scholarly journals Dispersion of Graphite Nanoplates in Polypropylene by Melt Mixing: The Effects of Hydrodynamic Stresses and Residence Time

Polymers ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 102
Author(s):  
Luís Lima Ferrás ◽  
Célio Fernandes ◽  
Denis Semyonov ◽  
João Miguel Nóbrega ◽  
José António Covas
Keyword(s):  
Residence Time ◽  
Stress Fields ◽  
Outer Diameter ◽  
Melt Mixing ◽  
Average Value ◽  
Local Degree ◽  
Computational Data ◽  
Polypropylene Melt ◽  
Hydrodynamic Stresses ◽  
Kinetics Of

This work combines experimental and numerical (computational fluid dynamics) data to better understand the kinetics of the dispersion of graphite nanoplates in a polypropylene melt, using a mixing device that consists of a series of stacked rings with an equal outer diameter and alternating larger and smaller inner diameters, thereby creating a series of converging/diverging flows. Numerical simulation of the flow assuming both inelastic and viscoelastic responses predicted the velocity, streamlines, flow type and shear and normal stress fields for the mixer. Experimental and computed data were combined to determine the trade-off between the local degree of dispersion of the PP/GnP nanocomposite, measured as area ratio, and the absolute average value of the hydrodynamic stresses multiplied by the local cumulative residence time. A strong quasi-linear relationship between the evolution of dispersion measured experimentally and the computational data was obtained. Theory was used to interpret experimental data, and the results obtained confirmed the hypotheses previously put forward by various authors that the dispersion of solid agglomerates requires not only sufficiently high hydrodynamic stresses, but also that these act during sufficient time. Based on these considerations, it was estimated that the cohesive strength of the GnP agglomerates is in the range of 5–50 kPa.

STUDY OF THE KINETICS OF DRYING BREWER’S SPENT GRAIN

2020 ◽  
Author(s):  
Т.Г. КОРОТКОВА ◽  
А.С. ДАНИЛЬЧЕНКО ◽  
Н.Ю. ИСТОШИНА
Keyword(s):  
Matter Content ◽  
Dry Matter Content ◽  
Drying Time ◽  
Brewer’S Spent Grain ◽  
Average Value ◽  
Free Moisture ◽  
Before And After ◽  
Spent Grain ◽  
Kinetics Of ◽  
Two Temperature

Исследована кинетика сушки сырой пивной дробины – вторичного продукта ООО «Белореченский пивоваренный завод» (Россия, Краснодарский край). Сушка проведена в двух температурных режимах – 60 и 55°С. Скорость сушильного агента при вынужденной конвекции составляла 4,5 м/с. Содержание сухого вещества определено по ГОСТ 31640–2012 в лабораторных условиях и составило 12,9%. Измерение убыли массы при сушке проведено с интервалом 5 мин. Общее время сушки навески пивной дробины в количестве 50 г – 420 мин при режиме 50°С, 360 мин – при 60°С. Среднее значение конечной влажности пивной дробины составило 11,85%. Построены кривые сушки и скорости сушки. Скорость сушки при удалении свободной влаги в первом периоде сушки, мин–1: при 60°С – 3,5, при 55°С – 3,0. Установлено, что содержание связанной влаги составляет в среднем 57% от массы влаги в навеске пивной дробины, свободной влаги – 43%. Анализ структуры навески пивной дробины под микроскопом до сушки и после нее подтвердил факт, что в исследованном материале количество связанной влаги больше, чем свободной. Наличие частиц размером 5–7 мм свидетельствует о значительном количестве клеточной влаги в неразрушенных капиллярах. Дальнейшее совершенствование технологии переработки пивной дробины должно быть направлено на разрушение клеточной структуры материала после его механического обезвоживания. The kinetics of drying of the crude brewer’s spent grain – a secondary product of LLC «Belorechensky brewery» (Russian Federation, Krasnodarregion) has been studied. Drying is carried out in two temperature modes – 60 and 55°C. The speed of the drying agent under forced convection was 4,5 m/s. The dry matter content was determined according to GOST 31640–2012 in laboratory conditions and was 12,9%. Measurement of mass loss during drying was performed at an interval of 5 min. The total drying time of the brewer’s spent grain sample in the amount of 50 gis 420 min at 50°C, 360 min – at 60°C. The average value of the final moisture content of brewer’s spent grain made up 11,85%. Curves of drying and drying speed are constructed. Drying speed when removing free moisture in the first drying period, min–1: at 60°C – 3,5, at 55°C – 3,0. It was found that the content on average of bound moisture is 57% of the mass of moisture in brewer’s spent grain, free moisture – 43%. Analysis of the structure sample of brewer’s spent grain a microscope before and after drying confirmed the fact that the amount of bound moisture in the studied material is greater than the amount of free moisture. The presence of particles of 5–7 mm in size indicates a significant amount of cellular moisture in undisturbed capillaries. Further improvement of the technology for processing brewer’s spent grain should be aimed at destroying the cellular structure of the material after its mechanical dehydration.

scholarly journals Characteristics and Kinetics of Rosin Pentaerythritol Ester via Oxidation Process under Ultraviolet Irradiation

Molecules ◽  
2018 ◽  
Vol 23 (11) ◽  
pp. 2816 ◽  
Author(s):  
Yuanlin Li ◽  
Xiongmin Liu ◽  
Qiang Zhang ◽  
Bo Wang ◽  
Chang Yu ◽  
...  
Keyword(s):  
Light Intensity ◽  
Oxidation Kinetics ◽  
Pseudo First Order Reaction ◽  
Initial Oxidation ◽  
Photo Oxidation ◽  
Average Value ◽  
Pentaerythritol Ester ◽  
Fundamental Information ◽  
The Stability ◽  
Kinetics Of

A self-designed reaction device was used as a promising equipment to investigate the oxidation characteristics and kinetics of rosin pentaerythritol ester (RPE) under UV irradiation. Photo-oxidation kinetics and the initial quantum yield (Φ) of RPE were calculated. The initial oxidation product of the photo-oxidation reaction—peroxide was analyzed by iodimetry. The peroxide concentration is related to the light intensity (I) and the temperature (T), and the increasing T and I would destabilize the RPE by accelerating peroxide forming. Photo-oxidation of RPE follows the pseudo first-order reaction kinetics. The relationship between activation energy and logarithm of light intensity (ln I) is linear, and it is expressed as Ea = −4.937ln I + 45.565. Φ was calculated by the photo-oxidation kinetics, and the average value of Φ was 7.19% in the light intensity range of 200–800 μW cm−2. This research can provide fundamental information for application of RPE, and help obtain a better understanding of the stability of rosin esters.

Solar Fixation of Atmospheric Nitrogen

2004 ◽  
Vol 126 (1) ◽  
pp. 626-632 ◽  
Author(s):  
Michael Epstein ◽  
Rudi Bertocchi ◽  
Jacob Karni
Keyword(s):  
Residence Time ◽  
Atmospheric Nitrogen ◽  
The Novel ◽  
Test Results ◽  
Hot Air ◽  
Economical Benefit ◽  
Fixation Reaction ◽  
Solar Receiver ◽  
Kinetics Of ◽  
Commercial Size

The thermal fixation of atmospheric nitrogen is explored, using a recently developed concept of a particle-seeded solar receiver. The thermodynamics and the kinetics of the formation of nitric oxide (NO) in air at temperatures of about 2300 K are analyzed, and the required residence time and the time to reach the steady state of the reaction between nitrogen and oxygen are calculated. The novel particle-seeded receiver concept is briefly described. The adaptation of the particle-seeded receiver to the fixation reaction in terms of heating rate of the air and residence time is validated based on previous test results and complementary calculations. A proposed method where the solar receiver/reactor is simultaneously coupled with power production, using the exhausted hot air from the reactor to generate electricity, is described. This concept can definitely increase the economical benefit of the process and, thus, its potential attractiveness. Some illustrative figures for a commercial size system are provided.

Kinetics of Drug Binding and Residence Time

2019 ◽  
Vol 70 (1) ◽  
pp. 143-171 ◽  
Author(s):  
Mattia Bernetti ◽  
Matteo Masetti ◽  
Walter Rocchia ◽  
Andrea Cavalli
Keyword(s):  
Computational Methods ◽  
Residence Time ◽  
Drug Target ◽  
Early Stage ◽  
Kinetic Constant ◽  
Theoretical Background ◽  
Drug Binding ◽  
Binding Kinetics ◽  
Kinetics Of

The kinetics of drug binding and unbinding is assuming an increasingly crucial role in the long, costly process of bringing a new medicine to patients. For example, the time a drug spends in contact with its biological target is known as residence time (the inverse of the kinetic constant of the drug-target unbinding, 1/ koff). Recent reports suggest that residence time could predict drug efficacy in vivo, perhaps even more effectively than conventional thermodynamic parameters (free energy, enthalpy, entropy). There are many experimental and computational methods for predicting drug-target residence time at an early stage of drug discovery programs. Here, we review and discuss the methodological approaches to estimating drug binding kinetics and residence time. We first introduce the theoretical background of drug binding kinetics from a physicochemical standpoint. We then analyze the recent literature in the field, starting from the experimental methodologies and applications thereof and moving to theoretical and computational approaches to the kinetics of drug binding and unbinding. We acknowledge the central role of molecular dynamics and related methods, which comprise a great number of the computational methods and applications reviewed here. However, we also consider kinetic Monte Carlo. We conclude with the outlook that drug (un)binding kinetics may soon become a go/no go step in the discovery and development of new medicines.

Development of Torrefaction Kinetics for British Columbia Softwoods

2012 ◽  
Vol 10 (1) ◽  
Author(s):  
Jianghong Peng ◽  
Xiaotao T. Bi ◽  
Jim Lim ◽  
Shabab Sokhansanj
Keyword(s):  
British Columbia ◽  
Weight Loss ◽  
Kinetic Model ◽  
Residence Time ◽  
Order Reaction ◽  
First Order Reaction ◽  
Chemical Components ◽  
First Order ◽  
One Step ◽  
Kinetics Of

Torrefaction is a thermal treatment without air or oxygen in the temperature range of 473-573 K. The pyrolysis kinetics of three chemical components (cellulose, hemicelluloses, and lignin) and wood at low temperatures of relevance to torrefaction conditions have been reviewed. A series of thermogravimetric (TG) experiments have been carried out to study the intrinsic torrefaction kinetics of major chemical components and British Columbia (BC) softwoods. The weight loss during BC softwood torrefaction was found to be mainly associated with the decomposition of hemicelluloses, although there was also certain degree of decomposition of cellulose and lignin. The weight loss of the BC softwoods during torrefaction could be approximately estimated from the chemical composition of wood species and the weight loss data for torrefaction of pure cellulose, hemicelluloses, and lignin, respectively. Based on the fitting of the TG curves of BC softwoods and three chemical components, two different torrefaciton models were proposed. The simple one-step (single-stage) kinetic model with the first order reaction can predict the reaction data reasonably well over the long residence time, with the final sample weight being strongly related to the torrefaction temperature. A two-component and one-step first order reaction kinetic model, on the other hand, gave improved agreement with data over short residence time, and can be used to guide the design and optimization of torrefaction reactors over the weight loss range of 0 to 40% at the temperature range of 533-573 K, which covers the typical range of industrially relevant operations.

Design strategies to address kinetics of drug binding and residence time

2015 ◽  
Vol 25 (10) ◽  
pp. 2019-2027 ◽  
Author(s):  
Kevin P. Cusack ◽  
Ying Wang ◽  
Michael Z. Hoemann ◽  
Jasmina Marjanovic ◽  
Roland G. Heym ◽  
...  
Keyword(s):  
Residence Time ◽  
Drug Binding ◽  
Design Strategies ◽  
Kinetics Of

Non—Isothermal Differential Scanning Calorimetry Studies on Nanocrystallization Kinetics of Fe81Si3.5B13.5C2 Amorphous Alloy

2011 ◽  
Vol 688 ◽  
pp. 180-185
Author(s):  
Yu Zhang ◽  
Wei Lu ◽  
Biao Yan ◽  
Yu Xin Wang ◽  
Ying Yang
Keyword(s):  
Activation Energy ◽  
Differential Scanning Calorimetry ◽  
Amorphous Alloy ◽  
Three Dimensional ◽  
Crystallization Mechanism ◽  
Scanning Calorimetry ◽  
Average Value ◽  
Initial Stage ◽  
Friedman Method ◽  
Kinetics Of

The nanocrystallization kinetics of the Fe81Si3.5B13.5C2amorphous alloy was investigated by differential scanning calorimetry (DSC). The apparent activation energy Ea, as well as the nucleation and growth kinetic parameters has been calculated by Kissinger and Ozawa methods. The changeable activation energy Eawith crystalline fraction α was obtained by the expended Friedman method without assuming the kinetic model function, and the average value of Eawas 364±20 kJ/mol. It was shown that the crystallization mechanism of initial stage (0<α<0.7) of the transformation was bulk crystallization with two and three dimensional nucleation graining growth which was controlled by diffusion. For the middle stage (0.7<α<0.9), the crystallization mechanism is surface crystallization with one dimensional nucleation graining growth at a near-zero nucleation rate. In the final stage(α>0.9)，the local Avrami exponents rose anomalously from 1.4 to about 2.0.

Research on Crystallization Kinetics of Calcium Sulfate Dihydrate Prepared by Bittern under 20°C and 120r/min Condition

2014 ◽  
Vol 926-930 ◽  
pp. 210-213
Author(s):  
Bi Jun Luo ◽  
Hai Hong Wu ◽  
Yu Qi Wang ◽  
Qi Zhang
Keyword(s):  
Experimental Data ◽  
Crystal Growth ◽  
Crystallization Kinetics ◽  
Residence Time ◽  
Calcium Sulfate ◽  
Nucleation Density ◽  
Growth Line ◽  
Calcium Sulfate Dihydrate ◽  
Kinetics Of

Crystallization kinetics experiment of calcium sulfate dehydrates, which is prepared by bittern under 20°C and 120r/min conditions, is carried out. According to the results of the experimental data, nucleation densityn0of gypsum crystals is proportional to the residence time, and the rate of crystal growth lineGis inversely proportional to the residence time. Meanwhile, the crystallization kinetics formula is derived to be:B0= 5.78×102G0.87.

scholarly journals Kajian Kinetika Pengaruh Lama Penyimpanan Terhadap Kadar Vitamin C Pada Buah Apel Malang (Malus Sylvestris)

Al-Kimia ◽  
2019 ◽  
Vol 7 (2) ◽  
Author(s):  
Anjar Purba Asmara ◽  
Hanik Khuriana Amungkasi
Keyword(s):  
Vitamin C ◽  
Room Temperature ◽  
Storage Time ◽  
Reaction Rate ◽  
Life Time ◽  
Direct Sunlight ◽  
Average Value ◽  
Malus Sylvestris ◽  
The Subject ◽  
Kinetics Of

An analysis for determining kinetics of effect of varied shelf-life time to the level of vitamin C in Malus sylvestris fruits has been conducted. It has used fresh apple Malang (M. sylvestris) from Batu (East Java) at their harvest time with the same size and color as the subject of the research. Therefore, the fruits were stored in room temperature and kept away from direct sunlight for 0, 1, 2, and 3 days. The fruits were extracted by using a juice blending technique with aquadest as the solvent. An iodimetric titration has been used to determine the effect of the varied storage time to the level of vitamin C in the samples. The result shows that the average value of vitamin C level in M. sylvestris stored in 0, 1, 2, and 3 days as much as 2.3904 mg/50g; 2.1073 mg/50g; 2.06695 mg/50g; and 1.9860 mg/50g, respectively. Statistic analysis of ANAVA-A and t-test confirms that there are significant differences between the level of vitamin C of M. sylvestris stored in 0, 1, 2, and 3 days. The conclusion about the kinetics of ascorbic acid degradation of M. sylvestris at 27 0C states three expressions as following as: the reaction is a second order reaction, the constants of reaction rate is 2.65 x 10-2 L(mol.days)-1, the half life is 15.786 days, and kinetics model for the reaction is C = (0.0265t + 1/C0)-1.

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