Combustion Of Poly Research Articles

Silver-zinc oxide heterojunction-induced electrical and charge transfer property

The solution combustion synthesis approach successfully synthesized the porous silver-zinc oxide nanocomposites (Ag-ZnO NCs). The pore generation and silver metal reduction occurred due to the evolution of gaseous byproducts during the combustion of poly(vinyl alcohol)-precursor complex. The low-resolution SEM and TEM images confirmed the porous nature of the synthesized NPs ad NCs. The nanoscale crystallite size (30 – 70 nm), crystallinity, and Ag-ZnO NCs heterojunction were confirmed from the XRD pattern and TEM/HRTEM/SAED analysis. The absence of a bandgap change between ZnO and NCs confirmed from the DRS-UV-vis analysis, indicating the non-inclusion of Ag in the ZnO lattice. The photoluminescence spectrum of doped NCs has less intensity than pure ZnO NPs, confirming the presence of charge transfer within the Ag-ZnO NCs, which prevents electron-hole recombination. The Mott–Schottky analysis confirmed the n– and p–type characters of the NCs, unlike that of ZnO NPs, which have only n-type characters. Thus, synthesizing nanomaterials by the solution combustion synthesis approach is a novel method for producing pure and electrical properties improved catalyst, which is beneficial in several applications such as catalysis and sensor.

Effect of diatomite on combustion of poly(vinyl chloride) plastisols

The effect of diatomite on the inflammability, combustibility, and smoke-forming ability of poly(vinyl chloride)-based plastisols has been studied. A substantial decrease in these characteristics takes place upon the introduction of 2–3% diatomite as compared with 10–15% for vermiculite and phlogopite fillers. This phenomenon is associated with a high viscosity of the plastisol melt filled with diatomite and its better foaming and carbonization, along with the formation of a high-porosity coke demonstrating heat-shielding behavior. The use of diatomite also improves the mechanical properties of the tested material.

Formation of PCDDs, PCDFs, and coplanar PCBs from polyvinyl chloride during combustion in an incinerator.

Exhaust gases from the combustion of poly(vinyl chloride) (PVC), polyethylene (PE), polystyrene (PS), poly(ethylene terephthalate) (PET), and theirvarious mixtureswere analyzed for PCDDs, PCDFs, and coplanar PCBs by gas chromatography/mass spectrometry (GC/MS) in order to investigate the role of PVC in these chlorinated compounds. Total amounts of dioxins (PCDDs + PCDFs) found in the samples were 11.7 ng/g PE alone, 1.17 ng/g from PS alone, 25.3 ng/g from PET alone, 448 ng/g from PE with PVC, 140 ng/g from PS with PVC, 126 ng/g from PET with PVC, 824 ng/g from PVC alone under low-CO level, and 8,920 ng/g from PVC alone under high-CO level. CO level in high-CO level condition was 880 ppm which was 20 times greater than that in low-CO level condition. Formation of coplanar PCBs ranged from 0.095 ng/g (PE alone) to 77 ng/g (PVC alone under high-CO level). There is a clear correlation between dioxin formation and chloride content. PCDFs composed 80% (PET + PVC)--98% (PET alone) of the total dioxins formed in the exhaust gases. The results indicate that PVC contributes significantly to the formation of PCDDs, PCDFs, and coplanar PCBs from mixtures of plastics upon combustion.

Oxidation of cysteamine induced by gas-phase radicals from combustion smoke of poly (methyl methacrylate)

In order to obtain fundamental knowledge on biological damage caused by the smoke from combustion of poly(methyl-methacrylate) (PMMA), we investigated the oxidation of cysteamine induced by PMMA smoke. We suggest that the long-lived and oxygen-centered radicals involved in PMMA smoke should play an important role in the oxidation of cysteamine. The mechanism for the oxidation of cysteamine by combustion smoke of PMMA was postulated as radical initiated chain reactions, taking into account the effect of pH, oxygen and radical concentrations.

Combustion and fire retardance of poly(2,6-dimethyl-1,4-phenylene ether)-high-impact polystyrene blends. II. Chemical aspects

The chemical reactions occurring during the intumescent process taking place in the combustion of the poly(2,6-dimethyl-1,4-phenylene ether )-high-impact polystyrene blends (PPE-HIPS) are studied in detail through the chemical characterization of the burnt and original material by infrared, pyrolysis-gas chromatographymass spectrometry, and direct insertion probe spectrometry. Evidence is given of thermal rearrangement in the blend of the polyether PPE chains to polybenzylic structures occurring in the heating conditions of pyrolysis or combustion, as previously shown, to take place in thermal degradation of PPE. The rearranged chain segments are shown to give a larger contribution to the intumescent char, while volatile blowing products are mostly formed by polystyrene and polybutadiene components. From PPE-HIPS blends, the volatilization of the fire-retardant triphenyl phosphate (TPP), which when heated alone volatilizes at a temperature below that of PPE-HIPS degradation, is delayed probably by hydrogen bonding with PPE. This allows TPP to play the typical flame inhibition role of volatile phosphorus compounds. Moreover, it is found that TPP favors the PPE rearrangement and henceforth increases the char yield of the burning blend, which is a typical condensed phase fire-retardant action.

Control of the HCl Emissions from the Combustion of PVC by In-Furnace Injection of Calcium-Magnesium-Based Sorbents

This is a laboratory study on the reduction of hydrochloric acid (HCl) emissions from the combustion of poly(vinyl chloride) (PVC), by in-furnace injection of calcium- and magnesium-based sorbents. Experiments were conducted in a nearly isothermal, electrically heated, drop-tube furnace, at gas temperatures of 850 and 1050°C. PVC and the sorbents were premixed in powder form and injected in the furnace, where combustion of the fuel, release of HCl, and chlorination of the sorbents took place. Combustion was globally fuel-lean, with bulk equivalence ratios in the range of 0.2–0.5; particle heating rates were 104–105 K/sec; gas residence times were ≈1 sec. Experiments burned pure pulverized PVC (to serve as a baseline) or PVC mixed with pulverized Ca(OH)2, Mg(OH)2, calcium acetate (CA), magnesium acetate (MA), calcium-magnesium acetate (CMA), calcium formate (CF), calcium propionate (CP), and calcium benzoate (CB). The particle size of PVC was in the range of 125–150 μm, the size of the sorbents varied but it was typically <100 μm. The Ca/Cl or Mg/Cl molar ratios were set to 1:2, reflecting a stoichiometric composition, except for CMA where the Ca/Cl ratio was set to either 1:6 or 1:3. The HCl reduction efficiency of the sorbents in these runs ranged from 3% to 98%. The calcium-based sorbents exhibited high HCl capture efficiencies (72–98%), especially the organic salts (89–-98%). The latter compounds, upon de volatilization of their organic components, formed high-porosity cenospheric particles, which imposed minimal mass diffusion limitations. The magnesium-based sorbents did not react significantly (3–5%) with HCl in this temperature range. However, a considerable fraction of the magnesium in CMA appears to have taken part in the chlorination reaction. Varying the gas temperature between 850°C and 1050°C did not significantly affect the HCl capture efficiency of the sorbents. Key words: HCl emissions; PVC combustion; clacium-based sorbents for HCl capture; calcium-magnesium-acetate (CMA)

Radical Formation from the Reaction of Combustion Smoke with Diphenylamine

We have attempted to examine the effects of radical scavengers, such as amines and phenols, to trap gasphase radicals produced from the combustion of Poly (methyl methacrylate)(PMMA), which might cause damage to a living body, using an electron spin resonance (ESR) spin-trapping technique.As a result, diphenylamine did not decrease the amount of radicals but rather increased it. It indicates that under the conditions of this study, gas-phase radicals were hardly trapped by radical scavengers and that the precursors to produce other kinds of radicals can exist.It was suggested that from the experiments using several peroxides, the precursors should be diacylperoxides produced from the combustion of PMMA.

Preparation of La1-xSrxMnO3 powders by combustion of poly(ethylene glycol)-metal nitrate gel precursors

La1−xSrxMnO3 powders were prepared by auto-ignited combustion of poly(ethylene glycol) (PEG)–metal–nitrate gel precursors. The thermal behaviour of the precursors strongly depends on the ratio of PEG to metal nitrate, which is closely related to the ratio of fuel to oxidizer. The burning behaviour in a furnace was successfully explained by valence concepts normally encountered in propellant chemistry. The formation of a pure perovskite phase was significantly influenced by the homogeneity of the gel precursor. Perovskite structured oxides were formed through two different paths, one of which was direct formation from the burning of a gel precursor and the other was a subsequent structural evolution by heat treatment after burning. The formation procedure of the perovskite and the morphology of powders could be explained in terms of the burning behaviour of the precursor and the role of organic residue.

The effect of the bulk equivalence ratio on the pah emissions from the combustion of PVC, poly(styrene), and poly(ethylene)

This is an investigation on the effects of the bulk equivalence ratio on the polynuclear aromatic hydrocarbon (PAH) emissions from the combustion of poly(vinyl-chloride) (PVC), poly(ethylene) (PE), and poly(styrene) (PS) particles. Steady-flow dispersions (clouds) of the above types of polymer particles, 150–212 μm in diameter, were burned in a drop-tube, electrically heated furnance at different bulk equivalence ratios ( ϕ bulk =0.1–7.3) or were pyrolyzed in N 2 . The gas temperature and residence time in the furnance were 1100°C and 1 s, respectively. (a) The total (specific) amounts of condensed and gaseous-phase PAH emissions increased with the equivalence ratio. In the present experiments, the recorded maxima in the total amounts of PAHs were obtained under pyrolysis in N 2 and accounted for 0.7, 4, and 4% of the input masses of PVC, PE, and PS, respectively. (b) PVC particles were found to oxidize effectively in air, since only minimal amounts of PAHs were produced at ϕ bulk <-1. Chlorinated organies were found at high ϕ bulk . or in N 2 . Combustion of PE and PS particles produced substantial amounts of PAHs at, or near, stoichiometric conditions. PE particles were prone to flash pyrolysis and readily formed group flames (“puffs”), even at mildly fuel-rich or near-stoichiometric conditions. (c) PAH emissions from pyrolysis of PE and PS were sensitive to the particle mass loading (mass of polymer per mass of N 2 ) in the furnance. This was not the case for PVC. (d) For all polymers, the percentage of naphthalene in the total amount of PAHs was influenced by the combustion conditions and experienced a minimum close to stoichiometry. (e) Finally, the experimentally measured molar fractions of pairs of selected PAH isomers were compared with those obtained from chemical equilibrium calculations. For all polymers, the pairs fluoranthene (F)—acephenanthrylene (AP) and cyclopenta[cd]pyrene (CP[ed]P)-benzo[ghi]fluoranthene (B[ghi]F) were at equilibrium, while the pairs fluoranthene (F)—pyrene (P) and benzo[k]fluoranthene (B[k]F)—benzo[a]pyrene (B[a]P) were not at equilibrium. PS produced much higher soot emissions than PE or PVC.

A study on the combustion characteristics of PVC, poly(styrene), poly(ethylene), and poly(propylene) particles under high heating rates

The combustion characteristics of four commonly encountered plastics: poly(styrene), PVC, poly(ethylene) and poly(propylene) were studied under conditions pertinent to incinerators, that is, high heating rates (in the order of 10,000 K/s) and elevated gas temperatures (1200–1500 K). Batches of spherical and monodisperse particles of these plastics were generated in the size range of 53–300 μm. Combustion of single particles, of known size and mass, was conducted in a laminar-flow drop-tube furnace, at controlled atmospheres. The radiation emitted from burning particles was monitored, along their flight path, by simultaneous three-color optical pyrometry and high-speed cinematography. With these techniques the total particle/flame combustion duration, as well as the flame temperature and diameter were measured. Results indicate that polymer particles (plastics) burned expediently with burntimes similar to those of light oil drops such as kerosene, hexadecane, etc. Both PVC and poly(styrene) burned with very luminous yellow flames, which were attributed to high soot loadings. The flame combustion of PVC was the brightest and fastest with steadily decreasing temperature and flame diameter, while that of poly(styrene) occurred mostly at constant flame diameter and mildly decreasing temperature. Combustion of both poly(ethylene) and poly(propylene) was dimmer and somewhat lengthier. Furthermore, in this temperature region, it is argued herein that the combustion of poly(styrene), poly(ethylene), and poly(propylene) occurred concurrently with, and was partially controlled by, pyrolysis reactions. PVC seemed to undergo significant pyrolysis prior to ignition; thereafter, combustion occurred in a premixed-like flame mode and, finally, dimly glowing combustion of the remaining char was observed. An energy balance during the flame combustion period enabled the calculation of the instantaneous burning rate and the average soot loading of the flame. PVC exhibited the highest soot volume fraction in its flame (3 × 10 −5), followed by poly(styrene) (3 × 10 −6), poly(propylene) (2.5 × 10 −6), and poly(ethylene) (1 × 10 −6). Moreover, it was observed that the rate of burning was the highest for PVC particles and the lowest for poly(ethylene).

Model for the generation of hydrogen chloride from the combustion of poly(vinyl chloride) under conditions of forcefully minimised decay

Experiments were carried out in which poly(vinyl chloride) (PVC) wire coating was decomposed electrically. Efforts were made to minimise the amount of decay of the hydrogen chloride generated, so that the decay rate remained much smaller than the generation rate. These experiments were used to create a model for the generation of HCl from PVC. The new model is based on physico-chemical principles and on the temperature-time pattern measured. Thus, although still partly empirical, it replaces a previous model, purely empirical. The model results were employed to obtain a very adequate fit of the entire set of experiments. The results were also used to determine the effects of two different types of metal wire (copper and carbon steel) on the HCl decay rate. Results of the new experiments were also fitted in conjunction with those of earlier experiments, in a larger reaction chamber. This was done in order to verify that the new overall model is, indeed, a good representation of the entire process. This work provides an independent confirmation of the validity of the total model for HCl generation, transport and decay reported previously.

Toxicity and incapacitation due to hydrogen chloride

AbstractHydrogen chloride is the principal product released during the combustion of poly(vinylchloride). It is classified as a sensory and pulmonary irritant. The toxicity of hydrogen chloride (HCl) has been the subject of numerous acute toxicological studies on rodents to determine the effect of HCl exposure on humans during fires. The lethality studies show that HCl destroys the upper respiratory tract and the eyes of rodents. A few of the rodent studies measured the HCl concentration required to produce incapacitation within a given short‐exposure period. These concentrations were higher than the lethal concentrations due to the fact that most deaths occur post‐exposure. The findings from rodent studies were basically confirmed by exposing non‐human primates (baboons) to high HCl concentrations for 5 min and measuring escape potential. In the baboon study, no statistical significance could be found between the time‐to‐effect parameters, failure modes and the HCl concentrations. The relevance of the baboon behavioral model and physiological response to human escape‐potential in a fire environment that contains HCl is questionable. In terms of the behavioral model, the baboons were able to carry out the escape routine with their eyes closed during the exposure. Inability to see was not considered incapacitating. Humans would have great difficulty escaping from a fire with their eyes closed. Furthermore, the baboons escaped by one simple action; jumping out. Most humans could not escape from a fire by one simple, instantaneous act. Based on the review of HCl toxicity and basic toxicological principles, elements required for the development of an appropriate animal incapacitation model for irritants are proposed. Exposure of animals to irritants, such as HCl, will only provide information on human escape impairment from fire when the animal models address the direct result of irritant effects on vision and respiratory function. Most of the preset studies measure the delayed, secondary systemic effects that produce asphyxia. Clearly, the measurement of vision or the lack of vision should be of primary importance in any irritant smoke incapacitation model.

Combustion of poly(1-methyl hexamethylene) and poly(1-methyl tetramethylene) and identification of the main decomposition products

The Bayer-ICI-Shell apparatus has been used to carry out combustion experiments on poly(1-methyl hexamethylene) (PH) and poly(1-methyl tetramethylene) (PT) using different air flow rates at various combustion temperatures. The products were adsorbed on charcoal followed by benzyl-alcohol desorption. They were separated and identified using gas chromatography. The non-oxidized products were identified as short chain, saturated and unsaturated hydrocarbons while the main oxidized products are short chain ketones and alcohols. The intensities of the chromatographic peaks of the separated products depend upon the temperatures and air flow rates in the combustion apparatus.

Main functions of iron compounds as smoke suppressant in poly(vinyl chloride) combustion

AbstractWhatever the state of the iron compounds as smoke suppressant during the combustion of poly(vinyl chloride), they lead rapidly to native αFe2O3 in the char residue left after dehydrochlorination. It causes incandescence of the char residue and catalyzes its oxidation into carbon monoxide and carbon dioxide that contributes to decreasing the amount of available carbon for the soot formation after self‐ignition. FeCl2 and FeCl3 are the precursors of αFe2O3, which is the true compound as smoke suppressant. Nevertheless, as intermediate, iron chlorides are able to modify the degradation processes, and they favor the formation of light tars instead of heavy tars. For that reason the iron compounds cause the formation of smoke at lower temperature than for pure PVC, but, as αFe2O3 is formed, the smoke production levels off and then decreases. The higher the ease of the iron compounds to give chlorides through reaction with HCI and further native αFe2O3, the higher the ease of the additive to cause the oxidation of the char residue sooner and in consequence to decrease the smoke level. In the PVC combustion three main steps may be distinguised: dehydrochlorination step between 200–300°C; tars aerosols formation from the char residue between 300°C and self‐ignition; at temperature higher than self‐ignition, formation of soot from the previous tars as precursors.

An application of the self‐ignition method of polymers: Anti‐smoke additive induced glowing effect in the combustion of poly(vinylchloride)

AbstractThe effect of anti‐smoke additives in poly(vinylchloride) (PVC) has been studied using self‐ignition methods. The self‐ignition reaction was followed thermally, visually and by gas—liquid chromatography of the gaseous phase around the sample. Particular emphasis was palced on the determination of the CO, CO2 and aromatic species. It is shown that ferrocence, among similar additives, considerably modifies the self‐ignition behaviour of PVC by inducing glowing phenomena of various kinds. In some cases this incandescence can lead to self‐ignition. From the analysis of carbon oxids and aromatic species as a function of time and temperature, it is possible to deduce that the anti‐smoke reaction is associated, at least partially, with reactions which lead to incandescence. These reactions transform the carbon into carbon oxides instead of producing, in the gaseous phase, molecules which on further condensation lead to aromatic species at the origin of the soot. In short, the anit‐smoke reaction appears to proceed mainly through a competing mechanism.

Formation of chlorinated hydrocarbons during combustion of poly (vinyl chloride)

Pilot-scale experiments were carried out to study the formation of chlorinated hydrocarbons through combustion of PVC. Vinyl chloride, dichloro-, trichloro-, tetrachloro-, pentachloro-, and hexachlorobenzenes were determined by GC/ECD. Furthermore, some peaks in the chromatogram were tentatively assigned to octachlorostyrene and PCB. The total amount of lipophilic organochlorinated compounds was determined by neutron activation analysis. The results indicate that incineration of PVC is not a major source of chlorinated hydrocarbons in the environment.

Combustion of poly(Vinyl chloride) studied by the moving wire technique

This paper is a demonstration of the utility of the Moving Wire Technique (MWT) for studying polymer pyrolysis, ignition and burning. The polymer is coated on a support wire and transported at a uniform and controlled speed through a heat or ignition source flame. An advantage of the MWT is that residence time, as seen by an observer moving with the wire, is resolved spatially in laboratory coordinates (residence time is the ratio of distance to wire speed). This allows greater precision in measurements of composition and temperature profiles and makes it easy to obtain smaples of the solid phase. In this study, we compared reagent and commercial grade poly(vinyl chloride) (PVC). Our heat source was the wake of a flat CH4−O2−N2 flame. Excess O2 for polymer combustion was a part of the flame gases in some experiments but was confined to an adjoining flowing “atmosphere” in others. Ignition in an O2-rich source flame required a minimum of about 20% excess O2. Above this value, the O2-level had no effect on the critical surface temperatures at ignition, which were 295±5°C for the pure PVC and 370±10°C for two different brands of commercial PVC. Earlier studies with the MWT indicated that critical ignition temperatures appear to be independent of the diameter and heat capacity of the support wire, and the thickness of the polymer coating. Ignition occurred at the first appearance of flammable gas, identified as principally benzene in pyrolysis experiments. Reagent PVC emitted HCl prior to ignition but the commercial PVC did not. Quenched samples of the solid phase were collected for analysis; the quenching was accomplished by rapid cooling with cold He. A long-lived free radical was detected in the burned PVC, which was charred.