Chemical shrinkage and thermomechanical characterization of an epoxy resin during cure by a novel in situ measurement method

• Combined measurement of dimensional changes and mechanical properties during cure with a novel in situ method.
• Measurements carried out with a thermal heat flux cell combined with DMA allowing direct injection of liquid resin.
• Thermal heat flux cell heat of reaction close to DSC value.
• Phenomenological models proposed to describe the shrinkage and stiffness behavior as a function of degree of cure.

In this study, a novel technique is presented to enable the characterization of the dimensional changes and evolution of mechanical properties of a resin during cure. This is achieved using an innovative in situ device called thermal flux cell combined with a Dynamical Mechanical thermal Analyser (DMA). With this system, it is now possible to eliminate the sources of error induced while combining two or more instruments. This device consists into a mold containing the resin where the upper and lower surfaces acting as heat flux sensors. Changes in temperature and thermal flux are directly monitored as well as the dynamical displacement and the stiffness during the curing process. In this work, an epoxy DGEBA resin was used to demonstrate the innovative approach. The tested resin was characterized using different vibration frequencies and amplitudes of the DMA. The results were then processed in order to provide accurate data on gel time and cure kinetics behavior. The volume and mechanical changes were also derived from experimental data and linked to the degree of cure. Chemo and thermo-mechanical models were created to predict the changes in chemical shrinkage and stiffness during cure.

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