Synthesis and Characterization of Pyrimidine‐Based Novel Phthalonitrile Resins with Excellent Processing Performance and High Glass Transition Temperature

Abstract

Three phthalonitrile monomers containing pyrimidine ring and benzene ring side group were successfully synthesized with 4, 6‐dichloro‐2‐phenylpyrimidine, three kinds of phenols (resorcinol, bisphenol A and bisphenol AF) and 4‐nitrophthalonitrile via nucleophilic substitution reaction. All the phthalonitrile monomers exhibited excellent processing performance due to low melting points (Tm) (below 100 °C) and wide processing windows (difference between melting temperature and curing temperature) above 140 °C. By introducing pyrimidine ring and benzene ring side group, the lower melting point of monomers did not affect the thermal stability and thermal mechanical properties of the phthalonitrile resins based on different bisphenols. In particular, 5 % thermal decomposition temperature (T5%) and glass transition temperature (Tg) of phthalonitrile resin based on resorcinol surpassed 455 and 400 °C while storage modulus (E′) was 3209 MPa. Therefore, phthalonitrile resin containing pyrimidine ring and benzene ring side group have potential applications in the field of high temperature resistant polymers and composites.

Effect of post‐curing temperature on the retention of mechanical strength of phthalonitrile thermosets and composites after a long‐term thermal oxidative aging

“…This can be explained by curing chemistry and formation of three‐dimensional polymeric network including triazine moieties. According to the FTIR spectra, the absorption peaks at 1353, and 840 cm −1 correspond to a triazine structure, 1521 and 1718 cm −1 are related to an isoindoline structure, at 1006 cm −1 –to a phthalocyanine ring structure 52,53 …”

“…According to the FTIR spectra, the absorption peaks at 1353, and 840 cm À1 correspond to a triazine structure, 1521 and 1718 cm À1 are related to an isoindoline structure, at 1006 cm À1 -to a phthalocyanine ring structure. 52,53 The thermosets post-cured at different temperatures were studied with DMA and flexural tests to estimate an effect of the post-curing conditions on the material properties (Table 1). The mechanical characteristics of thermosets obtained in this work are in agreement with the previously published works.…”