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

Cure kinetics of model epoxides and related sulphur compounds-(1,3-oxothiol ane-2-thione)s-by hexahydrophthalic anhydride have been investigated by mea ns of dynamic differential scanning calorimetry (DSC). The apparent activat ion energy values (E) were determined for the whole conversion range by iso conversional methods of Friedman and Ozawa-Flynn-Wall. For the (1,3-oxothio lane-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 autoaccelerated initial st ages of the cure or the diffusion-controlled final stage. Further kinetic s tudies confirmed this hypothesis-an advanced approach based on non-linear r egression method revealed that model functions possess autocatalytical or n th dimensional nucleation features which give an additional insight into th e mechanism of cure process. Nucleation mechanism occurs probably due to st erical arrangements, which strongly influence non-dimensional growth in a c ross-linked network during the latter stage of cure, but prior to vitrifica tion, which however governs the nature of post-cure treatments and resulted therefrom deformations of the final network. The obtained kinetic paramete rs allow a prediction of the cure behaviour in extrapolated range of the de gree of conversion, time and temperature. (C) 2000 Elsevier Science Ltd. Al l rights reserved.