scholarly journals The transition nanoreactor-nanoparticle in epoxy polymers curing process

2008 ◽  
Vol 2 (4) ◽  
pp. 281-284
Author(s):  
Georgiy Kozlov ◽  
◽  
Musa Bashorov ◽  
Abdulakh Mikitaev ◽  
Gennady Zaikov ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Euclidean Space ◽  
Reaction Rate ◽  
Typical Feature ◽  
Reaction Rate Constant ◽  
Conversion Degree ◽  
Curing Process ◽  
Epoxy Polymers ◽  
Curing Reaction ◽  
Fractal Space

It has been shown that for curing reaction in fractal space the reaction rate constant reduction is typical. Another typical feature of this reaction is the formation of a large number of microgels with smaller molecular weight in comparison with reaction in Euclidean space at the same conversion degree. The dimensional border between nanoreactor and nanoparticle for the curing reaction under consideration has been obtained.

scholarly journals Kinetics and Thermodynamics Study of Ultrasound-Assisted Depolymerization of k-Carrageenan in Acidic Solution

2020 ◽  
Vol 15 (1) ◽  
pp. 280-289
Author(s):  
Ratnawati Ratnawati ◽  
Nita Indriyani
Keyword(s):  
Molecular Weight ◽  
Rate Constant ◽  
Reaction Rate ◽  
Acidic Solution ◽  
Biomedical Application ◽  
Bond Cleavage ◽  
Reaction Rate Constant ◽  
Order Kinetic ◽  
Kinetics And Thermodynamics ◽  
Ultrasound Assisted

K-carrageenan is a natural polymer with high molecular weight ranging from 100 to 1000 kDa. The oligocarrageenan with low molecular weight is widely used in biomedical application. The aim of this work was to depolymerize k-carrageenan in an acidic solution with the assistance of ultrasound irradiation. The ultrasonication was conducted at various pH (3 and 6), temperatures (30-60 °C), and depolymerization time (0-24 minutes). The results show that the depolymerization reaction follows pseudo-first-order kinetic model with reaction rate constant of 1.856×10-7 to 2.138×10-6 s-1. The reaction rate constant increases at higher temperature and lower pH. The Q10-temperature coefficients of the depolymerization are 1.25 and 1.51 for pH 6 and 3, respectively. The enthalpy of activation (ΔH‡) and the Gibbs energy of activation (ΔG‡) are positive, while the entropy of activation (ΔS‡) is negative, indicating that the activation step of the ultrasound-assisted depolymerization of k-carrageenan is endothermic, non-spontaneous, and the molecules at the transition state is more ordered than at the ground state. The ΔH‡ and the ΔS‡ are not affected by temperature, while the ΔG‡ is a weak function of temperature. The ΔH‡ and ΔS‡ become smaller at higher pH, while the ΔG‡ increases with the increase of pH. The kinetics and thermodynamics analysis show that the ultrasound-assisted depolymerization of k-carrageenan in acidic solution is possibly through three mechanisms, i.e. bond cleavage due to cavitational effect of microbubbles, hydroxyl radical and hydrogen peroxide, as well as proton. Copyright © 2020 BCREC Group. All rights reserved 

Studies on Curing Kinetics Parameter of TDI-PPG-MOCA Polyurethane by FTIR

2011 ◽  
Vol 328-330 ◽  
pp. 966-969 ◽  
Author(s):  
Qing Zhen Wen ◽  
Chao Yu ◽  
Jin Hua Zhu ◽  
Tian Yu Liu
Keyword(s):  
Reaction Rate ◽  
Curing Kinetics ◽  
Crosslinking Reaction ◽  
Curing Process ◽  
Second Order Reaction ◽  
Reaction Rate Constants ◽  
Curing Reaction ◽  
Different Temperatures ◽  
Measured Effect ◽  
Kinetics Parameter

The curing process of polyurethanes was investigated with FTIR method. The curves of conversion (α)VS curing reaction time (t) at different temperatures were obtained .The curing reaction of the system was found to be second order reaction. The reaction rate constants and activation energy had been measured. Effect of the use lever of curing agent and temperatures on curing reaction was discussed. The results showed that when the mole ratio of NCO/OH is smaller than 1, the crosslinking reaction take place at high temperature.

scholarly journals Rheokinetic study of crosslinking of α,ω-dihydroxy oligo(alkylene maleate)s with a trisisocyanate

2003 ◽  
Vol 68 (3) ◽  
pp. 147-162 ◽  
Author(s):  
Branko Dunjic ◽  
Jasna Djonlagic ◽  
Slavko Vukasinovic ◽  
Maurice Sepulchre ◽  
Marie-Odile Sepulchre ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Reaction Rate ◽  
Loss Modulus ◽  
Phase Segregation ◽  
Mechanical Analysis ◽  
Rheological Parameters ◽  
Crosslinking Reaction ◽  
Curing Process ◽  
Segmental Mobility ◽  
Time Curve

The crosslinking reaction of three series of ?,?-dihydroxy oligo(alkylene maleate)s with a trifunctional isocyanate was followed by dynamic mechanical analysis and FTIR spectroscopy. The evaluation of rheological parameters such as storage G? and loss modulus G", was recorded. A typical G?versus time curve has a characteristic "S" shape, indicating autoacceleration of the crosslinking reaction. The whole curing process starting from G?equal G", or the beginning of gelation is described by a second - order phenomenological rheokinetic equation which takes into account the autoacceleration effect, the latter being a consequence of the superposition of both the chemical reaction and phase segregation. It appears that the crosslinking reaction rate depends on the concentration of the functional groups, i.e., on the molecular weight of the polyester prepolymer and on the length of the aliphatic sequence in the repeating unit or the segmental mobility. The crosslinking rate decreases in the order: poly(octamethylene maleate) > poly(hexamethylene maleate) > poly(butylene maleate).

scholarly journals The influence of fatty acid composition on the kinetics of the vegetable oil methanolysis reaction

2021 ◽  
Vol 10 (2) ◽  
pp. 24-31
Author(s):  
Milan Kostić ◽  
Olivera Stamenković ◽  
Vlada Veljković
Keyword(s):  
Fatty Acids ◽  
Fatty Acid Composition ◽  
Fatty Acid ◽  
Acid Composition ◽  
Rate Constant ◽  
Reaction Rate ◽  
Unsaturated Fatty Acids ◽  
Reaction Rate Constant ◽  
Conversion Degree ◽  
Kinetics Of

The base-catalyzed methanolysis of roadside pennycress, olive, melon, grapeseed, hempseed, sunflower, and plum kernel oils was performed in the presence of KOH (1% to the oil weight) at the temperature of 60° C and the methanol/oil molar ratio of 6:1. The aim of this work was to reveal the influence of the fatty acid composition of the oils on the kinetics of these methanolysis reactions. The irreversible pseudo-first-order reaction was used for modeling the kinetics of the methanolysis reactions, and the reaction rate constant was correlated with the content of unsaturated fatty acids in the oil. The value of the reaction rate constant increases linearly with increasing the unsaturated fatty acids content in the oil. The applicability and reliability of the model were confirmed by high values of the coefficient of determination and low values of the mean relative percentage deviation between the calculated and experimental triacylglycerols conversion degree.

scholarly journals Examinations of Polish brown and hard coals in terms of their use in the steam gasification process

2017 ◽  
Vol 33 (1) ◽  
pp. 15-34 ◽  
Author(s):  
Stanisław Porada ◽  
Tadeusz Dziok ◽  
Grzegorz Czerski ◽  
Przemysław Grzywacz ◽  
Andrzej Strugała
Keyword(s):  
Reaction Rate ◽  
Raw Materials ◽  
Calorific Value ◽  
Reaction Rate Constant ◽  
Steam Gasification ◽  
Reactivity Index ◽  
Conversion Degree ◽  
Carbon Conversion ◽  
Reaction Rate Constants ◽  
Gaseous Products

Abstract In order to determine the suitability of Polish coals for steam gasification, five Polish hard coals and three brown coals, which are used for power and heat production, were examined in this work. The examinations of the process of steam gasification were conducted with the use of a laboratory plant which allows for measurements within a broad pressure range with the thermovolumetric method. Reactivity evaluations for the examined coals were conducted on the basis of an analysis of the shape of the kinetic curves of formation of major gasification products and a comparison of the curves of the carbon conversion degree of the examined raw materials. In order to evaluate the reactivity of the examined coals, the following factors were utilized: a comparison of the shape of the curves of the carbon conversion degree and the maximal value of the carbon conversion degree, the time of partial conversion τ0.5, the reactivity index R0.5, as well as the reaction rate constant of carbon conversion. The yields, composition and calorific value of the resulting gas were determined as well as the reaction rate constants of formation of particular gaseous products of gasification. Additionally, for the examined coals, ash fusibility and the content of selected impurities, e.g. sulfur, chlorine and mercury, were given.

Study on Curing Kinetics of Natural Rubber Dried by Microwave

2013 ◽  
Vol 807-809 ◽  
pp. 2809-2812
Author(s):  
Mei Chen ◽  
Fu Quan Zhang ◽  
Yong Zhou Wang ◽  
Mao Fang Huang
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Weight Distribution ◽  
Reaction Rate ◽  
Curing Kinetics ◽  
Peak Height ◽  
Peak Position ◽  
Curing Temperature ◽  
Conversion Degree ◽  
Kinetics Of

In this article, the curing kinetics of natural rubber (NR) dried by microwave at frequency of 2450MHz was studied using vulcameter, as well as molecular weight. Seen from the results, the molecular weight distribution of NR dried by microwave was wide, the reaction rate of NR dried by microwave at any temperatures increased with conversion degree (α) increment and passed through a maximum at the value ofαbetween 0.1 and 0.3, the peak height ofαwas increased with a shift in peak position towards a higherαvalue, which provided evidences that the curing behavior illustrated autocatalytic characteristics and depended on curing temperature.

Monitoring Polymer-Assisted Mechanochemical Cocrystallisation Through in Situ X-Ray Powder Diffraction

2020 ◽  
Author(s):  
Luzia S. Germann ◽  
Sebastian T. Emmerling ◽  
Manuel Wilke ◽  
Robert E. Dinnebier ◽  
Mariarosa Moneghini ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Powder Diffraction ◽  
Reaction Rate ◽  
Polymer Additives ◽  
Time Resolved ◽  
X Ray

Time-resolved mechanochemical cocrystallisation studies have so-far focused solely on neat and liquid-assisted grinding. Here, we report the monitoring of polymer-assisted grinding reactions using <i>in situ</i> X-ray powder diffraction, revealing that reaction rate is almost double compared to neat grinding and independent of the molecular weight and amount of used polymer additives.<br>

scholarly journals Determination of exothermic batch reactor specific model parameters

2019 ◽  
Vol 292 ◽  
pp. 01063
Author(s):  
Lubomír Macků
Keyword(s):  
Rate Constant ◽  
Reaction Rate ◽  
Batch Reactor ◽  
Specific Model ◽  
Reaction Rate Constant ◽  
Order Reaction ◽  
First Order Reaction ◽  
Model Parameters ◽  
Reactor Model ◽  
First Order

An alternative method of determining exothermic reactor model parameters which include first order reaction rate constant is described in this paper. The method is based on known in reactor temperature development and is suitable for processes with changing quality of input substances. This method allows us to evaluate the reaction substances composition change and is also capable of the reaction rate constant (parameters of the Arrhenius equation) determination. Method can be used in exothermic batch or semi- batch reactors running processes based on the first order reaction. An example of such process is given here and the problem is shown on its mathematical model with the help of simulations.

Preparation and Properties of Silicon-Containing Arylacetylene Resins with Octa(maleimidophenyl)silsesquioxane

2012 ◽  
Vol 557-559 ◽  
pp. 1152-1156
Author(s):  
Yan Zhou ◽  
Fu Wei Huang ◽  
Fa Rong Huang ◽  
Lei Du
Keyword(s):  
Thermal Stability ◽  
Dielectric Constant ◽  
Dielectric Properties ◽  
Thermal Polymerization ◽  
Curing Process ◽  
Thermal Stabilities ◽  
Curing Reaction ◽  
Air Atmosphere ◽  
Ft Ir ◽  
Dsc Analyses

Modified silicon-containing arylacetylene resins (DMSEPE-OMPS) were prepared from poly(dimethylsilyleneethynylenephenyleneethynylene) (DMSEPE) and Octa(maleimidophenyl)- silsesquioxane (OMPS). The curing reaction of DMSEPE-OMPS resin was studied by FT-IR and DSC techniques. Thermal stability and dielectric properties of cured DMSEPE-OMPS resins were determined. FT-IR and DSC analyses indicate that thermal polymerization of DMSEPE-OMPS resin occurs in the curing process. Thermal stabilities of cured DMSEPE-OMPS resins under N2 and air atmosphere decrease gradually with the increment of OMPS components. The incorporation of OMPS can obviously reduce dielectric constant of DMSEPE-OMPS resins.

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