Preparation, processabilityand durability of high-performance novolac epoxy resin for pultrusion

Aiming to meet the demand for high-temperature-resistant resins used for pultruded fiber-reinforced polymer composites, a novel F51 novolac epoxy resin (F51) epoxy system cured with methyl nadic anhydride (MNA) is developed and modified with reactive diluents to improve processability. The thermomechanical, processability, mechanical properties and durability of the modified resin are systematically evaluated. An improved Arrhenius model integrating hourly average temperature is established for conservative long-term performance prediction. Results show that the unmodified MNA/F51 system has a 46.3 °C higher glass transition temperature (T_g) and higher mechanical strength than the commercial E51 bisphenol-A epoxy resin cured with methylhexahydrophthalic anhydride (MHHPA/E51) system, but fails to meet pultrusion viscosity requirements. The optimized F51-TM₅ resin with 5 wt% trimethylolpropane triglycidyl ether (TMPTE) achieves a T_g of 168.3 °C, satisfactory process performance and excellent mechanical performance. Moreover, the diluted F51-TM₅ resin system remains a T_g above 150 °C after 28-day accelerated aging in 80 °C water/seawater/alkaline solution, and the modified Arrhenius model yields more accurate and conservative (maximum difference reaches 19.5%) life predictions for the diluted F51-TM₅ resin system, especially for environments with large temperature fluctuations. This work provides a cost-effective resin formulation balancing high-temperature resistance and processability for advanced composites.