Stages Of Thermal Degradation Research Articles

The Effect of Intumescent Flame Retardant Contained Microencapsulated Red Phosphorus on the Flame Retardance and Thermal Degradation Behaviour of Epoxy Resin

The effect of intumescent flame retardant (IFR) contained microencapsulated red phosphorus on the flame retardance of E-44 epoxy resin (EP) was studied. The test results indicated that good flame retardancy can be realized when epoxy resin treated with 30% IFR. Thermogravimetric analysis showed that the charring amount at high temperature of EP can increase substantially when IFR was incorporated. In order to further explain this phenomenon, Dolye integration method of thermal degradation dynamics was employed to study the thermal degradation process of EP treated with IFR based on the microencapsulated red phosphrous according to the thermal gravimetry analysis results.The activation energy and reactor order of different thermal degradation stages were obtained. The results of thermal degradation dynamics implied the intumescent flame retardants can improve the flame retardance of the epoxy resin through decrease the degradation speed and increase the activation energy of the second thermal degradation stage.

Effects of Curing Method on the Gas Separation Performance of Phenolic Resin/Poly(vinyl Alcohol)-Based Carbon Membrane Materials

A novel cheap blended precursor phenolic resin/poly(vinyl alcohol) (PR/PVA) was developed to prepare carbon membranes. The effect of two curing methods (i.e., crosslinker and preoxidation) on the gas separation performance of their derived carbon membranes was investigated. Thermogravimetric analysis (TGA), Differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy were used to analyze the thermal stability of precursor and the changes in functional groups on membrane surface. The gas permeation of carbon membranes was tested for H2 and N2. The results show that PR, PR/PVA, and two PR/PVA cured samples have three thermal degradation stages. The thermal stability for original PR/PVA membrane is significantly improved via the method of preoxidation or crosslinker. Similar crosslinking structure is formed by the two curing methods. However, carbon membranes from crosslinker method present two-fold higher in hydrogen permeability and four-fold higher in selectivity than that from preoxidation method.

Non-isothermal degradation kinetics for polycarbonate/ polymethylphenylsilsesquioxane composites

AbstractThe thermal degradation behaviors of PC/PMPSQ (polymethylphenylsilsesquioxane) systems were investigated by thermogravimetric analysis (TGA) under non-isothermal conditions in nitrogen atmosphere. During non-isothermal degradation, Kissinger and Flynn-Wall-Ozawa methods were used to analyze the thermal degradation process. The results showed that a remarkable decrease in activation energy ( E ) was observed in the early and middle stages of thermal degradation in the presence of PMPSQ, which indicated that the addition of PMPSQ promoted the thermal degradation of PC. Flynn-Wall-Ozawa method further revealed that PMPSQ significantly increased the activation energy of PC thermal degradation in the final stage, which illustrated that the PMPSQ stabilized the char residues and improved the flame retardancy of PC in the final period of thermal degradation process

Thermal stability of poly(vinyl chloride)/layered double hydroxide nanocomposites

AbstractEffects of nanoscale dispersed layered double hydroxides (LDHs) on thermal stability of poly(vinyl chloride) (PVC) in thermal and thermooxidative degradation processes are investigated by dynamic and isothermal thermogravimetric analysis (TGA), discoloration test, fourier transform infrared (FTIR), and ultraviolet‐visible (UV‐vis) spectroscopic techniques. During both stages of thermal degradation, the degradation temperatures, including onset degradation temperature and temperature of the maximum degradation rate, increase, and the final residue yield of the PVC/LDH nanocomposites reaches 14.7 wt %, more than double that for neat PVC. The thermooxidative degradation process is more complex. During the first two stages, the presence of nanoscale dispersed LDH particles enhances the thermal stability, whereas in the last stage accelerates the thermal degradation possibly due to the accumulation of heat released. Additionally, the studies of the isothermal thermooxidative degradation process by FTIR and UV‐vis spectra indicate that both polyene backbone formation and some carbonyl groups are simultaneously developed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Synthesis, characterization, molecular modeling and antimicrobial activity of 2-(2-(ethylcarbamothioyl)hydrazinyl)-2-oxo- N-phenylacetamide copper complexes

Six Cu(II) complexes of 2-(2-(ethylcarbamothioyl)hydrazinyl)-2-oxo- N-phenylacetamide (H 3APET) have been prepared and characterized by elemental analyses, spectral (IR, UV–vis, 1H NMR and ESR) as well as magnetic and thermal measurements. The data revealed that the ligand acts as ON bidentate, ONS tridentate or ONNS tetradentate forming structure in which each copper atom is a tetrahedral or tetragonal environment. The bond length, bond angle, HOMO, LUMO, dipole moment and charges on the atoms have been calculated to confirm the geometry of the ligand and the investigated complexes. Kinetic parameters were determined for each thermal degradation stage of the Cu(II) complexes using Coats–Redfern and Horowitz–Metzger methods. Moreover, the ligand and its complexes were screened against bacteria Staphylococcus aureus, Escherichia coli, Candida and fungi, Albicans and Aspergillus flavus using the inhibitory zone diameter.

Kinetic investigation on thermal decomposition of organophosphorous compounds

Abstract In this paper, the thermal behaviours of two organophosphorous compounds, N,N-dimethyl-N′,N′-diphenylphosphorodihydrazidic (NDD) and diphenyl amidophosphate (DPA), were studied by thermogravimetery (TG), differential thermal analysis (DTA) and differential scanning calorimetery (DSC) techniques under non-isothermal conditions. The results showed that NDD melts about 185 °C before it decomposes. NDD decomposition occurs in two continuous steps, in the 190–410 °C temperature range. First thermal degradation stage for NDD results a broad exothermic peak in the DTA curve that is continued with a small exothermic peak at the end of decomposition process. On the other hand, applying TG-DTA techniques indicates that DPA melts about 150 °C before it decomposes. This compound decomposes in the temperature range of 230 to 330 °C in two steps. These steps are endothermic and exothermic, respectively. Activation energy and pre-exponential factor for the first step of decomposition of each compound were found...

Non-isothermal kinetic study of the thermal decomposition of N-{bis[benzyl(methyl)amino]phosphoryl}-2,2-dichloroacetamide and N-{bis[dibenzylamino]phosphoryl}-2,2-dichloroacetamide

In this paper, the thermal behaviours of N-{bis[benzyl(methyl) amino]phosphoryl}-2,2-dichloroacetamide (BMA) and N-{bis[dibenzylamino]phosphoryl}-2,2-dichloroacetamide (DBA) were studied by thermogravimetery (TG) and differential scanning calorimetery (DSC) techniques under the non-isothermal conditions. The results showed that BMA melts about 120 °C before it decomposes. BMA decomposition occurs in three continuous steps, in the 170–400 °C temperature range. Each thermal degradation stage for BMA results an exothermic peak in the DSC curve. On the other hand, applying TG-DSC techniques indicates that DBA melts about 175 °C before it decomposes. This compound decomposes in the temperature range of 200–600 °C in three steps. Activation energy and pre-exponential factor for each compound were found by means of Kissinger method and were verified by Ozawa–Flynn–Wall method. Activation energy obtained by Kissinger method for the first stage of BMA and DBA decompositions are 151.8 (±2.0) KJ mol−1 and 138.7 (±2.6) KJ mol−1, respectively. Finally, the thermodynamic parameters (ΔG #, ΔH # and ΔS #) for first step decomposition of DBA and BMA were determined.

Swelling properties of copolymeric hydrogels of poly(ethylene glycol) monomethacrylate and monoesters of itaconic acid for use in drug delivery.

Copolymeric hydrogels of poly(ethylene glycol) monomethacrylate (PEGMA) (P) have been synthesized for use in drug-delivery. New copolymeric hydrogels were prepared by free radical solution polymerization of PEGMA and monomethyl itaconate (MMI) or monoethyl itaconate (MEI), using ethyleneglycol dimethacrylate and tetraethyleneglycol dimethacrylate, respectively, as cross-linkers. The effect of copolymer composition on swelling behavior, thermal decomposition and drug release was studied. Three compositions of each copolymer were studied: 70P/30MMI (or MEI), 80P/20MMI (or MEI) and 90P/10MMI (or MEI). The largest equilibrium swelling degree was observed in gels containing the highest content of MMI or MEI (84.22 +/- 0.22 wt % for 70P/30MEI; 79.56 +/- 0.64 wt % for 70P/30MMI). The swelling process was in accordance with Fick's Second Law. Methotrexate (MTX), an anticancer agent used in the treatment of different hyperproliferative epithelial diseases, was chosen to be loaded in the gels. The drug was included by immersion of the copolymeric disks in an aqueous solution of the drug. The amount of MTX in the xerogels was between 5.34 +/- 0.06 mg MTX/g (90P/10MMI) and 14.94 +/- 0.91 mg MTX/g (80P/20MEI). Two stages of thermal degradation for unloaded and MTX-loaded gels were determined; the presence of the drug in the polymeric matrices decreased the temperature of the first stage of thermal degradation. MTX release was also in accordance with Fick's Second Law. The length of total drug release (340 +/- 30 min-1502 +/- 81 min) could be modulated as a function of the comonomer composition of the hydrogel.

Thermal degradation and smoke suspension of cotton cellulose modified with THPC and its lanthanide metal complexes

Complexes of cell–THPC–urea–ADP with transition metal ion Co2+ and lanthanide metal ions such as La3+, Ce4+, Nd3+ and Sm3+ have been prepared. The thermal behavior and smoke suspension of the samples are determined by TG, DTA, DTG and cone calorimetry. The activation energies for the second stage of thermal degradation have been obtained by following Broido equation. Experimental data show that for the complexes of cell–THPC–urea–ADP with the metal ions, the activation energies and thermal decomposition temperatures are higher than those of cell–THPC–urea–ADP, which shows these metal ions can increase the thermal stability of cell–THPC–urea–ADP. Moreover, these lanthanide metal ions can more increase thermal stability of samples than do the transition metal ion Co2+. The cone calorimetry data indicate that the lanthanide metal ions, similar to transition metal Co2+, greatly decrease the smoke, CO and CO2 generation of cell–THPC–urea–ADP, which can be used as smoke suppressants.

Thermal degradation kinetics and lifetime estimation for polycarbonate/polymethylphenylsilsesquioxane composite

The thermal degradation behaviors of polycarbonate/polymethylphenylsilsesquioxane (FRPC) composites were investigated by thermogravimetric analysis (TGA) under isothermal conditions in nitrogen atmosphere. The isothermal kinetics equation was used to describe the thermal degradation process. The results showed that activation energy (E), in the case of isothermal degradation, was a quick increasing function of conversion (α) for polycarbonate (PC) but was a strong and decreasing function of conversion for FRPC. Under the isothermal condition, the addition of polymethylphenylsilsesquioxane (PMPSQ) retardanted the thermal degradation and enhanced the thermal stability of PC during the early and middle stages of thermal degradation. It also indicated a possible existence of a difference in nucleation, nuclei growth, and gas diffusion mechanism in the thermal degradation process between PC and FRPC. Meanwhile, the addition of PMPSQ influenced the lifetime of PC, but the composite still met the demand in manufacturing and application.

Spectral, magnetic, thermal, antimicrobial, and eukaryotic DNA studies on acetone [N-(3-hydroxy-2-naphthoyl)]hydrazone complexes

Acetone [N-(3-hydroxy-2-naphthoyl)] hydrazone (H2AHNH) has been prepared and its structure confirmed by elemental analysis and 1H NMR spectroscopy. It has been used to produce diverse complexes with Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and U(VI)O2 ions. The complexes obtained have been investigated by thermal analysis, spectral studies (1H NMR, IR, UV–visible, ESR), and magnetic measurements. IR spectra suggest that H2AHNH acts as a bidentate ligand. The electronic spectra of the complexes and their magnetic moments provide information about geometries. The ESR spectra give evidence for the proposed structure and the bonding for some Cu(II) complexes. Thermal decomposition of the Ni(II) and Cu(II) complexes afforded metal oxides as final products. Kinetic data were obtained for each stage of thermal degradation of some of the complexes using the Coats–Redfern method. The formation of complexes in solution was studied pH-metrically and the order of their stability constants (log K) was found to be U(VI)O2 > Cu(II) > Zn(II) > Ni(II) > Cd(II) > Co(II). Antimicrobial and eukaryotic DNA studies were carried out.

Thermogravimetric and spectrometric characterizations of poly(styrene‐co‐divinylbenzene) containing phosphinic and phosphonic acid groups

AbstractDerivatized poly(styrene‐co‐divinylbenzene) resins have been prepared from the commercial crosslinked polystyrene by the aromatic electrophilic substitution reaction using PCl3/AlCl3 or PCl5/AlCl3, followed by base‐promoted hydrolysis. The unmodified copolymer and their phosphored derivatives have been characterized by thermogravimetric (TG) analysis to evaluate their thermal stability in nitrogen atmosphere. The influence of phosphorylation and phosphonation of crosslinked copolymer on its thermal behavior was evaluated. The TG and DTG curves of modified copolymers have clearly shown two thermal degradation stages. The modified copolymers have presented higher thermal stability than unmodified one, showing that the introduction of phosphinic or phosphonic acid groups modifies their kinetic pathways. The decomposition temperatures and thermal stability were dependent on the phosphorous amount incorporated on the commercial resin. The modified copolymers were also evaluated by spectrometric method (FTIR, using KBr pellet). The phosphorous content of the modified copolymers was determined by colorimetric method based on sodium molybdate reagent (determination at 830 nm). POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers

Thermal Degradation Kinetics of Ethylene-Vinyl Acetate Copolymer Containing Hydrotalcite and Red Phosphorus

The thermal degradation of flame-retarded ethylene-vinyl acetate copolymer (EVA) composites containing hydrotalcite (LDH) and red phosphorus (RP) are studied by thermogravimetric analysis. Four kinetics analysis models, i.e., the Kissinger method, the Flynn-Wall method, the Friedman method, and the Kissinger-Akahira-Sunose (KAS) method, are used to study the thermal degradation kinetics of the EVA/LDH composites. The apparent activation energy (E a ) data calculated from the four methods are compared. The E a results indicate that the addition of LDH and RP affects mainly the first thermal degradation stage of EVA.

Degradation of different polystyrene/thermoplastic starch blends buried in soil

Blends of PS and TPS were prepared using two different plasticizers: glycerol or buriti oil by solvent casting technique. PS/TPS blends were submitted to degradation by soil burial tests in perforated boxes for 6 months and later analyzed by TG and CPMAS 13C NMR. After degradation, blends with glycerol presented less stages of thermal degradation and NMR signals of minor intensity compared to the original blends. The presence of TPS at contents of 50% or greater improved the degradation of the blends. After 6 months, PS/TPS blends with buriti oil presented only one thermal degradation stage with a significant increase in mass loss. Moreover, all absorptions related to starch disappeared in NMR spectra after soil buried test, probably due to the consumption of starch by microorganisms. These results revealed that PS’s degradability can be improved when TPS plasticized with buriti oil is added to it.

Modification and characterization of semi-crystalline poly(vinyl alcohol) with interpenetrating poly(acrylic acid) by UV radiation method for alkaline solid polymer electrolytes membrane

Semi-crystalline poly(vinyl alcohol) was modified by UV radiation with acrylic acid monomer to get interpenetrating poly(acrylic acid) modified poly(vinyl alcohol), PVAAA, membrane. The stability of various PVAAA membranes in water, 2 M CH 3OH, 2 M H 2SO 4, and 40 wt% KOH aqueous media were evaluated. It was found that the stability of PVAAA membrane is stable in 40 wt% KOH solution. The PVAAA membranes were characterized by differential scanning calorimetry, X-ray diffraction, and thermogravimetry analysis. These results show that (1) the crystallinity in PVAAA decreased with increasing the content of poly(acrylic acid) in the PVAAA membranes. (2) The melting point of the PVAAA membrane is reduced with increasing the content of poly(acrylic acid) in the membrane. (3) Three stages of thermal degradation were found for pure PVA. Compared to pure PVA, the temperature of thermal degradation increased for the PVAAA membrane. The various PVAAA membranes were immersed in KOH solution to form polymer electrolyte membranes, PVAAA-KOH, and their performances for alkaline solid polymer electrolyte were conducted. At room temperature, the ionic conductivity increased from 0.044 to 0.312 S/cm. The result was due to the formation of interpenetrating polymer chain of poly(acrylic acid) in the PVAAA membrane and resulting in the increase of charge carriers in the PVA polymer matrix. Compared to the data reported for different membranes by other studies, our PVAAA membrane are highly ionic conducting alkaline solid polymer electrolytes membranes.

Characterization of polyaniline via pyrolysis mass spectrometry

In this work, direct insertion probe pyrolysis mass spectrometry technique was applied to investigate the thermal and the structural characteristics of electrochemically prepared HCl and HNO3-doped polyaniline (PANI) films. It has been determined that the thermal degradation of both samples showed three main thermal degradation stages. The first stage around 50–60°C was associated with evolution of solvent and low-molecular-weight species adsorbed on the polymer, the second stage just above 150°C was attributed to evolution of dopant-based products, and the final degradation stage at moderate and elevated temperatures was associated with evolution of degradation products of the polymer. Chlorination and nitrolysis of aniline during the electrochemical polymerization were detected. Extent of substitution increased as the electrolysis period was increased. Furthermore, for the HNO3-doped PANI, the evolution of CO2 at elevated temperatures confirmed oxidation of the polymer film during electrolysis. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Studies on Gasification of Coir Pith

Coir pith is considered as an undesirable waste of coir industries. It is difficult to burn coir pith in normal atmospheric conditions. It decomposes slowly, taking 8-10 years for complete decomposition due to higher lignin content of 37 to 45%. Being dust, it is easily blown by wind. When ignited, it does not burn completely and emits continuous smoke for several days polluting the environment. Therefore, the study was conducted to produce combustible gas from coir pith through fluidized bed gasification process. A fluidized bed gasifier was developed. Coir pith of0.511 mm mean particle size was used as feed material. Thermogravimetric studies were also conducted to determine the combustion behaviour of coir pith. Thermograms obtained for raw coir pith revealed distinct stages of thermal degradation and the ignition temperature was found to be 550°C. Minimum fluidizing velocity of 0.1 m/s was adopted for sand bed. A general trend of increasing gas yield with increasing air factor and slightly decreasing trend of calorific value were noticed. The average gas composition was found to be 2.3 to 6.5%, 9.1 to 16.2% and 6.4 to 20.5% for CH4, Hz, and CO, respectively. The combustible gas was well burnt in a low calorific burner, which will fulfill the thermal needs, or the combustible gas can be used in the dual fuel engine to produce mechanical power or electricity. The average calorific value of the gas was found to be 4.23 MJ/m3

Stacking of lamellae in Mg/Al hydrotalcites: Effect of metal ion concentrations on morphology

A hybrid nanocomposite based on the intercalation of carbonate anion has been synthesized through co-precipitation technique. Powder X-ray diffraction patterns (PXRD) showed pure layered double hydroxide (LDH) phases having crystallite size around 20 and 13 nm in ‘ a’ and ‘ c’ crystallographic directions, respectively. Fourier transform infrared and Raman spectroscopy measurements exhibit shifting of bands with increase of divalent metal ion concentration and it further suggests the presence of carbonate anions. Differential scanning calorimetry (DSC) and thermogravimetry analysis (TGA) exhibit the three stages of thermal degradation, which is characteristic behaviour of layered double hydroxide. CHN and energy dispersive X-ray analysis support the PXRD and spectroscopy results. The nature of charge observed through Zeta potential analyzer is positive. Transmission electron microscope (TEM) exhibits the characteristic LDH platelet morphology with the platelets stacked one above the other.

Thermal behaviour kinetic study of dihydroglyoxime and dichloroglyoxime

Glyoxime derivatives have increasingly gained attention because of their potential for generation of energetic materials. In this paper, the thermal behaviours of dihydroglyoxime (DHG) and dichloroglyoxime (DCG) in a nitrogen atmosphere were studied under non-isothermal conditions by thermogravimetry (TG) and differential scanning calorimetry (DSC) techniques. The results showed that the decomposition of DCG occurs in two continuous steps, in the 160–230 °C temperature range. Each thermal degradation stage for DCG results an exothermic peak in the DSC curve. On the other hand, applying TG–DSC techniques indicates that DHG sublimates about 178 °C before it decomposes. Also, the influence of the different heating rates such as 5, 10, 15 and 20 °C min − 1 on the thermal behaviour of both compounds was investigated. The results of DSC experiments indicate that the peak temperature of DCG decomposition and sublimation temperature for DHG were increased, as the heating rate was increased. The kinetic parameters such as activation energy and pre-exponential factor for each compound were found by means of the Kissinger method and were verified by the Ozawa–Flynn–Wall method. Based on the values of activation energy obtained by the Kissinger method, the first stage of DCG decomposition has an activation energy about 100 kJ mol − 1 and the sublimation process for DHG has an activation energy about 259 kJ mol − 1. Finally, the thermodynamic parameters (Δ G #, Δ H # and Δ S #) for decomposition of DCG and sublimation of DAG were determined.

Synthesis, thermal and spectral studies of first-row transition metal complexes with girard P reagent-based ligand

A new series of first-row transition metal complexes with 1-acetylpyridinium chloride-4-benzoyl thiosemicarbazide (H 2GPBzIT) have been prepared and characterized by elemental analysis, spectroscopic and magnetic measurements. The proton-ligand ionization constants were determined potentiometrically using Irving–Rossotti technique. The stability constants of complexes were also calculated and were found in agreement with the seq uence of stability constants of Irving and Williams. Thermal stability and degradation kinetics have been measured using thermogravimetric analyzer. Kinetic parameters were obtained for each stage of thermal degradation of complexes using Coats–Redfern method.