In situ synthesis and characterization of ZnS/epoxy nanocomposites via gas‐liquid state reaction method

In this article, the ZnS/epoxy nanocomposites were successfully prepared by the reaction of zinc acetate and H₂S gas via a simple step. Epoxy resin acted as the matrix for the formation of ZnS nanoparticles (10–20 nm) in the reaction system and kept them from agglomerating. The structure, composition, and mechanical properties of the resultant products were successfully investigated by powder X‐ray diffraction, transmission electron microscope, field emission scanning electron microscope, energy dispersive X‐ray fluorescence, and universal testing machine. Meanwhile, by employing differential scanning calorimetry (DSC) we had studied, under nonisothermal condition, the kinetic analysis of the cure reaction which was performed using two classic models: Kissinger and Flynn‐Wall‐Ozawa. The activation energy of curing reaction was 74.63 kJ/mol and 77.57 kJ/mol, respectively, by Kissinger's and Flynn‐Wall‐Ozawa's methods. The possible mechanism of preparation of ZnS/epoxy composites was discussed in this article. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Thermal degradation kinetics of poly(O,O‐diethyl‐O‐allylthiophosphate‐co‐acrylonitrile) in nitrogen

The nonisothermal degradation kinetics of the copolymer poly(O,O‐diethyl‐O‐allylthiophosphate‐co‐acrylonitrile), which was synthesized with O,O‐diethyl‐O‐allylthiophosphate and acrylonitrile, were studied by thermogravimetry/derivative thermogravimetry techniques. The kinetic parameters, including the activation energy and the pre‐exponential factor of the copolymer degradation process, were calculated by the Kissinger and Flynn–Wall–Ozawa methods. The thermal degradation mechanism of the copolymer was also studied with the Satava–Sestak method. The results show that the activation energies were 138.17 kJ/mol with the Kissinger method and 141.63 kJ/mol with the Flynn–Wall–Ozawa method. The degradation of the copolymer followed a kinetic model of a phase boundary reaction and the kinetic equation could be expressed as G(α) = 1 ? (1 ? α)⁴ [where G(α) is the integral function of conversion and α is the extent of conversion of the reactant decomposed at time t]. The reaction order was 4. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and curing kinetics of bisphenol A type novolac epoxy resins

A bisphenol A type novolac resin (Bis‐ANR) was synthesized from bisphenol A and formaldehyde; the resulting novolac was epoxidized to generate a bisphenol A type novolac epoxy resin (Bis‐ANER). The chemical structures of Bis‐ANR and Bis‐ANER were confirmed by ¹H‐NMR spectroscopy and IR spectroscopy; the molecular weights and molecular weight distributions were determined by gel permeation chromatography. In addition, the curing process of Bis‐ANER with 4,4′‐diaminodiphenyl sulfone was studied in both dynamic and isothermal modes with differential scanning calorimetry. The dynamic curing kinetic analysis was evaluated with both the Kissinger and Flynn–Wall–Ozawa methods, and the curing activation energy values were obtained. The isothermal curing reaction exhibited autocatalytic behavior, and the curing kinetics were described with the Kamal kinetics model, which accounted for both the autocatalytic and diffusion‐control effects. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 858–868, 2006     

Cure kinetics of an epoxidized hemp oil based bioresin system

A novel epoxidized hemp oil (EHO) based bioresin was synthesized by epoxidation in situ with peroxyacetic acid. In this research the cure kinetics of an EHO based bioresin system cured with triethylenetetramine (TETA) was studied by differential scanning calorimetry using both isothermal and nonisothermal data. The results show that the curing behavior can be modeled with a modified Kamal autocatalytic model that accounts for a shift to a diffusion‐controlled reaction postvitrification. The total order of the reaction was found to decrease with an increase in temperature from ～ 5.2 at 110°C to ～ 2.4 at 120°C. Dynamic activation energies were determined from the Kissinger (51.8 kJ/mol) and Ozawa‐Flynn‐Wall (56.3 kJ/mol) methods. Activation energies determined from the autocatalytic method were 139.5 kJ/mol and ?80.5 kJ/mol. The observed negative activation energy is thought to be due to an unidentified competitive reaction that gives rise to the appearance of k₂ decreasing with increasing temperature. The agreement of fit of the model predictions with experimental values was satisfactory for all temperatures. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Cure kinetics of an epoxy resin containing naphthyl/dicyclopentadiene moieties and bis‐phenoxy (3‐hydroxy) phosphine oxide system and properties of its cured polymer

The cure kinetics of naphthyl/dicyclopentadiene epoxy resin and bisphenoxy (3‐hydroxy) phosphine oxide was investigated by differential scanning calorimetry (DSC) under nonisothermal and isothermal condition. The advanced isoconversional method was used to study the nonisothermal DSC data, the effective activation energy of the curing system in the early stage agreed with the value calculated from the Kissinger model and then increased because of the hindrance of molecular mobility. Autocatalytic behavior was shown in the isothermal DSC measurement, which was well described by Kamal model in the early curing stage. In the later stage, a crosslinked network structure was formed and the curing reaction was mainly controlled by diffusion. The diffusion factor was introduced to optimize the Kamal model and correct the deviation of the calculated data. The physical properties of the cured polymer were evaluated by dynamic mechanical thermal analyses, thermogravimetric analyses, and limiting oxygen index test, which exhibited relatively high glass transition temperature, thermal stability, and flame retardancy. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of Hyperbranched Poly (Trimellitic Anhydride Ethylene Glycol) Epoxy (HTME) on Thermal Degradation Activation Energies of HTME/Diglycidyl Ether of Bisphenol-A Epoxy Hybrid Resin by Kissinger and Flynn–Wall–Ozawa Method

The thermal degradation behavior and kinetics of hyperbranched poly (trimellitic anhydride ethylene glycol) epoxy (HTME)/diglycidyl ether of bisphenol-A epoxy (DGEBA) hybrid resin was investigated with thermogravimetric analysis (TGA) by using Kissinger method and Flynn–Wall–Ozawa method. The results show that the thermal degradation activation energies of DGEBA, 9 wt% HTME-1/91wt% DGEBA, 3 wt% HTME-2/97 wt% DGEBA, 9 wt% HTME-2/91 wt% DGEBA, 15 wt% HTME-2/85 wt% DGEBA, and 9 wt% HTME-3/91wt% DGEBA are 152.5, 144.4, 135.4, 133.2, 121.8 and 143.0 kJmol^?1, respectively, by Kissinger method. and the activation energies are 173.3, 165.0, 163.2, 151.7, 137.7 and 159.7 kJmol^?1, respectively by Flynn–Wall–Ozawa method. With the increase of HTME content, the activation energies of HTME/DGEBA hybrid resin decrease. Although molecular weight or generation of hyperbranched epoxy resins (HTME) has little effect on the thermal degradation activation energies and other kinetics data.     

Cure kinetics of an acrylated epoxidized hemp oil‐based bioresin system

In this work, the cure kinetics of a novel acrylated epoxidized hemp oil (AEHO)‐based bioresin was investigated for the first time by differential scanning calorimetry (DSC) using both isothermal and nonisothermal conditions. This new bioresin was synthesized by the acrylation of a previously epoxidized hemp oil (EHO) bioresin. The curing of the AEHO bioresin showed an autocatalytic behavior with the vitrification phenomenon preventing the conversion reaching unity for all the temperatures studied. It was found that the curing behavior can be modeled with high accuracy using a modified Kamal autocatalytic model that takes into account the vitrification phenomenon. Dynamic activation energies were determined from the Kissinger and Ozawa–Flynn–Wall methods, resulting in 58.87 and 62.02 kJmol^?1, respectively. In addition, activation energies associated with the autocatalytic model constants, k₁ and k₂, were established to be equal to 58.94 and 45.32 kJmol^?1, respectively. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Thermal decomposition kinetics of thermotropic copolyesters made from trans‐p‐hydroxycinnamic acid and p‐hydroxybenzoic acid

A series of thermotropic copolyesters were synthesized by direct thermal melt polycondensation of p‐acetoxybenzoic acid (PHB) with trans‐p‐acetoxycinnamic acid (PHC). The dynamic thermogravimetric kinetics of the copolyesters in nitrogen were analyzed by four single heating‐rate techniques and three multiple heating‐rate techniques. The effects of the heating rate, copolyester composition, degradation stage, and the calculating techniques on the thermostability and degradation kinetic parameters of the copolyesters are systematically discussed. The four single heating‐rate techniques used in this work include Friedman, Freeman–Carroll, Chang, and the second Kissinger techniques, whereas the three multiple heating‐rate techniques are the first Kissinger, Kim–Park, and Flynn–Wall techniques. The decomposition temperature of the copolyesters increases monotonically with increasing PHB content from 40 to 60 mol %, whereas their activation energy exhibits a maximal value at the PHB content of 50 mol %. The decomposition temperature, activation energy, the order, and the frequency factor of the degradation reaction for the thermotropic copolyester with PHB/PHC feed ratio of 50/50 mol % were determined to be 374°C, 408 kJ/mol, 7.2, and 1.25 × 10²⁹ min^?1, respectively. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 445–454, 2004     

Study on curing kinetics and curing mechanism of epoxy resin based on diglycidyl ether of bisphenol a and melamine phosphate

The curing kinetics of the diglycidyl ether of bisphenol A/melamine phosphate (DGEBA/MP) was analyzed by the DSC technique. The Kissinger and Flynn–Wall–Ozawa methods were applied to determine the dynamic kinetics of the DGEBA/MP system. The activation energies obtained by these two methods were 83.9 and 85.6 kJ/mol, respectively. An autocatalytic equation was applied to determine the isothermal curing kinetics of the DGEBA/MP system. The DGEBA/MP system exhibits autocatalytic behavior in the isothermal curing procedure, whose kinetics fits well with the autocatalytic mechanism. The obtained isothermal curing activation energy of the DGEBA/MP system was 110.0 kJ/mol. The curing mechanism of DGEBA with melamine phosphate was investigated using FTIR, ¹³C solid‐state NMR, and ³¹P solid‐state NMR. It involved an epoxide–amine reaction, etherification of phosphoric acid and epoxy, dehydration, and thermal oxidation of the hydroxyl group of the DGEBA/MP system. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 892–900, 2004     

Characterization of four different lignins as a first step toward the identification of suitable end‐use applications

To determine the most appropriate use of lignin, surface, structural, and thermal characteristics of lignin was investigated in this work. It was observed that kraft lignin (KL), the lignin of prehydrolysis liquor (LPHL), lignosulfonate of NSSC process (LSL), and lignosulfonates (LSs) of sulfite pulping process had 0.67, 0.25, 0.90, and 1.52–2.25 meq/g anionic charge density, and 6.3, 2.1, 10.1, and 8.8–10.1 nm hydrodynamic diameter, respectively. These results suggested that LSL and LSs could be used more effectively than other lignin as filler modifiers, flocculants, and dispersants. The combustion studies of the lignin samples suggested that KL and LPHL combusted more efficiently than other samples, as they had high heating (calorific) values of 27.02 and 19.2 MJ/kg, the apparent activation energy of 126.64 and 99.14 kJ/mol based on Flynn–Wall–Ozawa method and 122.16 and 94.73 kJ/mol based on Kissinger–Akahira–Sunose and no ash, respectively. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42336.     

Silicon–aluminum synergistic mechanism in flame retardancy of epoxy resin

In this article, the Kissinger method and the Flynn‐Wall‐Ozawa method were used to calculate the activation energy of thermal degradation process. Similar results were found in above two methods that the flame retardants polyepoxyphenylsilsesquioxane (PEPSQ) and aluminum hydroxide (ATH) improved the activation energy of epoxy resin (EP). The Flynn‐Wall‐Ozawa method further revealed that the addition of PEPSQ and ATH played an important role in improving the heat resistance and thermal stability of the system and produced synergistic effect in flame retardancy of EP through the significantly increment of the activation energy, especially in the final stage of the EP thermal degradation process. POLYM. COMPOS., 35:1553–1558, 2014. © 2013 Society of Plastics Engineers     

Thermogravimetric and kinetic analyses of the thermal decomposition of fuel wood

The results of studies of the thermal transformations of granulated wood biofuel performed by thermogravimetry and differential scanning calorimetry in an atmosphere of argon at heating rates of 5, 10, 20, and 30 K/min are reported in this paper. The results of the analysis were used for the determination of the preexponential factor and activation energy of the thermal decomposition of wood biofuel based on the Kissinger, Kissinger–Akahira–Sunose, and Ozava–Flynn–Wall isoconversion model-free methods. The values of activation energy for the release of volatile substances in the course of the thermal decomposition of wood granules varied in ranges of 87–250 and 76–242 kJ/mol.     

环氧树脂插层纳米复合材料固化动力学研究

运用自制的有机蒙脱土，采用浇模固化成型法制备环氧树脂／二乙烯三胺／有机蒙脱土纳米复合材料，对固化产物利用XRD（X射线衍射）分析有机蒙脱土的层间距变化，确定产物为插层型的纳米复合材料，并用DSC（差示扫描量热法）跟踪环氧树脂固化行为。运用Kissinger,Flynn-Wall-Ozawa,Crane方法对环氧树脂的固化反应过程进行分析，求出活化能和反应级数等动力学以在数。结果发现，加入有机化蒙脱土后使固化反应活化能和频率下降，从而有利于固化工艺的实现，便于纳米复合材料实际应用。     

纳米玻璃粉掺杂双酚A型环氧树脂基复合材料的热稳定性能研究

采用双酚A型环氧树脂为基体,短切玻璃纤维和纳米玻璃粉为填料,通过模压加工工艺制备了双酚A型环氧树脂基复合材料。使用热失重分析仪和扫描电子显微镜分析研究了纳米玻璃粉含量对复合材料热稳定性能的影响,同时利用Kissinger法和Flynn?Wall?Ozawa法求解了双酚A型环氧树脂基复合材料的热分解动力学参数。结果表明,添加短切玻璃纤维后,双酚A型环氧树脂的最大热分解温度从365 ℃提高至369 ℃,而随着纳米玻璃粉的加入,其最大热分解温度进一步提升5 ~16 ℃。且复合材料的残炭率在65.41 %~69.15 %之间,相比双酚A型环氧树脂、短切玻璃纤维增强双酚A型环氧树脂基复合材料分别提高了69.88 %~71.51 %、22.95 %~27.11 %。同时纳米玻璃粉的加入也使得复合材料的热分解活化能得到提升,最高为153.14 kJ/mol,相比双酚A型环氧树脂单体及短切玻璃纤维材料增强双酚A型环氧树脂基复合材料的热分解活化能135.65 kJ/mol、137.46 kJ/mol显著增加。结果表明,纳米玻璃粉的引入改变了双酚A型环氧树脂基复合材料的内部微观结构,从而提高了其热稳定性能。     

Kinetic study of the effect of poly(phenyl sulfone) on the curing of an epoxy/amine resin by conventional and by temperature‐modulated differential scanning calorimetry

Kinetic studies of the curing reaction of semi‐interpenetrating polymer networks (semi‐IPNs) based on diglycidyl ether of bisphenol‐A (DGEBA) and 4,4′‐diaminodiphenylmethane (DDM), containing poly(phenyl sulfone) (PPSU), were carried out using differential scanning calorimetry (DSC) and temperature‐modulated DSC (TMDSC), under both isothermal and dynamic conditions. The curing kinetics is discussed in the framework of three kinetic models: the Kissinger and the Flynn–Wall–Ozawa models, and the autocatalytic model developed by Kamal. To describe the cured reaction in its latter stage, we used the semi‐empirical relationship proposed by Chern and Poehlein to consider the influence of diffusion on reaction rate. The cure mechanism for the system studied remained broadly autocatalytic regardless of PPSU content, and it became far more diffusion controlled at higher PPSU content and lower cure temperatures. The vitrification time of the resins was obtained with TMDSC by following the changes on the complex modulus of heat capacity, , and exhibited a strong dependence on the PPSU content in the semi‐IPN systems. Copyright © 2005 Society of Chemical Industry     

环氧树脂固化反应动力学研究及其活性增韧

采用动态DSC法跟踪环氧树脂E-51／固化剂5784体系的反应历程,确定固化温度,利用Kissinger方程和Crane方程对固化反应动力学进行分析,通过红外分析确定聚硫橡胶的增韧方式,研究不同聚硫橡胶用量列固化产物力学性能的影响,采用扫描电镜分析试样断口形貌。研究结果表明：该固化体系的动力学参数为表观活化能△E=63．946kJ／mol,指前因子Ak=1．90×10^5,反应能级n=0．91,聚硫橡胶增韧环氧树脂通过化学键合来实现,并且效果明显。     

Thermal Behavior and Decomposition Kinetics of Bis(2,2,2‐trinitroethyl)‐oxalate as a High Energy Dense Oxidizer and its Mixture with Nitrocellulose

A new propellant formulation (NC‐BTNEOx) based on bis(2,2,2‐trinitroethyl)oxalate (BTNEOx) as a high energy dense oxidizer (HEDO) mixed with nitrocellulose (NC) matrix was prepared and studied. BTNEOx was prepared and characterized by nuclear magnetic resonance (NMR) and X‐ray diffraction (XRD). Photos of the prepared formulation obtained by scanning electron microscope (SEM) clarified a good mixing of the nitrocellulose (NC) matrix with BTNEOx. A smokeless burning was observed and recorded for the prepared NC‐BTNEOx by a high speed camera. The thermal behavior and decomposition kinetics of the NC matrix, BTNEOx and their mixture have been investigated nonisothermally by using thermogravimetric analysis (TGA) and Differential scanning calorimetry (DSC). Isoconversional (model‐free) methods; Kissinger, Ozawa and Flynn−Wall (OFW) and Kissinger−Akahira−Sunose (KAS), were used to determine the kinetic parameters of the studied samples. The results proved that BTNEOx has melting temperature at 104.1 °C and maximum peak temperature at 200.6 °C, also it has effective activation energy in the range of 107–110 kJ/mol. The prepared NC‐BTNEOx has no endothermic peak and has exothermic peak at 201.7 °C which means that a composite might be formed due to the mixing of BTNEOx with NC. The prepared NC‐BTNEOx has effective activation energy in the range of 172–180 kJ/mol. BTNEOx required more study to proof the possibility of replacing the nitroglycerine in a smokeless double base propellant.     

A study on the curing kinetics of epoxycyclohexyl polyhedral oligomeric silsesquioxanes and hydrogenated carboxylated nitrile rubber by dynamic differential scanning calorimetry

A new organic–inorganic hybrid material was prepared through reactive blending of hydrogenated carboxylated nitrile rubber (HXNBR) with epoxycyclohexyl polyhedral oligomeric silsesquioxanes (epoxycyclohexyl POSS). The structure of the composite was characterized by Fourier transform infrared spectroscopy (FTIR) and solid‐state ¹³C Nuclear Magnetic Resonance spectra (solid‐state ¹³C‐NMR). The differential scanning calorimetry (DSC) at different heating rates was conducted to investigate the curing kinetics. A single overall curing process by an nth‐order function (1 ? α)ⁿ was considered, and multiple‐heating‐rate models (Kissinger, Flynn–Wall–Ozawa, and Crane methods) and the single‐heating‐rate model were employed. The apparent activation energy (E_a) obtained showed dependence on the POSS content and the heating rate (β). The overall reaction order n was practically constant and close to 1. The isoconversion Flynn–Wall–Ozawa method was also performed and fit well in the study. With the single‐heating‐rate model, the average E_a for the compound with a certain POSS content, 66.90–104.13 kJ/mol was greater than that obtained with Kissinger and Flynn–Wall–Ozawa methods. Furthermore, the calculated reaction rate (dα/dt) versus temperature curves fit with the experimental data. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effects of modifiers in organoclays on the curing reaction of liquid‐crystalline epoxy resin

The effects of three organoclays (Cloisite 10A, 93A, and 30B) with different modifiers on the curing reaction of a liquid‐crystalline epoxy (LCE) resin based on 4,4′‐diglycidyloxybiphenyl and the curing agent sulfanilamide were studied. The curing kinetics of the LCE and clay composites were analyzed with differential scanning calorimetry. The Flyann–Wall–Ozawa and Kissinger–Akahira–Sunose methods were used to calculate the activation energies at different conversions. All three alkylammonium ions lowered the reaction activation energy and catalyzed the epoxy ring‐opening reaction with the diamine curing agent. 30B, with two hydroxy groups of quaternary ammonium, showed the highest catalysis because the hydroxy groups facilitated the curing process. 10A and 93A had similar catalytic abilities. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1329–1334, 2005     

Curing behavior and thermal properties of multifunctional epoxy resin with methylhexahydrophthalic anhydride

The curing behavior and thermal properties of bisphenol A type novolac epoxy resin (bisANER) with methylhexahydrophthalic anhydride (MHHPA) at an anhydride/epoxy group ratio of 0.85 was studied with Fourier‐transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), and thermogravimetry. The results showed that the FTIR absorption intensity of anhydride and epoxide decreased during the curing reaction, and the absorption peak of ester appeared. The dynamic curing energies were determined as 48.5 and 54.1 kJ/mol with Kissinger and Flynn–Wall–Ozawa methods, respectively. DSC measurements showed that as higher is the curing temperature, higher is the glass transition. The thermal degradation of the cured bisANER/MHHPA network was identified as two steps: the breaking or detaching of ? OH, ? CH₂? , ? CH₃, OC? O and C? O? C, etc., taking place between 300 and 450°C; and the carbonizing or oxidating of aromatic rings occurring above 450°C. The kinetics of the degradation reaction was studied with Coats–Redfern method showing a first‐order process. In addition, vinyl cyclohexene dioxide (VCD) was employed as a reactive diluent for bisANER (VCD/bisANER = 1 : 2 w/w) and cured with MHHPA, and the obtained network had a higher T_g and a slight lower degradation temperature than the undiluted system. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2041–2048, 2007