Two-parameter Autocatalytic Model Research Articles

Curing and Molecular Dynamics Simulation of MXene/Phenolic Epoxy Composites with Different Amine Curing Agent Systems.

Herein, the curing kinetics and the glass transition temperature (Tg) of MXene/phenolic epoxy composites with two curing agents, i.e., 4,4-diaminodiphenyl sulfone (DDS) and dicyandiamine (DICY), are systematically investigated using experimental characterization, mathematical modeling and molecular dynamics simulations. The effect of MXene content on an epoxy resin/amine curing agent system is also studied. These results reveal that the MXene/epoxy composites with both curing agent systems conform to the SB(m,n) two-parameter autocatalytic model. The addition of MXene accelerated the curing of the epoxy composite and increased the Tg by about 20 K. In addition, molecular dynamics were used to simulate the Tg of the cross-linked MXene/epoxy composites and to analyze microstructural features such as the free volume fraction (FFV). The simulation results show that the introduction of MXene improves the Tg and FFV of the simulated system. This is because the introduction of MXene restricts the movement of the epoxy/curing agent system. The conclusions are in good agreement with the experimental results.

Non-isothermal kinetics of epoxy resin curing reaction under compressed CO2

The non-isothermal curing kinetics of epoxy resin system consisting of diglycidyl ether of bisphenol A (DGEBA) and m-xylylenediamine (MXDA) were investigated by high-pressure differential scanning calorimetry at different heating rates of 5, 10, 15 and 20 K min−1 under compressed carbon dioxide (CO2) of 0.1–8 MPa. The activation energies were determined by isoconversional Kissinger–Akahira–Sunose method and Vyazovkin numerical method, and the average values decreased from 53.5 to 46.8 and 54.1 to 44.5 kJ mol−1, respectively, when the CO2 pressure increased from 0.1 to 8 MPa. It is indicated that the curing reaction of epoxy resin occurs more easily under higher-pressure CO2 due to the promoted molecular movement, especially in the supercritical state. The non-isothermal curing kinetics were investigated by nth-order model and two-parameter autocatalytic model (Sestak–Berggren model), and the latter one analyzed by Malek method exhibited good agreement with the experimental data except the initial and final stages of the curing reaction.

Study on the optimum ratio and non-isothermal curing kinetics of EP2008/EP2008-S system

This paper systematically reports the optimum ratio and non-isothermal curing kinetics of EPOLAM 2008 RESIN (EP2008)/EPOLAM 2008-S HARDENER (EP2008-S) system studied using Differential Scanning Calorimetry (DSC). In view of the gel time, viscosity, and curing reaction heat, the optimum ratio of m (EP2008)/m (EP2008-S) can be confirmed as 100:20. Subsequently, non-isothermal curing kinetics of the composite system with the optimum ratio of m (EP2008)/m (EP2008-S) is investigated by dynamic DSC. The kinetics mechanism function is analyzed with the nth-order model and two-parameter (m and n) autocatalytic model (Sestak–Berggren model). Results indicated that the Malek method discloses the autocatalytic behavior, and that the two-parameter autocatalytic model is able to well simulate the curing reaction. Through the analysis of chemical composition of EP2008/EP2008-S and the value of E a , the possible curing reaction mechanism can be explained.

Influence of Polymer Coated CaCO3 on Vulcanization Kinetics of Natural Rubber/Sulfur/N-Oxydiethyl Benzthiazyl Sulfenamide (BSM) System

The effect of polymethyl methacrylate (PMMA)-encapsulated calcium carbonate on the kinetics of the vulcanization of natural rubber (NR) with a vulcanizing agent (sulfur) accelerated by N-oxydiethyl benzthiazyl sulfenamide (BSM) has been studied. The PMMA coating (4% by weight of CaCO3) was prepared by dispersion polymerization, and compositions of five NR composites were 10, 15, 20 phr of treated CaCO3 and 20 and 40 phr of untreated CaCO3. The vulcanization kinetics was determined by oscillating disc rheometry (ODR) and the kinetic parameters were determined by the model equations. The kinetic analysis suggests that the two-parameter auto catalytic model is the more appropriate one to elucidate the kinetics of the vulcanizing reaction of the present system. These parameters support the nature of the experimental ODR curves (degree of conversion–time plots). The encapsulated CaCO3 leads to a change in vulcanization reaction and has an effect on the kinetic parameters E, ln K0, m and n, and consequently on the overall reactivity.

Study on a novel thermoset nanocomposite form DGEBA–cycloaliphatic diamine and metal nanoparticles

The thermo-physical properties of diglycidyl ether of bisphenol A (DGEBA)/isophoronediamine (IPDA) with iron nanoparticles were investigated using DSC, DMT, and TG analysis. Because of the higher values of the glass transition, it is recognized that the optimum behavior of the three-component system corresponds to the 10% loading level of iron nanoparticles. The addition of iron nanoparticles into the epoxy matrix resulted in a significant increment in the storage modulus and crosslink density. Also, the DGEBA/IPDA/10% iron nanoparticles showed an enhanced thermal stability owing to the introduction of iron nanoparticles as reinforcing filler. Curing reaction of DGEBA/IPDA with 10% iron nanoparticles was investigated by DSC at dynamic mode. Activation energy was calculated based on Kissinger method (66.52 kJ mol−1). Also, the advanced isoconversional method is utilized to describe the curing reaction process. In the dynamic DSC analyses, the curing kinetics could be successfully described with the two-parameter autocatalytic model (Sěstak–Berggren equation) and the overall reaction order was about 2.78.

Synthesis and nonisothermal reaction of a novel acrylonitrile-capped poly(propyleneimine) dendrimer with epoxy resin

A novel acrylonitrile-capped poly(propylene imine) dendrimer (PAN4) was synthesized and characterized with FTIR and 1H-NMR. PAN4 and its precursor (poly(propylene imine) dendrimer (1.0GPPI) were employed to cure bisphenol A epoxy resin (DGEBA), and the nonisothermal reaction kinetics of DGEBA/PAN4 and DGEBA/1.0GPPI was systematically investigated using a differential scanning calorimeter (DSC) in a comparative way. The apparent activation energies determined with the Kissinger method were 59.7 kJ/mol for DGEBA/1.0GPPI and 53.9 kJ/mol for DGEBA/PAN4. Applied the Malek method, it was found that a two-parameter autocatalytic model (SB(m, n)) could well simulate the reaction rates, and further analysis of the reaction rate constants showed PAN4 could cure DGEBA at a greatly decreased rate by a factor a more than ten compared with 1.0GPPI control.

Curing Kinetics and Rheology of Diglycidyiether of Bisphenol-A Modified by Poly(ethylene glycol) Flexible Chains

The curing reaction of the system bisphenol-A glycidol ether epoxy resin modified by poly (ethylene glycol) (PEO) and flexible amine (D-230) as curing agent has been studied by means of differential scanning calorimetry (DSC) and thermal scanning rheometry. The curing kinetic parameters have been calculated from the non-thermal DSC curve. The kinetic analysis suggests that the two-parameter autocatalytic model is more appropriate to describe the kinetics of the curing reaction of the system. Increasing the PU content leads to an increase in the heat of curing and has a little effect on the kinetic parameters apparent activation energy (Ea), pre-exponential factor (A), and order of the reaction (m and n). The rheological properties were measured by isothermal curing evolution. Introduction of PEO flexible chains delayed the polymerization. It has been confirmed that the introduction of PEO chains in the structure of the epoxy resin increases the mobility of the molecular segment of the epoxy networks and results in the decrease in glass transition temperature.

Nonisothermal reaction kinetics of DGEBA with four-armed starlike polyamine with benzene core (MXBDP) as novel curing agent

A four-armed starlike polyamine with a benzene nucleus (MXBDP) was prepared, characterized, and employed as the novel curing agent for epoxy resin of bisphenol A (DGEBA). Nonisothermal reaction kinetics of DGEBA/MXBDP was systematically investigated using a differential scanning calorimeter (DSC) in terms of a model-fitting Málek approach and a model-free advanced isoconversional method of Vyazovkin (AICM). A two-parameter autocatalytic model of Šesták–Berggren (SB( m, n) model) was substantiated to be able to well describe the nonisothermal reaction rate of DGEBA/MXBDP. In addition, the correlation between effective activation energy E α upon fractional conversion α was determined with the AICM. The result showed E α dropped quickly at the initial stage of the reaction up to α ≈ 10%, then showed a relative constant value of ≈57 kJ/mol for α ≈ 10–35%, and finally decreased again from ≈57 to ≈45 kJ/mol until the completion, which implicates quite complex mechanisms of the reaction.

The kinetic analysis of isothermal curing reaction of an unsaturated polyester resin: Estimation of the density distribution function of the apparent activation energy

The kinetic process of isothermal curing of an unsaturated polyester resin samples has been studied. The differential isoconversional method is used to yield dependency of the apparent activation energy, E a , on the degree of cure. It was found that the dependence of E a on α is complex, but in the conversion range α = 0.10–0.50, E a is practically constant. It was found that the gelling stage of curing process is mainly controlled chemically which can be best described by two-parameter autocatalytic model. At higher values of α, when vitrification point is reached, the change in rate-limiting step was observed. As the consequence of shifting effect from the kinetics to diffusion control, the kinetic law equation is modified with additional diffusion term. It was found that the experimentally obtained density distribution function of the apparent activation energy can be approximate by unbalanced modified Gaussian distribution function with quite satisfactory precision.

A kinetic study of non-isothermal decomposition process of anhydrous nickel nitrate under air atmosphere

Abstract The non-isothermal decomposition process of anhydrous nickel nitrate under air atmosphere was investigated. The kinetic analysis of decomposition process was performed using Friedman (FR), Kissinger–Akahira–Sunose (KAS) and Flynn–Wall–Ozawa (FWO) isoconversional methods. The kinetic model was determined by the Malek's method. The composite differential method I was used for checking the established reaction model. It was found that the value of Ea calculated by composite differential method (Ea=147.1 kJ mol−1) represents the medium value between the values of the apparent activation energy calculated by FR (Ea,FR=152.8 kJ mol−1) and FWO (Ea,FWO=143.1 kJ mol−1) methods. Using two special functions (y(α) and z(α)), it was found that the two-parameter autocatalytic model (Sestak–Berggren (SB) kinetic model) with kinetic exponents M=0.23 and N=1.14 is the most adequate one to describe the decomposition kinetics of the studied system at various heating rates. The obtained non-isothermal differential conversion curves from the experimental data show the results being accordant with those theoretically calculated. It was concluded that the SB kinetic model can be used for a quantitative description of non-isothermal decomposition process of anhydrous nickel nitrate which involves the partially overlapping nucleation and growth phases.

Cure Kinetics of DGEBA with Hyperbranched Poly (3-hydroxyphenyl) Phosphate as Curing Agent Studied by Non-isothermal DSC

The cure kinetics of diglycidyl ether of bisphenol A (DGEBA) with hyperbranched poly(3-hydroxyphenyl) phosphate(HHPP) as the curing agent was investigated by means of non-isothermal differential scanning calorimetry (DSC) at various heating rates. The results were compared with the corresponding results by using 1,3-dihydroxybenzene(DHB) as a model compound. The results show that HHPP can enhance the cure reaction of DGEBA, resulting in the decrease of the peak temperature of the curing curve as well as the decrease of the activation energy because of the flexible P O groups in the backbone of HHPP. However, both the activation energy of the cured polymer and the peak temperature of the curing curve are increased with DHB as a curing agent. The cure kinetics of the DGEBA/HHPA system was calculated by using the isoconversional method given by Malek. It was found that the two-parameter autocatalytic model (Sestak-Berggren equation) is the most adequate one to describe the cure kinetics of the studied system at various heating rates. The obtained non-isothermal DSC curves from the experimental data show the results being accordant with those theoretically calculated.

Kinetic analysis of solid-state processes

A simple method for kinetic analysis of solid-state processes has been developed. A criteria capable of classifying different processes is explored here with a view toward visualizing the complexity of solid-state kinetics. They provide a useful tool for the determination of the most suitable kinetic model. The method has been applied to the analysis of crystallization processes in amorphous ZrO2 and RuO2. It is found that the crystallization kinetics of as-prepared sample exhibits a complex behavior under nonisothermal conditions. This is probably due to an overlapping of the nucleation- and crystal-growth processes at the beginning of crystallization. As a consequence, the Johnson–Mehl–Avrami nucleation-growth model cannot be applied. A two-parameter autocatalytic model provides a good description of the crystallization process under isothermal and nonisothermal conditions.

Kinetics analysis of the curing reaction of fast cure epoxy prepregs

In this article, the curing kinetics of two fast cure flip-chip epoxy encapsulants under both isothermal and nonisothermal conditions are investigated by differential scanning calorimetry. The method allows determination of the most suitable kinetic model and corresponding parameters. The kinetic analysis suggests that the two-parameter autocatalytic model is more appropriate to describe the kinetics of the curing reaction. There are certain differences between the kinetic data from isothermal and that from nonisothermal measurements. The apparent activation energy Ea and pre-exponential factor A of E-AB1 determined from nonisothermal experiments were higher than the isothermal values, whereas the Ea and A of E-RV2 determined from both methods are relatively close. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1501–1508, 1999

Kinetics analysis of the curing reaction of fast cure epoxy prepregs

In this article, the curing kinetics of two fast cure flip-chip epoxy encapsulants under both isothermal and nonisothermal conditions are investigated by differential scanning calorimetry. The method allows determination of the most suitable kinetic model and corresponding parameters. The kinetic analysis suggests that the two-parameter autocatalytic model is more appropriate to describe the kinetics of the curing reaction. There are certain differences between the kinetic data from isothermal and that from nonisothermal measurements. The apparent activation energy Ea and pre-exponential factor A of E-AB1 determined from nonisothermal experiments were higher than the isothermal values, whereas the Ea and A of E-RV2 determined from both methods are relatively close. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1501–1508, 1999

Addition of a reactive diluent to a catalyzed epoxy-anhydride system. I. Influence on the cure kinetics

The effect of a reactive diluent (RD) on the kinetics of the curing of an epoxy resin, based on diglycidyl ether of bisphenol A (DGEBA), with a carboxylic anhvdride derived from methyl-tetrahydrophthalic anhydride (MTHPA) catalyzed by a tertiary amine has been studied. The reactive diluent was a low-viscosity aliphatic diglycidyl ether, and the compositions per 100 parts by weight (pbw) of DGEBA were 10, 30, and 50 pbw of RD with the stoichiometric quantity of MTHPA and 1 pbw of catalyst. The curing kinetics was monitored by differential scanning calorimetry (DSC), and the kinetic parameters were determined from the nonisothermal DSC curves by the method described by Málek. The kinetic analysis suggests that the two-parameter autocatalytic model is the more appropriate to describe the kinetics of the curing reaction of this epoxy-anhydride system. The kinetic parameters thus derived satisfactorily simulate both the nonisothermal DSC curves and the isothermal conversion-time plots. Increasing the RD content leads to a small increase in both the nonisothermal and the isothermal heats of curing and has a slight effect on the kinetic parameters E, ln A, m, and n, and, consequently, on the overall reactivity of the system. On the other hand, the increase of the RD content significantly affects the structure of the crosslinked epoxy. It is confirmed that the introduction of aliphatic chains in the structure of the epoxy increases the mobility of the segmental chains in the glass transition region. The consequence of this chemical modification is a decrease of the glass transition temperature, Tg. © 1996 John Wiley & Sons, Inc.