On the thermal degradation of poly(styrene sulfones). VII. Evaluations of poly(styrene sulfone) thermal stability using invariant kinetic parameters

The thermal degradation behavior of poly(styrene sulfone) was investigated by thermogravimetric analysis (TGA) measurement. This study described its thermal stability by applying the invariant kinetic parameter (IKP) method. The thermogravimetric and differential thermogravimetric analyses of different compositions of poly(styrene sulfones) were carried out over the temperature range 100–500°C under nitrogen. The kinetic parameters (preexponential factor and activation energy) of thermal decomposition of poly(styrene sulfone) can be obtained by dynamic measurement of TGA. The IKP method assumes that the kinetic parameters are independent of the experimental conditions. These parameters are computed without any hypothesis on the form of the kinetic degradation function. Invariant activation energies of the degradation of poly(styrene sulfone) show that the thermal stability decreases as the SO₂ content of poly(styrene sulfone) increases due to the thermal instability of the C? S bond. The relation equation, Ea_inv = 237.0 ? 290.5X_SO2, where X_SO2 is the molecular fraction of SO₂, was obtained to describe the effect of sulfur dioxide on the thermal stability of poly(styrene sulfone). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1698–1705, 2002     

Kinetic study of the thermal decomposition of (2‐phenyl‐1,3‐dioxolane‐4‐yl) methyl methacrylate and 2‐hydroxyethyl methacrylate copolymers

The kinetics of nonisothermal decomposition of (2‐phenyl‐1,3‐dioxolane‐4‐yl) methyl methacrylate (PDMMA), 2‐hydroxyethyl methacrylate (HEMA), and vinyl‐pyrrolidone (VPy) copolymers were investigated by thermogravimetry (TG) and differential thermal analysis (DTA). The data indicated that the major weight loss occurs in the range of 270 to 450°C. The decomposition characteristics showed essentially two regimes and varied depending on the temperature and the copolymer composition. The apparent kinetic parameters of the decompositions were estimated from both TG and DTA data by using the alternative calculation methods. The results suggest that the weight loss rates may be represented, depending on the type of sample, by a reaction model of overall order 1.0 to 1.6, with an activation energy of approximately 65–95 kJ mol^?1. The DTA data estimated considerably higher values for the overall activation energies, around 198–240 kJ mol^?1. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1500–1508, 2005     

Effect of diluents on the decomposition behavior of vinyl ester resin

An acidic vinyl ester resin (～6 mg KOH per gram of solid) was prepared by reacting a bisphenol‐A‐based epoxy resin with acrylic acid in the presence of tributylamine. The acrylated epoxy resin thus obtained was characterized by Fourier transform infrared spectroscopy. Five samples of vinyl ester resin containing styrene and methyl methacrylate (MMA) in the weight ratios 40:0, 30:10, 20:20, 10:30, and 0:40 were prepared at 30°C. These samples were cured, using 2 phr benzoyl peroxide, at 90 ± 2 °C for 1 h. The decomposition behavior of all the samples was studied by thermogravimetric analysis (TGA) at 10°C min^?1. The TG and dynamic thermogravimetry (DTG) thermograms showed single‐step degradation in the individual cases of styrene and MMA, whereas a two‐step degradation process was observed when styrene was mixed with MMA in any proportion. For all the samples, the order of the reaction was one for the first step. This value was calculated with the Coats and Redfern equation in accordance with the best‐fit analysis and further confirmed by linear regression analysis. From this value of reaction order (n), the activation energy (E) and pre‐exponential factor (Z) were calculated, and the validity of the data was checked by statistical analysis. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1952–1956, 2003     

The effect of CTBN concentrations on the kinetic parameters of decomposition of blends of cardanol‐based epoxidized novolac resin modified with carboxyl‐terminated liquid copolymer

Cardanol‐based novolac resins were separately prepared with different mole ratios of cardanol‐to‐formaldehyde with different acid catalysts. These resins were epoxidized with epichlorohydrin, in basic medium, at 120°C. The resins were, separately, blended with different weight percentages of carboxyl‐terminated butadiene acrylonotrile copolymer and cured with polyamine. Structural changes during blending were studied by FTIR spectroscopic analysis. Coats–Redfern equation was utilized to calculate the kinetic parameters, viz., order of decomposition reaction (n), activation energy (E), pre‐exponential factor (Z), and rate decomposition constant (k), for the decomposition of the samples. It was found that the degradation of the epoxies and their blend samples proceeded in two steps. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Kinetics of thermodegradation of palm kernel oil derived medium‐chain‐length polyhydroxyalkanoates

Oligomeric hydroxyalkanoic acids have potential industrial, medical, and pharmaceutical applications and they can be produced from the degradation of high molecular weight polyhydroxyalkanoates by a number of different ways. Thermal decomposition takes place in the absence of organic solvent and other chemicals and this justified the method of producing low molecular weight PHA as green chemistry. The kinetics for thermal degradation of medium‐chain‐length polyhydroxyalkanoates (mcl‐PHA) prepared from saponified palm kernel oil (SPKO) was studied by thermogravimetric analysis (TGA) technique. Employing the nonisothermal Kissinger's method, the degradation activation energy, E_d, and pre‐exponential factor, A, were 129 kJ mol^?1 and 1.15 × 10¹⁰ s^?1, respectively. Specific degradation rate constant, k was found to increase at higher heating rate. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis,characterization, and thermal degradation kinetics of the copolymer poly(4‐methoxybenzyl methacrylate‐co‐isobornyl methacrylate)

A copolymer of 4‐methoxybenzyl methacrylate and isobornyl methacrylate was synthesized by atom transfer radical polymerization. The structure of poly(4‐methoxybenzyl methacrylate‐co‐isobornyl methacrylate) was confirmed by means of Fourier transform infrared, ¹H‐NMR, and ¹³C‐NMR techniques. The molecular weight distribution values of the copolymer were determined with gel permeation chromatography. The number‐average molecular weight and polydispersity index values of poly(4‐methoxybenzyl methacrylate‐co‐isobornyl methacrylate) were found to be 12,500 and 1.5, respectively. The kinetics of the thermal degradation of the copolymer was investigated with thermogravimetric analysis at different heating rates. The activation energy values obtained with the Kissinger, Flynn–Wall–Ozawa, and Tang methods were determined to be 166.38, 167.54, and 167.47 kJ/mol, respectively. Different integral and differential methods were used, and the results were compared with these values. Doyle approximation was also used for comparing the experimental results to master plots. An analysis of the experimental results suggested that the reaction mechanism was an R₁ deceleration type in the conversion range studied. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Copolymerization kinetics of poly(acrylonitrile‐ran‐2‐ethenyl‐pyridine) and its degradation apparent activation energy

2‐Ethenyl‐pyridine (EPD) was first used to successfully copolymerize with acrylonitrile (AN) in a H₂O/dimethyl formamide (DMF) mixture by using azobisisobutyronitrile as the initiator. Kinetics of copolymerization and degradation of poly(AN‐ran‐EPD) were discussed. The kinetic equation of copolymerization and the apparent activation energy of degradation of poly(AN‐ran‐EPD) were obtained. In H₂O‐rich reaction medium, copolymerization followed the suspension polymerization more, but in DMF‐rich reaction medium, copolymerization followed the solution polymerization more. Increase in DMF concentration in the solvent mixture lead to a rapid increase in the degradation apparent activation energy. The apparent activation energy decreased quickly with an increase in EPD concentration, and such a change became less prominent as the molar ratio of EPD/AN went beyond 3/100. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Investigation of thermal degradation and flammability of polyamide‐6 and polyamide‐6 nanocomposites

In this paper, polyamide‐6 and polyamide‐6 nanocomposites were prepared by direct melt intercalation technique. The thermal degradation behavior of both polyamide‐6 and polyamide‐6 clay nanocomposites has been studied. The apparent activation energy of the nanocomposites is almost the same with that of pure polymer under nitrogen, but the apparent activation energy of the nanocomposites is greatly enhanced in air atmosphere. This increasing trend coincides with the thermal analysis and the cone calorimeter results, which may suggest that the polymer/clay nanocomposites have a higher thermal stability and lower flammability. The kinetic analysis also indicates that the pyrolytic degradation and the thermal oxidative degradation of PA6 and PA6/OMT nanocomposites are two kinds of different reaction models. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2297–2303, 2007     

Evaluating the thermal stability of high performance fibers by TGA

The thermal degradation of eight types of high performance fibers (HPFs) was measured under nitrogen and air atmosphere. The degree of degradation, as measured by weight loss using thermogravimetric analysis (TGA), and the characteristic degradation temperatures were obtained. The kinetics of the thermal degradation has also been analyzed according to the Freeman–carroll method and the activation energies of the HPFs were estimated. The experimental results show that para‐aramids (Kevlar® 29, 49, 129, and Twaron®2000) have similar thermal stability, but their thermal degradation temperatures and activation energies in air are different from those in nitrogen, which means that the thermostability of the fiber depends not only on its intrinsic structure but also on the atmosphere and temperature of testing environment. Terlon® fiber shows higher degradation temperature as a copolymer of para‐aramid, and its initial degradation temperature is 476.4°C in air. It can also be found that the PBO (poly(p‐phenylene benzobisoxazole)) fiber has the highest thermal degradation temperature among the samples tested, but its activation energy is not the highest in both air and nitrogen atmosphere. And the UHMW‐PE (ultra high molecular weight polyethylene) fiber has the lowest thermal degradation temperature, and it begins to degrade when the temperature reaches 321.8°C under air atmosphere. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 937–944, 2006     

Synthesis,characterization, and thermal degradation kinetics of poly(decamethylene 2‐oxoglutarate)

Poly(decamethylene 2‐oxoglutarate) [poly (DMOG)] was synthesized by a melt polycondensation reaction. The structure of poly(DMOG) was confirmed by means of Fourier transform infrared, ¹H‐NMR, and ¹³C NMR spectroscopies. The molecular weight distribution values of poly(DMOG) were determined with size exclusion chromatography. The number‐average molecular weight, weight‐average molecular weight, and polydispersity index values of poly(DMOG) were found to be 13,200, 19,000, and 1.439, respectively. Also, characterization was made by thermogravimetry (TG)–dynamic thermal analysis. The kinetics of the thermal degradation of poly (DMOG) was investigated by thermogravimetric analysis at different heating rates. TG curves showed that the thermal decomposition of poly(DMOG) occurred in one stage. The apparent activation energies of thermal decomposition for poly(DMOG), as determined by the Tang method, the Flynn–Wall–Ozawa method, the Kissinger–Akahira–Sunose method, and the Coats–Redfern method were 122.5, 126.8, 121.4, and 122.9 kJ/mol, respectively. The mechanism function and pre‐exponential factor were also determined by the master plots method. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and thermal stability properties of boron‐doped silicone resin

In this article, a novel boron‐doped silicone resin (BSR) was synthesized by hydrolysis‐polycondensation method, with propyl‐triethoxysilane (PTES), dimethyl‐diethoxysilane (DMDES), and boric acid (BA) as starting materials, using absolute ethyl alcohol as solvent and hydrochloric acid as catalyst. The structures of the BSR were characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), X‐ray photoelectron spectroscopy (XPS), and gel permeation chromatography (GPC). FTIR spectra showed characteristic B? O? Si and Si? O? Si stretching modes. XPS and NMR results confirmed further that boron element was doped successfully into the main chains of the silicone resin as Si? O? B bond motifs, and hydroxyl groups from BA were condensed properly with Si? OH or Si? OR to form cross‐linked structure of BSR with narrowed molecular weight distributions in optimum experimental condition. The thermal stability of the BSR was studied by thermogravimetry analysis and derivative thermogravimetry. The thermal degradation temperature of the silicone resin improved greatly after doping element boron into the main chain, and the thermal stability of the BSR was influenced by the content of boron. The thermal degradation mechanism of this BSR was also discussed. The degradation process can be divided into two stages, the weight loss in the first stages may be corresponding to the loss of the small groups and weaker bonds in the chains, such as ? CH₃, and ? C₃H₇, the weight loss in the second stage may be corresponding to the loss of the group as ? OC₂H₅. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40934.     

Antimicrobial properties and thermal stability of polycarbonate modified with 1‐alkyl‐3‐methylimidazolium tetrafluoroborate ionic liquids

Four water immiscible ionic liquids (ILs): 1‐hexyl‐3‐methylimidazolium tetrafluoroborate, 1‐heptyl‐3‐methylimidazolium tetrafluoroborate, 1‐octyl‐3‐methylimidazolium tetrafluoroborate and 1‐dodecyl‐3‐methylimidazolium tetrafluoroborate have been synthesized. Polycarbonate (PC) films containing ILs were prepared by solvent casting from methylene chloride solutions. Scanning electron microscopy measurements showed the high homogeneity of PC/IL films with the IL content up to 4 wt %. The tendency to IL aggregation was observed for polymeric films with higher IL content (5%). PC/IL composites were found to have the reduced thermal decomposition temperature under both an air and a nitrogen atmosphere in comparison with the neat PC. The effect of IL content on the antimicrobial activity of PC films against Escherichia coli bacteria was studied. Pronounced antimicrobial efficacy was revealed for PC/IL films for all studied ILs starting from 3 wt % of IL. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40050.     

酚酞烯丙胺型苯并噁嗪树脂的合成、表征及其聚合物的热分解动力学

以酚酞、烯丙胺、多聚甲醛为原料,合成了具有烯丙基的新型酚酞型苯并嗪树脂(PT-ala)。用FT-IR、¹H NMR和DSC表征了其结构和固化特性,并用TG-DTG方法对其聚合物在氮气中的热分解过程动力学进行了详细的研究。结果表明:用Kissinger法和Ozawa法求得的聚合物热分解活化能分别为189.65 kJ·mol^-1和215.11 kJ·mol^-1;用Coats-Redfern法证实了酚酞烯丙胺型聚苯并嗪的热分解反应为一级反应;在氮气氛中维持60 s寿命的最高使用温度为285℃。     

Thermal decomposition kinetics of poly(nButMA‐b‐St) diblock copolymer synthesized by ATRP

The reaction mechanism of decomposition process and the kinetic parameters of the poly(n‐butyl methacrylate‐b‐styrene), poly(nButMA‐b‐St), diblock copolymer synthesized by atom transfer radical polymerization (ATRP) were investigated by thermogravimetric analysis (TGA) at different heating rates. TGA curves showed that the thermal decomposition occurred in one stage. The apparent activation energies of thermal decomposition for copolymer, as determined by the Kissinger's, Flynn–Wall–Ozawa and Tang methods, which does not require knowledge of the reaction mechanism (RM), were 112.52, 116.54, and 113.41 kJ/mol, respectively. The experimental results were compared with master plots, in the range of the Doyle approximation. Analysis of experimental results suggests that in the conversion range studied, 3–18%, the actual RM is an A₂ sigmoidal type. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Thermogravimetric study of thermal degradation of polyetherimide

Thermal stability in nonoxidizing atmosphere of a polyetherimide (PEI) is investigated by thermogravimetry (TG). It is observed that thermal degradation of this product consists of two overlapping processes, which are conveniently separated by fitting the TG curves to mixtures of generalized logistic functions. Thus, each process is represented by a single function. The analysis of the fitting parameter values obtained for the main degradation process in different isothermal and heating ramp conditions allows to obtain insightful kinetic parameters (critical temperature, energy barrier, and reaction‐order) which allow to make predictions in both isothermal and nonisothermal contexts. There is a minimum temperature for each process to occur and a ramp‐energy barrier related to the process rate. In the ramp context, the values of these two parameters explain that, although one process starts at lower temperature, it proceeds at a very low rate until reaching temperatures at which the other process goes much faster. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42329.     

Kinetic analysis of thermal degradation of NR/EPDM blends: Effect of the reactive compatibilization

The effect of mercapto‐modified EPDM (EPDMSH) and thioacetate‐modified EPDM (EPDMTA) on the thermal degradation of NR/EPDM (70 : 30 wt %) blends has been investigated under anaerobic and aerobic conditions. The anaerobic condition consisted of compression‐molding the samples at different times, higher than the optimum curing time established by the oscillatory disk rheometer. The aerobic conditions consisted of ageing the samples in an air circulating oven. EPDMTA in the blend resulted in a reasonable retention of mechanical properties of sample ageing in an air‐circulation oven, and a slight increase of crosslink density after ageing under anaerobic conditions. EPDMSH resulted in an accentuated ageing degradation under anaerobic and aerobic conditions. The kinetic parameters of thermal degradation were evaluated from non isothermal TGA experiments taken at different heating rates. The presence of functionalized copolymers in a proportion as low as 2.5 wt % in the blends resulted in a substantial increase of the activation energy, indicating an increase of the resistance against thermal degradation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2669–2675, 2007     

Thermal degradation kinetics of a commercial epoxy resin—Comparative analysis of parameter estimation methods

The thermal degradation behavior of a commercial epoxy resin, EpoFix® (Struers), has been investigated by thermogravimetry (TG), differential thermal gravimetry (DTG), and differential thermal analysis (DTA) under nonisothermal conditions in an argon atmosphere. Different methods (Kissinger, Flynn–Wall–Ozawa (FWO), Friedman isoconversion methods, and nonlinear least‐squares (NLSQ) estimation method) have been used to analyze the thermal degradation process and determine the apparent kinetic parameters. The methods produce similar results in terms of activation energy estimations. Nevertheless, the NLSQ method has several advantages over the other methods in terms of both characterizing the activation energy and modeling the thermal degradation—i.e., including this model in a resin degradation process simulation. However, it is interesting to combine the NLSQ method with other isoconversion methods: they can reflect the dependence and variability of the activation energies during pyrolysis processes, while providing a good starting point for a nonlinear procedure, especially with respect to the activation energy E. This work is the first step (apparent kinetic reaction) of complete simulation of experimental oven of degradation of epoxy resin coating of impregnate nuclear fuel sample. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42201.     

Effects of two‐dimensional programming on microstructures and thermal properties of shape memory polymer‐based composites

To evaluate the effects of two‐dimensional (2D) programming on thermal properties of shape memory polymer (SMP)‐based composites when exposed to high temperature, the specimens of composites were prepared and programmed. Then the morphology, thermal properties, dynamic evolution, and constituents of released gaseous products were characterized. Results indicate that the programmed composite is more compacted, but the proportion of interconnected voids is larger than that in the nonprogrammed sample. 2D programming causes molecular or segmental orientations in SMP, and leads to the decrease in the char yield from 16.1 to 8.1%. The programmed sample shows a lower thermal stability. Further, the melting enthalpy of nonprogrammed composite is 1012 J/g which is lower than 1100 J/g of the programmed sample. The prestored stress in oriented molecules or segments of SMP is more prone to cause the chain scissions. The dynamic evolution and constituents of released volatiles from nonprogrammed and programmed samples are similar, but the release amount of volatiles from the latter is larger. Finally, the more compacted charring layer of nonprogrammed composite is more efficient to prevent volatiles from releasing out. The 2D programming has a slight influence on the elemental contents of O, Si, and C in the charring layer. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45480.     

Thermal stability and kinetics analysis of rubber‐modified epoxy resin by high‐resolution thermogravimetric analysis

A dynamic heating rate mode of high‐resolution thermogravimetric analysis was used to study the thermal and thermal‐oxidative stability, as well as kinetics analyses, of a model liquid rubber‐modified epoxy resin, Ep/CTBN, made up of bisphenol A diglycidyl ether‐based epoxy and carboxyl‐terminated butadiene acrylonitrile rubber (CTBN). Results show that the thermal degradation of Ep/CTBN resin in nitrogen and air consists of two and three independent steps, respectively. Moreover, Ep/CTBN has a higher initial degradation temperature and higher activation energy than those of pure epoxy resin in both gases, indicating that the addition of CTBN to epoxy can improve the thermal and thermal‐oxidative stability of pristine epoxy resin. Kinetic parameters such as activation energy, reaction order, and preexponential factor of each degradation step of both Ep/CTBN and pure epoxy resins in air and nitrogen were calculated. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3594–3600, 2003     

Synthesis of liquid crystalline polymers from polyethylene terephthalate and 4‐acetoxybenzoic acid: A kinetic study

Liquid crystalline polymers (LCPs) have been synthesized from polyethylene terephthalate (PET) and 4‐acetoxybenzoic acid (OB) through melt step‐growth polymerization. The presence of liquid crystalline texture is first examined using optical polarizing microscopy. The thermal durability of the developed systems is studied through thermogravimetric analysis. The kinetics of the polymerization processes is analyzed. The effectiveness of three catalysts commonly used in polyesterification is investigated. The effect of reaction temperature is also examined. The progress of polycondensation reactions over time takes a nonlinear behavior of slight sigmoidal shape, irrespective of whether or not the reaction is catalyzed. Simple second and third order equations, along with a nonlinear model, are used to determine the kinetic parameters characterizing these reactions. The rate of reaction is enhanced when the reaction temperature is increased. Overall, second‐order kinetics well describes the polymerization reactions when the data set is divided into two regions. Antimony trioxide induces a more visible enhancement to the rate of reaction, compared to zinc acetate and sodium acetate. The presence of a catalyst generally increases the reaction activation energy. This indicates that entropy factors outweigh the increase in activation energy and drive the catalyzed reactions to completion. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012