Semicrystalline polyimide matrices for composites: Crystallization and properties

Abstract

New semicrystalline polyimide/oligoimide blends, designated for matrices in carbon fiber-reinforced composites, were developed. A specific advantage of the proposed polyimides is their ability to crystallize from the melt, therein retaining their crystallinity throughout the manufacturing process. The generation of crystallinity after melting, referred to as recrystallization, was investigated here as affected by blending the polyimides with oligoimides of a similar chemical structure. Based on thermal analysis and enthalpy measurements, comparative X-ray diffraction analyses, and polarized light microscopy of hot-stage-controlled crystallization, the recrystallization ability was determined for five different oligoimides. In some cases, the addition of oligoimides, both amorphous and crystalline, resulted in complete recrystallization. The main contribution of the oligoimides is suggested to be through plasticization, allowing segmental chain mobility during crystallization, and not via nucleation. A similar effect was obtained by lowering the molecular weight of the polyimide; this, however, generates mechanical property reduction, rendering the polyimide irrelevant to composite materials. Finally, it was shown that crystallization was also enhanced by carbon fibers, serving as a nucleating agent and generating transcrystallization.

Influence of the carbon nanofiller surface curvature on the initiation of crystallization in thermoplastic polymers

“…In some cases, a nanoller can initiate the crystallization of the polymer matrix, 18,[20][21][22][23][24][25] signicantly accelerating the formation of crystallites, or even initiating their formation in the polymer under conditions which do not normally favor the crystallization, as in the case of ODPA-P3 polyimide. 26 Crystallization of a polymer matrix in a nanocomposite may signicantly impact its mechanical and thermophysical properties, which should be taken into account when developing new composite materials.…”

“…Yudin et al 17,[23][24][25]29 investigated the crystallization initiation of the semicrystalline thermoplastic polyimide R-BAPB based on dianhydride 1,3-bis-(3 0 ,4-dicarboxyphenoxy)-benzene (dianhydride R) and 4,4 0 -bis-(4 00 -aminophenoxy)-diphenyl (diamine BAPB) in the composites with different nanollers. In particular, the authors have demonstrated that vapor grown carbon nanobers (VGCF) are twice as efficient in accelerating the crystalline formation as CNT.…”

The Nucleating Effect of Carbon Nanotubes on Crystallinity in R‐BAPB‐Type Thermoplastic Polyimide

“…Recently, [14][15][16] we have investigated the crystallization behavior of a new semicrystalline 1,3-bis(3,3 0 ,4,4 0 -dicarboxyphenoxy)benzene (R) and 4,4 0 -bis-(4-aminophenoxy)-biphenyl (BAPB) (R-BAPB)-type PI, presented below.…”

“…The effect of each of these factors on the ability of the PI to recrystallize and the conditions for crystallinity regeneration through the molding process of composite laminates were specified. [14][15][16] In this communication we report the preliminary results of work in progress, being a further step in the study of factors that influence the recrystallization of R-BAPB PI. It is based on the nucleating action of carbon nanotubes (CNTs) that are embedded at a very low concentration in the PI matrix.…”

High conductivity of defect doped polymers in metal–polymer–metal systems

“…In a second synthesis step additional heat treatment up to 320 °C gave rise to imidized polyimide precursors. In this case at heating PI (R-Oph 2 O) from 80 to 280 °C at a chosen heating speed, a partially crystalline state was produced [9]. The degree of crystallinity as obtained from X-ray investigations was about 30-40%.…”