Studies of the effects of copper, copper(II) oxide and copper(II) chloride on the thermal degradation of poly(vinyl chloride)

Investigations of the pyrolysis of poly(vinyl chloride) (PVC) in the presence of copper metal (Cu), copper(II) oxide (CuO) and copper(II) chloride (CuCl₂) are of potential importance because of the likelihood of the formation of these copper compounds during the thermal degradation of PVC-coated copper wires, a step in the recovery of copper from waste. The presence of Cu, CuO and CuCl₂ (i) retards the thermal degradation of PVC in air and in nitrogen and (ii) decreases the percentages of volatile products produced at both stages of the decomposition. These effects are greatest for PVC-CuO. The presence of copper, CuO or CuCl₂ in PVC has a major effect on the nature of the gaseous emissions of the thermal decomposition in air and in nitrogen. The concentrations of total chlorine, aliphatic hydrocarbons, aromatic hydrocarbons, chlorinated hydrocarbons and soot particulates are all affected relative to an equivalent amount of PVC. These changes are greatest for the PVC-CuO system for which total chlorine emissions in air and nitrogen are reduced by 40% in air and 20% in nitrogen, benzene emissions are reduced by greater than 90% in air and nitrogen, other aromatic and chloroaromatic emissions are reduced, and soot particulate emissions are reduced by more than 50% as the concentrations of aliphatic compounds are increased. These changes are consistent with the presence of copper or its compounds permitting more efficient combustion of the carbon content of the PVC and particularly in the case of PVC-CuO with the removal of chlorine during pyrolysis in the inorganic phase.     

Investigations on poly(vinyl chloride). IV. Effects of metal chlorides on the thermal decomposition of poly(vinyl chloride)

The effects of various metal oxides upon the thermal decomposition of poly(vinyl chloride) (PVC) were previously reported. In this work, 23 metal chlorides were investigated to determine their effects on the thermal decomposition of PVC by pyrolysis–gas chromatography at 500°C. Each metal chloride exhibits influences on the course of thermal decomposition of PVC almost similar to the corresponding metal oxide except for a few elements; the metal chlorides from acidic metal oxides accelerate the thermal decomposition of PVC, but the metal chlorides from basic metal oxides do not. On comparing the effects of metal oxides and metal chlorides on the thermal decomposition of PVC, most metal chlorides were found to accelerate the thermal decomposition of PVC more than the corresponding metal oxides, owing to ease of addition of the chlorine atoms released from metal chloride to the dehydrochlorinated chains. It is concluded from these results that the thermal decomposition of PVC containing metal salts is markedly influenced by the ease with which chlorine atoms are released from the corresponding metal chloride.     

Investigations on poly(vinyl chloride). III. Effects of metal oxides upon thermal decomposition of poly(vinyl chloride)

Thermal decomposition mechanisms of poly(vinyl chloride) (PVC) and the effects of a few metal oxides on the pyrolysis of PVC were previously reported. In the present work, 33 metal oxides were investigated to determine their effects on the thermal decomposition of PVC, by using a pyrolysis gas chromatograph. Most acidic oxides accelerate the recombination of chlorine atoms with double bonds, since PVC containing these metal oxides easily release lower aliphatics, toluene, ethylbenzene, o-xylene, and chlorobenzenes. On the other hand, most basic metal oxides, such as oxides of alkaline earths or silver, inhibit the recombination. These tendencies observed in the thermal decomposition of PVC agree with the contributions of corresponding metal salts to the dehydrochlorination of PVC proposed by other workers. This means that thermal decomposition or dehydrochlorination of PVC is affected by irregularities in head-to-tail linkages formed by the recombination of chlorine atoms during heat treatment of PVC.     

Investigations on poly(vinyl chloride). I. Evolution of aromatics on pyrolysis of poly(vinyl chloride) and its mechanism

Poly(vinyl chloride) (PVC) alone or mixed with 10 wt-% and 50 wt-% TiO₂, SnO₂, ZnO, and Al₂O₃ were pyrolyzed by using a pyrolysis gas chromatograph. Benzene, toluene, ethylbenzene, o-xylene, styrene, naphthalene, and various chlorobenzenes were identified. No hydrocarbons could be detected in pyrolysis products of any samples at 200°C. More aromatic hydrocarbons than aliphatic hydrocarbons are released from the PVC–TiO₂ system and in preheated PVC. The contrary result is observed in the PVC–ZnO and PVC–SnO₂ systems. Aromatics having methyl endgroups are easily released from the PVC–ZnO and PVC–SnO₂ systems and at elevated pyrolysis temperature, because methylene groups are easily isolated along the chain by ZnO, SnO₂ and the heating. The release of ethylbenzene o-xylene, and chlorobenzenes suggests a repeated dehydrochlorination and recombination of HCl and Cl₂ to double bonds along the chain. Possible decomposition mechanisms of PVC are discussed.     

A thermal decomposition study of polymers by tunable synchrotron vacuum ultraviolet photoionization mass spectrometry

The thermal decomposition of polymers (poly(vinyl chloride) (PVC) and polystyrene (PS)) has been studied with synchrotron VUV photoionization mass spectrometry at low pressure. Pyrolysis products formed at different temperatures have been identified by the measurement of photoionization mass spectra at different photon energies. The experimental results demonstrate the variation of the pyrolysis product pool of PVC at different temperatures, dividing the thermal decomposition process into two stages: the low‐temperature stage to form HCl and benzene, and the high‐temperature stage to form numerous large aromatic hydrocarbons. For the thermal decomposition of PS, four reaction categories are determined. This work reports a new application of synchrotron VUV photoionization mass spectrometry in the study of the thermal decomposition of polymers, and demonstrates its good performance in product analysis, which is expected to help understand the thermal decomposition mechanism of PVC, PS and other synthesized polymers. Copyright © 2009 John Wiley & Sons, Ltd.     

Correlation of thermal degradation mechanisms: Polyacetylene and vinyl and vinylidene polymers

The thermal degradation of poly(vinyl bromide) (PVB), poly(vinyl chloride) (PVC), poly(vinyl alcohol) (PVA), poly(vinyl acetate) (PVAc), poly(vinyl fluoride) (PVF), poly(vinylidene chloride) (PVC₂), and poly(vinylidene fluoride) (PVF₂) has been studied by direct pyrolysis–mass spectrometry (DP-MS) and flash pyrolysis–gas chromatography–mass spectrometry techniques. Vinyl and vinylidene polymers exhibit two competitive thermal degradation processes: (1) HX elimination with formation of polyene sequences which undergo further moleculaar rearrangements, and (2) main-chain cleavage with formation of halogenated or oxigenated compounds. The overall thermal degradation process depends on the prevailing decomposition reaction in each polymer; therefore, different behaviors are observed. The thermal degradation of polyacetylene (PA) has also been studied and found important for the elucidation of the thermal decomposition mechanism of the title polymers.     

Evolution of aromatic compounds in the thermal decomposition of vinyl polymers

The thermal decomposition products that evolve from poly(vinyl chloride) (PVC), poly(vinylbromide) (PVB), poly(vinyl alcohol) (PVA), and poly(vinylacetate) (PVAc) were analyzed by direct pyrolysis in the ion source of a mass spectrometer (MS). Our results indicate that in both stages of the decomposition process which occurred in the four vinyl polymers investigated several aromatic hydrocarbons were produced and that the relative amounts of benzene, napthalene, and anthracene were different in the two stages. This previously unreported information determines in a single scheme the thermal behavior of the title compounds.     

High-temperature pyrolysis of poly(vinyl chloride): Gas chromatographic-mass spectrometric analysis of the pyrolysis products from PVC resin and plastisols

A pyrolysis–gas chromatographic–mass spectrometric technique for analyzing the pyrolysis products from polymers in an inert atmosphere is described. Initial studies encompassing the pyrolysis of poly(vinyl chloride) homopolymer and a series of PVC plastisols (based on o-phthalate esters) have provided a complete qualitative and semi-quantitative analysis of the pyrolysis products from these materials. PVC resin yields a series of aliphatic and aromatic hydrocarbons when pyrolyzed at 600°C; the amount of aromatic products is greater than the amount of aliphatic products. Benzene is the major organic degradation product. A typical PVC plastisol [PVC/o-dioctyl phthalate (100/60)] yields, upon pyrolysis, products that are characteristic of both the PVC matrix and the phthalate plasticizer. The pyrolysis products from the plasticizer dilute those from the PVC portion of the plastisol and are, in turn, the major degradation products. There are no degradation products resulting from an interaction of the PVC with the plastisol. The pyrograms resulting from pyrolysis of the various plastisols of PVC can be used for purposes of “fingerprinting.” Identification of the major peaks in a typical plastisol pyrogram provides information leading to a precise identification of the plasticizer. The pyrolysis data from this study were related to a special case of flammability and toxicity.     

Thermal degradation and evolved gas analysis of epoxy (DGEBA)/novolac resin blends (ENB) during pyrolysis and combustion

The thermal degradation of epoxy (DGEBA) and phenol formaldehyde (novolac) resins blend was investigated by using thermogravimetric analysis (TGA) coupled with Fourier transform infrared spectroscopy and mass spectroscopy. The results of TGA revealed that the thermal degradation process can be subdivided into four stages: drying the sample, fast and second thermal decomposition, and further cracking process of the polymer. The total mass loss of 89.32 mass% at 950 °C is found during pyrolysis, while the polymer during the combustion almost finished at this temperature. The emissions of carbon dioxide, aliphatic hydrocarbons, carbon monoxide, etc., while aromatic products, are emitted at higher temperature during combustion and pyrolysis. It was observed that the intensities of CO₂, CO, H₂O, etc., were very high when compared with their intensities during pyrolysis, attributed to the oxidation of decomposition product.     

Thermal decomposition of polymer mixtures of PVC,PET and ABS containing brominated flame retardant: Formation of chlorinated and brominated organic compounds

The thermal decomposition of various mixtures of acrylonitrile butadiene styrene copolymer (ABS), ABS containing brominated epoxy resin flame retardant and Sb₂O₃, poly(ethylene terephthalate) (PET) and poly(vinyl chloride) (PVC) has been studied in order to clarify the reactions between the components of mixed polymers. More than 40 halogen-containing molecules have been identified among the pyrolysis products of mixed samples. Brominated and chlorinated aromatic esters were detected from the mixtures containing PET and halogen-containing polymers. A series of chlorinated, brominated and mixed chlorinated and brominated phenols and bisphenol A molecules have been identified among the pyrolysis products of polymer mixtures containing flame retarded ABS and PVC. It was established that the decomposition rate curves (DTG) of the mixtures were not simple superpositions of the individual components indicating interactions between the decomposition reactions of the polymer components. The maximal rate of thermal decomposition of both ABS and PET decreases significantly if the mixture contains brominated epoxy flame retardant and Sb₂O₃ synergist. The dehydrochlorination rate of PVC is enhanced in the presence of ABS or PET.     

Investigations on poly(vinyl chloride). II. Pyrolysis of chlorinated polybutadienes as model compounds for poly(vinyl chloride)

The pyrolysis of chlorinated polybutadienes (CPB) was investigated by using a pyrolysis gas chromatograph. CPB corresponds to poly(vinyl chloride) (PVC) constructed with head–head and tail–tail linkages of the vinyl chloride unit. Benzene, toluene, ethyl-benzene, o-xylene, styrene, vinyltoluene, chlorobenzenes, naphthalene, and methylnaphthalenes were detected in the pyrolysis products from CPB above 300°C, and no hydrocarbons could be detected at 200°C. The pyrolysis products from CPB were similar to those from PVC and new products could not be detected. Lower aliphatics, toluene, ethylbenzene, o-xylene, chlorobenzenes, and methylnaphthalenes were released more easily from pyrolysis of CPB than from PVC; amounts of benzene, styrene, and naphthalene formed were small. These results support the conclusion that recombination of chlorine atoms with the double bonds in the polyene chain takes place and that scission of the main chain may depend on the location of methylene groups isolated along the polyene chain during the thermal decomposition of PVC.     

Pyrolysis and combustion kinetics of microcapsules containing carbon nanofibers by thermal analysis–mass spectrometry

The thermal properties of microcapsules containing carbon nanofibers (CNFs) suspended in ethyl phenylacetate (EPA) were investigated by thermogravimetric analysis coupled with mass spectrometry (TGA–MS). The pyrolysis of these microcapsules consisted of two stages. During the first one (100–150 °C), the emissions of aromatic compounds coming from the decomposition of EPA were identified. In the second one (150–290 °C), NH₂–CO coming from primary amide decomposition was mainly detected.A multiple-step model was used to predict the thermal decomposition of the synthesized microcapsules under both inert and oxidant atmospheres. Furthermore, pyrolysis and combustion kinetic parameters such as pre-exponential factor and activation energy of these microcapsules were estimated by nonlinear regression. An excellent agreement between experimental and predicted data was observed and confirmed from the statistical point of view.     

Antimony oxide–PVC synergism: Laser pyrolysis studies of the interaction mechanism

Laser-probe pyrolysis is used to investigate the synergistic flame-retardancy effect observed for antimony oxide (Sb₂O₃)–PVC combinations. Molecular beam-mass analysis detection techniques permit direct sampling of the laser-vaporized species without the need for intermediate product collection stages. Laser pyrolysis of a PVC formulation containing 3 phr Sb₂O₃ provides the first direct evidence for the production of volatile SbCl₃ during thermal decomposition. Selective laser irradiation of PVC in the presence of unheated Sb₂O₃ in the sample cell reveals that HCl evolved from the polymer substrate rapidly reacts with Sb₂O₃(s) to form the volatile flame-retardant species SbCl₃. Similar results are observed for SbOCl(s). These reactions are distinct from those previously proposed, which involve the formation and subsequent thermal decomposition of intermediate solid-phase antimony oxychlorides, and demonstrate that the antimony compounds, rather than serving only as inert sources for SbCl₃, readily participate in direct chemical reactions with HCl. In addition to the composition of the reaction products, information is also obtained on their evolution characteristics from the sample cell.     

Thermal degradation study of tetrabromobisphenol A under the presence metal oxide: Comparison of bromine fixation ability

Thermal degradation of mixture of tetrabromobisphenol A (TBBA) and metal oxide (ZnO, Fe₂O₃, La₂O₃, CaO and CuO) has been studied under inert atmosphere. The formation of hydrogen bromide and brominated organic compounds is observed for pyrolysis of TBBA. The addition of metal oxide gives rise to considerable suppression of HBr as well as brominated organic compounds. The suppression owes to the bromination of oxides. The influence of oxide on thermal degradation of TBBA is discussed with emphasis on the conversion of bromine.     

IR laser ablative degradation of poly(ethylene terephthalate): Formation of insoluble films with differently bonded CO groups

IR laser-induced degradation of poly(ethylene terephthalate) (PET) was studied under different irradiation conditions and the ablated volatile and solid products were characterized by mass and infrared spectroscopy, gel-permeation chromatography, thermogravimetry and electron microscopy. The observed volatile products (carbon oxides, H₂, C_1-2 hydrocarbons, acetaldehyde, benzene and toluene) and less-volatile aromatic compounds are typical products of thermal degradation of PET. The ablatively deposited solid materials are a blend of soluble, structurally similar oligomers and of an insoluble polymer containing carbonyl groups bonded in a -C(O)OH arrangement. Thermal degradation of these deposited solids is controlled by decomposition of sublimed fractions and is easier than that of PET.     

Thermogravimetric studies on catalytic effect of metal oxide nanoparticles on asphaltene pyrolysis under inert conditions

This study investigated the catalytic effect of NiO, Co₃O₄ and Fe₃O₄ nanoparticles toward asphaltene thermal decomposition (pyrolysis) under inert conditions. Asphaltene adsorbed onto the selected nanoparticles were subjected to thermal decomposition up to 800?°C in a thermogravimetric analyzer. The presence of nanoparticles caused a significant decrease in the asphaltene decomposition temperature and activation energy. Activation energies for the process were calculated using the Ozawa?CFlynn?CWall method. All the selected metal oxide nanoparticles showed high catalytic activity toward asphaltene decomposition in the following order NiO?>?Co₃O₄?>?Fe₃O₄. This study confirms that metal oxide nanoparticles can significantly enhance the thermal decomposition of heavy hydrocarbons, like asphaltenes.     

Thermal degradation and evolved gas analysis of N,N′-bis(2 hydroxyethyl) linseed amide (BHLA) during pyrolysis and combustion

The thermal degradation of N,N′-bis(2 hydroxyethyl) linseed amide (BHLA) was investigated by thermogravimetric analysis coupled with Fourier transform infrared spectroscopy and mass spectroscopy (TG–FTIR–MS). Thermogravimetric analysis revealed that the thermal degradation process can be subdivided into three stages: sample drying (<200 °C), main decomposition (200–500 °C), and further cracking (>500 °C) of the polymer. The compound reached almost 800 °C during pyrolysis and combustion. The activation energy at the second step during combustion was slightly higher than that of pyrolysis emissions of carbon dioxide, aliphatic hydrocarbons, carbon monoxide, and hydrogen cyanide, and other gases during combustion and pyrolysis were detected by FTIR and MS spectra. It was observed that the intensities of CO₂, CO, HCN, and H₂O were very high when compared with their intensities during pyrolysis, and this was attributed to the oxidation of the decomposition product.     

Al(OH)3和Mg(OH)2对PVC热解特性的影响研究

利用热重分析仪并借助电导率测定法探讨了Al(OH)3和Mg(OH)2对PVC热解特性的影响,简要分析了其机理。结果表明:加入Al(OH)3和Mg(OH)2后均能增加PVC体系在第一阶段的最大热解速率和残炭量,最大热解速率增加约1倍,残炭量增加约4倍。并且分解产生的结晶水吸收大量的热量,惰性金属氧化物也有利于成核、炭层生长和凝聚,有着明显的阻燃和抑烟作用。HCl毒性气体的释放主要集中在体系的第一阶段,Al(OH)3能促使HCl提前释放,HCl的释放总量增加,Mg(OH)2也能促使HCl提前释放,但HCl的释放总量却是减少的。     

The effect of OCoAl‐LDH and OCoFe‐LDH on the combustion behaviors of polyvinyl chloride

The effects of the modified layered double hydroxide (LDH) of Co/Al (OCoAl‐LDH) and the modified LDH of Co/Fe (OCoFe‐LDH) on the combustion behaviors of polyvinyl chloride (PVC) during pyrolysis processes were compared and investigated. The thermal degradation and combustion behavior of the PVC composites were investigated by thermogravimetric analysis (TGA), microscale combustion calorimetry (MCC), and cone calorimetry (CONE). The results indicate that the incorporation of LDHs brought about the improved thermal stability and reduced heat release of PVC composites at a high temperature. The smoke‐suppression properties of the composites are investigated by steady‐state tube furnace (SSTF), and the results indicated that the toxic gases such as CH₄, CO, and N_xO were inhibited by both of the two LDHs, but the OCoFe‐LDH has a better effect on the smoke suppression. Subsequently, the char layer was investigated by scanning electron microscopy–energy‐dispersive spectrometry (SEM‐EDS) and Raman analysis. The results indicate that the LDHs can promote the dechlorination of PVC during the thermal oxidation process and can inhibit the production of HCl in inert gas. Generally, OCoAl‐LDH and OCoFe‐LDH can be potential catalysts for waste disposal and can improve the fire safety of PVC.     

Analysis of products from the pyrolysis of plastics recovered from the commercial scale recycling of waste electrical and electronic equipment

Three plastic fractions from a commercial waste electrical and electronic equipment (WEEE) processing plant were collected and investigated for the possibility of recycling them by batch pyrolysis. The first plastic was from equipment containing cathode ray tubes (CRTs), the second plastic was from refrigeration equipment, and the third plastic was from mixed WEEE. Initially, the decomposition of each of the plastics was investigated using a TGA linked to a FT-ir spectrometer which showed that the CRT plastic decomposed to form aliphatic and aromatic compounds, the refrigerator plastic decomposed to form aldehydes, CO₂, aromatic, and aliphatic compounds, and the mixed WEEE plastic decomposed to form aromatic and aliphatic compounds, CO₂, and CO. Each plastic mixture was also pyrolysed in a batch reactor to determine the halogen and metal content of the pyrolysis products, additionally, characterisation of the pyrolysis oils was carried out by GC–MS and the pyrolysis gases by GC–FID and GC–TCD. It was found that the halogen content of the oils was relatively low but the halogen and metal content of the chars was high. The pyrolysis oils were found to contain valuable chemical products and the pyrolysis gases were mainly halogen free, making them suitable as a fuel.