THERMAL DECOMPOSITION OF MOLECULAR COMPLEXES: II. β-QUINOL CLATHRATES

1963 ◽  
Vol 41 (9) ◽  
pp. 2137-2143 ◽  
Author(s):  
H. G. McAdie
Keyword(s):  
Carbon Dioxide ◽  
Thermal Decomposition ◽  
Melting Point ◽  
Guest Molecule ◽  
Lattice Distortion ◽  
Molecular Complexes ◽  
Enthalpy Change ◽  
Methyl Cyanide ◽  
Endothermal Effect ◽  
Energy Of Interaction

The β-quinol clathrates of nitrogen, carbon dioxide, methanol, and methyl cyanide decompose at temperatures well below the melting point of the host quinol lattice. The accompanying endothermal effect is broad, indicating that the decomposition occurs gradually over a considerable temperature range. The clathrate decomposition was verified by measurement of the gas evolved. The enthalpy change accompanying decomposition correlates closely with the energy of interaction of the guest molecule with the β-quinol lattice, and the decomposition of the clathrate is suggested to occur by a lattice distortion mechanism in which the size and shape of the guest molecule are important.

THERMAL DECOMPOSITION OF MOLECULAR COMPLEXES: I. UREA-n-PARAFFIN INCLUSION COMPOUNDS

1962 ◽  
Vol 40 (12) ◽  
pp. 2195-2203 ◽  
Author(s):  
H. G. McAdie
Keyword(s):  
Crystal Structure ◽  
Thermal Decomposition ◽  
Melting Point ◽  
Chain Length ◽  
Inclusion Compounds ◽  
Molecular Complexes ◽  
Enthalpy Change ◽  
Decomposition Process

The molecular complexes of urea and even-numbered n-paraffins up to C28 undergo thermal decomposition below the melting point of urea at temperatures which increase with the n-paraffin chain length. The decomposition is endothermal and is accompanied by changes in crystal structure, appearance, and by loss of the n-paraffin. Based on the enthalpy change a mechanism for the decomposition process is proposed.

THERMAL DECOMPOSITION OF MOLECULAR COMPLEXES: IV. FURTHER STUDIES OF THE β-QUINOL CLATHRATES

1966 ◽  
Vol 44 (12) ◽  
pp. 1373-1385 ◽  
Author(s):  
H. G. McAdie
Keyword(s):  
Thermal Decomposition ◽  
Guest Molecule ◽  
Molecular Complexes ◽  
X Ray Diffraction ◽  
Interpenetrating Networks ◽  
Guest Molecules ◽  
X Ray ◽  
Guest Species ◽  
Decomposition Increase ◽  
Thermal Stability Of

The endothermal decomposition of 18 β-quinol clathrates has been studied by thermo-analysis, calorimetry, and X-ray diffraction, and the decomposition process shown to be[Formula: see text]For those symmetrical guest molecules (M) which do not distort the β-quinol cavities from their normal dimensions, both temperatures and enthalpies of clathrate decomposition increase with increasing volume of the guest molecule. For those unsymmetrical guest species which require distortion of the cavities along their c-axis, temperatures and enthalpies of decomposition tend to decrease as the initial distortion required to accommodate the guest increases. Thermal stability of β-quinol clathrates is thus strongly influenced both by the size and shape of the guest molecule.The mechanism of thermal decomposition is suggested to involve a combination of the loss of stabilizing guest–wall interactions, together with increased thermal motion of the interpenetrating networks of hydrogen-bonded quinol molecules.

scholarly journals THERMAL DECOMPOSITION OF MOLECULAR COMPLEXES: III. UREA INCLUSION COMPOUNDS OF MONOSUBSTITUTED ALIPHATIC SERIES

1963 ◽  
Vol 41 (9) ◽  
pp. 2144-2153 ◽  
Author(s):  
H. G. McAdie
Keyword(s):  
Thermal Decomposition ◽  
Inclusion Compounds ◽  
Guest Molecule ◽  
Molecular Complexes ◽  
Decomposition Temperature ◽  
Urea Inclusion Compounds ◽  
Guest Species ◽  
Alkyl Bromides ◽  
Sufficient Energy ◽  
Urea Inclusion

Examination of the thermal decomposition of urea inclusion compounds has been extended to complexes of the even-numbered members of the following aliphatic series: n-alcohols, n-alkylamines, n-alkyl bromides, and n-carboxylic acids. The decomposition has been studied primarily by differential thermal analysis and an attempt made to correlate the observed decomposition temperatures and heats of decomposition with the particular guest species. The decomposition mechanism appears to involve acquisition of sufficient energy by the guest molecule to permit its diffusion from the canal, the decomposition temperature being related to the activation energy required for this diffusion process.

scholarly journals Thermal Decomposition of Kraft Lignin under Gas Atmospheres of Argon, Hydrogen, and Carbon Dioxide

Polymers ◽  
2018 ◽  
Vol 10 (7) ◽  
pp. 729 ◽  
Author(s):  
Qiangu Yan ◽  
Jinghao Li ◽  
Jilei Zhang ◽  
Zhiyong Cai
Keyword(s):  
Carbon Dioxide ◽  
Thermal Decomposition ◽  
Kraft Lignin

The thermal decomposition of RDX at temperatures below the melting point. V. The evolution of occluded volatile matter prior to the decomposition, and the influence of past history of the sample on the rate of decomposition

1972 ◽  
Vol 25 (11) ◽  
pp. 2337 ◽  
Author(s):  
JJ Batten
Keyword(s):  
Thermal Decomposition ◽  
Reaction Time ◽  
Melting Point ◽  
Ambient Temperature ◽  
Ultraviolet Light ◽  
Past History ◽  
Volatile Matter ◽  
Post Irradiation ◽  
Mechanism Of Decomposition ◽  
History Of

It is fist demonstrated that the occluded solvents and gases which are often present in RDX are expelled prior to zero reaction time of thermal decomposition. Thus they do not seriously interfere with the use of pressure increase as a measure of the extent of thermal decomposition. The rate of thermal decomposition of sublimed RDX at 195�C is then compared with the rate after the following treatments, (i) preliminary grinding of the crystals, (ii) preparation of the crystals by different techniques, (iii) mixing RDX with various solid additives, (iv) interruption of the reaction by cooling, and (v) pre-irradiation with ultraviolet light. The results indicated that treatments (i), (ii), and (iv) had little effect on the rate, whereas (iii) and (v) could markedly influence the rate. Their effects are discussed in terms of the mechanism of decomposition. The results also indicated that there was a post-irradiation reaction of RDX at ambient temperature.

Thermal Analysis of Nomex® and Kevlar® Fibers

1977 ◽  
Vol 47 (1) ◽  
pp. 62-66 ◽  
Author(s):  
J. R. Brown ◽  
B. C. Ennis
Keyword(s):  
Thermal Analysis ◽  
Thermal Decomposition ◽  
Glass Transition ◽  
Melting Point ◽  
Transition Region ◽  
High Temperatures ◽  
High Performance ◽  
Polymer Melt ◽  
Glass Transition Region ◽  
Dta Curves

DTA, TG, and TMA curves of commercial Kevlar® 49 and Nomex® fibers have been used to assess their behavior at high temperatures. The fibers lost absorbed water around 100°C, and a glass transition was reflected in the DTA and TMA curves in the region of 300°C. Difficulties in the interpretation of DTA and TMA curves in the glass-transition region and in the assignments of Tv‘s for these high-performance fibers are discussed. Whereas Kevlar 49 showed both a crystalline melting point (560°C) and a sharp endothermal thermal decomposition (590°C), Nomex showed only the latter (440°C) and no evidence of melting from the DTA curves. The endothermal decomposition peaks apparently correspond to “polymer melt temperatures” reported for related materials, and correlate well with the TG and TMA features. During thermal analysis of Kevlar 49, oxidation occurs more readily than thermal decomposition, but the latter predominates for Nomex. Differences between dyed and undyed Nomex were due to differences in yarn constitution.

scholarly journals Study on Thermal Decomposition Behaviors of Terpolymers of Carbon Dioxide, Propylene Oxide, and Cyclohexene Oxide

2018 ◽  
Vol 19 (12) ◽  
pp. 3723 ◽  
Author(s):  
Shaoyun Chen ◽  
Min Xiao ◽  
Luyi Sun ◽  
Yuezhong Meng
Keyword(s):  
Carbon Dioxide ◽  
Thermal Stability ◽  
Thermal Decomposition ◽  
Thermogravimetric Analysis ◽  
Propylene Carbonate ◽  
Cyclohexene Oxide ◽  
Block Polymers ◽  
Rate Method ◽  
Poly Propylene ◽  
Thermal Stability Of

The terpolymerization of carbon dioxide (CO2), propylene oxide (PO), and cyclohexene oxide (CHO) were performed by both random polymerization and block polymerization to synthesize the random poly (propylene cyclohexene carbonate) (PPCHC), di-block polymers of poly (propylene carbonate–cyclohexyl carbonate) (PPC-PCHC), and tri-block polymers of poly (cyclohexyl carbonate–propylene carbonate–cyclohexyl carbonate) (PCHC-PPC-PCHC). The kinetics of the thermal degradation of the terpolymers was investigated by the multiple heating rate method (Kissinger-Akahira-Sunose (KAS) method), the single heating rate method (Coats-Redfern method), and the Isoconversional kinetic analysis method proposed by Vyazovkin with the data from thermogravimetric analysis under dynamic conditions. The values of ln k vs. T−1 for the thermal decomposition of four polymers demonstrate the thermal stability of PPC and PPC-PCHC are poorer than PPCHC and PCHC-PPC-PCHC. In addition, for PPCHC and PCHC-PPC-PCHC, there is an intersection between the two rate constant lines, which means that, for thermal stability of PPCHC, it is more stable than PCHC-PPC-PCHC at the temperature less than 309 °C and less stable when the decomposed temperature is more than 309 °C. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and thermogravimetric analysis/infrared spectrometry (TG/FTIR) techniques were applied to investigate the thermal degradation behavior of the polymers. The results showed that unzipping was the main degradation mechanism of all polymers so the final pyrolysates were cyclic propylene carbonate and cyclic cyclohexene carbonate. For the block copolymers, the main chain scission reaction first occurs at PC-PC linkages initiating an unzipping reaction of PPC chain and then, at CHC–CHC linkages, initiating an unzipping reaction of the PCHC chain. That is why the T−5% of di-block and tri-block polymers were not much higher than that of PPC while two maximum decomposition temperatures were observed for both the block copolymer and the second one were much higher than that of PPC. For PPCHC, the random arranged bulky cyclohexane groups in the polymer chain can effectively suppress the backbiting process and retard the unzipping reaction. Thus, it exhibited much higher T−5% than that of PPC and block copolymers.

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