The Experts below are selected from a list of 17643 Experts worldwide ranked by ideXlab platform

Youn Suk Lee - One of the best experts on this subject based on the ideXlab platform.

  • Microwave-assisted micro-encapsulation of phase change material using zein for smart food packaging applications
    Journal of Thermal Analysis and Calorimetry, 2017
    Co-Authors: Suman Singh, Myungho Lee, Kirtiraj K. Gaikwad, Youn Suk Lee
    Abstract:

    Novel zein/tet (tetradecane) and zein/tet/APC (aqueous potassium chloride) micro-encapsulated functional materials were synthesized using a microwave-assisted encapsulation technique. This technique can produce microcapsules in a very short time. In this study, we optimized the methodology used to obtain micro-encapsulation structures based on zein (a maize protein). Zein was mixed with functional materials in ratios of 1:1 and 1:2 (w/v) using ethanol as a solvent. After sonication, each mixture was treated up to 550 s at a power of 450 W in a microwave oven. Subsequently, nitrogen was pumped into the solution for 1 h to remove any residual ethanol from the system and the samples were freeze-dried to yield the dry powder. The thermal performance was analyzed using differential scanning calorimetry and thermogravimetric analysis. The encapsulation morphology and chemical structure were analyzed using scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. Tetradecane was found to be properly encapsulated in the microstructure of zein under two different conditions with an average capsule diameter of 13950 nm. The melting Point, Crystallization Point, and latent heat of encapsulated zein/tet are 4.95, 0.68 °C, and 107 J g−1, respectively. Thermal cycling tests indicated that zein/tet and zein/tet/APC have good thermal stability with negligible changes in their melting and Crystallization temperatures. Heat management with tet has been modified using potassium chloride to support a suitable temperature range for food packaging. The encapsulated materials can be potentially used for temperature control during the transport of temperature-sensitive products.Graphical Abstract

Gerhard Nagele - One of the best experts on this subject based on the ideXlab platform.

  • modeling deswelling thermodynamics structure and dynamics in ionic microgel suspensions
    Journal of Chemical Physics, 2019
    Co-Authors: Mariano E Brito, Alan R Denton, Gerhard Nagele
    Abstract:

    Ionic microgel particles in a good solvent swell to an equilibrium size determined by a balance of electrostatic and elastic forces. When crowded, ionic microgels deswell owing to a redistribution of microions inside and outside the particles. The concentration-dependent deswelling affects the interactions between the microgels and, consequently, the suspension properties. We present a comprehensive theoretical study of crowding effects on thermodynamic, structural, and dynamic properties of weakly cross-linked ionic microgels in a good solvent. The microgels are modeled as microion- and solvent-permeable colloidal spheres with fixed charge uniformly distributed over the polymer gel backbone, whose elastic and solvent-interaction free energies are described using the Flory-Rehner theory. Two mean-field methods for calculating the crowding-dependent microgel radius are investigated and combined with calculations of the net microgel charge characterizing the electrostatic part of an effective microgel pair potential, with charge renormalization accounted for. Using this effective pair potential, thermodynamic and static suspension properties are calculated, including the osmotic pressure and microgel pair distribution function. The latter is used in our calculations of dynamic suspension properties, where we account for hydrodynamic interactions. Results for diffusion and rheological properties are presented over ranges of microgel concentration and charge. We show that deswelling mildly enhances self- diffusion and collective diffusion and the osmotic pressure, lowers the suspension viscosity, and significantly shifts the suspension Crystallization Point to higher concentrations. This paper presents a bottom-up approach to efficiently computing suspension properties of crowded ionic microgels using single-particle characteristics.Ionic microgel particles in a good solvent swell to an equilibrium size determined by a balance of electrostatic and elastic forces. When crowded, ionic microgels deswell owing to a redistribution of microions inside and outside the particles. The concentration-dependent deswelling affects the interactions between the microgels and, consequently, the suspension properties. We present a comprehensive theoretical study of crowding effects on thermodynamic, structural, and dynamic properties of weakly cross-linked ionic microgels in a good solvent. The microgels are modeled as microion- and solvent-permeable colloidal spheres with fixed charge uniformly distributed over the polymer gel backbone, whose elastic and solvent-interaction free energies are described using the Flory-Rehner theory. Two mean-field methods for calculating the crowding-dependent microgel radius are investigated and combined with calculations of the net microgel charge characterizing the electrostatic part of an effective microgel pair ...

  • modeling deswelling thermodynamics structure and dynamics in ionic microgel suspensions
    arXiv: Soft Condensed Matter, 2019
    Co-Authors: Mariano E Brito, Alan R Denton, Gerhard Nagele
    Abstract:

    Ionic microgel particles in a good solvent swell to an equilibrium size determined by a balance of electrostatic and elastic forces. When crowded, ionic microgels deswell owing to a redistribution of microions inside and outside the particles. The concentration-dependent deswelling affects the interactions between the microgels, and consequently the suspension properties. We present a comprehensive theoretical study of crowding effects on thermodynamic, structural, and dynamic properties of weakly cross-linked ionic microgels in a good solvent. The microgels are modeled as microion- and solvent-permeable colloidal spheres with fixed charge uniformly distributed over the polymer gel backbone, whose elastic and solvent-interaction free energies are described using Flory-Rehner theory. Two mean-field methods for calculating the crowding-dependent microgel radius are investigated, and combined with calculations of the net microgel charge characterizing the electrostatic part of an effective microgel pair potential, with charge renormalization accounted for. Using this effective pair potential, thermodynamic and static suspension properties are calculated including the osmotic pressure and microgel pair distribution function. The latter is used in our calculations of dynamic suspension properties, where we account for hydrodynamic interactions. Results for diffusion and rheological properties are presented over ranges of microgel concentration and charge. We show that deswelling mildly enhances self- and collective diffusion and the osmotic pressure, lowers the suspension viscosity, and significantly shifts the suspension Crystallization Point to higher concentrations. The paper presents a bottom-up approach to efficiently computing suspension properties of crowded ionic microgels using single-particle characteristics.

Ty A Newell - One of the best experts on this subject based on the ideXlab platform.

  • characterization of supercooling suppression of microencapsulated phase change material by using dsc
    Journal of Thermal Analysis and Calorimetry, 2006
    Co-Authors: Jorge L Alvarado, Charles P Marsh, C Sohn, M Vilceus, V Hock, Gary E Phetteplace, Ty A Newell
    Abstract:

    Supercooling suppression of microencapsulated n-tetradecane was measured using differential scanning calorimetry. Results indicate that the degree of supercooling is positively affected by the amount and type of nucleating agent present in bulk and microencapsulated n-tetradecane which it is used as a phase change material (MPCM). Results also demonstrate that the melting Point of the n-tetradecane is fairly independent of nucleating agent concentration (0 – 4%). Conversely, the latent heat of fusion of n-tetradecane decreases considerably with nucleating agent amount and the initiation of Crystallization Point is inversely proportional to cooling rate.

Suman Singh - One of the best experts on this subject based on the ideXlab platform.

  • Microwave-assisted micro-encapsulation of phase change material using zein for smart food packaging applications
    Journal of Thermal Analysis and Calorimetry, 2017
    Co-Authors: Suman Singh, Myungho Lee, Kirtiraj K. Gaikwad, Youn Suk Lee
    Abstract:

    Novel zein/tet (tetradecane) and zein/tet/APC (aqueous potassium chloride) micro-encapsulated functional materials were synthesized using a microwave-assisted encapsulation technique. This technique can produce microcapsules in a very short time. In this study, we optimized the methodology used to obtain micro-encapsulation structures based on zein (a maize protein). Zein was mixed with functional materials in ratios of 1:1 and 1:2 (w/v) using ethanol as a solvent. After sonication, each mixture was treated up to 550 s at a power of 450 W in a microwave oven. Subsequently, nitrogen was pumped into the solution for 1 h to remove any residual ethanol from the system and the samples were freeze-dried to yield the dry powder. The thermal performance was analyzed using differential scanning calorimetry and thermogravimetric analysis. The encapsulation morphology and chemical structure were analyzed using scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. Tetradecane was found to be properly encapsulated in the microstructure of zein under two different conditions with an average capsule diameter of 13950 nm. The melting Point, Crystallization Point, and latent heat of encapsulated zein/tet are 4.95, 0.68 °C, and 107 J g−1, respectively. Thermal cycling tests indicated that zein/tet and zein/tet/APC have good thermal stability with negligible changes in their melting and Crystallization temperatures. Heat management with tet has been modified using potassium chloride to support a suitable temperature range for food packaging. The encapsulated materials can be potentially used for temperature control during the transport of temperature-sensitive products.Graphical Abstract

Mariano E Brito - One of the best experts on this subject based on the ideXlab platform.

  • modeling deswelling thermodynamics structure and dynamics in ionic microgel suspensions
    Journal of Chemical Physics, 2019
    Co-Authors: Mariano E Brito, Alan R Denton, Gerhard Nagele
    Abstract:

    Ionic microgel particles in a good solvent swell to an equilibrium size determined by a balance of electrostatic and elastic forces. When crowded, ionic microgels deswell owing to a redistribution of microions inside and outside the particles. The concentration-dependent deswelling affects the interactions between the microgels and, consequently, the suspension properties. We present a comprehensive theoretical study of crowding effects on thermodynamic, structural, and dynamic properties of weakly cross-linked ionic microgels in a good solvent. The microgels are modeled as microion- and solvent-permeable colloidal spheres with fixed charge uniformly distributed over the polymer gel backbone, whose elastic and solvent-interaction free energies are described using the Flory-Rehner theory. Two mean-field methods for calculating the crowding-dependent microgel radius are investigated and combined with calculations of the net microgel charge characterizing the electrostatic part of an effective microgel pair potential, with charge renormalization accounted for. Using this effective pair potential, thermodynamic and static suspension properties are calculated, including the osmotic pressure and microgel pair distribution function. The latter is used in our calculations of dynamic suspension properties, where we account for hydrodynamic interactions. Results for diffusion and rheological properties are presented over ranges of microgel concentration and charge. We show that deswelling mildly enhances self- diffusion and collective diffusion and the osmotic pressure, lowers the suspension viscosity, and significantly shifts the suspension Crystallization Point to higher concentrations. This paper presents a bottom-up approach to efficiently computing suspension properties of crowded ionic microgels using single-particle characteristics.Ionic microgel particles in a good solvent swell to an equilibrium size determined by a balance of electrostatic and elastic forces. When crowded, ionic microgels deswell owing to a redistribution of microions inside and outside the particles. The concentration-dependent deswelling affects the interactions between the microgels and, consequently, the suspension properties. We present a comprehensive theoretical study of crowding effects on thermodynamic, structural, and dynamic properties of weakly cross-linked ionic microgels in a good solvent. The microgels are modeled as microion- and solvent-permeable colloidal spheres with fixed charge uniformly distributed over the polymer gel backbone, whose elastic and solvent-interaction free energies are described using the Flory-Rehner theory. Two mean-field methods for calculating the crowding-dependent microgel radius are investigated and combined with calculations of the net microgel charge characterizing the electrostatic part of an effective microgel pair ...

  • modeling deswelling thermodynamics structure and dynamics in ionic microgel suspensions
    arXiv: Soft Condensed Matter, 2019
    Co-Authors: Mariano E Brito, Alan R Denton, Gerhard Nagele
    Abstract:

    Ionic microgel particles in a good solvent swell to an equilibrium size determined by a balance of electrostatic and elastic forces. When crowded, ionic microgels deswell owing to a redistribution of microions inside and outside the particles. The concentration-dependent deswelling affects the interactions between the microgels, and consequently the suspension properties. We present a comprehensive theoretical study of crowding effects on thermodynamic, structural, and dynamic properties of weakly cross-linked ionic microgels in a good solvent. The microgels are modeled as microion- and solvent-permeable colloidal spheres with fixed charge uniformly distributed over the polymer gel backbone, whose elastic and solvent-interaction free energies are described using Flory-Rehner theory. Two mean-field methods for calculating the crowding-dependent microgel radius are investigated, and combined with calculations of the net microgel charge characterizing the electrostatic part of an effective microgel pair potential, with charge renormalization accounted for. Using this effective pair potential, thermodynamic and static suspension properties are calculated including the osmotic pressure and microgel pair distribution function. The latter is used in our calculations of dynamic suspension properties, where we account for hydrodynamic interactions. Results for diffusion and rheological properties are presented over ranges of microgel concentration and charge. We show that deswelling mildly enhances self- and collective diffusion and the osmotic pressure, lowers the suspension viscosity, and significantly shifts the suspension Crystallization Point to higher concentrations. The paper presents a bottom-up approach to efficiently computing suspension properties of crowded ionic microgels using single-particle characteristics.