The kinetics of cure of epoxides and related sulphur compounds studied by dynamic DSC

摘要

Cure kinetics of model epoxides and related sulphur compounds-(1,3-oxothiolane-2-thione)s-by hexahydrophthalic anhydride have been investigated by means of dynamic differential scanning calorimetry (DSC). The apparent activation energy values (E) were determined for the whole conversion range by isoconversional methods of Friedman and Ozawa-Flynn-Wall. For the (1,3-oxothiolane-2-thione)s under investigation E lie in the range of 73.5-281.6 kJ/mol and show some instability regions at either the autoacceleate initial stages of the cure or the diffusion-controlled final stage. Further kinetic studies confirmed this hypothesis-an advanced approach based on non-linear regression method revealed that model functions possess autocatalytical or nth dimensional nucleation features which give an additional insight into the mechanism of cure process. nucleation mechanism occurs probably due to sterical arrangements,which strongly influence non-dimensional growth in a cross-linked network during the latter stage of cure, but prior to vitrification, which however governs the nature of post-cure treatments and resulted therefrom deformations of the final network. The obtained kinetic parameters allow a prediction of the cure behaviour in extrapolated range of the degree of conversion, time and temperatur.