Temperature for curing phthalonitrile-terminated poly(phthalazinone ether nitrile) reduced by a mixed curing agent and its curing behavior

Abstract

A mixture of ammonium molybdate tetrahydrate and urea (AMTU) was developed successfully to catalyze phthalonitrile to afford 2,4,6-tris(2-cyanophenyl)-1,3,5-triazine. Then AMTU was employed as a curing agent to promote the curing reaction of phthalonitrile-terminated poly(phthalazinone ether nitrile) (PPEN-Ph), and the effect of the novel curing agent was studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The initial curing temperature and apparent activation energy E_a (based on the Kissinger equation) were reduced from 268.5 °C and 201.5 kJ mol⁻¹ using the common curing agent ZnCl₂, to 223.0 °C and 78.4 kJ mol⁻¹ using AMTU, respectively, under identical curing conditions. Moreover, the resulting thermosetting resin over AMTU showed excellent thermal stability; the T_d5% and T_d10% were 487 °C and 540 °C, respectively, and the char residue was up to 75% at 800 °C. These results indicated that AMTU could reduce the curing temperature for PPEN-Ph effectively, and it may be a good candidate as a curing agent for phthalonitrile resins.