Kenneth A. Hodd

The catalysed reaction of isocyanate and epoxide groups: A study using differential scanning calorimetry

Abstract Using differential scanning calorimetry (DSC) and IR spectroscopy the catalysed reactions of phenylglycidylether and 4,4′-diisocyanatodiphenylene methane (MDI) have been studied. The initial reaction with both the catalysts used, tetraethylammonium bromide (R4NBr) and ethylmethylimidazole (EMI), has the trimerisation of the isocyanate which occurs at 150–175°C and this was a more strongly promoted event at room temperature by EMI. The second reaction observed in the DSC thermograms was between isocyanate and epoxide to form oxazolidone. Again EMI was the more efficient catalyst. The heat of MDI trimerisation was found to be −155.6 kJ mol −1 , whilst the heat of oxazolidone formation was −141.9 kJ mol −1 .

Studies in heterocyclic polymers. Part VI. A weight-loss study of the formation of a polybenzoxazole

Abstract The cyclisation of an aromatic poly( o -hydroxyamide) to form polybenzoxazole has been studied by combining isothermal weight-loss and thermogravimetric analyses. The thermogravimetric data were analysed by the method of Gyulai and Greenhow [4] to derive values for the apparent activation energy of the cyclisation process which was found to double at about 50% conversion (74–155 kJ mole −1 . A similar result was observed when the process was studied in the presence of low concentrations of p -toluene sulphonic acid, which appears to have a moderate catalytic effect upon the cyclisation process. The apparent order of reaction of the process has been found to be close to 2, contrary to previous studies which have assumed it to be unimolecular.

A thermoanalytical study of the cure of xylok 225 resin

Abstract The cure of Xylok 225 resin with a range of concentrations of hexamethylene tetramine has been studied by DTA, DTA-TG and DSC. The process has also been followed by IR spectroscopy. Two reaction peaks were observed during the cure, an exotherm occurring near to 150°C and an endotherm near to 250°C. The exotherm appeared to be affected by the concentration of hexamethylene tetramine, at a low concentration (4.8%) its onset was delayed until near 190°C, whilst at a higher concentration (13.0%) the heat of reaction was diminished. Both the exothermic and endothermic phases of cure were accompanied by evolution of volatiles.