Epoxy Curing Studies with Isothermal Differential Scanning Calorimetry Method

Significance of Epoxy Curing Analysis

Epoxy resins are key thermosetting polymers used in coatings, adhesives and electronic materials due to their mechanical strength, electrical insulation, chemical resistance and minimal shrinkage. Proper curing management directly influences the final thermal and mechanical performance of epoxy-based products.

Objectives and Overview of Study

This study applies isothermal differential scanning calorimetry (DSC) to investigate the curing kinetics of an epoxy adhesive at two temperatures (120 °C and 140 °C). The aim is to determine how cure time and temperature affect the degree of cure and to optimize processing parameters.

Methodology and Instrumentation

• Sample Preparation: Epoxy glue was sealed in aluminium pans, with an empty pan as reference.
• DSC Conditions: Shimadzu DSC-60 Plus under nitrogen flow (100 mL/min), heating at 10 °C/min to target temperature, held for varying durations, cooled to room temperature, then reheated to 250 °C.
• Data Analysis: Residual exothermic enthalpies from the second heating cycle were used to calculate the percentage degree of cure at each hold time.

Main Results and Discussion

At 140 °C the epoxy reached complete cure within six minutes, evidenced by the absence of residual exothermic peaks and the appearance of a glass transition around 115 °C. At 120 °C, curing progressed more slowly, achieving approximately 97.2% cure after 15 minutes, with residual peaks still observable. Comparative analysis clearly shows faster reaction rates and higher cure extents at 140 °C.

Benefits and Practical Applications

The described isothermal DSC method offers rapid, quantitative determination of cure kinetics, facilitating formulation development, quality control and process optimization in industrial and research laboratories. It provides insights for predicting final product properties and ensuring reproducible cure conditions.

Future Trends and Opportunities

Combining DSC with spectroscopic or dielectric analysis could enable real-time cure monitoring. Automation of DSC protocols and advanced kinetic modeling may accelerate the development of new bio-based or high-performance epoxy systems and support inline process control.

Conclusion

Isothermal DSC effectively quantifies epoxy curing behavior, demonstrating the strong influence of temperature on cure rate. This method enables precise determination of complete cure points, supporting improved material design and process reliability.

Used Instrumentation

Shimadzu DSC-60 Plus differential scanning calorimeter; aluminium sample pans; nitrogen purge.

References

• Ng F, Couture G, Philippe C, Boutevin B, Caillol S. Bio-based aromatic epoxy monomers for thermoset materials. Molecules. 2017;22(1):149.
• Shimadzu. DSC-60 Application Data Book.
• Thermal Methods of Analysis. Blackie Academic & Professional; 1995.
• Introduction to Thermal Analysis. Kluwer Academic Publishers; 2001.
• Hardis R, Jessop JLP, Peters FE, Kessler MR. Cure kinetics characterization & monitoring of an epoxy resin using DSC, Raman spectroscopy, and DEA. Composites Part A. 2013;49:100-108.