Thermal degradation mechanisms of poly[diethyl 2-(methacryloyloxy)ethyl phosphate] by Py-GC/MS

Thermal decomposition properties of poly[diethyl 2-(methacryloyloxy)ethylphosphate] (PDMP) were studied using a stepwise pyrolysis-gas chromatography/mass spectrometry (stepwise Py-GC/MS) method. The individual mass chromatograms of the various pyrolysates were correlated with the pyrolysis temperature in order to elucidate the degradation mechanisms. The scission of PDMP in helium atmosphere showed the presence of two-stage pyrolysis regions. Triethylphosphate reached maximum evolution at the initial pyrolysis temperature, indicating that scisson of PDMP was initiated by the selective cleavage at the chain end and phosphate ester side chain as the dominant pyrolysis mechanism in the first stage. This local instability at chain end and phosphate ester side chain might explain the thermal instability of PDMP at lower pyrolysis temperatures. Acetaldehyde and water, as major products, were formed in significant amounts above 300 °C, indicating that random chain scission became the dominant pyrolysis mechanism in the second stage. Thus, the random chain scission reaction favored the occurrence of crosslinking and cyclization through chain transfer of carbonization catalyzed by phosphate ester along with the evolution of the arylene-containing and cyclic compounds. From mechanism analysis of PDMP pyrolysis, the introduction of a chemically bonded phosphorous-containing pendant group could promote its fire retardancy to form the high char yield of solid residue.     

Thermooxidative degradation behavior of poly(silphenylene–siloxane)s

Copolymers of poly(silphenylene–siloxane) with dimethylsiloxane and diphenylsiloxane with various end groups were synthesized through an Si? H/Si? OR polycondensation process. The thermooxidative degradation behaviors of the copolymers were investigated by thermogravimetric analysis and IR spectrometry techniques. All of the polymers were characterized by a two‐step mass loss. The first one, which peaked at 510–545°C in differential thermogravimetric curves, was mostly caused by the main‐chain depolymerization, whereas the second one, which reached its maximum around 650°C, was caused by side‐group oxidation and Si? C bond scission. The main‐chain depolymerization occurred over a temperature range of some 470–580°C, whereas Si? C bond scission and side‐group oxidation occurred over a temperature range of about 585°C to above 720°C. The incorporation of phenyl groups in the end groups greatly retarded the temperature for the degradation onset of the main chain to 120°C higher. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Thermal degradation behaviour of aromatic poly(ester–imide) investigated by pyrolysis–GC/MS

The thermal degradation behaviours of a novel aromatic poly(ester–imide) (PEI) derived from pyromellitic dianhydride and 2,7-bis(4-aminobenzoyloxy)naphthalene have been investigated by thermogravimetric analysis (TGA) and by pyrolysis–gas chromatography/mass spectrometry (pyrolysis–GC/MS). The weight of PEI fell slightly in the temperature range of 350–450 °C in the TGA analysis, but the major weight loss occurred at 520 °C. Evolve gas analysis (EGA) of the PEI showed maximum release of pyrolyzates at 550 °C. The chemical structure of the volatile products resulted from the PEI pyrolysis at different temperatures was identified by pyrolysis–GC/MS. The cleavage of the ester linkage within the polymer chain initiated at 350 °C, and bond scission in the partially hydrolyzed pyromellitimide unit occurred in the temperature range of 450–500 °C. The bonds within the pyromellitimide unit started to cleave at 550 °C. The extensive decomposition of the pyromellitimide segment within the polymer backbone occurred at 600 °C. The possible thermal degradation pathways of this PEI are proposed on the basis of the pyrolysis products.     

Thermal degradation of EVA and EBA—A comparison. I. Volatile decomposition products

This is the first in a series of papers in which structural changes during thermal degradation of ethylene-vinyl acetate (EVA) and ethylene-butyl acrylate (EBA) copolymers are compared. EVA, containing 11.4 mol% vinyl acetate (VA) and EBA, containing 5.4 mol% butyl acrylate (BA), were pyrolyzed at 280°C in nitrogen for 30 min. In another series of pyrolysis, EVA containing 1.2, 2.2, and 11.4 mol% VA were treated at 150–190°C for 3 h. The volatile decomposition products were collected in cooled traps respectively gas bags and then analysed with GC-MS and ion-chromatography. EVA is rather labile. The main volatile decomposition product is acetic acid. A linear decomposition rate was found already at the lowest investigated pyrolysis temperature, 150°C. After 30 min at 280°C every 15th of the acetate side groups had been eliminated. EBA is much more stable to pyrolysis. Thirty minutes at 280°C resulted in a decomposition of one out of 1500 BA groups. Butene is the main volatile decomposition product. Ester pyrolysis is supposed to account for the degradation of both types of polymers. The big difference in reactivity is presumably due to conformational differences. The ester pyrolysis mechanism will result in random unsaturations in EVA and carboxylic groups in EBA. To a minor extent acetaldehyde is formed when EVA is degraded. According to the mechanisms suggested, carbonyl groups remain in the main chain. Contrary to what is reported for poly(butyl acrylate), no alcohol was formed when pyrolysing EBA. This indicates that adjacent acrylate groups are needed for alcohol formation. For both types of polymer, scissions of the main chain results in hydrocarbon fragments mainly. In addition, acrylate containing fragments are observed when EBA is degraded. EVA, however, does not give any acetate-containing fragments.     

Thermal stability of new sorption materials based on polysiloxanes

The thermal stability of the unmodified, aminated, and thiocarbamoylated polysiloxanes has been studied. The siloxane matrix is stable in the temperature range up to 800°C. For the first time, mass spectrometry has been applied to the analysis of the composition of the gaseous products of thermal decomposition of the studied polysiloxanes. It has been shown that, in the process of thermal decomposition, the terminal functional groups are detached and oxidized. Water, ammonia, nitrogen, carbon, and sulfur (in the case of thiourea-modified sorbent) oxides are formed predominantly. The quantitative removal of functional groups during heating up to 800°C has been confirmed by IR spectroscopy. A mechanism of thermal decomposition of polysiloxane xerogels has been proposed. It has been found that adsorption of platinum increases the thermal stability of the samples.     

Thermal Decomposition Performance of Unsymmetrical Dimethylhydrazine (UDMH) Oxalate

The thermal decomposition behavior of unsymmetrical dimethylhydrazine (UDMH) oxalate was studied using differential scanning calorimetry (DSC), thermogravimetric analysis (TG/DTG), and thermogravimetric analysis combined with infrared spectroscopy (TG‐IR). The endothermic decomposition of UDMH oxalate occurred at temperatures between 180.4 °C and 217.6 °C, the maximum decomposition temperature is 199.2 °C. The kinetic parameters of the decomposition reaction were calculated based on the Kissinger equation. The TG‐IR spectra indicated that the thermal main decomposition products of UDMH oxalate are CO₂,H₂O and NH₃.     

Synthesis and thermal decomposition of poly(dodecamethylene terephthalamide)

A kind of semiaromatic polyamide, poly(dodecamethylene terephthalamide) (PA12T) was synthesized via a polycondensation reaction of terephthalic acid and 1,12‐dodecanediamine. The structure of prepared PA12T was characterized by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance (¹H‐NMR), and elemental analysis. The mechanical properties of PA12T were also studied. The thermal behavior of PA12T was determined by differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical analysis. Pyrolysis products and thermal decomposition mechanism of PA12T were analyzed by pyrolysis‐gas chromatography/mass spectrometry (Py‐GC/MS). Melting temperature (T_m), glass transition temperature (T_g), and decomposition temperature (T_d) of PA12T are 310°C, 144°C, and 429°C, respectively. The Py‐GC/MS results showed that the pyrolysis products were mainly composed of 32 kinds of compounds, such as benzonitrile, 1,4‐benzenedicarbonitrile, N‐methylbenzamide, N‐hexylbenzamide, and aromatic compounds. The major pyrolysis mechanisms were β‐CH hydrogen transfer process, main‐chain random scission, and hydrolytic decomposition. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Synthesis and characterization of novel sulfonated poly(arylene ether ketone)s derived from 4,4'-sulfonyldiphenol

Summary Novel sulfonated poly(arylene ether ketone)s were prepared directly by aromatic nucleophilic polycondensation of 4,4'-sulfonyldiphenol with various ratios of 4,4'-difluorobenzophenone to 5,5'-carbonylbis(2-fluorobenzenesulfonate) in dimethyl sulfoxide. The resulting polyelectrolytes were characterized by IR, NMR, TGA and DSC. The 10% weight loss temperature of the products is higher than 510°C, and their glass transition temperature is above 260°C. The introduction of 4,4'-sulfonyldiphenol with powerful electron-withdrawing group, -SO₂₋, into the main chain of sulfonated poly(arylene ether ketone)s improves the thermal stability against desulfonation. The ion-exchange capacity and swelling of the polyelectrolyte membranes were measured, which are higher than 1.23meq/g and not higher than 20.9%, respectively. The membranes show very good perspectives in polymer electrolyte fuel cell (PEMFC) application. Received: 27 March 2002 / Revised version: 7 May 2002 / Accepted: 13 May 2002     

Thermal stability and decomposition mechanism of poly(p‐acryloyloxybenzoic acid and poly (p‐methacryloyloxybenzoic acid) and their graft copolymers with polypropylene,Part II

Thermal stability and decomposition mechanism of poly(p‐acryloyloxybenzoic) acid (PABA), p‐methacryloyloxybenzoic acid (PMBA), and their graft coproducts of PP were studied by differential scanning calorimetry, direct pyrolysis mass spectrometry, and TG/IR system, combined thermogravimetric analyzer, and FTIR spectrometer. The homopolymers and corresponding grafts were found to be stable in nitrogen atmosphere but started to decompose under atmospheric conditions when heated above 230°C. PABA and PAPA‐g‐PP showed a better thermal stability compared to the other polymer. The degradation proceeded predominantly by decomposition of side groups giving phenol, benzoic acid, hydroxybenzoic acid, carboxylic and carbonyl groups, and by decomposition of phenol into cyclodiene mainly. It was also seen that the degradation path did not greatly changed whether the PABA or PMBA were homopolymers or grafted onto PP but the induction temperature of grafted polymers was seen at some 10–20°C higher. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Thermal decomposition of cyclotriphosphazenes. I. Alkyl-aminoaryl ethers

1,3,5-Triisopropoxy-1,3,5-tris(4-aminophenoxy)-cyclotriphosphazene-[CTP (I)], 1,3,5-trineopentoxy-1,3,5-tris(4-aminophenoxy)-cyclotriphosphazene [CTP (II)], and 1,1,3,5-tetraneopentoxy-3,5-bis(4-aminophenoxy)-cyclotriphosphazene [CTP (III)] were prepared from hexachlorotricylophosphazene. Thermal decomposition of the crude CTP (I), CTP (II), and CTP (III) was studied by thermogravimetry, differential scanning calorimetry, and thermal volatilization analysis. Solid, gaseous, and high boiling degradation products were collected at different steps of thermal decomposition and identified by using infrared and gas chromatography mass spectrometry. On heating to 600°C, CTP (I) shows three main steps of weight loss, whereas both CTP (II) and CTP (III) show two overlapping steps. The first step of thermal decomposition of CTP (I) is observed at 150–200°C, where elimination of part of the aliphatic substituents and polymerization of the CTP (I) occurs. The opening of tricyclophosphazene rings at 220–370°C provokes further elimination of aliphatics and ammonia and formation of crosslinked structures. Phosphorus oxynitride structure bonded with carbonized polyaromatics is formed in the third step of thermal decomposition, accompanied by the elimination of aromatics and chain fragments at 400–500°C. In the case of CTP (II) and (III), simultaneous evaporation of virgin CTPs, opening of the phosphazene ring, and elimination of aliphatic substituents with the formation of crosslinked polymeric structures occur at 210–350°C. A phosphorus oxynitride-aromatic carbonized structure similar to that from CTP (I) is formed at 350–600°C. The process is accompanied by the elimination of aromatics and chain fragments. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 461–472, 1998     

Nitrogen-containing products from the thermal decomposition of flexible polyurethane foams

The thermal decomposition of a polyester and a polyether flexible foam in a nitrogen atmosphere has been studied by gas chromatography, mass spec-trometry and elemental ultramicroanalysis. It is shown that the decomposition behaviours of the two foams are similar. At low temperatures (200 to 300 °C) there is a rapid and complete loss of the tolylene diisocyanate unit of each foam as a volatile yellow smoke leaving a polyol residue. The smoke has been isolated as a yellow solid (common to both foams) which contains virtually all of the nitrogen of the original foams and, under the conditions of test, is stable at temperatures up to 750 °C. Nitrogen-containing products of low molecular weight (mainly hydrogen cyanide, acetonitrile, acrylonitrile, pyridine and benzonitrile) observed during the high temperature decomposition (over 800 °C) of the foams are shown to be derived from the yellow smokes. At 1000 °C, approximately 70% of the available nitrogen has been recovered as hydrogen cyanide.     

Thermal decomposition of strontium oxalate — effect of various atmospheres

Decomposition products have been prepared from strontium oxalate monohydrate by heating for 2 h at 410, 470 and 510 °C in presence of air, water vapour at various pressures, nitrogen, hydrogen or carbon dioxide atmosphere. Structural, textural and morphological changes have been studied by X-ray diffraction and electron microscopy; the influence of various atmospheres is discussed. Differential thermal analysis and thermogravimetry reveal that dehydration of the starting material proceeds in two steps: a main dehydration process takes place at 180 °C, followed by the release of a small amount of water (～5%) at 270 °C. Decomposition of oxalate into carbonate covers the range 400 – 480 °C; a very small endotherm is observed at 450 °C, masked by a strong exotherm (530 °C) due to the release of energy probably accompanying the conversion of the amorphous decomposition product of the oxalate into a crystalline form.     

Electrical conductivity changes associated with thermal decomposition of phenolic- and silicone-based materials

Electrical conductivity changes during thermal decomposition of several phenolic and silicone materials have been measured while increasing temperature from 25 to ～ 700°C at a rate of 10°C per minute in a nitrogen atmosphere, The materials are based on phenolic and silicone resins and are reinforced with glass chopped fabric or cloth. The electrical results are correlated with mass loss and thermal decomposition product data obtained using mass spectroscopy and thermal gravimetric analysis. Peaks in the conductivity temperature dependence and deviations from ohmic behavior are found to be associated with material decomposition and/or outgassing. An excellent correlation is obtained between thermal stability and temperature-dependent electrical properties. Results suggest that electrical conductivity can be used as a thermal analytical tool in characterizing these materials.     

A methacrylate monomer bearing nitro,aryl, and hydroxyl side groups: Homopolymerization,characterization, dielectric,and thermal degradation behaviors

2‐Hydroxy‐3‐(4‐nitrophenoxy)propyl methacrylate (HNPPMA) monomer was synthesized. The poly(HNPPMA) was prepared by free radical polymerization (FRP) method. The characterization of poly(HNPPMA) was carried out using FT‐IR, NMR, differential scanning calorimetry, and GPC techniques. The thermal stability and degradation behavior of this polymer have been studied by using thermogravimetry (TG), GC‐MS, NMR, and FT‐IR. The results were in comparison to poly[2‐hydroxy‐3‐(1‐naphtyloxy)propyl methacrylate] sample with α‐naphtyloxy side group prepared by the same method in the our previous study. The effect of thermal activation on non‐isothermal decomposition kinetics of poly(HNPPMA) was investigated using thermogravimetric analysis according to Flynn‐Wall‐Ozawa method. The dielectric measurements of poly(HNPPMA) and doped with europium(III)chloride (EuCI₃) were investigated by impedance analyzer technique in range of 10–4000 Hz frequency by depending on the alternating current conductivities. The mode of thermal degradation including formation of the main products of poly(HNPPMA) degraded from ambient temperature to 500 °C was identified. S°, the cold ring fraction (CRF) was collected from room temperature to 500 °C. The structure of the degradation products has also been studied depending on the GC‐MS analysis. The thermal degradation mechanism for poly(HNPPMA) with radical degradation processes thought to dominate at high temperature was proposed based on GC/MS, NMR, FT‐IR, and taking into account the new products and differences in stability. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43925.     

Temperature‐dependent pyrolytic product evolution profile for polypropylene

The composition of the pyrolysis products of plastics depends on disintegration of the macromolecule into variety of hydrocarbon fractions. In this work, a detailed gas chromatographic study of pyrolysis products of polypropylene (PP) between 200 and 600°C was carried out. The pyrograms have been analyzed in terms of amount of different products evolved at various pyrolysis temperatures. At low pyrolysis temperatures (200–300°C), the yield of lighter hydrocarbons (C5‐C10) is low; it gradually increases until maximum decomposition temperature (446°C) and decreases thereafter. The following reaction types were considered to explain the decomposition mechanism of PP: (a) main chain cleavage to form chain‐ terminus radicals; (b) intramolecular hydrogen transfer to generate internal radicals; (c) intermolecular hydrogen transfer to form both volatile products and radicals; and (d) β‐scission to form both volatiles and terminally unsaturated polymer chains. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A study of thermal decomposition of alkanethiols in pressure reactor

The thermal decomposition of four alkanethiols was investigated in this paper. The test was processed in a pressure reactor at 200–400 °C. GC/MS and GC/SCD were used to detect the products of thermal decomposition. The result indicates that the alkane groups of alkanethiols have great influence on the thermal stability of alkanethiols. N-butylthiol, isobutylthiol and n-hexylthiol begin to pyrolyse at about 250 °C and more than 75% decomposes at 400 °C after being maintained for 4 h. However, tert-octylthiol can be broken down at lower temperature below 200 °C and almost 75% decomposes at 250 °C after 4 h. The main product of thermal decomposition is H₂S and a free radical reaction is used to explain the decomposition mechanism.     

Thermal decomposition kinetics of iodine-doped polyacetylene in vacuum

The thermal stability of iodine-doped polyacetylene films, (CHI_y)_x, has been studied by means of electrical conductivity measurements, measurements on weight loss, and mass spectrometric analysis of desorbing species. When heated between room temperature and 125°C in vacuum, these films proved to be of poor thermal stability, being unstable at temperatures above 20°C. During the thermal treatments, molecular iodine desorbs from the films, resulting in an appreciable dopant weight loss with accompanying decrease in the electrical conductivity. The decomposition process does not follow simple kinetics.     

Carnallite decomposition into magnesia,hydrochloric acid and potassium chloride: A thermal analysis study; formation of pure periclase

A thermal analysis study of the one-stage decomposition of small (mg) quantities of carnallite, KCl. MgCl₂, 6H₂O → KCl + MgO + 5H₂O ↑ + 2HCl ↓, showed that dehydration and hydrolysis require temperatures above 300 °C. Decomposition of greater amounts, and analysis of the products, showed that at 450 °C, 88 to 90% of the magnesium occurs as chloride-free high-purity periclase. At higher temperatures increasing amounts of chlorides remain in the periclase and are difficult to separate. Unglazed porcelain is a suitable material for the decomposition vessel.     

Vinyl‐addition type norbornene copolymers containing flexible spacers and sulfonated pendant groups for proton exchange membranes

Novel sulfonated poly(2‐butoxymethylenenorbornene‐co‐2‐(6‐phenoxy‐hexyloxymethylene)‐5‐norbornene [sP(BN/PhHN)] were prepared successfully through vinyl‐addition type polymerization and then sulfonated with concentrated sulfuric acid (98%) as sulfonating agent in a component solvent. The sP(BN/PhHN)‐40 with the maximal degree of sulfonation of 40% can be obtained by controlling the sulfonating reaction time from 8 to 20 h, and a proton conductivity of 3.35 × 10^?3 S/cm was achieved at 70°C. The methanol permeabilities of these membranes were in the range from 0.26 to 6.58 × 10^?7 cm²/s, which were remarkably lower than Nafion (2.36 × 10^?6 cm²/s). TEM analysis revealed that these side‐chain type membranes have a microphase separated structure composed of hydrophilic side‐chain domains and hydrophobic polynorbornene main chain domains. Sulfonated polynorbornene containing soft spacers displayed better properties, such as lower water uptake, high thermal properties, mechanical properties, and low methanol permeability. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Thermal oxidative and photo‐oxidative degradation of polytetrahydrofuran studied using 1H NMR, 13C NMR and GPC

The products and mechanism of the thermal oxidative degradation at 180 °C and the photo‐oxidative degradation at 40 °C of polytetrahydrofuran have been investigated using ¹H NMR, ¹³C NMR and GPC. The NMR analysis was assisted by the use of DEPT ¹³C spectra, two‐dimensional NMR spectroscopy (COSY, HMQC and HMBC) and chemical shift simulation software. The NMR spectra of both thermally and photolytically degraded samples were similar showing that the degradation mechanisms were similar. GPC indicated that both chain scission, leading to lower molar mass products, and chain extension, leading to higher molar mass products, occurred initially. NMR analysis of the initial soluble degraded polymers showed that chain scission resulted in formate, aldehyde, propyl ether, butyl ether and propanoyl chain ends, and in‐chain ester groups were also formed. For longer periods of degradation, crosslinked gels were formed but these were not amenable to detailed structural characterisation by high‐resolution NMR to determine the crosslink mechanism. Copyright © 2004 Society of Chemical Industry