Low‐viscosity and soluble phthalonitrile resin with improved thermostability for organic wave‐transparent composites

Abstract

High processing viscosity and poor solubility limit the application of heterocyclic polymers for fabricating organic wavetransparent composites for aerospace applications. In this paper, a novel resin, poly(phthalazinone ether bisphenol fluorene) encapped with phthalonitrile (PPEBF-Ph), was synthesized and used as the matrix. Biphenol-based phthalonitrile monomer BP-Ph was also synthesized and blended with PPEBF-Ph to further lower the processing viscosity. Solubility tests showed that the resin was soluble in dimethylformamide, N,N-dimethyl acetamide, N-methylpyrrolidone, dimethyl sulfoxide, chloroform, and other solvents. Differential scanning calorimetry and rheological studies revealed that the mixed resins exhibited low processing viscosity and a wide processing window below the gel temperature. Thermogravimetric analysis indicated that the cured resins were stable below 510-530 8C under nitrogen atmosphere after 6 h of curing (decreased by 40-60% compared with previous reports on phthalonitrile resin). In air, the char yields of the resins reached 20-30% when heated at 800 8C. The composites were reinforced by a quartz fiber cloth and exhibited a dielectric constant of 2.94-3.27 in an electromagnetic field with frequency ranging from 8 to 18 GHz. Retention of the bending modulus exceeded 70% at 400 8C according to dynamic mechanical analysis, indicating excellent mechanical stability was obtained.

Synthesis and properties of a novel high-temperature vinylpyridine-based phthalonitrile polymer

“…6,19 Furthermore, a solvent is not required during the cross-linking course of phthalonitrile, which enables the polymer to be free of voids and defects during the curing process. [20][21][22] In recent decades, researchers have emphasized the structural design of the phthalonitrile monomer to improve the comprehensive properties of resins. [23][24][25] It is generally well-known that the aromatic and/or heterocyclic structures endow the phthalonitriles with outstanding properties.…”

Synthesis and Properties of A Low Melting Point Phthalonitrile Resin Containing High Density Nitrile Groups

“…Because of the high melting point and poor processability of the first generation of phthalonitrile monomers, flexible aromatic ether segments were introduced into the molecular structure of the monomers by Keller at Naval Laboratory (NRL) . At present, aliphatic aromatic ether, poly(ether imide), poly‐(arylene ether ketone), poly‐(arylene ether) and poly‐(arylene ether nitrile) have been reported. These monomers are usually prepared by the reaction of activated dihalogenated aromatic hydrocarbons and appropriate proportions of bisphenols to form phenolic intermediates, and then end‐capped with 4‐nitrophthalonitrile.…”

Preparation and characterization of phthalonitrile resin within hyperbranched structure

“…4,5 The phthalonitrile which had been cured at a high temperature can maintain good mechanical properties at 380-400 C and has better high-temperature resistance compared with traditional temperature-resistant resins such as poly (arylene ether nitrile)s, 6 polyimide, benzoxazine 7,8 , and bismaleimide. [9][10][11] However, when applied in high-temperature fields, such as aviation and aerospace, the thermostability of phthalonitrile still needs to be improved. A kind of dinitrile monomer, which contained silicon element with carbon-nitrogen bond in the middle, was synthesized through the reaction of dichlorosilane with amino phenoxy phthalonitrile by Zongbo Zhang et al 12 The results of thermogravimetric analysis (TGA) showed that the cured product had good properties.…”