Copyrolysis of block polypropylene with waste wood chip

In this study, the copyrolysis of waste wood chip (WC) and block polypropylene (PP) was studied to investigate how the characteristics of bio-oils are affected by copyrolysis. The thermogravimetric analysis performed with a temperature rise of 20 °C/min, from room temperature to 600 °C, showed that the decomposition temperature of PP was a little higher via copyrolysis than the single-component pyrolysis. This result suggests that the characteristics of the pyrolysis of PP were affected by the pyrolysis products of WC. The Py-GC/MS analysis of the copyrolysis products detected some new compounds that had not been detected in the single-component pyrolysis products, indicating interactions between the products of WC and PP pyrolyses. The results of the experiments using a fixed bed reactor showed improved properties of the bio-oil obtained from the copyrolysis compared to those of the bio-oil obtained from the single-component pyrolysis: increased carbon and hydrogen contents, decreased water content and a significantly increased heating value.     

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 Polymer Mixtures Containing Poly(vinyl chloride)

Thermal decomposition of a series of 1 : 1 mixtures of typical polymer waste materials [polyethylene (PE), poly(propylene) (PP), polystyrene (PS), polyacrylonitrile (PAN), polyisoprene, poly(methyl methacrylate) (PMMA), polyamide‐6 (PA‐6), polyamide‐12 (PA‐12), polyamide‐6,6 (PA‐6,6), and poly(1,4‐phenylene terephthalamide) (Kevlar)] with poly(vinyl chloride) (PVC) was examined using thermal analysis and analytical pyrolysis techniques. It was found that the presence of polyamides and PAN promotes the dehydrochlorination of PVC, but PVC has no effect on the main decomposition temperature of polyamides. The hydrogen chloride evolution from PVC is not altered when other vinyl polymers or polyolefins are present. The thermal degradation of PAN is retarded significantly, whereas that of the other vinyl polymers is shifted to a slightly higher temperature in the presence of PVC. Among the pyrolysis products of PAN‐PVC mixture methyl chloride was found in comparable amount to the other gaseous products at 500°C pyrolysis temperature.     

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.     

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.     

Coal flash pyrolysis: 2. Polymethylene compounds in low temperature flash pyrolysis tars

Pyrolysis of coals at low temperatures (< 600 °C) produces tars containing the precursors of the low molecular weight aliphatic hydrocarbons, such as ethylene and propylene, observed on flash pyrolysis of the coals at higher temperatures (700–800 °C). This is shown by further pyrolysis of these low temperature tars at high temperatures. Various methods, including isolation by h.p.l.c. were used to confirm the presence of straight chain paraffin and olefin pairs (C₁₄C₂₆ and above) in the low temperature tars. Pyrolysis of pure paraffins and olefins in this molecular weight range at temperatures > 700 °C produce ethylene, propylene and other cracking products similar to those obtained on flash pyrolysis of coal.     

Pyrolysis of benzenethiol

Flow pyrolysis of benzenethiol at 700 °C or vacuum pyrolysis of benzenethiol at 800 °C yields benzene, diphenyl sulphide and diphenyl disulphide as the major products. Dibenzothiophene, biphenyl, thianthrene and diphenyl trisulphide are minor products. Co-pyrolysis of benzene-d₆ and natural isotopic abundance benzenethiol yields deuterated and non-deuterated products, indicating that the product-forming sequence is initiated by phenyl radical formation. The phenyl radicals abstract hydrogen atoms from benzenethiol to yield benzene and phenylthio radicals. Coupling of phenylthio radicals yields diphenyl disulphide. Diphenyl sulphide and the minor products are diphenyl disulphide pyrolysis products.     

Thermal degradation mechanism of poly(ether imide) by stepwise Py–GC/MS

The thermal degradation of poly(ether imide) (PEI) was studied through a combination of thermogravimetric analysis and stepwise pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS) techniques with consecutive heating of the samples at fixed temperature intervals to achieve narrow temperature pyrolysis conditions. The individual mass chromatograms of various pyrolysates were correlated with pyrolysis temperatures to determine the pyrolysis mechanism. The major mechanisms were two‐stage pyrolysis, involving main‐chain random scission, and carbonization. In the first stage, the scission of hydrolyzed imide groups, ether groups, and isopropylidene groups produced CO+CO₂ and phenol as the major products and was accompanied by chain transfer of carbonization to form partially carbonized solid residue. In the second pyrolysis stage, the decomposition of the partially carbonized solid residue and remaining imide groups formed CO+CO₂ as the major product along with benzene and a small amount of benzonitrile. The yield of CO+CO₂ was the largest fraction in the total ion chromatogram of the evolved gas mixtures. Hence, the thermal stability of the imide group was identical to the maximum thermogravimetry loss rates in the two‐stage pyrolysis regions. Afterward, carbonization dominated the decomposition of the solid residue at high temperatures. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1151–1161, 2001     

Pyrolysis of brown coals. 2. Decomposition of acidic groups on heating in the range 100–900 °C

The pyrolysis of a Yallourn brown coal in the acid form and several different cation forms has been studied at temperatures up to 900 °C, in regard to the decomposition of acid groups, the relation between oxygen products evolved and these groups, and the fate of cations. The exchange of carboxyl groups changes the amounts of both carbon dioxide and water evolved on pyrolysis, indicating that oxygen-containing groups other than carboxyl are affected by the exchange. The total acid-group content of the acid-form coal heated at different temperatures can be related to the sum of the acid group content of the residual char, and carbon dioxide and carbon monoxide evolved during pyrolysis. The results, in general, confirm the conclusion reached previously in regard to pyrolysis carried out at temperatures up to 300 °C. Pyrolysis in nitrogen at 900 °C releases all oxygen from the acid-form coal. In cation coals the amount of oxygen retained in the char in combination with the cation depends on the type of cation and the extent of reaction with nitrogen in the pyrolysis atmosphere.     

Pyrolysis of municipal solid waste

A state-of-the-art review describing the characteristics of municipal solid waste (MSW) and assessing the chemistry and technology of pyrolysis of municipal solid waste is presented. The economics of the pyrolysis process are outlined. Combustibles constitute on average about 60% of the weight of MSW and result in an average heating value (“as received” basis) of about 3,000 to 6,000 Btu/Ib. This makes MSW attractive for thermal treatment. Municipal solid waste can be converted to gas, liquid and solid products by pyrolysis. Due to the complexity in composition of MSW the exact mechanism of pyrolysis is not known. Both homogeneous and heterogeneous reactions occur at the same time and both heat and mass transfer take place during the process. The relative yields of different products depends on the temperature of pyrolysis and the rate of heating. High pyrolysis temperatures and high heating rates favour the production of gases indicating high energies of activation for gasification reactions. At low temperatures, below 800°C, the pyrolysis process is reaction-rate controlled, while at high temperatures, above 1,200°C, the process is diffusion-rate controlled. Conditions of good heat and mass transfer are required for gasification of MSW. The residual char after pyrolysis can be gasified by further treatment with steam, hydrogen or carbon monoxide and water. The heat available from the products of pyrolysis is sufficient to sustain the process and yield some excess energy. Three types of reactor design have been generally used in the investigation of pyrolysis of MSW; fixed bed reactor, fluidized bed reactor and rotary kiln reactor. The advantages and weak points of each of these are briefly discussed. The costs of disposal of MSW by pyrolysis appear to be competitive with incineration.     

Effect of zeolite filler on the thermal degradation kinetics of polypropylene

In this study, the thermal degradation behavior of polypropylene (PP) and PP–zeolite composites was investigated. Clinoptilolite, a natural zeolitic tuff, was used as the filler material in composites. The effects of both pure clinoptilolite and silver‐ion‐exchanged clinoptilolite on the thermal degradation kinetics of the PP composites was studied with differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Polymer degradation was evaluated with DSC at heating rates of 5, 10, and 20°C/min from room temperature to 500°C. The silver concentration (4.36, 27.85, and 183.8 mg of Ag/g of zeolite) was the selected parameter under consideration. From the DSC curves, we observed that the heat of degradation values of the composites containing 2–6% silver‐exchanged zeolite (321–390 kJ/kg) were larger than that of the pure PP (258 kJ/kg). From the DSC results, we confirmed that the PP–zeolite composites can be used at higher temperatures than the pure PP polymer because of its higher thermal stability. The thermal decomposition activation energies of the composites were calculated with both the Kissinger and Ozawa models. The values predicted from these two equations were in close agreement. From the TGA curves, we found that zeolite addition into the PP matrix slowed the decomposition reaction; however, silver‐exchanged zeolite addition into the matrix accelerated the reaction. The higher the silver concentration was, the lower were the thermal decomposition activation energies we obtained. As a result, PP was much more susceptible to thermal decomposition in the presence of silver‐exchanged zeolite. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 143–148, 2006     

Effect of high polymerization temperature on the microstructure of isotactic polypropylene prepared using heterogeneous ticl4/mgcl2 catalysts

The effects of alkylaluminum and polymerization temperature on propylene polymerization without an external donor in the use of a TiCl₄–MgCl₂–diether(BMMF) catalyst were investigated. The results indicated that with increasing polymerization temperature the concentrations of [mmmm] of heptane‐insoluble poly(propylene) (PP) fraction increased. Crystallization analysis fractionation (CRYSTAF) results showed the fractions of different crystallization temperatures were changed according to various polymerization temperatures. The activity with Et₃Al as cocatalyst at 100°C was much lower than that at 70°C. However, the activity with i‐Bu₃Al at 100°C was as high as that at 70°C. The fraction of high‐crystallization temperature of PPs obtained with i‐Bu₃Al increased with increasing polymerization temperature, which was opposite to that with Et₃Al, thus implying that the copolymerization of propylene with the monomer arising from Et₃Al led to the lower crystallization ability of PPs obtained with Et₃Al. The terminal groups of PP suggested that the chain‐transfer reaction by β‐H abstraction was the main chain‐transfer reaction at 120°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3980–3986, 2003     

Pyrolysis of polyolefins in high-boiling solvents

The pyrolysis of polyethylene and polypropylene in vacuum residue and coal-tar pitch solvents was studied in a batch reactor at atmospheric pressure in a temperature range of 380–420°C. Aliphatic hydrocarbons and C₅–C₃₂ normal olefins and isoolefins were the main pyrolysis products of the polyolefins and vacuum residue, which also underwent thermal degradation at these temperatures. The total conversion of a polypropylene-vacuum residue mixture into gaseous and distillate products was nearly additive; upon the pyrolysis of polypropylene in pitch and of polyethylene in vacuum residue and pitch, the yield of distillate products decreased and the paraffin/olefin ratio in these products increased. The observed regularities were explained by hydrogen transfer from the solvents to the intermediate radical products of the thermal decomposition of polymer chains. The reactions of the resulting of olefins with the solvents can also occur to a lesser degree. The greatest deviations from additivity were observed in the pyrolysis of polyethylene in the solvents used.     

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.     

Thermal transitions in polyimide transfer under sliding against steel,investigated by Raman spectroscopy and thermal analysis

Polyimides (PI) are known for their extremely high thermal stability and lack of a glass transition temperature below their decomposition point. Therefore, they are frequently used in high‐demanding tribological applications. The tribological characteristics of sintered polyimide (SP‐1) are presently investigated as a function of the sliding temperature that is artificially varied between 60°C and 260°C under fixed load in counterformal contact with a steel plate. For obtaining low friction and wear, a transfer film needs to develop onto the sliding counterface, induced by viscous polymer flow. As surface plastification is more difficult for high‐performance materials, for example, polyimide, a transition towards low friction and stabilized wear rates is observed at temperatures higher than 180°C in accordance with the occurrence of plate‐like transfer particles, while high friction and no transfer was observed at lower temperatures. This transition is correlated to a peak value in both friction and wear at 180°C and is further explained by Raman spectroscopy performed on the worn polymer surfaces and temperature‐modulated differential scanning calorimetry. It is concluded that the intensity of C‐N‐C related absorption bands is minimal at 180°C and is complementary to the intensity of the C?C phenylene structure that is maximal at 180°C. The orientation of the C‐O‐C structure slightly decreases relative to the sliding surface at higher bulk temperatures. The amount of C?O functional groups is the lowest at 140°C, while its orientation progressively enhances at higher bulk temperatures. At 140°C also, the lowest wear rates were measured. The 180°C transition temperature with a peak value in both friction and wear corresponds to a secondary transition measured in the specific complex heat capacity, pointing out that the overall bulk temperature is presently more important than local flash temperatures for causing transitions in tribological behavior. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1407–1425, 2006     

Styrene‐assisted free‐radical graft copolymerization of maleic anhydride onto polypropylene in supercritical carbon dioxide

The free‐radical graft copolymerization of maleic anhydride (MAH) onto polypropylene (PP) with the assistance of styrene (St) in supercritical carbon dioxide (CO₂) was studied. The effects of the St concentration and initiator concentration on the functionality degree of the grafted PP in supercritical CO₂ were investigated. The addition of St drastically increased the MAH functionality degree, which reached a maximum when the molar ratio of MAH and St was 1:1. St, an electron‐donating monomer, could interact with MAH through charge‐transfer complexes to form the St–MAH copolymer (SMA), which could then react with PP macroradicals to produce branches by termination between radicals. There was SMA in the grafting reaction system characterized by Fourier transform infrared and differential scanning calorimetry. Furthermore, the highest MAH functionality degree was obtained when the concentration of 2,2′‐azobisisobutyronitrile (AIBN) was 0.6 wt % based on PP. The effects of the temperature and pressure of supercritical CO₂ on the functionality degree of the grafted PP were analyzed. An increase in the temperature accelerated the decomposition rate constant of AIBN, thereby promoting the grafting reaction. In addition, an increase in the temperature increased the diffusion of monomers and radicals in the disperse reaction system of supercritical CO₂. The highest degree of functionality was found at 80°C. Also, the functionality degree of grafted PP decreased with an increase in the pressure of supercritical CO₂ within the experimental range. The morphologies of pure PP and grafted PP were significantly different under polarizing optical microscopy. The PP spherulites were about 38 μm in size, and the grafted PP spherulites were significantly reduced because of heterogeneous nucleation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 853–860, 2003     

Review of the kinetics of pyrolysis and hydropyrolysis in relation to the chemical constitution of coal

Kinetic data show that the pyrolysis reactions of hard coal may be interpreted in terms of parallel first order reactions, relating to the coal functional groups which can be considered as predecessors of the pyrolysis products. This relation is confirmed by C-, H- and O-balances of pyrolysis products and those of the corresponding predecessor structural groups of the coal. The activation energies measured are of the same order of magnitude as the bonding energies of bridge CC bonds between the aromatic ring-systems in the coal molecule. These observations suggest a mechanism of coal pyrolysis, consisting of the following steps: rupture of CC bridges; formation of radical groups; and recombination of radicals to stable molecules part of which, i.e., those of low molecular weight, diffuse out of the solid matter whereas the rest (whose diffusion in the pore system of the solid is prevented due to their higher molecular weight) react with each other at higher temperatures to give coke, releasing elementary hydrogen. In the presence of hydrogen > 500 °C, additional reactions of partial hydrogenation of polynuclear aromatics with subsequent hydrocracking will occur, leading to increased formation of highly aromatic tar, BTX, CH₄ and H₂O.     

Investigation of the Pyrolytic Degradation of Ion Exchange Resins by Means of Foil Pulse Pyrolysis Coupled with Gas Chromatography/Mass Spectrometry

Abstract

Cationic (LEWATIT S100) and anionic ion exchangers (LEWATIT M500MB) were thermally decomposed in amounts of 15–60 μg in a foil pulse pyrolyzer. The gaseous products were gas-chromatographically separated and identified by mass spectrometry. Cationic resins release mainly sulfur dioxide and benzene at temperatures up to 500°C. At higher temperatures, degradation products like ethylbenzene, styrene, hydrogen sulfide, benzene, and toluene are increasingly observed. Their ratio strongly depends on the applied temperatures. After fractionated pyrolysis of a single sample with rising temperatures, mainly benzene, hydrogen sulfide, and carbon disulfide are produced at 1000°C, leaving behind a residue of pyrolysis coke. Anionic resins generate mainly trimethylamine and methyl chloride up to 400°C. With rising temperatures, the formation of styrene, p-methylstyrene, and p-ethylstyrene dominates. Pyrolysis of anionic resins ends at about 900°C without leaving behind significant amounts of residue. Kinetic data for several of the observed degradation reactions were calculated.     

Thermal desorption and pyrolysis direct analysis in real time mass spectrometry of Nafion membrane

Perfluorosulfonic acid ionomer membranes have been widely used as proton conducting membranes in various electrochemical processes such as polymer electrolyte fuel cells and water electrolysis. While their thermal stability has been studied by thermogravimetry and analysis of low molecular weight products, their decomposition mechanism is little understood. In this study a newly developed methodology of thermal desorption and pyrolysis in combination with direct analysis in real time mass spectrometry is applied for Nafion membrane. An ambient ionization source and a high-resolution time-of-flight mass spectrometer enabled unambiguous assignment of gaseous products. Thermal decomposition is initiated by side chain detachment above 350°C, which leaves carbonyls on the main chain at the locations of the side chains. Perfluoroalkanes are released above 400°C by main chain scission and their further decomposition products dominate above 500 °C. DFT calculation of reaction energies and barrier heights of model compounds support proposed decomposition reactions.     

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.