Effects of cure treatment on glass transition temperatures for a BADGE-DDM epoxy resin

Abstract

SYNOPSISThe extent of cure for epoxy resin (BADGE) with a small excess of amine hardener (DDM, 4 w/o) was determined by assay of the epoxy groups using near infrared spectroscopy. The importance of the specification of the operational definition of glass transition temperatures is clearly established by comparison of different methods of determining glass transition temperatures.For isothermal cures, there were broad tan 6 loss peaks, while for postcure, there was a large reduction in size of the loss peak at extended times. This suggests that there is a change in network structure that is not related to the extent of reaction of epoxy groups, because X, -0.99 after 30 min at 180°C.

Influence of cure treatment on extent of reaction and glassy modulus for BADGE‐DDM epoxy resin

“…These structural changes affected the glass-transition temperatures as reported previously 13 and the glassy modulus in the present results.…”

“…Thus, the linear branch for shorter cure times was also the region where there was a linear decrease in the specific volume, which was directly related to the extent of reaction as shown previously. 13 In that article (see Fig. 11) there was a sharp discontinuity at X e ϭ 0.87, which was the same as the discontinuity found for the relationship between T g i and rt .…”

“…The T g i was determined from the intercept of the glassy plateau with the transition slope of the log EЈ versus the temperature curve as defined previously. 13 The room temperature density ( rt ) was determined by weighing samples of the resins in air and immersed in water.…”

“…13 However, it is useful to have a single parameter and our choice was T g i , which was discussed in detail recently. 13 The T g i is the most useful single parameter because it models the relationship between the cooperative rearrangement of chain segments and the temperature dependence of such molecular motion. Thus, it is sensitive to the flexibility of the junctions as discussed earlier.…”

Mechanical behavior of tetrafunctional/phenol novolac epoxy mixtures cured with a diamine

“…15 From Table I, T g value of cure 1, 172°C, is practically the final curing temperature for this path. T g values are 30°C above their final curing temperatures for cures 2 and 3.…”