Waste poly(vinyl chloride) pyrolysis with hydrogen chloride abatement by steelmaking dust

Experimental study on PVC-based materials (PVC = poly(vinyl chloride)) pyrolysis; in the presence of various amounts of steelmaking dust was performed. Dust from steel manufacture employing zinc plated scrap contains a considerable amount of zinc oxide (ZnO) and its utilization in metallurgy is quite complicated. However, the dust can react with hydrogen chloride (HCl) released from heated PVC in the temperature range of 200–400°C. Material balance of the pyrolysis process was studied by thermogravimetry, and the data obtained were compared with the results of larger laboratory oven experiments. In excess of PVC, the amount of captured HCl stoichiometrically corresponds to the content of ZnO; additional HCl is probably captured by FeCl₂, while FeCl₃ is not formed at elevated temperatures. In excess of the dust, the captured amount of HCl is approximately 100%. The suggested co-pyrolysis seems to be a promising method to prevent the formation of dangerous chlorinated organic compounds during the thermal treatment of waste PVC. Furthermore, the obtained ZnCl₂ is a valuable material and the zinc depleted dust can be reused in metallurgy instead of its disposal.     

Combined relaxation study of poly(vinyl chloride) blends with chlorinated poly(ethylene), hydroxyl-terminated poly(butadiene), and ethylene-propylene-diene terpolymer

A number of blends based on suspension poly(vinyl chloride) and stabilizers with poly(ethylene) chlorinated in a fluidized-bed reactor containing 21.8% chlorine, hydroxyl-terminated poly(butadiene), and ethylene-propylene-diene terpolymer have been studied using such methods as thermally stimulated current depolarization and dynamic mechanical analysis. Some dielectric and thermodynamic parameters (τ_max, τ_o, E_a, ΔH^*, ΔS_E^*, ΔG^*, μ_eff) have been determined. Blends containing randomly chlorinated poly(ethylene) exhibited dipole–dipole interactions between the macromolecules of poly(vinyl chloride) which decreased at the expense of the long sequences of nonchlorinated methylene groups. Simultaneously, an increased physical interaction between poly(vinyl chloride) and the additives was observed in blends containing chlorinated poly(ethylene) and/or hydroxyl-terminated poly(butadiene), and ethylene-propylene-diene terpolymer. On the basis of the data of dynamic mechanical analysis obtained a heterogeneous structure of the blends is suggested. The development of a boundary interfacial layer with a proper region of relaxation proves the formation of compatible structures between the components. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1595–1608, 1998     

Thermal decomposition of flame retardants: Mixtures of chlorinated polymers with Sb2O3 and (BiO)2CO3

The thermal decomposition products that evolve from mixtures of poly(vinyl chloride) (PVC), poly(vinylidene chloride) (PVC₂), and chlorinated paraffin (CP) with Sb₂O₃ and (BiO)₂CO₃, respectively, have been analyzed by a method of direct pyrolysis in the ion source of a mass spectrometer. This method allowed us to detect volatile products with masses as high as 226 (SbCl₃), 314 (BiCl₃), 484 (Sb₄), 580 (Sb₄O₆), and 836 (Bi₄). Except for SbCl₃, this is the first direct evidence of the presence of these species in the gas phase. The volatilization rate profiles of these species versus the pyrolysis temperature have been also determined. Our data confirm that the effectiveness of the title mixtures as flame-retardant agents depends on the transport of volatile metal products in the flame and provide direct evidence of the presence of metallic Sb and Bi below the polymer ignition temperatures.     

Structure of chlorinated poly(vinyl chloride). V. Molecular parameters of chlorinated poly(vinyl chloride)

The molecular parameters of samples of chlorinated poly(vinyl chloride) (CPVC) and chlorinated β,β-dideuterated poly(vinyl chloride) (β,β-d₂-CPVC) were determined by gel permeation chromatography (GPC), light scattering, osmometry, and viscometry. Comparison of GPC, light scattering, osmometric, and viscometric data resulted in a discussion of the possibility of degradation and the causes of changes in the solution properties in chlorination of PVC and ββ-dideuterated poly(vinyl chloride) (ββ-d₂-PVC). The results obtained are discussed in relation to the mechanism of chlorination of PVC.     

The rôle of commercial pigments in the photo-degradation of poly(vinyl chloride) (PVC)

Two commercially produced pigments (fillers), CaCO₃ and TiO₂ (rutile type), were examined for their influence on the photo-degradation and photo-oxidation of poly(vinyl chloride) (PVC). Both pigments decrease the rate of oxygen uptake and formation of hydroperoxy (OOH) and carbonyl (CO) groups during uv irradiation. They also decrease the amount of HCl evolved. TiO₂ increases the service life of mechanical properties of PVC samples much better than CaCO₃.     

Thermal decomposition of poly(vinyl chloride) and chlorinated poly(vinyl chloride). II. Organic analysis

A concerted study of poly(vinyl chloride), chlorinated poly(vinyl chloride), and poly(vinylidene chloride) polymers by spectroscopy, thermal analysis, and pyrolysis-gas chromatography resulted in a proposed mechanism for their thermal degradation. Polymer structure with respect to total chlorine content and position was determined, and the influence of these polymer units on certain of the decomposition parameters is presented. Distinguishing differences were obtained for the kinetics of decomposition, reactive macroradical intermediates, and pyrolysis product distributions for these systems. It was determined that chlorinated poly(vinyl chloride) systems with long-chain ? CHCI? units were more thermally stable than the unchlorinated precursor, exhibited increasing activation energy for the dehydrochlorination, and produced chlorine-containing macroradical intermediates and chlorinated aromatic pyrolysis products. The poly(vinyl chloride) polymer was relatively less thermally stable, exhibited decreasing activation energy during dehydrochlorination, and produced polyenyl macro-radical intermediates and aromatic pyrolysis products.     

NMR studies of chlorinated poly(vinyl chloride) and polybutadiene

Molecular structures of chlorinated poly(vinyl chloride) and polybutadiene have been studied by high resolution NMR. The spectra of the chlorinated polymers give broad signals. New peaks appear in the lower fields of the ? CH₂? and ? CHCl? groups with increasing chlorine content. The chlorination of poly(vinyl chloride) takes place predominantly on ? CH₂? rather than on ? CHCl? , e.g., a 70% chlorinated polymer has about 10 mole-% of ? CCl₂? groups. Polybutadiene reacts first with chlorine by addition to give a head-to-head poly(vinyl chloride), and then the substitution of the hydrogen atom takes place. Chlorinated polybutadiene with 70% Cl has about 18 mole-% of ? CCl₂? . The multiplets characteristic of spin-spin couplings in the spectrum of the original poly(vinyl chloride) are still observed in that of the highly chlorinated product. This fact shows that a considerable number of poly(vinyl chloride) sequences of certain lengths persist in the highly chlorinated polymer.     

Homopolymers and vinyl chloride copolymers of vinyl esters of chlorinated fatty acids from umbelliferae and limnanthes douglasii

Homopolymers and copolymers of vinyl esters of chlorinated C₁₈, C₂₀, and C₂₂ fatty acids with vinyl chloride have been prepared and evaluated. The incorporation of the vinyl ester of chlorinated C₁₈, C₂₀, and C₂₂ acids as comonomers with vinyl chloride produced more flexible copolymers than have other comonomers, yet none have imparted the plasticization that can be obtained by an equal amount of external plasticizer.     

Study on the thermal degradation of high performance fibers by TG/FTIR and Py-GC/MS

The thermal degradation behaviors of Kevlar 49, Kevlar 129 (Poly(p-phenylene terephthamide), Nomex (polyisophthaloyl metaphenylene diamine), and PBO(poly(p-phenylene benzobisoxazole)) fibers were measured by TG/FTIR and Py-GC/MS. The characteristic temperatures of the fibers in air were obtained by TG. It indicated that the initial degradation temperature of the PBO is the highest. The initial degradation temperature of Nomex fiber is the lowest, but the end decomposition temperature of Nomex is the highest. The gases released by the pyrolysis in air were mainly CO₂, CO, H₂O, NO, and HCN, also containing a small amount of NH₃, and the absorption peaks of CO₂ were the strongest. The results of Py-GC/MS showed that CO₂ and benzene were the most pyrolysis fragment. With the change of pyrolysis temperature, the chromatogram and mass spectra results take a large variety. The pyrolysates can help us to study the pyrolysis process of high performance fibers.     

A novel approach to synthesis of functional CPVC and CPE or graft copolymers—in situ chlorinating graft

A new process of graft copolymerization of poly(vinyl chloride) (PVC) and polyethylene (PE) with other monomers was developed. The grafted chlorinated poly(vinyl chloride) (CPVC) and chlorinated polyethylene (CPE) were synthesized by in situ chlorinating graft copolymerization (ISCGC) and were characterized. Convincing evidence for grafting and the structure of graft copolymers was obtained using FT‐IR, ¹H‐NMR, gel permeation chromatography (GPC), and the vulcanized curves. Their mechanical properties were also measured. The results show that the products have different molecular structure from those prepared by other conventional graft processes. Their graft chains are short, being highly branched and chlorinated. The graft copolymers have no crosslinking structure. The unique molecular structure will make the materials equipped with special properties. Copyright © 2007 John Wiley & Sons, Ltd.     

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.     

Thermal degradation and evolved gas analysis of thiourea-formaldehyde resin (TFR) during pyrolysis and combustion

Thiourea formaldehyde resin (TFR) has been synthesized by condensation of thiourea and formaldehyde in acidic medium and its thermal degradation has been investigated using TG-FTIR-MS technique during pyrolysis and combustion. The results revealed that the thermal decomposition of TFR occurs in three steps assigned to drying of the sample, fast thermal decomposition of polymers, and further cracking. The similar TG and DTG characteristics were found for the first two stages during pyrolysis and combustion. The combustion process was almost finished at 680?°C, while during pyrolysis a total mass loss of 93 wt% is found at 950?°C. The release of volatile products during pyrolysis are NH₃, CS₂, CO, HCN, HNCS, and NH₂CN. The main products in the second stage are NH₃ CO₂, CS₂, SO₂, and H₂O during combustion. In the next stage, the combustion products mentioned above keep on increasing, but some new volatiles such as HCN, COS etc., are identified. Among the above volatiles, CO₂ is the dominant gaseous product in the whole combustion process. It is found that the thermal degradation during pyrolysis of TFR produced more hazardous gases like HCN, NH₃, and CO when compared with combustion in similar conditions.     

The structure of chlorinated poly(vinyl chloride). VI. Comparison of the chlorination of poly(vinyl chloride) and β,β-d2-poly(vinyl chloride) with 1H-NMR and 13C-NMR spectroscopy

Samples of chlorinated poly(vinyl chloride) (CPVC) and chlorinated β,β-dideuterated poly(vinyl chloride) (β,β-d₂-CPVC) were prepared under identical reaction conditions. The microstructure of CPVC and β,β-d₂-(CPVC) was characterized by a combination of ¹H-NMR, ¹³C-NMR spectroscopy, and analytically determined chlorine content. A difference was observed in the reaction rates of chlorination of PVC and β,β-d₂-PVC, and, in their thermal chlorination in solution, also in the structure of the chlorinated products. It was proved that in the chlorination of β,β-d₂-PVC a new chlorine atom can also enter the original? CHCl? group. The results are discussed from the standpoint of the chlorination mechanism.     

Structure of chlorinated poly(vinyl chloride). I. Determination of the mechanism of chlorination from infrared and NMR spectra

Infrared and NMR spectra of chlorinated poly(vinyl chloride) (CPVC) and of chlorinated α-deuterated poly(vinyl chloride) (α-d-CPVC) have been measured. It was found that the CDCl unit of α-d-PVC does not undergo chlorination. By assuming an analogous mechanism of chlorination in normal PVC, the populations of all the three possible types of two-carbon sequences (? CH₂? CHCl? , ? CHCl? CHCl, ? CHCl? CCl₂) in CPVC could be determined. The mechanism of chlorination of PVC is discussed from the viewpoint of the previous findings on the conformational structure of this polymer. Differences in structure between suspension- and solution-chlorinated PVC have been established.     

Polymerization of vinyl chloride by the Ti(O-n-Bu)4–AlEt3–epichlorohydrin catalyst system

The polymerization of vinyl chloride was carried out by using a catalyst system consisting of Ti(O-n-Bu)₄, AlEt₃, and epichlorohydrin. The polymerization rate and the reduced viscosity of polymer were influenced by the polymerization temperature, AlEt₃/Ti(O-n-Bu)₄ molar ratios, and epichlorohydrin/Ti(O-n-Bu)₄ molar ratios. The reduced viscosity of polymer obtained in the virtual absence of n-heptane as solvent was two to three times as high as that of polymer obtained in the presence of n-heptane. The crystallinity of poly(vinyl chloride) thus obtained was similar to that of poly(vinyl chloride) produced by a radical catalyst. It was concluded that the polymerization of vinyl chloride by the present catalyst system obeys a radical mechanism rather than a coordinated anionic mechanism.     

Miscible blends of amorphous polymers

Thirty-five polymethacrylate/chlorinated polymer blends were investigated by differential scanning calorimetry. Poly(ethyl), poly(n-propyl), poly(n-butyl), and poly(n-amyl methacrylate)s were found to be miscible with poly(vinyl chloride) (PVC), chlorinated PVC, and Saran, but immiscible with a chlorinated polyethylene containing 48% chlorine. Poly(methyl) (PMMA), poly(n-hexyl) (PHMA), and poly(n-lauryl methacrylate)s were found to be immiscible with the same chlorinated polymers, except the PMMA/PVC, PMMA/Saran, and PHMA/Saran blends, which were miscible. A high chlorine content of the chlorinated polymer and an optimum CH₂/COO ratio of the polymethacrylate are required to obtain miscibility. However, poly(methyl), poly(ethyl), poly(n-butyl), and poly(n-octadecyl acrylate)s were found to be immiscible with the same chlorinated polymers, except with Saran, indicating a much greater miscibility of the polymethacrylates with the chlorinated polymers as compared with the polyacrylates.     

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.     

Pyrolysis of poly(vinyl chloride)

A pyrolysis–gas chromatography–mass spectrometric technique has been developed to study the thermal degradation of poly(vinyl chlorides) polymerized at different temperatures. Hydrogen chloride and benzene evolution during successive stages of pyrolysis have been quantitatively determined and correlated to the tacticity and molecular weight of the polymer. It was found that lowering the temperature of polymerization and molecular weight depresses benzene evolution and increases char weight but does not affect the HCl yield. It is suggested that the syndiotactic trans microstructure favored at low temperature of polymerization yields polyenes which cannot cyclize to form benzene. As the molecular weight decreases, the increase in number of vinyl chain ends facilitates pyrolytic crosslinking and char formation.     

Poly(vinyl chloride) Nanocomposites

Poly(vinyl chloride) is one of the major thermoplastics beside other commodities polymers like polyethylene and polystyrene. However, some of its main characteristics such as plasticity, thermal and photo stability are inferior to other commodity polymers. Adding nano scale inorganic fillers to poly(vinyl chloride) or other polymers in view to obtain polymer nanocomposites with superior properties has drawn the attention of many researchers in the last decades. Poly(vinyl chloride) nanocomposites are obtained mainly by in situ polymerization, solution based or mixing techniques. The resulting products show improvement of most important properties of poly(vinyl chloride) such as thermal, mechanical, rheological, flammability, antibacterial, etc. This paper presents preparation ways of poly(vinyl chloride) nanocomposites using different nano fillers and the improved properties compared with those of virgin poly(vinyl chloride).