Browsing by Author "Smith, D. A."
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Item Open Access Combined pyrolysis and radiochemical gas chromatography for studying the thermal degradation of polymers(College of Aeronautics, 1968-11) Bishop, D. P.; Moffitt, B. R.; Smith, D. A.Pyrolysis gas chromatography and radioactive tracer techniques have been used independently to study the thermal degradation of polymers. In these laboratories the two techniques have been combined to elucidate some of the mechanisms of the thermal degradation of epoxy resins and polyimides. This paper describes the apparatus developed for this work.Item Open Access The effect of curing conditions on the extent of cure of Polyester Resin Crystic 189 (Scot-Bader Ltd.)(College of Aeronautics, 1968-06) Smith, D. A.The cross-linking, or cure, of Scot Bader Polyester Resin Crystic 139 (L.V.) was investigated by examining the resin during cure by means of acetone Soxhlet extractions and Barcol hardness tests. The experiments were designed to test Funke’s hypothesis that in the cure of polyester resins the nature of the final network is predetermined by conditions before the gel Point, and that post-gel conditions affect the rate of cure but not the nature of the final network and the final degree of conversion. Funke’s work was based on analysis of the final products of hydrolytic degradation of polyesters, which is quite different from the methods used in this investigation. It was concluded that the evidence did not support Funke’s hypothesis and explanations are afforded for this and suggestions for future work are recorded.Item Open Access A preliminary investigation of the reaction between phenyl glycidyl ether (2.3 epoxy propyl, phenyl ether) and phenyl isocyanate(College of Aeronautics, 1961-04) Smith, D. A.Isocyanates have been in use for some time as cross-linking agents for polyester and polyether polymers. These form three-dimensional network polymers on crosslinking and are familiar commercial materials. This cross-linking system has the merit that it is possible to produce a wide range of materials from a given isocyanate or polyester by varying the reaction proportions, catalysts and so on. In addition, these materials possess a useful range of physical properties. In the present work the chemical basis of cross-linking epoxide resins with isocyanates has been investigated. Previous work on the subject has been largely empirical and though certain workers have produced cross-linked polymers by this means, the precise nature of the cross-linking process has not been established. As an initial step it was decided to investigate the nature of the link between the two types of compound, using monofunctional model compounds. These were phenyl glycidyl ether (2-3 epoxy propyl phenyl ether), and phenyl isocyanate. Phenyl glycidyl ether resembles in structure the active part of the epoxide resin molecule, and phenyl isocyanate is similar to toluene di-isocyanate, which is frequently used in isocyanate cross-linking mechanisms. A reaction has been found to take place giving a crystalline material which is a one-to-one addition compound of the two reagents, together with a red oil, which may be a mixture of alkyl anilides. The structure of the crystalline material has not been fully proved, but is believed to be a 2-oxazolidone.Item Open Access The pyrolytic degradation of epoxy resins in nitrogen at 400 to 700 degrees C(College of Aeronautics, 1969-03) Bishop, D. P.; Smith, D. A.The thermal degradation of a bisphenol-A based epoxy resin (EP 274) cured with 4,4’ -diaminodiphenyl methane (DDM) and with phthalic anhydride (PA) was studied using pyrolysis gas chromatography. Conclusive evidence for some of the degradation mechanisms of these resins was obtained by pyrolysing samples containing various 14C labelled groups and analysing the products using a combined gas chromatography and radiochemical technique.Item Open Access The reaction of perfluoroglutaric acid with methyl magnesium iodide. Part 2(College of Aeronautics, 1968-08) Smith, D. A.Perfluoroglutaric acid when treated with methyl magnesium iodide afforded hexafluoro-2,6-dimethylpyran-2,6-diol in high yield and 2,213,3,4,4-hexafluoro- 5-oxocaproic acid in low yield. The former appeared to exist in a range melting form (61.-79°C) and also in a very labile form melting at 96-98°C. Problems associated with the formation of this latter form were investigated. The hexafluoro-2,6-dimethylpyran-2,6-diol yielded a monosemi-carbazone and also a mono and a di1(2,4-dinitrophenylhydrazone). The mono (2,4-dinitro phenylhydrazone) appeared to be cyclic. Reduction, both with lithium aluminium hydride and sodium borohydride yielded 3,3,4,415,5-hexafluoro-n-heptane-2,6-diol. Reaction with anhydrous calcium sulphate gave 3,3,414,515-hexafluoro-2- methylcyclohex-l-ene-6-one. The acid product of the original reaction of perfluoroglutaric acid and methyl magnesium iodide was characterised as a 2,4-dinitrophenylhydrazone and as an S-benzylthiouronium salt. Infra-red spectroscopic evidence suggests the latter compound exists in a straight chain form.Item Open Access Some aspects of the thermal degradation of epoxide resins. Part 1(College of Aeronautics, 1965-03) Stuart, J. M.; Smith, D. A.This Note contains a review of previous work in the field of pyrolytic degradation of epoxide resins, and a description of the development of an instrument for this purpose, using the principle of gas chromatography. The method depends on the pyrolysis of the material using an electrically heated filament, the difficulties of this method are critically examined, and attempts to overcome them described. The pyrolytic degradation in a nitrogen atmosphere, of unhardened epoxide resin was investigated, likewise the degradation of resin hardened with 1:2 diamino ethane and triethylenetetramine, is described. An attempt has been made to explain, in terms of possible degradation reactions, the actual compounds detected in the pyrolytic break-down.Item Open Access Some reactions of perfluoroglutaric acid(College of Aeronautics, 1964-11) Smith, D. A.Perfluoroglutaric acid when reacted with methyl magnesium iodide affords 2,6 diol 2,6 dimethyl hexafluoro pyranI in high yield and 4-one, 1,2,3 hexafluoro caproic II acid in low yield. The former material appears to exist in a range-melting form (64-79°C) and a very labile form of melting point 96-98°C. The 2,6 diol 2,6 dimethyl hexafluoro pyranI yields a mono semi carbazoneIII, and also a monoIV and a di 2:4 dinitro phenyl hydrazone. V The mono 2:1l dinitrophenyl hydrazone appears to be cyclic. Reduction both with lithium aluminium hydride and sodium borohydride yields 2,6 diol 3,4,5 hexafluoro n-heptane.VI There is evidence to suggest that reaction with dried calcium sulphate gives 2 ene, 2 methyl 3,4,5 hexafluor 6 one cyclo-hexaneVII Reaction with benzoyl chloride affords 2,6 dibenzoate, 2,6 dimethyl hexafluoro pyran.VIII 4 one 1,2,3, hexafluorocaproic acid was characterised as a 2:4 dinitro phenyl hydrazoneIX and also as an S benzyl thio-uranium salt.X Infra-red spectral evidence suggests the S benzyl thio uranium salt probably exists in the straight chain form. Numbers in the above text refer to the Flow Sheet, Figure 1.Item Open Access A study of the thermal degradation of an amine-cured epoxide resin at temperatures below 350 degrees C(College of Aeronautics, 1967-01) Patterson-Jones, C.; Smith, D. A.An epoxy resin made by the reaction of the diglycidyl ether of bis-phenol A and diaminodiphenyl methane was thermally degraded in vacuo at temperatures between 200°C and 350°C. The effect of degradation was examined by means of measurement of changes in the dielectric properties of the material and also by examination of compounds evolved by the cured resin. Definite evidence for the evolution of N-methyl aniline and N:N-dimethylaniline is advanced and added evidence for a dehydration reaction is put forward. Possible degradation mechanisms are discussed.Item Open Access The thermal degradation of aromatic polyimides in nitrogen at 700 degrees C(College of Aeronautics, 1969-03) Bishop, D. P.; Smith, D. A.The thermal degradation of aromatic polyimides in nitrogen at 700°C was studied using pyrolysis gas chromatography, infra red spectroscopy, and radiochemical techniques. Degradation medaanisms were postulated to account for the breakdown products found. Particular attention was paid to the ratio of CO2/C0 evolved during pyrolysis and this was found to vary with the moisture content of the polyimide and with the pyrolysis temperature.Item Open Access Visit to America September 11th - September 25th, 1967(College of Aeronautics, 1967-10) Smith, D. A.Item Open Access Visit to America September 11th - September 25th, 1967(College of Aeronautics, 1967-10) Smith, D. A.