Synthesis And Properties Of The New Dual Phthalonitrile Resin

Phthalonitrile polymers are an important class of high-performance polymers. These polymers are derived by heating the phthalonitrile derivatives for an extended period of time at elevated temperatures by addition curing reaction of cyano groups from phthalonitrile derivatives. Because of their outstanding thermal and thermal-oxidative stability, good machanical properties, low flammability, water and chemical resistance, and easy processability, phthalonitile polymers have been found many applications in advanced technologies such as aerospace and marine.A kind of catalyst, ammonium molybdate was developed in this paper to promote the curing reaction of phthalonitrile resins with aromatic amine as curing agent. The results indicated that the catalyst could improve the curing rate, and the curing rate and the viscosity of the reactive system could be regulated by the concentration of the catalyst used in the reaction. The complete cured materials could achieve char yields up to 70% at 800oC in nitrogen environment, above 60% at 800oC in air environment. When the concentration of curing agent was in the range of 2-3 wt% and the concentration of catalyst was 1 wt%, the material possessed the excellent properties. This bisphthalonitrile polymer exhibits excellent thermal and thermal-oxidative stability. Additionally, complex delta and viscosity changes that accompany the phthalonitrile polymerization reaction were investigated by performing rheometric measurements on the oligomeric phthalonitrile prepolymers. When frequency was 1.2Hz, the gel time was the shortest. Moreover, during the non-isothermal rheometric measurements, the gel time can be imitated to a curve.Besides, a series of low-melting bisphthalonitrile oligomers with variable length of aromatic ether Nitrile linkages between the terminal phthalonitrile units has been successfully synthesized. The structure of the resin was supported by FTIR, 1H-NMR, and 13C-NMR spectra. This type of bisphthalonitrile oligomers melt around 60oC and polymerize at around 220oC. Thus, the development of low-melting bisphthalonitrile oligomers has enhanced bisphthalonitrile processability. The low-melting point of the oligomers gave rise to a large processing window for these materials. And the polymeriaztion of these oligomers has been studied with only BDB as the bisphthalonitrile curing additives, because the curing reaction of this type was easier than BPh. When n was more than 6, the thermal and thermal-oxidative stability of the resins declined distinctly, expecially over 600oC.At last, a type of material obtained by blending two types of bisphathalonitriles was on research. BPh/6PEN- BAPh has better thermal and thrmal-oxidative stability than 6PEN-BAPh. According to the research, this material has enhanced bisphthalonitrile processing window around 30oC without sacrificing the other properties necessary for high temperature polymer applications.