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     

Structural and Preliminary Explosive Property Characterizations of New 3,4,5‐Triamino‐1,2,4‐triazolium (Guanazinium) Salts

Two new highly stable energetic salts were synthesized in reasonable yield by using the high nitrogen‐content heterocycle 3,4,5‐triamino‐1,2,4‐triazole and resulting in its picrate and azotetrazolate salts. 3,4,5‐Triamino‐1,2,4‐triazolium picrate (1) and bis(3,4,5‐triamino‐1,2,4‐triazolium) 5,5′‐azotetrazolate (2) were characterized analytically and spectroscopically. X‐ray diffraction studies revealed that protonation takes place on the nitrogen N1 (crystallographically labelled as N2). The sensitivity of the compounds to shock and friction was also determined by standard BAM tests revealing a low sensitivity for both. B3LYP/6–31G(d, p) density functional (DFT) calculations were carried out to determine the enthalpy of combustion (Δ_cH (1) =−3737.8 kJ mol⁻¹, Δ_cH (2) =−4577.8 kJ mol⁻¹) and the standard enthalpy of formation (Δ_fH° (1) =−498.3 kJ mol⁻¹, (Δ_fH° (2) =+524.2 kJ mol⁻¹). The detonation pressures (P (1) =189×10⁸ Pa, P (2) =199×10⁸ Pa) and detonation velocities (D (1) =7015 m s⁻¹, D (2) =7683 m s⁻¹) were calculated using the program EXPLO5.     

Synthesis,Crystal Structure,and Thermal Behavior of 3‐(4‐Aminofurazan‐3‐yl)‐4‐(4‐nitrofurazan‐3‐yl)furazan (ANTF)

The energetic material 3‐(4‐aminofurazan‐3‐yl)‐4‐(4‐nitrofurazan‐3‐yl)furazan (ANTF) with low melting‐point was synthesized by means of an improved oxidation reaction from 3,4‐bis(4′‐aminofurazano‐3′‐yl)furazan. The structure of ANTF was confirmed by ¹³C NMR spectroscopy, mass spectrometry, and the crystal structure was determined by X‐ray diffraction. ANTF crystallized in monoclinic system P2₁/c, with a crystal density of 1.785 g cm⁻³ and crystal parameters a=6.6226(9) Å, b=26.294(2) Å, c=6.5394(8) Å, β=119.545(17)°, V=0.9907(2) nm³, Z=4, μ=0.157 mm⁻¹, F(000)=536. The thermal stability and non‐isothermal kinetics of ANTF were studied by differential scanning calorimetry (DSC) with heating rates of 2.5, 5, 10, and 20 K min⁻¹. The apparent activation energy (E_a) of ANTF calculated by Kissinger's equation and Ozawa's equation were 115.9 kJ mol⁻¹ and 112.6 kJ mol⁻¹, respectively, with the pre‐exponential factor lnA=21.7 s⁻¹. ANTF is a potential candidate for the melt‐cast explosive with good thermal stability and detonation performance.     

Thermodegradation kinetics of epoxy/DDS/POSS system

The thermodegradation kinetics of a hybrid inorganic–organic epoxy system formed by diglycidyl ether of bisphenol A, DGEBA/DDS, modified with octahedral oligomeric silsesquioxane, octa(aminopropylsilsesquioxane) was studied. The average activation energy of thermodegradation of this system was calculated by the integral method developed by Flynn–Wall–Ozawa (E = 105.01 kJ mol⁻¹) and by Coats and Redfern method (E = 113.07 kJ mol⁻¹). Lifetime and half‐life time of the materials system were predicted using the kinetic parameters. The results obtained from the two methods accorded well with each other. POLYM. COMPOS., 28:755–761, 2007. © 2007 Society of Plastics Engineers     

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     

Thermal degradation kinetics of thermotropic poly(p‐oxybenzoate‐co‐p,p′‐biphenylene terephthalate) fiber

An advanced heat‐resistant fiber (trade name Ekonol) spun from a nematic liquid crystalline melt of thermotropic wholly aromatic poly(p‐oxybenzoate‐p,p′‐biphenylene terephthalate) has been subjected to a dynamic thermogravimetry in nitrogen and air. The thermostability of the Ekonol fiber has been studied in detail. The thermal degradation kinetics have been analyzed using six calculating methods including five single heating rate methods and one multiple heating rate method. The multiple heating‐rate method gives activation energy (E), order (n), frequency factor (Z) for the thermal degradation of 314 kJ mol⁻¹, 4.1, 7.02 × 10²⁰ min⁻¹ in nitrogen, and 290 kJ mol⁻¹, 3.0, 1.29 × 10¹⁹ min⁻¹ in air, respectively. According to the five single heating rate methods, the average E, n, and Z values for the degradation were 178 kJ mol⁻¹, 2.1, and 1.25 × 10¹⁰ min⁻¹ in nitrogen and 138 kJ mol⁻¹, 1.0, and 6.04 × 10⁷ min⁻¹ in air, respectively. The three kinetic parameters are higher in nitrogen than in air from any of the calculating techniques used. The thermostability of the Ekonol fiber is substantially higher in nitrogen than in air, and the decomposition rate in air is higher because oxidation process is occurring and accelerates thermal degradation. The isothermal weight‐loss results predicted based on the nonisothermal kinetic data are in good agreement with those observed experimentally in the literature. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1923–1931, 1999     

Nonisothermal crystallization behavior of a luminescent conjugated polymer,poly(9,9‐dihexylfluorene‐alt‐2,5‐didodecyloxybenzene)

The nonisothermal crystallization kinetics of poly(9,9‐dihexylfluorene‐alt‐2,5‐didodecyloxybenzene) (PF6OC12) from the melt were investigated using differential scanning calorimetry under different cooling rates. Several analysis methods were used to describe the nonisothermal crystallization behavior of PF6OC12. It was found that the modified Avrami method by Jeziorny was only valid for describing the early stage of crystallization but was not able to describe the later stage of PF6OC12 crystallization. Also, the Ozawa method failed to describe the nonisothermal crystallization behavior of PF6OC12. However, the method developed by combining the Avrami and Ozawa equations could successfully describe the nonisothermal crystallization kinetics of PF6OC12. According to the Kissinger method, the activation energy was determined to be 114.9 kJ mol^?1 for the nonisothermal melt crystallization of PF6OC12. Copyright © 2006 Society of Chemical Industry     

Computed Thermodynamic and Explosive Properties of 1‐Azido‐2‐nitro‐2‐azapropane (ANAP)

Some thermodynamic and explosive properties of the recently reported 1‐azido‐2‐nitro‐2‐azapropane (ANAP) have been determined in a combined computational ab initio (MP2/aug‐cc‐pVDZ) and EXPLO5 (Becker–Kistiakowsky–Wilson's equation of state, BKW EOS) study. The enthalpy of formation of ANAP in the liquid phase was calculated to be Δ_fH°, ANAP(l)=+297.1 kJ mol⁻¹. The heat of detonation (Q_v), the detonation pressure (P), and the detonation velocity of ANAP were calculated to be Q_v=−6088 kJ kg⁻¹, P=23.8 GPa, D=8033 m s⁻¹. A mixture of ANAP and tetranitromethane (TNM) was investigated in an attempt to tailor the impact sensitivity of ANAP, but results obtained indicate that the mixture is almost as sensitive as pure ANAP. On the other hand, ANAP and TNM were found to be chemically compatible (¹H, ¹³C, ¹⁴N NMR; DSC) and a 1 : 1 mixture (by weight) of both components was calculated to have superior explosive properties than either of the individual components: Q_v=−6848 kJ kg⁻¹, P=27.0 GPa, D=8284 m s⁻¹.     

Thermal decomposition behavior of oligo(4‐hydroxyquinoline)

In this study, the kinetic parameters and reaction mechanism of decomposition process of oligo(4‐hydroxyquinoline) synthesized by oxidative polymerization were investigated by thermogravimetric analysis (TGA) at different heating rates. TGA‐derivative thermogravimetric analysis curves showed that the thermal decomposition occurred in two stages. The methods based on multiple heating rates such as Kissinger, Kim–Park, Tang, Flynn–Wall–Ozawa method (FWO), Friedman, and Kissinger–Akahira–Sunose (KAS) were used to calculate the kinetic parameters related to each decomposition stage of oligo(4‐hydroxyquinoline). The activation energies obtained by Kissinger, Kim–Park, Tang, KAS, FWO, and Friedman methods were found to be 153.80, 153.89, 153.06, 152.62, 151.25, and 157.14 kJ mol^?1 for the dehydration stage, 124.7, 124.71, 126.14, 123.75, 126.19, and 124.05 kJ mol^?1 for the thermal decomposition stage, respectively, in the conversion range studied. The decomposition mechanism and pre‐exponential factor of each decomposition stage were also determined using Coats–Redfern, van Krevelen, Horowitz–Metzger methods, and master plots. The analysis of the master plots and methods based on single heating rate showed that the mechanisms of dehydration and decomposition stage of oligo(4‐hydroxyquinoline) were best described by kinetic equations of A_n mechanism (nucleation and growth, n = 1) and D_n mechanism (dimensional diffusion, n = 6), respectively. POLYM. ENG. SCI., 54:992–1002, 2014. © 2013 Society of Plastics Engineers     

High‐Temperature Structural Transformations of 1,1‐Diamino‐2,2‐dinitroethene (FOX‐7)

Stuctural transformations of 1,1‐diamino‐2,2‐dinitroethene (FOX‐7) were investigated in the temperature range 298–513 K by means of DSC, TG, isothermal calorimetry, PXRD, IR spectroscopy, and electron microscopy. The data obtained confirm the existence of the high‐temperature δ‐FOX‐7 polymorph stable above 480 K. The heat effect of the γ→δ transformation is − 4.6 J g⁻¹ (−680 J mol⁻¹). Metastable γ‐phase formed in the reverse process δ→γ has a perfect crystal structure and is stable towards thermal decomposition. Possible mechanisms of sharp deceleration of thermal decomposition of FOX‐7 at the 40 % conversion are discussed.     

The Kinetics of the Main Decomposition Process of Aminoguanidium 5,5′‐azobis‐1H‐tetrazolate

In this study, the kinetics of the thermal decomposition of aminoguanidinium 5,5′‐azobis‐1H‐tetrazolate (AGAT), which is one of the promising fuel candidates of the new gas generating agents for airbags, was investigated. The kinetic model that fits the main decomposition of AGAT was examined, and the activation energy was obtained. The main decomposition of AGAT was a single elementary process according to the result of mass spectrometry. The recommended kinetic model for the main decomposition of AGAT is Avrami–Erofeev equation (n=4). The activation energies for the main decomposition obtained under helium by non‐isothermal analysis and isothermal analysis were 207 and 209 kJ mol⁻¹, respectively.     

Catalytic para‐xylene maximization: III. Hydroisomerization of meta‐xylene on H‐ZSM‐5 catalysts containing different platinum contents

Hydroisomerization of meta‐xylene was carried out using catalysts containing 0.15–0.60 wt% Pt on H‐ZSM‐5 zeolite, in a pulsed microreactor system connected to a gas chromatograph at a flow of hydrogen of 20 cm³ min⁻¹ and temperatures of 275–500 °C. Increasing temperature, increased isomerization with low rates. Increasing Pt content of the catalyst, decreased hydrodealkylation considerably via masking strong acid sites as revealed by temperature programmed desorption of ammonia measurements. Formation of trimethylbenzenes was inhibited by Pt incorporation in the H‐ZSM‐5 zeolite. The activation energies obtained for meta‐xylene hydroisomerization were relatively low (24.4–61.6 kJ mol⁻¹) on all catalysts under study. Para‐xylene yields in the xylenes mixture of product relative to the corresponding thermodynamic equilibrium values amount to about 0.8–0.9 at temperatures of 400–500 °C but were lower at lower temperatures. © 1999 Society of Chemical Industry     

Non‐Isothermal Kinetic Study of the Thermal Decomposition of Melamine 3‐Nitro‐1,2,4‐triazol‐5‐one Salt

Study on thermal behavior of 3‐nitro‐1,2,4‐triazol‐5‐one (NTO) salts was required to obtain important data for application purposes. These compounds have been shown to be useful intermediates for gun propellant ingredients, high energetic ballistic modifiers for solid propellants and other potential applications. In this paper, thermal decomposition and non‐isothermal kinetics of melamine 3‐nitro‐1,2,4‐triazol‐5‐one salt (MNTO) were studied under non‐isothermal conditions by DSC and TG methods. The kinetic parameters were obtained from analysis of the DSC and TG curves by Kissinger and Ozawa methods. The critical temperature of thermal explosion (T_b) was 574 K. The results show that MNTO is thermally more stable than NTO when compared in terms of the critical temperature of thermal explosion. Finally, the values of ΔS^#, ΔH^#, and ΔG^# of its decomposition reaction were calculated.     

High‐resolution thermogravimetry of poly(2,6‐dimethyl‐1,4‐phenylene oxide)

The thermal degradation and kinetics of poly(2,6‐dimethylphenylene oxide) (PPO) were studied by high‐resolution thermogravimetry. The thermogravimetry measurements were conducted at an initial heating rate of 50°C min⁻¹, resolution 4.0, and sensitivity 1.0 in both nitrogen and air from room temperature to 900°C. A two‐step degradation process was clearly revealed in air at the temperatures of 430°C and 521°C. The thermal degradation temperatures and kinetic parameters of the PPO appear to be higher in air than in nitrogen, indicative of a higher thermostability in air. The temperature, activation energy, order, and frequency factor of the thermal degradation of the PPO in nitrogen are 419°C, 100–120 kJ mol⁻¹, 0.5, and 13–17 min⁻¹, respectively. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1887–1892, 1999     

Kinetics of radiation‐induced grafting of 2‐hydroxyethyl methacrylate onto chloroprene rubber membrane and computer verification

Grafting of 2‐hydroxyethyl methacrylate(HEMA) onto chloroprene rubber(CR) membrane was carried out in ethanol by direct cobalt‐60 gamma ray irradiation. The kinetics of the grafting reaction was studied in respect of concentration of monomer, dose rate and temperature. The experimental results show that the functional relationship equation is dg₀/dt = k[M]^1.5 Ḋ. The apparent activation energy and collision frequency factor of the grafting polymerization are 46.2 kJ mol⁻¹ and 4.98 × 10⁷ mg cm⁻² kGy⁻¹ mol^−1.5 litre^1.5, respectively. The work established the relationship of the initial grafting rate (dg₀/dt) with various effect factors: ln (dg₀ dt) = 17.7 − 5560(1/T) + 1.5 ln [M] + ln Ḋ. This equation is also verified for the first time by a software named SMR, which function is using multiple linear regression to calculate the regression coefficient of a linear equation. © 1999 Society of Chemical Industry     

RAFT polymerization of N‐vinyl pyrrolidone using prop‐2‐ynyl morpholine‐4‐carbodithioate as a new chain transfer agent

RAFT polymerization of N‐vinyl pyrrolidone (NVP) has been investigated in the presence of chain transfer agent (CTA), i.e., prop‐2‐ynyl morpholine‐4‐carbodithioate (PMDC). The influence of reaction parameters such as monomer concentration [NVP], molar ratio of [CTA]/[AIBN, i.e., 2,2′‐azobis (2‐methylpropionitrile)] and [NVP]/[CTA], and temperature have been studied with regard to time and conversion limit. This study evidences the parameters leading to an excellent control of molecular weight and molar mass dispersity. NVP has been polymerized by maintaining molar ratio [NVP]: [PMDC]: [AIBN] = 100 : 1 : 0.2. Kinetics of the reaction was strongly influenced by both temperature and [CTA]/[AIBN] ratio and to a lesser extent by monomer concentration. The activation energy (E_a = 31.02 kJ mol^?1) and enthalpy of activation (ΔH^?= 28.29 kJ mol^?1) was in a good agreement to each other. The negative entropy of activation (ΔS^? = ?210.16 J mol^‐1K^‐1) shows that the movement of reactants are highly restricted at transition state during polymerization. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

四硝基并哌嗪的催化热分解及机理研究

采用高压差示扫描量热法(PDSC)、热重分析法(TGA)和快速扫描傅里叶变换红外光谱法(FT-IR),研究了四硝基并哌嗪(TNAD)的热分解机理,并采用FT-IR技术和TG/MS(质谱)联用分析了TNAD热分解过程的凝聚相变化,确认其热分解机理与化学反应过程。研究表明,在1MPa压力下TNAD的分解过程较简单,无熔融吸热峰出现,属固相分解,主要放热峰出现在212.5～251.7℃。NTO-Pb、TNAD/φ-Pb、β-Cu和AD-Cu等铅铜盐对TNAD的催化作用明显,都能使其热分解反应提前,相比之下,β-Cu和NTO-Pb催化效果更好。炭黑、Al_2O_3、Al等添加剂对TNAD起到稀释作用,缓和了分解放热过程,可起到稳定燃烧的作用。TNAD热分解主要有2个历程,分解过程中产生的主要气体产物为HCHO、NO、HCN和-C2_H_2、-CHO等碎片离子。     

Synthesis,Crystal Structure,and Thermal Behaviors of 3‐Nitro‐1,5‐bis(4,4′‐dimethylazide)‐1,2,3‐triazolyl‐3‐azapentane (NDTAP)

The energetic material, 3‐nitro‐1,5‐bis(4,4′‐dimethyl azide)‐1,2,3‐triazolyl‐3‐azapentane (NDTAP), was firstly synthesized by means of Click Chemistry using 1,5‐diazido‐3‐nitrazapentane as main material. The structure of NDTAP was confirmed by IR, ¹H NMR, and ¹³C NMR spectroscopy; mass spectrometry, and elemental analysis. The crystal structure of NDTAP was determined by X‐ray diffraction. It belongs to monoclinic system, space group C2/c with crystal parameters a=1.7285(8) nm, b=0.6061(3) nm, c=1.6712(8) nm, β=104.846(8)°, V=1.6924(13) nm³, Z=8, μ=0.109 mm⁻¹, F(000)=752, and D_c=1.422 g cm⁻³. The thermal behavior and non‐isothermal decomposition kinetics of NDTAP were studied with DSC and TG‐DTG methods. The self‐accelerating decomposition temperature and critical temperature of thermal explosion are 195.5 and 208.2 °C, respectively. NDTAP presents good thermal stability and is insensitive.     

Kinetics of Bu‐NENA Evaporation from Bu‐NENA/NC Propellant Determined by Isothermal Thermogravimetry

Bu‐NENA (N‐butyl‐N‐nitratoethyl nitramine) base propellants have versatile qualities, such as, higher energy, reduced sensitivity, and enhanced mechanical properties. The evaporation of Bu‐NENA, which takes place in the propellant grains in the course of time, can reduce the physical properties of the propellants, weaken the propellant grains, cause the propellants to crack at stress‐concentrated points, and finally result in unfavorable increases or fluctuations of the burning rate and poor performance of the rocket motor. In this study, the evaporation of Bu‐NENA from a double base propellant was investigated using isothermal thermogravimetry. The results showed that the entire process of Bu‐NENA evaporation complied with the power law of evaporation rate with time. The values of kinetic parameters of Bu‐NENA evaporation were calculated: E _vap=67.68 kJ mol⁻¹ and A _vap=1.57×10⁵ s⁻¹. In comparison, the values of NG (nitroglycerin) evaporation were determined: E _vap=69.68 kJ mol⁻¹ and A _vap=1.33×10⁶ s⁻¹. The value of the activation energy of Bu‐NENA evaporation was close to that of NG, but the pre‐exponential factors differed by an order of magnitude. The evaporation of Bu‐NENA followed zero‐order kinetics at the early stage, and the enthalpy of Bu‐NENA evaporation was calculated to be 69.75 kJ mol⁻¹ according to Langmuir and Clausius‐Clapeyron equations.     

Synthesis and polymerization of fluorinated monomers bearing a reactive lateral group—part 7. Copolymerization of tetrafluoroethylene with ω‐hydroxy trifluorovinyl monomers

The radical copolymerization of tetrafluoroethylene (TFE) and trifluorovinyl ω‐hydroxy comonomers [F₂CCF(CH₂)_mOH with m = 1 (FA1) and m = 3 (FA3)] for the synthesis of fluorinated polymers bearing hydroxy side groups is presented. FA1 was prepared by dehydrofluorination of 2,2,3,3‐tetrafluoropropanol, whereas FA3 was obtained in a three‐step scheme starting from the radical addition of 1,2‐dichloroiodotrifluoroethane to allyl alcohol. The copolymerization conditions (in bulk or in solution in di n‐butyl ether) and the polymer compositions considerably influenced the molecular weights, the molecular weight distributions, and the thermal properties of these copolymers. The kinetics of copolymerization of both couples enabled to determine the reaction order to the initiator (being 0.9) and the close values of apparent activation energies for [TFE/FA1 (E_a = 52.4 kJ · mol⁻¹) and for TFE/FA3 (E_a = 46.8 kJ · mol⁻¹)] couples. From the Tidwell and Mortimer method, the relative reactivity ratios were calculated by elemental analysis or by ¹⁹F‐NMR spectroscopy, showing a higher reactivity of the TFE to incorporate the copolymer (r_TFE = 2.47 and r_FA1 = 0.41; r_TFE = 1.57 and r_FA3 = 0.45). The high values of the reaction order to the initiator and low molecular weights of copolymers were associated to the allylic chain transfer of the hydroxy comonomers and a mechanism of copolymerization was proposed. The comonomer diad and triad distribution was determined by the statistic theory and allowed one to calculate the average length of the comonomer sequences. Finally, the thermal decomposition of these cooligomers showed that those containing FA3 units are more thermostable than those synthesized from FA1, and that the higher the fluorinated alcohol content, the faster the thermal decomposition. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 189–202, 1999