Tris‐benzil crosslinked polyphenylquinoxalines

Abstract

Polyphenylquinoxalines (PPQ) were crosslinked with a tris‐benzil comonomer, to alleviate the inherenthigh temperature thermoplasticity, and evaluated as matrices in graphite reinforced composites. The room temperature flexural strength/modulus of Modmor IJ laminates were as high as 245,000 psi/16,6 × 106 psi. Essentially 100 percent retention of ambient mechanical properties was obtained at 371°C using a PPQ matrix from the fully‐crosslinked polymer prepared from 4,4′‐bis(4″‐oxybenzilyl) benzil (BOBB) and 3,3′‐diaminQbenzrdine. The degree of high temperature thermoplasticity in the composite was found to be more closely related to the final postcure temperature than to the BOBB crosslink density. The thermoplasticity essentially disappeared when the BOBB comonomer‐PPQ laminates were postcured at 482–510°C in nitrogen. Substitution of DMAC for the commonly used m‐cresol solvent system allowed facile preparation of prepreg to fabricate low‐void laminates and NOL rings.

New Thermosetting Polyphenylquinoxalines

“…In order to overcome this shortcoming in PPQs, a number of research groups have used approaches such as introducing condensed rings into the main chains of the PPQ macromolecules [4,5] or giving the PPQs a "crosslinked" structure [6]. An effective way of creating PPQs of "crosslinked" structure is to use tris(α-diketones) in their production [7][8][9][10], typical examples of which are 4,4´-bis[(4˝-oxybenzylyl)benzyl] [7][8][9][10] and 4,4´,4˝-tris[(phenylglyoxalyl)triphenylphosphine oxide] [10] Within the framework of this research, we carried out the synthesis of a tris(α-diketone) -N,N´,N˝-tris(4-benzylyl) mellitimide (I) and thermosetting PPQs based on it.…”