Thermal Decomposition of Polyimides in Vacuum

Johnston, Timothy; Gaulin, C. A.

doi:10.1080/10601326908051943

Cited by 37 publications

(6 citation statements)

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“…At a temperature of 680 °C, complete thermal decomposition of the PI occurs. The results obtained for the thermal stability of PI are consistent with the literature data [51, 52]. It is known that the introduction of inorganic filler significantly increases the thermal stability of polymers [53, 54, 55].…”

Section: Resultssupporting

confidence: 89%

Synthesis and radiation shielding properties of polyimide/Bi2O3 composites

Павленко

Черкашина

Yastrebinsky

2019

Heliyon

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Radiation shielding composites based on polyimide and Bi 2 O 3 were synthesized. Surface and physical-mechanical properties of polyimide/Bi 2 O 3 composites were studied. Bi 2 O 3 particles were modified by polymethylphenylsiloxane for the uniform distribution of filler in composites. This paper presents data on the production of composites in two ways: hot- and cold-pressing. The hot-pressing method for the synthesis of composites is preferable compared to the cold-pressing method (the density increases by 10–12%, and the Vickers microhardness by 10–20%). The results show that the introduction of Bi 2 O 3 significantly increases the thermal stability of the composites. At 680 °C, a polymer composite containing 10 wt% Bi 2 O 3 retains 9.7% of its mass, and at 60 wt% Bi 2 O 3 , retains 58.4%. The radiation-protective characteristics of the composites with respect to gamma radiation were evaluated by experimental and theoretical methods. High radiation-protective characteristics of the composites have been established in the gamma-quanta energy range of 0.1–1 MeV.

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Section: Resultssupporting

confidence: 89%

Synthesis and radiation shielding properties of polyimide/Bi2O3 composites

Павленко

Черкашина

Yastrebinsky

2019

Heliyon

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“…From our standpoint, these reactions of formation of CO2, including reaction 4), cannot e: plain its amount and the character of its evolution, if for no other reason that that there is no explanation of the formation of H20 in sufficient amounts during thermal degradation. Another mechanism for the formation of CO2 should also be mentioned: this is oxygen transfer, proposed by Johnston and Gaulin [4]; there is also a similar, but less likely mechanism of interaction between the carbonyl groups, with the formation of a crosslinked structure [5].…”

Section: Discussionmentioning

confidence: 99%

“…The problem of a detailed mechanism for the degradation of polyheteroarylenes, and polyimides in particular, remains unsolved, although many hypotheses and mechanisms have been suggested to explain the qualitative and quantitative compositions of the thermal degradation products [4,5,8,9]. In most papers, the mechanism of John Wiley & Sons, Limited, Chichester AkadOmiai Kiadr, Budapest …”

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confidence: 99%

“…A num 9er of papers have been published on the processes of thermal degradation of polyimides under vacuum and in an inert medium [3][4][5][6][7]. The problem of a detailed mechanism for the degradation of polyheteroarylenes, and polyimides in particular, remains unsolved, although many hypotheses and mechanisms have been suggested to explain the qualitative and quantitative compositions of the thermal degradation products [4,5,8,9].…”

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confidence: 99%

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Thermochemistry of Carbonization of Polypyromellitimide

Грибанов

Shibaev

Kol'tsov

et al. 1987

Journal of Thermal Analysis

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The mechanisms of thermal degradation processes in polypromellitimide films were investigated by mass-spectrometric thermal analysis and high-resolution NMR spectroscopy in the solid state. Both the structures of the solid residues of pyrolysis products of the PM polyimide and the process of carbonization proper up to 1200 ~ were studied. It was established that the breaking of the Ca,---O----Ca, bond in the diamine moiety is not the primary act of degradation of the molecular structure of the polymer, as might be expected on the basis of the value of the bond energy. The process of intermolecular crosslinking following polymer degradation under hightemperature conditions is completed by the formation of a complex nitrogen-containing heterocyclic structure.The search for promising methods of increasing the thermal stability of polyimides is related to the investigation of thermochemical processes occurring when polymers are heated at temperatures higher than that of the beginning, of degradation [1]. The directed process of the carbonization and graphitization of polyimides to prepare artificial carbon from them [2] is also impossible without investigation of the main relationships of the high-temperature transformations of the polymers.A num 9er of papers have been published on the processes of thermal degradation of polyimides under vacuum and in an inert medium [3][4][5][6][7]. The problem of a detailed mechanism for the degradation of polyheteroarylenes, and polyimides in particular, remains unsolved, although many hypotheses and mechanisms have been suggested to explain the qualitative and quantitative compositions of the thermal degradation products [4,5,8,9]. In most papers, the mechanism of John Wiley & Sons, Limited, Chichester AkadOmiai Kiadr, Budapest

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“…Since the publication of the first major monograph on polyimides [7], numerous papers have appeared on these polymers, particularly their thermal properties and behavior over a wide temperature range. In [8] there is a consideration of the thermal destruction of polyimides in vacuum. Another monograph [9] gives considerable attention to thermooxidative destruction of technical polyimides.…”

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The role of nitrogen atoms in forming the carbon structure in the carbonization of polymer composites

2008

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Data have been used from X-ray photoelectron spectroscopy, small-angle X-ray spectroscopy, nuclear magnetic resonance, IR Fourier spectroscopy, electron spectroscopy, and other current methods for polyacrylonitrile, polypyromellitimide, hydrated cellulose, hard coals, and various model compounds to examine the effects of the nitrogen atoms on carbonization and graphitization. The nitrogen atoms are found to have multiple effects on the thermochemical and thermophysical parameters of the polymer carbonization over a wide temperature range. In the derivation of the carbon structures, the nitrogen acts as a messenger combined agent, which gives rise to heterorings, which are transformed into intermediate aromatic compounds, which form the basis of the matrix synthesis consisting of ordered graphite-type structures.Polymer carbonization is a thermochemical process with a long history. The first researches in this area were simultaneous with the determination of the macromolecular nature of coal.Analyses of hard coals with various degrees of metamorphism show that in addition to carbon they contain various heteroatoms, amongst which nitrogen and sulfur are counted fairly frequently no matter what the local origin of the coal. One trend in coal chemistry was research on thermal treatment, which alters the coal composition and structure. It alters the basic applied parameters of coal as a fuel. From the viewpoint of the chemistry and physics of macromolecular compounds, the changes occurring in coals involve thermophysical and thermochemical reactions. The multiplet composition found in coals means that these processes are inseparable and have effects on the composition and properties of the heat-treatment products. Numerous researches [1][2][3] have shown that competition between destruction and structuring determines the trend in thermochemical processes. The heating conditions determine whether the coal will burn almost completely up to a certain temperature and be converted to gaseous and readily volatile products from thermal and thermal-oxidative destruction. With special technologies, a hard coal can be converted to carbon-saturated products, from which carbon materials and components are formed that are used in many branches of industry.The transformations in the polymers forming the main part of a coal are dependent on many factors, amongst which a considerable part is played by the elemental and functional compositions. Accumulated analytical data for the area have enabled one to build up qualitative and quantitative pictures of the transformation of the constituent elements over wide temperature ranges. The data allow one to observe fairly novel properties of the nitrogen atoms: they are preserved in the carbonized products, whereas the atoms of hydrogen, oxygen, sulfur, and certain other elements almost completely leave the sphere of thermochemical reactions up to temperatures of 1000-1200°C. However, most researchers have not drawn any further conclusions from the unusual thermal stability of nitrogen in th...

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Thermal Decomposition of Polyimides in Vacuum

Cited by 37 publications

References 2 publications

Synthesis and radiation shielding properties of polyimide/Bi2O3 composites

Synthesis and radiation shielding properties of polyimide/Bi2O3 composites

Thermochemistry of Carbonization of Polypyromellitimide

The role of nitrogen atoms in forming the carbon structure in the carbonization of polymer composites

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