A dynamic DSC study of the curing process of epoxy resin

Abstract

In order to expand the industrial usefulness of an isothermal time-temperature-transformation (TTT) cure diagram, a method to make it applicable to a solid-state sample involving only resins and a catalyst was studied by using dynamic DSC (DDSC) and cone plate dynamic mechanical analysis (DMA). To estimate how much curing occurred for an industrially used epoxy resin molding compound manufactured in a production process was also studied, together with its position in the TTT cure diagram. The TTT cure diagram proved to be useful for determining the differences between compounds without their dissolution in a solvent, and for estimating their heat history during the production process.

The isothermal curing of a diepoxide‐cycloaliphatic diamine resin by temperature modulated differential scanning calorimetry

“…After this step, a decay in | C | is observed, which is attributed to the vitrification of the system. 12–14, 16–23 As the crosslinking progresses, there is a characteristic time where the number of configurational states significantly decrease, and correspondingly, there is a decrease in the heat capacity of the system. In addition, assuming that the average relaxation time of segmental chains in the glassy state is between 50 and 100 s,36 and taking into account that the time scale of ADSC measurements is 60 s, it turns out that the relaxation process detected by ADSC, via the abrupt decay on | C |, corresponds to the macroscopic vitrification of the system.…”

“…Alternatively, other thermal analysis techniques such as dynamic mechanical analysis, 2, 6 torsional braid analysis (TBA),7, 8 and dielectric relaxation spectroscopy (DRS)9 have also been used to monitor the curing reaction and to study the relaxation associated with the vitrification phenomenon. In the nineties, Reading et al10, 11 introduced the temperature‐modulated differential scanning calorimetry (TMDSC), which has been shown to be a very useful technique for studying not only vitrification, but also the kinetics during the diffusion controlled step 12–23…”

Use of temperature‐modulated DSC in kinetic analysis of a catalysed epoxy–anhydride system

“…In the last decade, temperature‐modulated differential scanning calorimetry (TMDSC) has been revealed as a useful technique for characterising the thermal properties of polymeric systems,1, 2 and especially for studying curing reactions in thermosets 3–16. The kinetics of a curing reaction is complex because during crosslinking the viscosity of the system increases and the kinetics, which is initially controlled by the chemical reactivity of the functional groups, becomes controlled by the diffusion of these groups in the medium.…”

Isothermal Curing of Acetylene Functionalized Liquid Crystalline Thermoset Monomers

“…An S-shaped line typically represents the devitrification−vitrification−devitrification contour calculated during curing. Many studies of thermosetting systems have calculated physical transformation TTT − or CHT ,− , diagrams to help explain the physical transformations the curing system undergoes during a cure profile. All of these systems are nonliquid crystalline thermosetting materials, thus yielding only physical transformations.…”

“…A variety of methods and criteria have been established for the determination of both gelation and vitrification. Differential scanning calorimetry (DSC), thermal mechanical analysis (TMA), torsional braid analysis (TBA), viscosimetry, rheometry, thermal scanning rheometry (TSR), and dynamic mechanical thermal analysis (DMTA) are a few of the techniques used to determine physical transformations of curing systems. − ,− Although all of these methods have been used to construct transformation diagrams, for historical and practical reasons only TBA and rheologically based techniques are reviewed below.…”