfactant), as well as high viscosity, show that at the same power input per unit mass HE3 impeller produces much smaller droplets. In the case of fast coalescence (low dispersed phase viscosity, no surfactant), the model predicts similar droplets generated by both impellers. In the case of a dispersed phase of high viscosity, when the mobility of the drop surface is reduced, HE3 produces slightly smaller droplets.

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Section: Resultssupporting

confidence: 76%

Section: Geometry and Cfd Modelmentioning

confidence: 97%

Section: Breakage and Coalescence Modelsmentioning

confidence: 99%

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The Influence of Internal Intermittency, Large Scale Inhomogeneity, and Impeller Type on Drop Size Distribution in Turbulent Liquid-Liquid Dispersions

Podgórska

2019

Entropy

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“…The latter result is consistent with prior observations that the interfacial tensions of aqueous-oil interfaces decorated with PVA decrease with PVA molecular weight and hydrolysis degree. [43,44] We note that the smallest radii of the droplets obtained are smaller than half the pitch of the cholesteric LC (p 0 /2 = 140 nm for 37.4 wt% S-811 and 165 nm for 29.9 wt% S-811). The polydispersity indices (PDI) of the nanoemulsions ranged from 0.35 ± 0.06 to 0.15 ± 0.01 with the general trend that the PDI decreased with a decrease in R v .…”

Section: Preparation Of Nanoemulsions Of Strongly Chiral Lcsmentioning

confidence: 77%

Strongly Chiral Liquid Crystals in Nanoemulsions

Yang

Palacio‐Betancur

Wang

et al. 2022

Small

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absorption spectra due to surface plasmon resonances; [2] and the elastic moduli of polystyrene polymer films decrease substantially below 40 nm. [3] These examples highlight how nanoscopic confinement provides an important route for expanding the palette of materials structures and properties. Of particular relevance to the study reported in this paper, liquid crystals (LCs) are known to be strongly influenced by confinement. [4][5][6] For example, confinement of LCs can lead to changes to topological defects present in a sample, [4] alteration of optical properties [5] and changes to the way in which LCs respond to external fields (e.g., electric fields). [6] The majority of past studies, however, have focused on confinement of LCs on the micrometer-scale with fewer studies exploring the submicrometer-scale. [7][8][9][10][11][12][13][14][15][16][17][18][19] The majority of past studies of LCs in submicrometer-scale confinement have involved the use of droplets of nematic LCs. [9][10][11][14][15][16][17][18][19] These studies have reported internal LC configurations that depend on droplet size and the chemistry of the confining surfaces. Gupta et al. [19] observed that nematic droplets confined within multilayered polyelectrolyte shells of poly(styrene sulfonate) and poly(allylamine hydrochloride) changed from a bipolar configuration to a radial configuration as the diameter decreased from 3 µm to 700 nm. An additional study by Zou et al. [9] found that a confinementinduced bipolar-to-radial configuration transition in nematic droplets occurred when the LC was in contact with an adsorbed layer of poly(styrenesulfonic acid) but not poly(styrenesulfonate sodium), suggesting that the effects of confinement are modulated by surface interactions. In contrast, Peng et al. [18] have reported that nematic nanodroplets confined in SiO 2 capsules assumed a uniform internal alignment as the droplet diameter decreased to 200 nm, with either tangential or homeotropic anchoring on the capsules. In addition to changes in internal structure, phase transitions from isotropic to nematic phases have been reported to occur at temperatures that increase, decrease, or are invariant with nanodroplet size. [15,18] These conflicting observations likely arise from differences in interfacial chemistry and/or LC elastic properties. More broadly, however, they both highlight the opportunity that exists to tune LC properties via nanoconfinement but also pinpoint the need for additional studies of LC nanodroplets, including investigations of the effects of confinement on nanodroplets formed from LCs other than nematics.Limits on the resolution of far-field optical microscopy also make studies of LC droplets on the submicrometer-scale Liquid crystal (LC) emulsions represent a class of confined soft matter that exhibit exotic internal organizations and size-dependent properties, including responses to chemical and physical stimuli. Past studies have explored micrometer-scale LC emulsion droplets but little is known about LC ordering within subm...

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“…As a kind of biodegradable and eco‐friendly materials, water‐soluble poly (vinyl alcohol) (PVA) has been widely used in various industrial applications, such as biodegradable materials, chemical engineering, and so on . The most important parameters influencing the physical properties of PVA are the molecular weight and alcoholysis degree . Due to the alcoholysis degree, PVA could be divided into 3 kinds with high (98%‐100%), medium (87%‐89%), and low alcoholysis degree (78%) .…”

Section: Introductionmentioning

confidence: 99%

Improved mechanical properties of poly (vinyl alcohol) films with glycerol plasticizer by uniaxial drawing

Tian

Zhou

et al. 2018

Polymers for Advanced Techs

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In this work, the uniaxial stretching poly (vinyl alcohol) (PVA) films with glycerol as plasticizer were prepared to explore the influence of drawing temperature and drawing ratio. The structure and property were investigated with scanning electron microscope, wide-angle X-ray diffraction, X-ray diffraction, differential scanning calorimetry, mechanical tests, etc. With the increase of stretching temperature, the melting and crystallization temperatures increased. The tensile strength and Young modulus of glycerol/PVA films increased first and then decreased; when the temperature was 80°C, the tensile strength and Young modulus reached to maximum values of 197.2 and 470 MPa, respectively. In addition, with the increase of draw ratio, the orientation degree of the PVA molecular chains increased, indicating the improved regularity of molecular chains. When the PVA films were stretched to 4 times, the tensile strength and Young modulus of the films reached 162 and 143 MPa, respectively, which were 4 and 1.3 times compared with those of unoriented films. These environmentally friendly PVA films with excellent mechanical properties would find wide applications in the industry such as packaging, coating, etc. KEYWORDS glycerol, orientation, poly (vinyl alcohol), uniaxial stretching 1 | INTRODUCTION As a kind of biodegradable and eco-friendly materials, water-soluble poly (vinyl alcohol) (PVA) has been widely used in various industrial applications, such as biodegradable materials, chemical engineering, and so on. 1-4 The most important parameters influencing the physical properties of PVA are the molecular weight and alcoholysis degree. 5-7Due to the alcoholysis degree, PVA could be divided into 3 kinds with high (98%-100%), medium (87%-89%), and low alcoholysis degree (78%). 8 Poly (vinyl alcohol) with medium alcoholysis degree could dissolve in both hot and cold water, while PVA with alcoholysis degree more than 99% could only dissolve in hot water with temperature higher than 95°C. Compared with PVA with low alcoholysis degree, high alcoholysis PVA possesses higher water resistance, mechanical properties, as well as oxygen barrier properties, therefore exhibiting wider applications. 3,9 Stretching is mainly divided into uniaxial stretching and biaxial stretching, and it is well known that after stretching of films above its glass transition temperature (T g ), the molecular chain or molecular chain segments will rearrange toward the direction of external force. 10-12 For semicrystalline polymers, 13 stretching is an effective method to obtain oriented films with excellent mechanical, optical, and thermal properties, 14,15 which has been carried out at large-scale production for nearly 80 years. 16 These end-use properties are essentially controlled by stretching-induced crystallization of the polymer, which is affected by the stretching mode and processing conditions, such as temperature, stretching rate, and draw ratio (DR). 17,18 The processing conditions have strong impact on the morphology, crystalline structure...

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Influence of poly(vinyl alcohol) molecular weight on drop coalescence and breakage rate

Cited by 11 publications

References 67 publications

The Influence of Internal Intermittency, Large Scale Inhomogeneity, and Impeller Type on Drop Size Distribution in Turbulent Liquid-Liquid Dispersions

The Influence of Internal Intermittency, Large Scale Inhomogeneity, and Impeller Type on Drop Size Distribution in Turbulent Liquid-Liquid Dispersions

Strongly Chiral Liquid Crystals in Nanoemulsions

Improved mechanical properties of poly (vinyl alcohol) films with glycerol plasticizer by uniaxial drawing

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