Incorporating the Heating Stage into Processability Maps for Epoxy Curing Optimization

Area of Science:

• Materials Science
• Polymer Chemistry
• Chemical Engineering

Background:

• Conventional time-temperature-transformation (TTT) and continuous-heating-transformation (CHT) diagrams inadequately represent complex curing cycles.
• Real-world curing involves dynamic heating ramps and isothermal holds, leading to deviations in predicted material behavior.

Purpose of the Study:

• To develop a comprehensive time-temperature-transformation diagram (TTT-β) that incorporates both heating ramps and isothermal stages for epoxy resin processability.
• To accurately model curing, degradation, vitrification, and gelation kinetics for optimized processing conditions.

Main Methods:

• Development of a TTT-β diagram integrating isoconversional models for kinetic evaluation.
• Experimental validation using epoxy-amine resins under industrial-relevant heating rates.
• Analysis of thermal degradation and vitrification effects on mechanical properties (ILSS, compressive strength, compressive modulus).

Main Results:

• The TTT-β diagram accurately captures curing kinetics during heating ramps, which are often neglected by conventional methods.
• Significant curing occurs during heating, impacting the reliability of traditional TTT and CHT diagrams.
• Thermal degradation was confirmed to negatively affect composite mechanical properties.

Conclusions:

• The proposed TTT-β diagrams provide a more reliable tool for defining optimal processing conditions for epoxy resins.
• Accurate consideration of the heating phase is critical for preventing premature degradation and ensuring desired mechanical performance.
• The developed charts aid in establishing safe curing parameters for industrial applications, improving composite quality.