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Dynamic mechanical analysis (DMA) is a thermo-analytical technique that is widely used as a part of polymer characterization. One of the most common tests consists of measuring viscoelastic properties as a function of temperature while subjecting the sample to controlled heating rates. In that tests, due to sample and instrument geometry and sample size, it is not possible to measure the temperature in all parts of the sample. As a result, the gradient of temperatures between different parts of the sample is unknown. Thus, an accurate estimation of the sample temperature in all its parts and of the temperature gradients between different parts are crucial for setting up experimental conditions and establishing confidence temperature ranges to better interpret the test results. In the present work, a simulation study is performed through the Comsol ™ software, to estimate the temperature distribution of samples of different density and heat capacity that are located inside a typical DMA furnace, which is subjected to different heating rates. The furnace has two gas inlets and three outlets and the sample is attached through standard 3-point bending fixtures. The results show that some of the temperature gradients produced in the sample high enough to significantly affect the viscoelastic response.

Rheology was used to characterise the curing process of the epoxy system consisting of a diglycidyl ether of bisphenol A [DGEBA(n=0)] and one, or a mixture of the two isomers of the curing agent 1,2-diaminocyclohexane (1,2-DCH). The trans isomer and a mixture cis–trans (30–70% respectively) of 1,2-DCH were used to investigate their different behaviour. In a previous article (L. Núñez et al., Therm Anal Calorim, 2005), it was reported that the values of gel time measured by dielectric analysis for the systems DGEBA(n=0)/trans-1,2-DCH and DGEBA(n=0)/cis–trans −1,2-DCH were very similar, while times to vitrification, as measured by modulated scanning calorimetry differed widely. In the present study, rheometry was used to corroborate the results obtained in the previous article for gel time and activation energy and also to analyse differences in the cure of the two epoxy systems studied by comparing the results reported here with those previously measured by DEA and DSC. [ABSTRACT FROM AUTHOR]