Behavior of volatile depletion for LaRC™‐PETI‐5 amide acid/N‐methylpyrrolidinone solution

Abstract

ABSTRACT:The fabrication of composites from polyimide precursors (polyamide acids) that involve condensation reactions requires the removal of volatiles (solvent and reaction by-products) prior to consolidation in order to achieve a void-free laminate. Volatile removal is commonly accomplished with a B-stage processing step. In this study, a PETAA/NMP (phenylethynyl terminated amide acid in Nmethylpyrrolidinone) solution and prepreg were characterized using therogravimetric analysis (TGA) and microdielectrometry. A master weight loss profile was constructed by superimposing measurements at various heating rates. The TGA results correlated well with the dielectric ionic conductivities. Under the same thermal conditions, volatiles were depleted at slower rates from the wet prepreg than the neat resin solution. Dielectric properties were more sensitive to the residual volatile contents than the TGA measurements in both the neat resin and wet prepreg. Dielectric sensing technology was demonstrated to be a feasible tool for future volatile management in the fabrication of PETI composites. This study demonstrates that the combination of TGA and dielectrometry provides useful information to develop proper processing conditions for composite fabrication from prepregs containing volatiles.

Novel phenylethynyl‐endcapped polyimide oligomers: Synthesis and characterization

“…The polyimide oligomers could be thermally cured into the thermosetted polyimide resins, and the thermal cure temperature of 3718C that we chose was the general thermal cure temperature of phenylethynyl endcapped polyimides for the primary evaluation on properties [18,24]. Figure 6 shows DMA curves of representative thermosetted polyimide resins (PI-1 and PI-2) and Table 4 summarizes the thermal properties of the thermally cured polyimide resins determined by DSC, DMA, and TGA.…”

“…The reactive endcapping agents which are commonly used in the polyimide matrix resins include maleic anhydride (MA) [7,8], nadic anhydride (NA) [9,10], and phenylethynylphthalic anhydride (PEPA) [11][12][13][14][15][16][17][18][19], in which MA and NA have been successfully employed in BMI and PMR (In Situ Polymerization of Monomer Reactants) type polyimide matrix resins [3,20,21]. In recent years, it was found that PEPA has some superior features over NA and MA, such as the stronger polymer chain-extending capability than the chain-crosslinking etc [4,[22][23][24][25][26][27][28][29][30][31]. The PEPA-endcapped polyimide resins showed outstanding thermo-oxidative stability, good mechanical properties, and high toughness.…”