Construction of improved isothermal TTT cure diagram based on an epoxy–amine thermoset

Abstract

Cure degree plays a pivotal role in determining the final properties of thermosetting resin, while the parameter cannot be visually presented by the classic isothermal time–temperature‐transformation (TTT) diagram. An improved isothermal TTT cure diagram is built for an epoxy–amine thermoset with the visual relationship between temperature, time, and cure degree during the whole curing. As for the improved isothermal TTT cure diagram, the curing surface and the gelation plane were developed using Vyazovkin method and rheological analysis in turn, and the variation between glass transition temperature (T g) and curing degree was described by Dibenedetto's equation. The obtained improved isothermal TTT diagram of epoxy–amine thermoset was constructed by the combination of calorimetric and rheological analysis. The fitting results of vitrification surface and gelation plane obtained via improved isothermal TTT diagram were in good agreement with experimental results. In addition, the experimental gelation curve of epoxy–amine thermoset is directly linked to the steepest location of curing surface. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47279.

Time-temperature-transformation (TTT) diagram of dual-curable epoxy thermosets obtained via two sequential epoxy-amine condensations

“…The activation energy obtained by KAS method of both formulations remains virtually constant in the 0.2-0.8 conversion range, as is generally reported in other works [9,12,34]. In general, this result suggests that the reaction mechanism is the same in this range of conversion and only a single kinetic model is needed to describe this process.…”

Network Formation and Physical Properties of Epoxy Resins for Future Practical Applications

“…Thus, great efforts have so far been made to gain a better understanding of gelation and vitrification during the curing process. 106 , 107 …”

“…No matter what temperature is chosen, the system will go through the gelation and/or the vitrification curve(s) after a certain time. Thus, great efforts have so far been made to gain a better understanding of gelation and vitrification during the curing process. , …”

“…Thus, great efforts have so far been made to gain a better understanding of gelation and vitrification during the curing process. 106,107 The reaction conversion at which the macroscopic gelation occurs, or the gel point, is usually determined by gel fraction measurement. Once a reaction system reaches the gel point, the insoluble component appears even in a good solvent, and then the fractional amount increases with increasing curing time.…”

Potential-Controlled Tensiometry: A Tool for Understanding Wetting and Surface Properties of Conductive Powders by Electroimbibition

“…47,48 While the wetting with deionized water is not significantly affected by the electric field, small NaCl contents (0.03 M) lead to a significant change for increasing electric fields and hence a transition from the Cassie−Baxter to Wenzel states. 48 For superaligned CNTs, a similar transition can already be observed at lower voltages between 10 and 15 V. 49 However, the MWCNTs compressed in the Washburn capillary in our investigation should not transit from the Cassie−Baxter to Wenzel states as no contact angles with water larger than 90°and thus no hydrophobic behavior can be observed. On the other hand, other groups observed a change in electrowetting properties for CNT based membranes at 1700 mV and changes from superhydrophobic properties to electroimbibition for CNT based sponges at 600 mV.…”