Pyrolysis Of Polytetrafluoroethylene Research Articles

Facial construction of high rate Na3V2(PO4)2F3/C microspheres with fluorocarbon layer by deep-eutectic solvent synthesis

Porous Na3V2(PO4)2F3 (NVPF) with micro-nano structure was prepared by a simple deep-eutectic solvent method with good crystallinity and uniformity. Surface modification was used to produce carbon-coated NVPF (NVPF/C). The unique morphologic architecture and surface modification improve the structural stability and interfacial chemical stability of NVPF, ensuring the excellent rate performance and cycle stability of NVPF/C. At 120 °C, secondary microspheres NVPF composed of nanoparticles are successfully synthesized. By liquid phase reaction in a deep-eutectic solvent X-ray diffraction analysis reveals that these microspheres have good crystallinity. The NVPF/C with an amorphous fluorocarbon coating layer is constructed by pyrolysis of polytetrafluoroethylene (PTFE). The mesoporous structure and the existence of the coating layer are clearly obvious under the high-definition transmission electron microscope. The amorphous fluorocarbon layer enhances the reversibility and transmission ability of Na+, improving the electrochemical kinetics. And the obtained NVPF/C cathode material displays high-rate performance. The as-prepared NVPF/C-F composites with 6 %wt coating of PTFE have a specific capacity of 110.6 mAh g−1 at 10 C, 106.4 mAh g−1 at 20 C and 94.6 mAh g−1 at 50 C. The capacity retention rate is 90.4 % after 700 cycles at 20 C. This research provides a facile and inexpensive approach for getting high-rate performance sodium-ion battery cathode materials.

Mechanisms of Pulmonary Toxicity of Perfluoro-n-Alkane Pyrolysis Products with Consideration of the Structural Features of the Blood-Air Barriers.

Perfluoroisobutylene a is pulmonotoxic chemical generated during pyrolysis of perfluoro-nalkanes (polytetrafluoroethylene). The mechanisms of acute pulmonary toxicity induced by perfluoroisobutylene have not been studied yet. The analysis of tissues of brown frogs showed that the products of polytetrafluoroethylene pyrolysis induce typical inflammatory response in the lungs (fluid accumulation, erythrocyte stasis, desquamation of the epithelium, and capillary plethora in lung septa) and oropharyngeal cavity (degeneration of ciliated epithelium, hyperemia of underlying vessels with plasmatic imbibition of the connective tissue, and margination of segmented leukocytes and monocytes). The absence of surfactant is a specific feature of the blood-air barrier of the oropharyngeal cavity in frogs compared to the lungs. It can be hypothesized that toxic effects of perfluoroisobutylene are determined by its influence on epithelial (pneumocytes and cells of nonkeratinized stratified ciliated epithelium) and endothelial cells. Even though the effects of the agent on surfactant cannot be excluded, they do not determine the probability of development of inflammatory response.

Boosting the volumetric energy of supercapacitors using polytetrafluoroethylene pyrolysis gas

Increasing the volumetric energy of carbon-based supercapacitors is of practical importance for the advancement of high-powered energy storage. Herein, we use the gases evolved from polytetrafluoroethylene pyrolysis at 800 °C to fluorine-dope an activated carbon, and directly synthesize a fluorine-doped highly porous graphite in the same environment. As supercapacitor materials in organic electrolyte, both resultant fluorine-doped carbons outperform their non-doped counterparts, delivering up to 40% gain in cell volumetric energy at high power cycling. F-doping increases volumetric capacitance (F cm−3) via increase in “real” areal capacity (uF cm−2) and/or increase in “real” volumetric surface area (m2 cm−3), and increases electron conductivity. Considering current collector and separator volume fractions, cells containing the fluorine-doped activated carbon electrode films of 100 and 50 μm deliver an impressive 12.9 Wh L−1 at 0.1 kW L−1 and 6.7 Wh L−1 at 2.15 kW L−1 respectively. We conclude that the gas-based F-doping method affords an effective and less hazardous route to produce fluorine-doped carbons for increased volumetric energy storage.

Toxic pulmonary edema due to inhalation of pyrolyzed polytetrafluoroethylene products in lab animals

Relevance.Thermal decomposition of various polymeric materials occur in emergency situations associated with fires, with pulmonotoxicants releasing in the environment. During pyrolysis of polytetrafluoroethylene (Teflon), a highly toxic perfluoroisobutylene is produced.Intention.To create an experimental animal model of toxic pulmonary edema due to products of thermal decomposition of polytetrafluoroethylene.Methodology.Polytetrafluoroethylene underwent pyrolysys at 440–750 0С during 6 minutes. Toxic pulmonary edema was modeled on rats via inhalation of pyrolysis products of polytetrafluoroethylene. An amount of polytetrafluoroethylene burned under these conditions with resulting death of 50 % of rats during 1 day was (2.68 ± 0.60) g. The toxic pulmonary edema diagnosis was confirmed histologically and by lung/body ratio.Results.In the pyrolysis products of polytetrafluoroethylene, highly toxic perfluoroisobutylene was found via gas chromatography with mass spectrometric detection, with relative content of 85.9 %. Such an exposure during 15 min increased (p = 0.01) lung/body ratio in laboratory animals in 3 hours. The toxic pulmonary edema diagnosis was confirmed histologically (signs of alveolar edema). Animals started to die 7 hours after the pyrolysis products inhalation.Conclusion.In the study on rats, toxic pulmonary edema was modeled via inhalation of pyrolysis products of polytetrafluoroethylene. This model can be used for searching etiotropic and pathogenetic therapy for poisoning with pulmonotoxicants.

The time-dependent quantitative analysis of a polytetrafluoroethylene pyrolysis product stream by inline FTIR spectroscopy

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The influence of inorganic materials on the pyrolysis of polytetrafluoroethylene. Part 2: The common oxides of Al, Ga, In, Zn, Cu, Ni, Co, Fe, Mn, Cr, V, Zr and La

The thermal decomposition of PTFE intimately mixed with the common oxides of selected metals (Al2O3, Ga2O3, In2O3, ZnO, CuO, NiO, Co3O4, Fe2O3, Mn2O3, Cr2O3, V2O5, ZrO2 and La2O3) was investigated by TGA-FTIR. Except for ZrO2, all the oxides undergo reaction with PTFE to produce some CO2. CuO and V2O5 react in bulk and speed up the degradation rate with V2O3 also lowering the mass-loss onset temperature by 60°C. Al2O3 moderately increases the yield of hexafluoropropylene and hexafluoroethane.

Mesoporous fluorine-doped carbon as efficient cathode material for oxygen reduction reaction

Fluorine-doped mesoporous carbons (F/Cs) were prepared by a simple hard-template method. The pyrolysis of polytetrafluoroethylene (PTFE) supported on SBA-15 silica at high temperatures resulted in the formation of mesoporous structures with graphitic pore walls. The F/Cs obtained at 1000°C possessed a surface area of 504m2g−1 and a pore size distribution centered at 6.7nm. Such F/Cs exhibited a comparable catalytic activity for oxygen reduction reaction (ORR) to that of commercial platinum/carbon (Pt/C) catalysts and better stability and methanol-tolerance in alkaline solutions.

The effect of copper- and nickel based catalysts on the pyrolysis of polytetrafluoroethylene

The effect of copper- and nickel based catalysts on the pyrolysis of polytetrafluoroethylene This research is an exploratory investigation into the catalytic reformation of polytetrafluoroethylene pyrolysis products. The work focused on the selective production of hexafluoropropylene and octafluorocyclobutane from PTFE waste and was conducted via the hyphenated techniques TGA-FTIR and TGA-GC/MS.

Enhanced cathode performance of nano-sized lithium iron phosphate composite using polytetrafluoroethylene as carbon precursor

Herein we report a facile and efficient solid state synthesis of carbon coated lithium iron phosphate (LiFePO4/C) cathode material achieved through the pyrolysis of polytetrafluoroethylene (PTFE). The current investigation is comparatively analyzed with the results of the composites of LiFePO4/C (LFP/C) synthesized using polystyrene-block-polybutadiene (PS-b-PBD), polyethyhylene (PE) and sucrose as carbon precursors. The optimized LFP/CPTFE composite is synthesized at 700 °C using 10 wt.% PTFE. The composite exhibits remarkable improvement in capacity, cyclability and rate capability compared to those of LFP/C synthesized using (PS-b-PBD), PE and sucrose. The specific discharge capacities as high as 166 mA h g−1 (theoretical capacity: 170 mA h g−1) at 0.2 C and 114 mA h g−1 at 10 C rates were achieved with LFP/CPTFE. In addition, the composite exhibits a long-term cycling stability with the capacity loss of only 11.4% after 1000 cycles. PTFE shifts the size distribution of the composite to nanometer scale (approximately 120 nm), however the addition of sucrose and other polymers do not have such an effect. According to TEM and XPS analysis, LFP/CPTFE particles are mostly coated with a few nanometers thick carbon layer forming a core–shell structure. Residual carbon does not contain fluorine.

The influence of inorganic materials on the pyrolysis of polytetrafluoroethylene. Part 1: The sulfates and fluorides of Al, Zn, Cu, Ni, Co, Fe and Mn

The thermal decomposition of PTFE intimately mixed with the solid sulfates and fluorides of selected metals (Al2(SO4)3, ZnSO4, CuSO4, NiSO4, CoSO4, FeSO4, AlF3, CuF2, NiF2, CoF2, FeF2 and MnF2) was investigated by TGA-FTIR. It was found that the sulfates affect the rate of pyrolysis with CuSO4 lowering mass-loss onset temperature by 60°C. The fluorides have no effect on the pyrolysis rate, with the exception of AlF3 which lowers the onset temperature by 35°C. It was also found that Al2(SO4)3 and NiSO4 moderately increase the yield of hexafluoropropylene, and that AlF3 shifts the product composition to almost exclusively hexafluoropropylene and hexafluoroethane.

Morphology and structure of micro- and nanosize polytetrafluoroethylene powders prepared by the gas-phase method

Formation of fluoropolymer nanoaerosols and micropowders in the gas products of polytetrafluoroethylene pyrolysis and the hierarchical self-organization of ultradispersed powders were revealed. The features of the molecular and supramolecular structures of powders were analyzed. Low- and high-molecular-weight fractions of the fluoropolymers, constituting the powder particles were identified, and a method for their partitioning was proposed.

The thermal desorption mass spectra of polytetrafluoroethylene modified under the action of radiation at elevated temperatures

The products of the pyrolysis of polytetrafluoroethylene (PTFE) in a vacuum modified under the action of gamma irradiation in the molten state were studied mass spectrometrically at various temperatures. Radiation modification was found to cause the appearance of an additional stage of the thermal decomposition of PTFE at decreased temperatures compared with not irradiated PTFE. The chemical composition of the gas components of thermal decomposition substantially changes after the irradiation of PTFE, which increases the molecular weight of decomposition products. A comparison with the results of an additional study of the thermal decomposition of tetrafluoroethylene copolymer with hexafluoropropylene is evidence of the formation of side CF3 groups in PTFE under irradiation. Data on the composition of gaseous products of PTFE radiolysis under gamma irradiation were obtained.

Flash pyrolysis of polytetrafluoroethylene (teflon) in a quartz assembly

A special quartz assembly has been designed for the generation of several interesting classes of volatile organofluorine compounds by flash pyrolysis of teflon powder under inert atmosphere. Perfluorinated volatile products obtained in the temperature range 600–1000 °C are collected separately in a tedlar bag and characterized unequivocally by spectral data.

Preparation and optical properties of nanostructured europium-doped γ-Al2O3

Europium-doped nanostructured monolithic alumina matrix was prepared by the alkoxide sol–gel method. The Eu3+ ions were introduced by impregnation. The resulting γ-Al2O3:Eu3+ samples were heat-treated in the presence of gaseous components from oxidative pyrolysis of polytetrafluoroethylene (PTFE). The textural properties and optical behavior of the samples obtained were investigated. It was found that after a subsequent heat-treatment in air at 1400°C, a strong blue fluorescence of Eu2+ was observed whereas in thermally sintered samples without fluorination only the Eu3+ ions were present.

A numerical simulation of the NBS cup furnace toxicity test

A numerical simulation of the NBS cup furnace toxicity test (Potts' Pot) is presented. The Navier-Stokes equations describing the hydrodynamics are solved numerically using the general-purpose computational fluid dynamics code, PHOENICS. In this initial study, the behaviour of the potentially toxic material is represented by introducing a tracer gas into the flow from the furnace fire model. This approach gives some idea of typical toxicity lifetimes inside the enclosure attached to the furnace. The results are displayed in contour and vector plots. They clearly show the recirculatory flow within the furnace pot and enclosure. This recirculation may play an important role in maintaining the toxicity of the particulate fraction that has been implicated in producing ultra-high toxicity products in this apparatus. An upper limit of 2–5 min is estimated the lifetime of the particulate toxicity during the oxidative pyrolysis of polytetrafluoroethylene (PTFE).

‘Polymer fume fever’ without polymer

‘Polymer fume fever’ (PFF), a temporary, intense, but only very rarely serious influenza-like syndrome previously related only to the pyrolysis of polytetrafluoroethylene (PTFE), may also be induced by fluorocarbon systems with molecular weights in the telomeric and possibly monomeric range.

Organic Polymer Biocompatibility and Toxicology

Abstract Adverse effects of organic polymers used for plasma extenders, tissue adhesives, bone cements, contraceptive devices, prostheses, artificial organs, food packaging, cooking, and laboratory ware are appraised. Parenteral polymer disintegration involves hydrolytic, redox, and degradation reactions. Accumulative toxicity of plasticizers, antioxidants, and monomers liberated from plastic containers warrants investigation. Main problems with heart-assist devices are clotting and blood destruction; with plasma extenders, thesaurismotic reactions; with acrylic bone glues, transitory hypotension; with artificial kidneys, loss of metabolic essentials; with silicone heart valves, uptake of lipids; with silicone chin implants, bone resorption; and with liquid silicone mammary amplification, lumpy breasts and mastitis. A polymer fume fever is linked with pyrolysis of polytetrafluoroethylene. Human solid-state carcinogenesis constitutes a calculated risk with polymer implants. In rodents, all solid polymers tested produced cancer; chemical carcinogenesis was induced by a polyvinyl chloride copolymer, vinyl chloride, polycaprolactam, liquid silicone, and some brands of polytetrafluoroethylene.

The particles resulting from polytetrafluoroethylene (PTFE) pyrolysis in air.

Abstract Particulate products from the pyrolysis of polytetrafluoroethylene (PTFE) in air were collected on membrane filters, then examined by electron microscopy, infrared, mass spectrography, chromatography, and chemical analysis. The residue differed from the composition of PTFE. Evidence indicated that the pyrolysis products were composed of a complex mixture of fluorinated acids and olefins. Humidity in the pyrolysis chamber greatly influenced the composition of the mixture of products.

Biochemical changes associated with toxic exposrues to polytetrafluoroethylene pyrolysis products.

Abstract Rats were exposed to the products of pyrolysis of polytetrafluoroethylene (PTFE) containing hydrolyzable fluoride equivalent to 50 ppm COF2 for one hour daily. After one exposure, urinary excretion of fluoride was four times normal. Weight loss of exposed animals indicated inhibition of metabolism. Changes in succinic dehydrogenase activity in vivo correlated with exposure to pyrolysis products of PTFE and with urinary fluoride concentrations. Toxic effects of daily sublethal exposures were found to be cumulative. The metabolic inhibition observed was reversible. The toxic syndrome of daily inhalation of pyrolysis products of PTFE is compatible with descriptions of fluoride poisoning.

The toxicity of polytetrafluoroethylene pyrolysis products including carbonyl fluoride and a reaction product, silicon tetrafluoride.

Abstract The toxicity of pyrolysis products (550°C) of polytetrafluoroethylene (PTFE) was evaluated by exposure of dogs, rabbits, guinea pigs, rats and mice. Carbonyl fluoride (COF2) was identified as the principal toxic component. One-hour exposures of rats showed a 24-hour LC50 of 370 ppm for the pyrolysis products and an LC50 of 360 ppm for COF2. When PTFE is pyrolyzed in the absence of silica, the products are less toxic to a slight degree. Pathology revealed changes in the lungs and livers of exposed animals. Irritation of the lungs may persist for some days.