Decomposition Of Polyvinyl Chloride Research Articles

Chlorine Fixing Ability of Electric Arc Furnace Dust During the Thermal Degradation of Polyvinyl Chloride under Oxidative Conditions

Electric arc furnace dust (EAFD) and polyvinyl chloride (PVC) are two hazardous wastes that are accumulated world-wide at an alarming rate. Utilising these two wastes simultaneously towards a sustainable recycling loop can greatly mitigate their environmental impact. Herein, EAFD was studied as a potential emission fixator of evolved gaseous HCl generated from the thermal decomposition of PVC under different operational conditions: EAFD-PVC mass ratio, solid reactants geometry, O2 partial pressure, holding temperature, holding time and heating rate. The highest chlorine fixation percentage was calculated to be 78.9% and was obtained at an EAFD-PVC mass ratio of 1:1 (thin disks geometry), while the rest escaped in the form of HCl/Cl2. No significant variation was observed on the percentage of fixed chlorine when the thermal treatment was performed using different geometries: long cylinder, thin disks, and powder forms with a maximum difference in fixation of only 5.6% between extremities. Increasing O2 partial pressure positively affected the chlorine fixation percentage increasing it from 39.9 to 48.4% at 0 and 21 kPa partial pressures, respectively. Increasing both the holding temperature and holding time under oxidative conditions negatively affected the percentage of fixed chlorine due to oxidation of formed FeCl2 back to Fe2O3. The heating rate did not show any significant effect on the amount of fixed HCl, suggesting that the speed of chlorination reactions can be identical to or faster than the decomposition rate of PVC. Overall, EAFD is believed to be an excellent candidate for capturing HCl contained in PVC upon thermal degradation.

A single-step upcycling of PVC-containing municipal solid waste compositions for greener chemicals and clean solids as fuel or oil absorbent

Polyvinyl chloride (PVC) containing municipal solid waste (MSW) streams are difficult to recycle and mostly landfilled due to various detrimental effects PVC causes to waste recycling. In this work, a single-step upcycling of PVC-containing commingled wastes in tetrahydrofuran was investigated using cellulose, PVC, polyethylene (PE), polypropylene (PP), and polystyrene (PS) to model the wastes. During the co-conversion, in-situ produced HCl derived from PVC decomposition acted as an acid catalyst to selectively decompose cellulose into liquid mainly containing levoglucosan (LGA) and furfural. It was also found that the presence of PE, PP, and PS in the mixture synergistically enhanced the cellulose-derived monomer productions and increased the reaction rate for producing the monomers by suppressing secondary reactions of HCl in the solvent. The maximum LGA yield from co-conversion of cellulose, PVC, and PS was 35.4% after a 5 min reaction compared to the 31.7% obtained without PS in the mixture. In addition to converting cellulose to chemicals, PVC-derived polyaromatics and partly decomposed PE, PP, and PS were recovered as solids. The dechlorinated solids had higher heating values up to 46.11 MJ/kg, achieved by co-converting cellulose, PVC, and PP. When used as oil absorbents in water, the solid recovered from converting cellulose, PVC, and PE mixture showed the highest absorption capability. Overall, the presented approach offers a promising way for upcycling PVC-containing wastes in which PVC properties and its molecular structure are leveraged to enhance the conversion.

Enhancement of interfacial adhesion to carbon fibers via electrostatic interaction using polyvinyl chloride as a model matrix

The purpose of this study is to provide a framework for spectroscopic investigation of an enhancement mechanism of the interfacial adhesion using a polyvinyl chloride (PVC) matrix as a model. PVC dissolved in a tetrahydrofuran solution was dropped onto carbon fiber (CF) or glass fiber (GF), and the interfacial shear strength was measured after annealing at various temperatures. The interfacial shear strength of PVC/CF increased significantly with the annealing temperature compared with that of PVC/GF. As characterized by Raman spectroscopy, the polyene content (an indicator of PVC degradation) in bulk PVC was positively correlated with the interfacial shear strength. PVC radicals were not detected at the annealing temperature in the electro spin resonance spectroscopy. It was demonstrated that the interaction between the ions (C+Cl−) formed during the decomposition of PVC (formation of polyene) and the π electrons in the benzene of CF; the cation–π interaction is attributable to the enhancement of the interfacial shear strength.

Thermodynamic, pyrolytic, and kinetic investigation on the thermal decomposition of polyvinyl chloride in the presence of franklinite

Thermal co-treatment of Electric Arc Furnace Dust (EAFD) and polyvinyl chloride (PVC) may provide a viable route for reprocessing these hazardous materials within the circular economy. To develop and optimise a commercial treatment process, the complex mechanistic pathway resulting from the reaction of these two wastes must be understood. Franklinite (ZnFe2O4) is a major zinc containing phase in EAFD and to date, little work has been undertaken on the decomposition of PVC in its presence. Herein, we present a thermodynamic, pyrolytic, and kinetic study of PVC degradation in the presence of ZnFe2O4. It was found that ZnFe2O4 decomposed to its associated halides. Additionally, the kinetics data confirmed the catalytic activity of ZnFe2O4, dropping the de-hydrochlorination onset temperature of PVC from 272 to 235 °C. The distribution of the activation energy with conversion suggests the presence of several competitive reactions each with a different energy barrier. In such a case, reaction channelling can take place leading to selective zinc chlorination. Moreover, since the reduction of Fe2O3 is slow at low temperatures, it is recommended to operate at a temperature as low as 235 °C which can promote the chlorination selectivity towards zinc leaving iron bearing compounds in their stable form (Fe2O3).

Leaching behavior of zinc and lead from electric arc furnace dust – Poly(vinyl) chloride residues after oxidative thermal treatment

Oxidative thermal treatment of electric arc furnace dust (EAFD) mixed with poly(vinyl) chloride (PVC) was carried out to study the impact of oxidizing environment on the extraction of valuable metals. The effect of oxygen partial pressure, temperature and holding time of the thermal treatment, as well as the pH of the leaching solution were considered as operational variables in this study. HCl evolved during PVC decomposition was found to react with the metal oxides present in EAFD producing metal chlorides. It was found that thermal treatment above 350 °C caused significant vaporization of lead and zinc chlorides. After thermal treatment, the residue was leached in water, the cheapest available leaching reagent. Zinc and lead were extracted with recoveries up to ∼100%, while iron recovery was as low as 12.5% being suppressed by oxidation of ferrous iron. Operating under oxidative conditions supresses the post dissolution of iron in water by oxidizing Fe3O4 to Fe2O3 and by oxidizing any formed FeCl2 back to Fe2O3. The solution pH was also found to significantly affect the extraction of both lead and iron, especially at pH values above 4.0 where a sharp drop in metals recovery was observed. The obtained results present base for development of sustainable solution for treatment of PVC and EAFD wastes.

A comprehensive understanding of the synergistic effect during co-pyrolysis of polyvinyl chloride (PVC) and coal

In this work, the co-pyrolysis behaviors of polyvinyl chloride (PVC) with coal were investigated using the reactive molecular dynamics (ReaxFF MD) simulations. The weight loss characteristics of PVC and coal pyrolysis obtained from ReaxFF MD simulations were in good agreement with the thermo-gravimetric (TG) experimental results. The synergistic effect on the production of inorganic gas, organic gas, and tar were investigated via co-pyrolysis simulations. The results showed that coal promoted HCl release by providing extra H for Cl radicals. It led to more H being retained in the de-HCl PVC, resulting in an increase of C2H4 yield and a decrease of C2H2 yield. PVC promoted the generation of CO2, CO and CH2O, while inhibited the generation of H2O. PVC had little effect on coal pyrolysis tar yield because little H radicals were generated from PVC pyrolysis. However, large amount of H and OH radicals were generated from coal pyrolysis, leading to a promoting effect on the decomposition of PVC and the secondary reactions of PVC pyrolysis tars. Kinetic results suggested that the synergistic effect reduced the activation energy by 13% at low temperature stage, while reduced the activation energy by 36% at high temperature stage during PVC/coal co-pyrolysis.

Co-hydrothermal carbonization of sewage sludge and polyvinyl chloride for the production of high-quality solid fuel with low nitrogen content

Sewage sludge (SS) and polyvinyl chloride (PVC) are typical solid wastes. Their co-hydrothermal carbonization behavior was investigated in this study. The low-nitrogen solid fuel (0.94 wt%) with high heating value (9.84 MJ·Kg−1) was prepared through parameter optimization at 240 °C for 1.5 h under water loading amount of 0.84 g·cm−3. In an acidic environment, the stubborn protein in SS could be converted into free amino acids, which were generated by the decomposition of PVC under hydrothermal conditions. The stubborn N could be translated into easy-to-remove N, such as nitrile–N and inorganic N, and the dehydration reaction was evidently promoted. The acidic environment at high temperatures caused the dissolution of ash in SS and improved the combustion performance of hydrochar. FT-IR results showed that, with increased PVC loading proportion, -C=N- was converted into -C=O-. Co-hydrothermal carbonization could effectively improve the combustion performance of hydrochar. The addition of PVC could lead to the generation of increased volatile matter, fixed carbon, and unsaturated CC, and the combustion temperature range shifted to a high range. However, the generation of graphite-like carbon was caused by further increasing the PVC loading proportion, which hindered the improvement of its combustion performance. In the parameter optimization study, the increased water loading amount (from 0.54 g·cm−3 to 0.84 g·cm−3) had the most evident effect on the N content in the hydrochar (from 1.50 wt% to 0.94 wt%), which promoted the denitrification efficiency (from 60.11% to 75.00%) and the conversion of -C=N- components, and prevented further polymerization of solid products.

Comparing the effects of different metal oxides on low temperature decomposition of PVC

Polyvinyl chloride (PVC) is one of the most widely used plastics in the world. When PVC is heated, HCl will form, causing equipment corrosion, product quality decline, environmental pollution and other problems. Therefore, more attention is paid to recycling of PVC than other plastics. In this study, the reaction mechanisms of PVC with different metal oxides (MOx: CaO, ZnO, CuO, MgO, Fe2O3, Al2O3) at low temperature (310 °C) were compared, with focus on chlorine capture and dehydrochlorination product (De-Cl PVC) property. The results showed that when the radius of metal ion was smaller, the extrapolated onset temperature (Ti) of PVC-MOx pyrolysis tended to be lower, such as PVC-ZnO, PVC-CuO and PVC-Al2O3. Direct reaction of PVC and MOx was deduced for PVC-CuO and PVC-ZnO pyrolysis, based on the lower Ti and peak temperature (Tmax) than that of PVC pyrolysis. MOx that did not significantly lower Tmax was supposed to react with HCl that dissociated from PVC. The addition of ZnO significantly reduced the release of HCl (0.5%) and captured 97.6% of chlorine as inorganic chloride salts. However, the chloride salts produced from PVC-MgO pyrolysis could decompose at low temperature, thus releasing HCl again, and the C atoms in PVC-CuO system could react with copper chloride salts and H2O, to form and release HCl. The capture effects of chlorine by Fe2O3 and Al2O3 were not good. With addition of MOx, all De-Cl PVCs were rich in C=C-H and (C)3C-H structures. Fe2O3, MgO and CuO reduced the release of volatile hydrocarbons, while CaO, ZnO and Al2O3 increased the release of volatile hydrocarbons. Except for CaO and CuO, the other MOx increased the amount of residual hydrocarbon (De-Cl PVC).

A New Pressure‐induced Mechanism of Polyvinyl Chloride Pyrolysis with Formation of Nanodiamonds

AbstractApplication of high pressure to molecular compounds with high compressibility can initiate chemical reactions, unexpected under normal conditions. Here we present the evidence of pressure‐induced change in the mechanism of dehydrochlorination at polyvinyl chloride (PVC) pyrolysis. PVC pyrolysis was investigated at pressures from 2 to 9 GPa and temperatures up to 1600 °C. At critical pressures of 8–9 GPa, decomposition of PVC starts at 500 °C and results in formation of ultrasmall nanodiamonds. Based on density functional theory calculations, we show that intermolecular linking by single C−C bonds during dehydrochlorination is responsible for the scenario of carbonization, leading to nanodiamonds formation. At decreased pressure, carbonized product consists mainly of graphite‐like carbon, implying that high‐pressure intermolecular dehydrochlorination of PVC becomes inferior to “normal”, intramolecular one. Our study suggests that at low pressures, random intermolecular linking of PVC with formation of single HCl molecules may trigger “normal”, HCl‐catalyzed dehydrochlorination.

Dechlorination of polyvinyl chloride by hydrothermal treatment with cupric ion

Hydrothermal treatment (HTT) is able to remove chlorine effectively from polyvinyl chloride (PVC), however, the reaction temperature is critical in practical application. Less energy-intensive hydrothermal dechlorination condition with cupric ion (Cu2+) has been proposed in this study. In particular, Cu2+ was applied in HTT of PVC at temperature ranging from 200 °C to 240 °C. It has been found that the introduction of Cu2+ distinctly accelerated PVC decomposition and dechlorination at 220 °C. When Cu2+ concentration was increased from 0.01 mol/L to 0.20 mol/L, the dechlorination efficiency was significantly improved from 15.46 %–67.89 %. Dramatic dechlorination occurred as residence time was longer than 15 min during HTT. Besides, both elimination and substitution dominated the HTT dechlorinaton. The facilitated dechlorination after the addition of Cu2+ was mainly due to the enhanced dispersion and formation of micropores in hydrochar. On the whole, HTT could be a promising pretreatment technology for copper-containing PVC in electronic wastes to prepared chlorine free hydrochar for combustion or pyrolysis applications, the optimal HTT condition would be 220 °C, 60 min with 0.1 mol/L Cu2+.

Coupling carbon dioxide and magnetite for the enhanced thermolysis of polyvinyl chloride

To valorize plastic wastes, pyrolysis of polyvinyl chloride (PVC) was conducted as a case study. In an effort to build the more sustainable pyrolysis platform for PVC, CO2 was particularly employed as a reactive gas medium, and magnetite (Fe3O4) was used to explore the feasibility of enhancing CO2-assisted PVC pyrolysis. The favorable effect of Fe3O4 on syngas generation from pyrolysis of PVC was apparent to yield highest concentration of H2 (0.28 mol% at 590 °C) and CO (4.34 mol% at 800 °C) in the presence of 0.1 g Fe3O4/1 g PVC. The GC-TOF analysis of tar generated from thermal decomposition of PVC evidenced more breakdown of PVC hydrocarbons in the presence of Fe3O4, which led to the enhanced production of syngas. In the presence of 0.01 g Fe3O4, the evolution of CO was observed at lower temperature (7.1 mol% at 680 °C) than the case without Fe3O4, and further addition of Fe3O4 up to 0.5 g gradually increased the CO level in the latter stage of pyrolysis (up to 4.5 mol% at 900 °C), which is attributed to the enhanced Boudouard reaction. Good adsorption ability of biochar products was also demonstrated in the removal of methylene blue. Collectively, the use of Fe3O4 in CO2-assisted pyrolysis of plastics could open the possibility of utilizing waste plastics in thermo-chemical process for energy recovery and environmental application.

Thermal degradation and flame retardancy of flexible polyvinyl chloride containing solid superacid

The objective of the present article was to study the thermal degradation behavior and flame retardancy of flexible polyvinyl chloride (PVC) composites containing TiO2/SO 4 2− solid superacid because of its strong catalytic ability for esterification and dehydration. The TiO2/SO 4 2− solid superacid was synthesized by using precipitation immersion method, and its structure was investigated by X-ray diffraction. As expected, the value of limiting oxygen index for PVC/Sb2O3/(TiO2/SO 4 2− ) composite was 32.5% and the char yield of PVC/Sb2O3/(TiO2/SO 4 2− ) composite was significantly improved compared to neat PVC in thermogravimetry tests. In addition, the peak heat release rate and smoke production rate of PVC/Sb2O3/(TiO2/SO 4 2− ) decreased by 14% and 42%, respectively, compared with neat PVC. Moreover, the results of cone calorimetry tests and electron micrograph of char residue showed that the char yield of TiO2/SO 4 2− was enhanced, resulting in a strong char layer structure with outstanding fire retardance cone. In conclusion, the results of this work showed that the addition of solid superacid promoted the decomposition and dehydration of PVC, which formed a compact and continuous char layer on the surface of the material. Hence, the study provides a new perspective for producing composites with excellent flame retardancy and smoke suppression properties of PVC.

Production of biofuel precursor chemicals from the mixture of cellulose and polyvinylchloride in polar aprotic solvent

Polyvinylchloride (PVC) is the major halogen source in municipal solid waste (MSW) and its recycling is problematic. PVC can not only cause various environmental problems by releasing halogens, but also negatively impact other MSW compositions during waste to energy conversion. For instance, co-pyrolysis of biomass with PVC increases solid residue and promotes the formation of CO and CO2 from cellulose. Herein, we report an approach to dehydrochlorinate PVC while simultaneously enhancing the production of valuable chemicals from cellulose. Specifically, cellulose and PVC were co-converted in tetrahydrofuran (THF). It was found that co-conversion of cellulose with PVC significantly increased liquid yield from cellulose and shortened the conversion time compared to converting cellulose alone. Levoglucosan was the major product from cellulose and its highest yield of 40% was achieved with 2.5 wt% of PVC at 335 °C after only 8 min of reaction. We have shown that the in-situ generated HCl derived from PVC decomposition serves as acid catalyst to enhance glycosidic bond cleavage in cellulose. Moreover, using a THF/water co-solvent could further enhance the conversion rate and increased liquid yield to a maximum of 92.55%. Pyrolysis of the solid residue did not release chlorinated organics, suggesting that PVC was fully dechlorinated in THF. The present study may be applied to convert PVC-containing, cellulose rich MSW for higher valued products in environmentally friendly approach.

PYROLYSIS MODELING OF PVC USING DISTRIBUTED ACTIVATION ENERGY MODEL- MICRO SCALE TESTING

<p>Polyvinyl chloride (PVC) is a common thermoplastic whichfinds widespread applications in the construction industryfor usage inceiling linings, flooring materials, electrical cables and roofing materials.Several fire requirements are put on these types of applications. For fire safety engineering and product development, thermo-chemical decomposition modeling of PVC isrequired. The FIRETOOLS project investigates the possibilities to predict real scale fire behavior of building products, content and barriers by means of using material data on successively increasing scale. This paper focuses on the material modeling and studiesthe thermo-chemical decomposition of PVC using Distributed Activation Energy Model (DAEM). </p>

English

A composite membrane was prepared by mixing epoxidized natural rubber (ENR) and polyvinyl chloride (PVC). An inorganic filler, MgO, was introduced into the polymer matrix by certain percentages to form a mixed matrix membrane (MMM). The resulting membranes were characterized using FTIR, TGA, SEM and gas permeability test. FTIR results showed the incorporation of MgO inside the membrane matrix with the appearance of an absorption peak at 3700 cm-1 which represents the formation of Mg(OH)2. Thermogram from TGA analysis showed two degradation stages at 250-350°C and 370-500°C, which correspond to the decomposition of PVC and ENR and the residue of fillers at 600°C. SEM images of the membranes showed that pores were developed as fillers were introduced to the membrane. The size of the pores also increased with the increase of filler percentage. As for gas permeation test, the permeability values of CO2 and N2 for ENR/PVC membrane were the lowest. The permeability values increased with the addition of MgO to the membrane. The permeability of CO2 was also the highest for all membranes.

Effect of zinc borate and wood flour on thermal degradation and fire retardancy of Polyvinyl chloride (PVC) composites

The thermal decomposition, fire retardancy and mechanical properties of wood-flour–polyvinyl chloride composites (WF–PVC) were investigated. Thermogravimetric analysis (TGA) tests showed that the addition of wood flour (WF) and zinc borate (ZB) significantly influenced the thermal degradation behavior of PVC and WF–PVC composite. WF reduced the initiation temperature (Tinitial) for thermal degradation of PVC, while ZB scarcely affected the initial temperature of WF–PVC. WF retarded the thermal decomposition of PVC in the early stage while ZB increased the rapidest decomposition temperature and reduced the decomposition rate of WF–PVC. The mechanism of thermal decomposition of the composite was analyzed by Fourier transform infrared (FTIR) spectroscopy using the attenuated total reflectance (ATR) method. The decrease of CH bonds and increase of CC bonds indicated WF and ZB promote the crosslinking and charring reactions of PVC. According to the cone calorimetry (CONE) tests, WF had a positive effect on fire performance of PVC but had little effect on smoke suppression. In contrast, the incorporation of ZB had little effect on flame retardancy of WF–PVC but it was an effective smoke suppressant, decreasing the total smoke produced (TSP) by more than 50%. Mechanical results indicated that ZB had some negative effects on the strength properties of WF–PVC, however the modulus increased compared with the untreated composite.

Kinetic Study of Thermal De-Chlorination of PVC-Containing Waste

The presence of organic compounds on wastes, especially plastics, is considered an important source of energy. However, most of these plastics contain polyvinyl chloride (PVC), causing recycling problems when it is considered a thermal valorization process for its treatment [1], preventing the use of those residues on these processes, which main goal is the energy recovery [2,3]. A possible solution is to remove the chlorine from PVC containing waste through a pyrolysis process before being subjected to a thermal treatment, for energetic valorization. In this work, it was developed a kinetic model for the thermal decomposition of PVC, in view of its de-chlorination. DTA/TGA testing were performed at different temperatures (between the range of decomposition temperatures of the PVC molecule) indicated a first order reaction and an activation energy of 133800 J/mol, value very close to the one obtained in others works reported [4]. A factorial plan was carried out with different temperatures, performed in lab scale, in which best results were obtained at the temperature of 340 °C, proving the kinetic model obtained.

Effects of polyvinyl chloride and aluminum trichloride on structure and property of polyaniline composite films by electron beam deposition

AbstractPolyaniline (PANI) composite films were prepared on silicon and quartz glass substrates by electron beam deposition (EBD), using polyvinyl chloride (PVC), aluminum trichloride (AlCl3), and mixture of PVC and AlCl3 as dopants. Molecular structure, morphology, optical, and electrical properties of PANI composite films were investigated by Fourier transform infrared spectroscopy, UV–vis spectroscopy, four‐probe method, and atomic force microscope. The results show that PANI film prepared by EBD has a similar molecular structure with initial powder. PVC is dehydrochlorinated under electron beam irradiation, but HCl fails to protonate the quinoid site of PANI during films deposition. AlCl3 doped in PANI films induces the decrease of surface resistance and the formation of a two‐layered morphological structure in composite film. In addition, AlCl3 enhances the decomposition of PVC and increases the surface resistance of (AlCl3, PVC)‐doped PANI composite film. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers

Wood-Polyvinyl Chloride Composite for Insulation of Electrical Wires: Fabrication and Investigation of Properties

In this study, five series of wood—polyvinyl chloride composite samples were prepared by granules production followed by extrusion process for insulation of cuprous wires. The effects of wood flour content and its size on thermal stability, physical, mechanical, and electrical properties of these composites were investigated. The obtained results show that the density as well as the mechanical properties decreases, as the wood flour content increases. Also, wood flour composites with smaller particles have better mechanical properties and lower density. Thermal decomposition of these composites was investigated by thermogravimetric analysis (TGA). In general, thermal decomposition of polyvinyl chloride is inhibited by the addition of wood flour to the polyvinyl chloride compound. Moreover, electrical tests showed high amounts of wood flour can’t be used when high volume resistivity is necessary.

Hyphenation of a thermobalance to soft single photon ionisation mass spectrometry for evolved gas analysis in thermogravimetry (TG-EGA)

Abstract The potential of hyphenating thermogravimetry (TG) and soft photo ionisation mass spectrometry (EBEL-SPI-MS) for fundamental and applied research and material analysis has been demonstrated by a newly developed TG-SPI quadrupole MS coupling (TG-SPI-QMS). Thermal decomposition of three common plastics, polyethylene (PE), polystyrene (PS) and polyvinylchloride (PVC) has been studied. While the decomposition of PE and PS in inert atmosphere takes place in a one step process (main mass loss at about 490 and 420 °C, respectively), PVC decomposes in a two step mechanism. The organic signature of the PE decomposition shows homologous series of alkenes and polyenes, while PS is forming mainly styrene mono- and oligomers. In the PVC decomposition, firstly hydrogen chloride (HCl) is eliminated in a hydro-dechlorination reaction (1st mass loss step: 285–305 °C), this is accompanied by the emission of the carbon skeletons of small aromatics (predominately benzene and naphthalene). In the second step (2nd ma...