Deep eutectic solvent for curing of phthalonitrile resin: Lower the curing temperature but improve the properties of thermosetting

Abstract

Long curing duration and high curing temperature are commonly known to restrict the application of the phthalonitrile resin. In this study, a deep eutectic solvent (DES) containing ZnCl2 and urea has been developed to improve the curing process of the resorcinol-based phthalonitrile resin (DPPh) without sacrificing the useful properties of the resin. For the molar ratio of ZnCl2 and urea as 1:1 (ZnCl2-urea (1–1)), the initial curing temperature and apparent activation energy of the system were recorded as 179.5°C and 90.1 kJ/mol, respectively, indicating a reduction of 31.2% and 39.0% as compared to the pristine ZnCl2 system. More importantly, with curing time of 6 h and post-curing temperature of 300°C, the temperature at 5% weight loss as well as glass transition temperature of the resin with DES as the curing agent were 523.1°C and 370.2°C, respectively, demonstrating a significant improvement as compared to the resin cured with ZnCl2. In addition, the satisfactory long-term oxidation stability of the resin could also be obtained by employing the new curing agent. The findings from this study open a functional pathway for facile preparation of the high-performance curing agent for the phthalonitrile resin.

Self-Curing Phthalonitrile Resin with Disulfide Bond as the Curing Group

“…Jian et al developed two self-curing biobased PN resins based on natural magnolol derivatives, in which the monomer based on the honokiol derivative exhibited a wide processing window of 163 °C and a low melting point below 70 °C. In order to reduce the curing temperature of PN resins, numerous researchers have developed many kinds of curing agents such as metal salts, amines, phenols, and strong organic acids − to promote the polymerization of nitrile groups. The curing mechanism of these curing systems was thought to be a nucleophilic addition mechanism.…”