Activation Energy Of Thermal Decomposition Research Articles

Synthesis of Hybrid Cellulose Acetate Membranes and Application of the Flynn-Wall-Ozawa Isoconversional Method

The synthesis of hybrid materials is a promising alternative in the production of materials with optimized properties. In this context, the classic cellulose acetate membranes are being modified. It is worth mentioning that knowing the thermal stability of cellulosic materials is an essential factor in their use since organic polymers have low thermal resistance, limiting their applicability. This work evaluates the synthesis and the study of the thermal degradation kinetics of hybrid cellulose acetate membranes. The synthesis was carried out using the sol-gel process, with the phase inversion technique, through the reaction of cellulose acetate with organometallic precursors: tetraethyl orthosilicate, TEOS; 3-aminopropyl triethoxysilane, APTES, and titanium isopropoxide, TiPOT, in fixed composition. Thermal characterization was performed with thermogravimetric analysis at different heating rates under a nitrogen atmosphere. The kinetic parameter of thermal decomposition activation energy, Ea, was estimated with the isoconversional method proposed by Flynn-Wall-Ozawa (FWO). The degradation kinetics shows that the change in the chemical composition of the samples directly interferes with their thermal properties. Thus, it is possible to observe that the activation energy found for the reference sample, AC-Pure, in the first and second batches was 233.5 and 219.05 kJ/mol, respectively. The composition modification results in an increase in activation energy, in which sample B0//100-30 recorded 310.31 and 226.05 kJ/mol in the first and second batches; and sample B100//0-30 reached 452.73 and 424.74 kJ/mol. It is clear that the increase in the thermal resistance of the samples is associated with the change in the chemical composition and must be attributed to the increase in the TEOS content in the composition due to the formation and increase in the presence of siloxane groups in the material.

Preparation and Properties of Ultra-fine HNS-IV

Ultra-fine 2,2’,4,4’,6,6’- Hexanitrostilbene (HNS-IV) was obtained by HNS-II by vibration cavity comminute. This method uses only alcohol and deionized water, which can be viewed as a green technology. The morphology, particle size, specific surface area, thermal decomposition property and the threshold energy for slapper detonator were compared between HNS-IV and HNS-II in this paper. Results show that after HNS pulverizing, the particle size decreased from 27.18μm to 1.44μm, the specific surface area increased from 0.73m2•g−1 to 9.10m2•g−1. DSC analysis shows that the decomposition peak temperature Td decreases and the melting temperature Tm increases after pulverizing. It is speculated that in the explosive reaction with very high heating rate, the enthalpy of decomposition will be increased by pulverizing, which will be more conducive to detonation growth and explosive reaction. According to the calculation of thermal decomposition kinetics, the decomposition and activation energy Ea of HNS decreases after pulverizing, and the thermal decomposition reaction rate of HNS-IV increases when the temperature is less than 409.6°C. The initiation threshold test of the impact plate shows that the 50% initiation threshold energy of HNS- II is 1.242J, and the 50% initiation threshold energy of HNS-IV is 0.558J, and the initiation threshold for slapper detonatorer is significantly reduced by 55%. This means that the ultra-fine HNS-IV is very suitable as the main ingredient in the booster in the EFI initiation.

Reaction kinetics, pyrolytic behavior and product characterization of dewatered solids from spent fermentation coir wastes using a fixed batch reactor

Solid residues after pretreatment and hydrolysis of coir pith and Bit fiber waste was dewatered, dried and pyrolyzed at 300, 350, and 400 °C using a fixed bed batch pyrolyzer. The products were characterized using ultimate analysis, FTIR and GCMS. Bit fiber yielded more bio-oil (26.3 %), rich in 4-Methoxy phenol (60.94 %) and a Higher Heating Value of 27.06 MJ kg−1. Coir pith bio-oil with Higher Heating Value of 27.16 MJ kg−1, was rich in 2-Methoxy Phenol, which are principal lignin degradation products. Non condensable gases included mixture of methane, carbon dioxide and isomers of butene. Activation energy for thermal decomposition was studied using Coats and Redfern model from thermogravimetric data at heating rates of 10 and 15 k min−1, which showed two major phases of decomposition. Activation energy was higher for devolatilization phase of bit fiber waste (132 kJ/ mol) owing to higher percentage of lignin than in coir pith waste (Ea = 114 kJ/ mol).

Thermal decomposition, flame propagation, and combustion reactions behaviours of stearic acid by experiments and molecular dynamic simulation

To better look into the thermal decomposition and combustion progress of stearic acid (C18H36O2), the experimental tests and Reaction Force Field (ReaxFF) molecular dynamics simulation were conducted. Also, an investigation into the flame propagation characteristics and the reaction mechanisms of stearic acid was explored under different conditions. The thermal decomposition activation energy of stearic acid obtained by the TG tests was 105.01 kJ/mol. This is consistent with the initial decomposition stage reaction activation energy calculated to be 94.273 kJ/mol in the simulation. The flame propagation process of stearic acid combustion was explored and involved three stages: the flame growth stage, the stable flame stage, and the flame decay stage. The flame growth stage was subdivided into the flame growth inside the tube, upper the tube, and mushroom-shaped cloud. Besides, the flame growth stage could correspond to three flame propagation velocity peaks. Furthermore, the simplified reaction mechanism scheme for stearic acid radicals could explain the macro flame propagation behaviours. The main reaction pathway through which the C18H36O2 molecules were decomposed into C2H4 and C2H3, C2H5, and other free radicals was found to correspond to the initial flame growth stage, and the flame decay stage was dominated by the generation of final reaction products (H2O, CO2, and CO2, etc.). Concerning the overall reaction mechanism, the unburned stearic acid was continuously ignited, and the combustion products were continuously generated at the same time, thereby corresponding to the stable flame propagation stage. According to the flame propagation process and the simulation results, combustion reaction mechanisms of stearic acid were constructed.

3D printed peripheral vascular stents based on degradable poly(trimethylene carbonate‐b‐(L‐lactide‐ran‐glycolide)) terpolymer

AbstractPoly(L‐lactic acid) (PLLA) is a biocompatible material and has found its application in bioresorbable vascular stents (BVS). However, the crystallization of pure PLLA makes it brittle as a medical implant device. In this work, the biodegradable poly(1,3‐trimethylene carbonate‐b‐(L‐lactide‐ran‐glycolide acid)) (PTLG) terpolymers with improved mechanical performance were developed and processed into peripheral vascular stents by a novel 3D 4‐axial printing technology. The PTLG terpolymers were successfully synthesized by ring‐opening copolymerization of L‐lactic acid (LLA), 1,3‐trimethylene carbonate (PTMC) and glycolide acid (GA) units. The crystallinity and mechanical properties of the PTLG terpolymers with various degradation rate depends on the chain sequence structure and the component contents. Compared with the stent prepared by laser engraving, the peripheral vascular stent prepared by the 3D 4‐axial printing technology exhibit a finer structure and smoother strut surface. It was found that both the strut diameters and the molecular weight of PTMC affect the radial force of the stents and that the apparent activation energy of thermal decomposition of the stents is mainly influenced by the molecular weight of PTMC and the component ratio. Therefore, the addition of the PTMC segment can effectively improve the flexibility of the PTLG terpolymer stent and the 3D printed PTLG terpolymer‐based stent. Furthermore, CCK‐8 and live/dead staining suggested that the stents have good biocompatibility.

New Hybrid PVC/PVP Polymer Blend Modified with Er2O3 Nanoparticles for Optoelectronic Applications.

Polymer blend hybrid nanocomposites are of great importance for future optoelectronic applications. This paper presents the preparation of new polymer blend hybrid nanocomposites based on PVC/PVP modified with Er2O3 nanoparticles. A low-cost solution casting method has been used to prepare the polymer nanocomposites at 0.0, 0.1, 0.3 and 0.6 wt% of Er2O3. X-ray diffraction (XRD), Fourier transform infrared (FTIR), Raman spectroscopy, and environmental scanning electron microscopy (ESEM) measurements have all been used to examine the impact of a varying wt% of Er2O3 on the structural and optical characteristics of PVP/PVC polymer blends. The PVC/PVP polymer blend and Er2O3 nanoparticles showed a strong interaction, which was validated by XRD, FTIR, and Raman spectrum investigations. The SEM micrographs showed a remarkable complexation among the components of the polymer nanocomposites. The activation energies for thermal decomposition of PVC/PVP doped with different Er2O3 concentrations were less than that of the pure polymer film. The linear and nonlinear refractive indexes, dispersion energy, optical susceptibility and the energy gap values were found to be Er2O3 concentration-dependent. With an increase in Er2O3 concentration to 0.1 and 0.3 wt%, the dispersion energy and nonlinear refractive index improved, and thereafter decreased when the concentration was further increased to 0.6For the film doped with 0.1 wt% Er2O3, the optical band gap (Eopt) of the composite film enhanced by about 13%. The optical absorption measurements revealed clear improvements with the addition of erbium oxide. Higher refractive index values of PVC/PVP/Er2O3 films qualify the polymer blend as a cladding for electro-optic modulators. Our results indicated that the PVC/PVP/Er2O3 polymer films could be suitable for optoelectronic space applications.

Facile preparation of Fe/N-based biomass porous carbon composite towards enhancing the thermal decomposition of DAP-4

Fe/N-based biomass porous carbon composite (Fe/N-pCarbon) was prepared by a facile high-temperature carbonization method from biomass, and the effect of Fe/N-pCarbon on the thermal decomposition of energetic molecular perovskite-based material DAP-4 was studied. Biomass porous carbonaceous materials was considered as the micro/nano support layers for in situ deposition of Fe/N precursors. Fe/N-pCarbon was prepared simply by the high-temperature carbonization method. It was found that it showed the inherent catalysis properties for thermal decomposition of DAP-4. The heat release of DAP-4/Fe/N-pCarbon by DSC curves tested had increased slightly, compared from DAP-4/Fe/N-pCarbon-0. The decomposition temperature peak of DAP-4 at the presence of Fe/N-pCarbon had reduced by 79°C from 384.4°C (pure DAP-4) to 305.4°C (DAP-4/Fe/N-pCarbon-3). The apparent activation energy of DAP-4 thermal decomposition also had decreased by 29.1 J/mol. The possible catalytic decomposition mechanism of DAP-4 with Fe/N-pCarbon was proposed.

Applying the Inelastic Thermal Spike Model to the Investigation of Damage Induced by High‐Energy Ions in Polymers

AbstractThis work reports on damage production in polymers by high‐energy ions within the framework of the inelastic thermal spike model (i‐TS). The model is used to describe the effective size of the damaged region around the ion path (the track size) in amorphous poly(methyl methacrylate) (PMMA) and the semicrystalline poly(p‐phenylene sulphide) (PPS), poly(ethylene terephthalate) (PET), and poly(vinylidene difluoride) (PVDF). Track size calculations are compared to experimental data deduced from measurements of crater size, bond‐breaking cross‐sections, changes in crystallinity and electron density, track etching, and electrical depolarization. The use of data obtained from distinct types of damage provides a broad platform to test the applicability of the model to polymers. This work shows that the i‐TS correctly describes the dependence of the track size on energy loss obtained from most experimental probes, when the activation energy of thermal decomposition of the polymers is used as the criterion of track formation, using an electron–phonon mean free path of ≈3 nm. As damage is not uniform across the ion track radial dimension, there are fine variations in the experimental damage radii that can only be accounted for by using multiple activation processes. Amorphization radii of the semicrystalline polymers are not directly correlated to melting induced by the ions.

Characterization and Testing for Lowest Eutectic Mixture of TNBA/DNTF

AbstractIn this work, electrostatic spraying was used to prepare TNBA/DNTF eutectic mixtures with different mass ratios. The T−X phase diagram and the H−X phase diagram were drawn from the DSC curves of the eutectic mixtures. The morphology, composition, structure, thermal decomposition properties, mechanical sensitivity, thermal sensitivity, and detonation properties of the lowest eutectic were characterized by scanning electron microscope (SEM), energy dispersive X‐ray spectroscopy (EDS), X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (IR), X‐ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC) and thermogravimetric analysis‐mass spectrometry (TG‐MS), thermal sensitivity tests, mechanical sensitivity tests, and detonation performance calculations. The results showed that the best molar ratio of TNBA to DNTF was 59.41 : 40.59, whereas the best mass ratio was 60.17 : 39.83. The microscopic morphology was free of sharp edges and corners, the component proportions were the same as before electrostatic spraying, the surface elements were evenly distributed, and the crystal structure was essentially the same as those of the raw materials. The melting temperature was 352.0 K, which was 21.0 K and 33.1 K lower than those of the TNBA and DNTF raw materials, respectively. The thermal decomposition reaction rate constant (k), activation energy (EK), and preexponential factor (AK) of the lowest eutectic were 0.398 s−1, 81.34 kJ ⋅ mol−1, and 4.86×107 s−1, respectively. In the lowest eutectic, the component TNBA began to thermally decompose first, followed by DNTF. The main decomposition products of the lowest eutectic were CH4, H2O, H2, CO, N2, NH3, CO2, and N2O, with a small amount of C. The impact sensitivity (H50), friction sensitivity (P), and 5 s explosion temperature (T5s) of the lowest eutectic mixture were 39.7 cm, 28 %, and 563 K, respectively. Its detonation performance (OB=−36.52 %, QD=−4658 kJ ⋅ kg−1, vD=7598.37 m ⋅ s−1) was intermediate between those of TNBA and DNTF. The main detonation products were CO2, N2, CO, C(d), H2O, Br, and CH2O2.

Mechanical properties, thermal stability, and thermal degradation kinetics of silicone rubber/ethylene‐vinyl acetate copolymer/magnesium sulfate whisker composites compatibilized by ethylene‐acrylic acid copolymer

AbstractSilicone rubber/ethylene‐vinyl acetate copolymer/magnesium sulfate whisker composites containing ethylene‐acrylic acid copolymer (MS/SR/EVM/EAA) as a compatibilizer were successfully prepared. Moreover, the magnesium sulfate whisker surface was modified with 3 wt% of silane coupling agent (KH570), resulting in composites including (unmodified magnesium sulfate whisker) uMS/SR/EVM, (modified magnesium sulfate whisker) mMS/SR/EVM, and mMS/SR/EVM/EAA were compared. The values of thermal decomposition activation energy (Ea) calculated by the two different methods (Kissinger and Friedman methods) show that the composites filled with 5 and 20 phr whiskers have lower values of activation energy (Ea) than the SR/EVM blend. The tensile strength of composites with a 5 phr modified whisker is 14.5 MPa, which is higher than that of the SR/EVM blend and uMS5/SR/EVM composite. The tear strength of the composite with 20 phr mMS is 51.6 kN m−1, much higher than that of the composite with 20 phr uMS and SR/EVM blend. The mechanical properties were also investigated after thermal aging of the composites at 85°C for 48 h. The thermal conductivity of the composites with high filler loading was studied.

Stable perylene diimide radical/alkylamine complex linked by asymmetric [CO⋯H⋯N]−1 -type strong H-bond and its color switching properties

Radical anions of electron-deficient systems are widely used, but they are easily reoxidized upon exposure to air. Therefore, the stabilization of radical anions under ambient conditions is of great significance, but still remains a scientific challenge. Here, perylene diimide radical anion species is stabilized by an asymmetric anionic low barrier strong hydrogen bond, which is reported firstly. The exchange of a hydrogen atom between one hydrogen atom in nitrogen atom of alkyl amine and the oxygen atom of the carbonyl on perylene diimide radical anion occurs to form such asymmetric anionic type strong hydrogen bond. This bond energy of hydrogen bond is evaluated by the apparent activation energy of thermal decomposition, and it is about 50 kcal/mol. The geometric states in this hydrogen bond depend on external conditions, including solvents and pH value, which will cause the change of their photophysical properties. The hydrogen bond complex shows excellent pH-responsive color switching performance based on the difference in geometric states of this hydrogen bond.

Determination of Melting Parameters of Cyclodextrins Using Fast Scanning Calorimetry.

The first evidence of native cyclodextrins fusion was registered using fast scanning calorimetry (FSC) with heating rates up to 40,000 K s-1. The endothermal effects, detected at low heating rates, correspond to the decomposition processes. Upon the increase of the heating rate the onset of these effects shifts to higher temperatures, reaching a limiting value at high heating rates. The limiting temperatures were identified as the melting points of α-, β- and γ-cyclodextrins, as the decomposition processes are suppressed at high heating rates. For γ-cyclodextrin the fusion enthalpy was measured. The activation energies of thermal decomposition of cyclodextrins were determined by dependence of the observed thermal effects on heating rates from 4 K min-1 in conventional differential scanning calorimetry to 40,000 K s-1 in FSC. The lower thermal stability and activation energy of decomposition of β-cyclodextrin than for the other two cyclodextrins were found, which may be explained by preliminary phase transition and chemical reaction without mass loss. The obtained values of fusion parameters of cyclodextrins are needed in theoretical models widely used for prediction of solubility and solution rates and in preparation of cyclodextrin inclusion compounds involving heating.

Bio-derived polyurethanes obtained by non-isocyanate route using polyol-based bis(cyclic carbonate)s—studies on thermal decomposition behavior

Non-isocyanate polyurethanes (NIPUs) constitute one of the most prospective groups of eco-friendly materials based on their phosgene-free synthesis pathway. Moreover, one of the steps of their obtaining includes the use of carbon dioxide (CO2), which allows for the promotion of the development of carbon dioxide capture and storage technologies. In this work, non-isocyanate polyurethanes were obtained via three-step synthesis pathway with the use of epichlorohydrin. In the I step, the addition reaction of epichlorohydrin with polyhydric alcohols was conducted for diglicydyl ethers obtaining. In the II step carbon dioxide reacted with diglicydyl ethers to obtain five-membered bis (cyclic carbonate)s in the cycloaddition reaction. Then, one-pot polyaddition reaction between bis (cyclic carbonate) and dimerized fatty acids-based diamine allowed for non-isocyanate polyurethanes (NIPU)s preparation. Three bio-based materials (two semi-products and one bio-NIPU) and three petrochemical-based materials (two semi-products and one NIPU) were obtained. The selected properties of the products of each step of NIPUs preparation were compared. Fourier transform infrared spectroscopy FTIR and proton nuclear magnetic resonance 1H NMR measurements allowed to verify the chemical structure of all obtained products. The average molecular masses of the semi-products were measured with the use of size exclusion chromatography SEC. Moreover, thermal stability and thermal degradation kinetics were determined based on thermogravimetric analysis TGA. The results confirmed that the activation energy of thermal decomposition was lower for semi-products and NIPUs prepared with the use of petrochemical-based epichlorohydrin than for their bio-based counterparts.

A Service Life Prediction Method of Stranded Carbon Fiber Composite Core Conductor for Overhead Transmission Lines.

The effect of temperature on the service life of stranded carbon fiber composite core conductors was studied based on the kinetic theory of material pyrolysis. The thermal decomposition activation energy calculation for stranded carbon fiber composite cores was carried out by thermogravimetric analysis (TGA). The activation energy E of stranded carbon fiber composites was calculated according to the Flynn–Wall–Ozawa, Kissinger, and Coast–Redfern methods, which were 168.76 kJ/mol, 166.79 kJ/mol, and 160.35 kJ/mol, respectively. The results from these different treatments were within 10% or less, and thus the thermochemical reactions of stranded carbon fiber composite cores were considered to be effective. The life prediction model of the carbon fiber composite core was developed based on the kinetic equation of thermal decomposition. The service life is related to the reaction mechanism function G(α) and the reaction rate parameter k(t). The reaction mechanism function G(α) = ((1 − α)−3.3 − 1)/3.3 and the reaction rate parameter k(t) = 2.14 × 1012exp(E/RT) were obtained by fitting the thermal weight loss data of stranded carbon fiber composite cores. Based on the 5% mass loss criterion for the end of life of stranded carbon fiber composites, the service life of the carbon fiber composite core is given at various operating temperatures.

Morphology and properties of CL-20/MTNP cocrystal prepared via facile spray drying

Cocrystal of 2,4,6,8,10,12-hexaazaisowurtzitane/1-methyl-3,4,5-trinitropyrazole (CL-20/MTNP) in a 1:1 molar ratio is a promising energetic material, since it combines the superior detonation performance of CL-20 and good mechanical sensitivity of MTNP. In order to promote its progress to practical use, a rapid, facile and candidate large-scale manufacture method-spray drying was used to prepare the CL-20/MTNP cocrystal in this study. The morphology, crystal structure and thermodynamic behavior of the resulted CL-20/MTNP-SD cocrystal, raw materials and the cocrystal prepared via solvent evaporation method (CL-20/MTNP-E) were systematically studied by scanning electron microscopy (SEM), X-ray diffraction spectroscopy (XRD) and differential scanning calorimetry (DSC), respectively. The resulted CL-20/MTNP-SD cocrystal shows a regular spherical shape with diameter narrowly distributed from 0.2 µm to 2 µm. This morphology is different from the rod-like shape of CL-20/MTNP-E cocrystal. The crystal structure and thermal behavior CL-20/MTNP-SD is similar to the CL-20/MTNP-E cocrystal, and totally different to the raw materials. Additionally, the initiation temperature and activation energy for thermal decomposition of the CL-20/MTNP-SD cocrystal are slightly lower than the CL-20/MTNP-E cocrystal. The short pulse slapper sensitivity of cocrystals have been investigated. The spray drying method endows CL-20/MTNP cocrystal with the ability of being initiated by short-duration impulse. And the slapper impact initiating threshold of CL-20/MTNP-SD cocrystal is even lower than the commonly used initiating explosive 2,2′,4,4′,6,6′-hexanitrostilbene (HNS). This result evokes a prospective application of CL-20/MTNP-SD cocrystal as an initiating explosive for short impulse shockwave.

Thermolysis and sensitivities of solid propellants using characterized nano oxidizers involving energy performance evaluation

This investigation was devoted to exploring the thermal decomposition and sensitivity characteristics of solid propellants using nano-AN and nano-AP as oxidizers. The morphology, surface elements, and crystal structure of nano-AP and nano-AN were investigated by SEM, BET, EDS, and XRD. DSC and TG-MS were used to investigate the thermal decomposition mechanism of nano-AP and nano-AN solid propellants. The mechanical sensitivity of the different solid propellants containing nano-AN and nano-AP was tested and their energy performance was also evaluated. The results show that the microscopic morphology of nano-AN and nano-AP is network-like with the one-dimensional scale less than 100 nm, and the crystal phases of the two are consistent with the raw AN and raw AP, respectively. The thermal decomposition activation energy of AN/CMDB-4 propellant containing nano-AN is 717.46 kJ/mol, while that of AP/HTPB-6 propellant containing nano-AP is 422.33 kJ/mol. The main decomposition products of AN/CMDB-4 propellant are CO2, N2O, NO, CH2O, CO, N2, H2O, CH4 and H2. The products of CO2, N2O, NO, CH2O, CO, N2, H2O, CH4 and H2 are also generated during the decomposition of AP/HTPB-6 propellant. With the increase of nano-AN and nano-AP in propellants, the mechanical sensitivity of AN/CMDB solid propellant decreases, while that of AP/HTPB solid propellant increases. The theoretical standard specific impulse Isp of AN/CMDB and AP/HTPB propellants are 2439.5 N·s/kg and 2449.3 N·s/kg, respectively. The above conclusions show that nano-AP and nano-AN can improve the thermal decomposition performance and the safety of solid propellants, which are expected to be widely used in solid propellants.

Pyrolysis of engineered beach-cast seaweed: Performances and life cycle assessment

The blooming of beach-cast seaweed has caused environmental degradation in some coastal regions. Therefore, a proper treating and utilizing method of beach-cast seaweed is demanded. This study investigated the potential of producing power or biofuel from pyrolysis of beach-cast seaweed and the effect of the ash-washing process. First, the raw and washed beach-cast seaweeds (RS and WS) were prepared. Thereafter, thermogravimetric analysis (TG), bench-scale pyrolysis experiment, process simulation, and life cycle assessment (LCA) were conducted. The TG results showed that the activation energies of thermal decomposition of the main organic contents of RS and WS were 44.23 and 58.45 kJ/mol, respectively. Three peak temperatures of 400, 500, and 600 °C were used in the bench-scale pyrolysis experiments of WS. The 600 °C case yielded the most desirable gas and liquid products. The bench-scale pyrolysis experiment of RS was conducted at 600 °C as well. Also, an LCA was conducted based on the simulation result of 600 °C pyrolysis of WS. The further process simulation and LCA results show that compare to producing liquid biofuel and syngas, a process designed for electricity production is most favored. It was estimated that treating 1 ton of dry WS can result in a negative cumulative energy demand of -2.98 GJ and carbon emissions of -790.89 kg CO2 equivalence.

Synthesis, characterization and thermal degradation kinetics of a new pyrazole derived methacrylate polymer, poly(1,3-diphenyl-1H-pyrazol-5-yl methacrylate).

A new pyrazole derived methacrylate monomer, 1,3-diphenyl-1H-pyrazol-5-yl methacrylate, was synthesized from the reaction of 1,3-diphenyl-5-pyrazolone with methacryloyl chloride in the presence of triethylamine. After that, its homopolymerization was carried out by free radical polymerization method at 60 °C initiated with benzoyl peroxide. Spectral characterizations were achieved by 1H-NMR andFTIR spectroscopies. The kinetics of thermal degradation of the new polymer, poly(1,3-diphenyl-1H-pyrazol-5-yl methacrylate), poly(DFPMA), were investigated by thermogravimetric analysis (TGA) at different heating rates. The initial decomposition temperature of the polymer changed from 216.3 °C to 243.5 °C depending on the increasing heating rate. The thermal decomposition activation energies in a conversion range of 7-19% were 79.45 kJ/mol and 81.56 kJ/mol by the Flynn-Wall-Ozawa and Kissinger methods, respectively. Thermodegradation mechanism of the poly(DFPMA) were investigated in detail by using different kinetic methods available in the literature such as Coats-Redfern, Tang, Madhusudanan and Van Krevelen. Among all these methods, the best result was obtained for Coats-Redfern method (E =90.93 kJ/mol) at the optimum heating rate of 15 °C/min for D1 mechanism. That means the thermodegradation mechanism of poly(DFPMA) proceeds over a one-dimensional diffusion type deceleration mechanism.

Synthesis of Cinnamoyl‐Amino Acid Ester Derivatives and Structure‐Activity Relationship Based on Thermal Stability, Dielectric, and Theoretical Analysis

AbstractIn this study, cinnamic acid derivatives were synthesized from the reaction of benzaldehyde derivatives with malonic acid in the presence of pyridine and piperidine. These compounds were then respectively reacted with glycine and L‐alanine methyl ester hydrochloride based on triazine methodology to obtain novel cinnamoyl‐amino acid ester derivatives. The structure of these compounds were established via 1H, 13C APT, FT‐IR, MS and elemental analysis. The synthesized novel compounds were studied in terms of structure‐activity relationship based on dielectric, thermal stability, and theoretical analysis. Dielectric analysis was carried out in terms of amino acid type and aromatic substituted group (electron‐withdrawing or releasing group factor). Amino acid side chain differences make alanine conjugates have higher ϵ′ values compared to glycine conjugates. Thermal stability analysis was performed for the compounds (10 and 16) with the highest dielectric constants. Thermal decomposition activation energies were calculated as 95 kJ mol−1 and 100 kJ mol−1 for 10 and 16, respectively. HOMO‐LUMO energy levels and other related properties of the target compounds were analyzed and a correlation was observed between HOMO‐LUMO energy band gap and dielectric constant.

Thermal Decomposition Mechanism of Molecular Perovskite Energetic Material (C6NH14)(NH4)(ClO4)3(DAP‐4)

AbstractThe recently developed ammonium perchlorate‐based molecular perovskite has been demonstrated to exhibit excellent comprehensive performance as an energetic material. This ABX3‐type molecular perovskite energetic material consists of a high symmetry ternary structure framework stabilized through ionic bonds. In this work, the thermal decomposition mechanism of (C6NH14)(NH4)(ClO4)3 (DAP‐4) was extrapolated by analyzing its thermal decomposition characteristics, gas products, kinetic parameters, and condensed phase change results along with temperature‐varying, with the help of DSC‐TG‐MS‐FTIR and in‐situ FTIR experiment. The results show that a rapid reaction occurs once the decomposition of DAP‐4 starts at 383.7 °C, with the maximum thermal weight loss rate reaches 97.4 %. By using Kissinger's and Ozawa's method, the calculated activation energy of thermal decomposition of DAP‐4 was estimated to be 124.3 kJ/mol and 128.6 kJ/mol, respectively, demonstrating good reliability of our results. The gas products during the thermal decomposition were found mainly include NH3, H2O, HNCO, HCN, CO, HCl, and CO2. The decomposition process of DAP‐4 contains three stages. The first stage involves crystal form changes and H+ transfer of DPA‐4, followed by the collapse of the cage skeleton in the second stage. The third stage mainly involves a rapid redox reaction at high temperatures to generate great heat.