Structure-property relationships in PMR-15-type polyimide resins: IIH. New polyimides incorporating triazoles, quinoxalines, pyridopyrazines and pyrazinopyridazines

Abstract

Polyimide oligomers (prepolymers) and resins of the PMR-15 type have been prepared from 5-norbomene-2,3-dicarboxylic half acid ester (NE), 3,3',4,4'-benzophenone tetracarboxylic diester (BTDE) and a series of diamines incorporating 1,2,3-triazole, quinoxaline, pyrido[2,3-b]pyrazine, pyrido[3,4-b]pyrazine, benzo[g]quinoxaline, pyrazino-[2,3]-d]pyridazine and bis(pyrido[3,4-b]pyrazino)benzene ring systems. Two tetraamines in the bis(pyrazino[2,3-d]pyridazino)benzene ring system were also employed. Selected diamine monomers from the above ring systems provde PMR-15-analogue resins of higher thermal and thermooxidative stability than PMR-15 itself. The physical behaviour during oligomerization and curing of PMR systems has been studied by dynamic mechanical thermal analysis (DMTA). Traces akin to that from PMR-15 are obtained using certain diamine monomers (e.g. triazole and pyrido[3,4-b]pyrazine containing) but a featureless thermogram is observed using tetraamines in the bis(pyrazino[2,3-dj]pyridazino) benzene system.

The effect of methyl and methoxy substituents on dianilines for a thermosetting polyimide system

“…8 MDA, NE, and BTDE are solids at room temperature (RT) and are typically dissolved in alcohols, such as methanol, at 50 wt% 13 and “staged” to enable imidization to form prepolymers (Figure 1). 14 BTDE is dissolved in methanol, followed by the NE, while stirring at RT. 14 The MDA is then added to the ester solution and stirred at RT until the diamine dissolves and then heated to imidize/stage the resin.…”

“…14 BTDE is dissolved in methanol, followed by the NE, while stirring at RT. 14 The MDA is then added to the ester solution and stirred at RT until the diamine dissolves and then heated to imidize/stage the resin. The molar ratio of 2:2.087:3.087 NE/BTDE/MDA is used to form the idealized structure in Figure 1 with a molecular weight of approximately 1500 g mol −1 .…”

“…The molar ratio of 2:2.087:3.087 NE/BTDE/MDA is used to form the idealized structure in Figure 1 with a molecular weight of approximately 1500 g mol −1 . 14 The monomer mixture is then pre-impregnated onto the desired fibers at slightly elevated temperatures (50–70°C) to drive off the solvent. 14 Prepregs are then stacked in the desired orientation.…”

“…14 The monomer mixture is then pre-impregnated onto the desired fibers at slightly elevated temperatures (50–70°C) to drive off the solvent. 14 Prepregs are then stacked in the desired orientation. The prepreg stacks are then placed in an autoclave and subjected under a nitrogen atmosphere with a pressure of 20 atm while being cured at 204°C for 1 h to complete the imidization process and then postcured at 315°C for 4 h. 8,14…”

“…14 Prepregs are then stacked in the desired orientation. The prepreg stacks are then placed in an autoclave and subjected under a nitrogen atmosphere with a pressure of 20 atm while being cured at 204°C for 1 h to complete the imidization process and then postcured at 315°C for 4 h. 8,14…”