Spontaneous Three‐Layer Formation in the Curing of Polyimide/Epoxy Blends

Abstract

Morphological structures of epoxy resin toughened by a fluorinated polyimide were observed by SEM. Three layers formed spontaneously parallel to the film surface in the range of polyimide weight fraction w = 0.14–0.20, when the samples were cured at 130 °C. The two outer layers consisted mostly of the epoxy‐rich phase. The middle layer consisted of bicontinuous domains of polyimide‐ and epoxy‐rich phases with a characteristic domain size much smaller than the outer layer thickness. At w = 0.10–0.13, aggregates of polyimide‐rich particles formed. Observation of the morphological development at w = 0.15 suggested that polyimide‐rich domains were distributed over the whole sample in the early period.magnified image

Dynamically Asymmetric Phase Separation and Morphological Structure Formation in the Epoxy/Polysulfone Blends

“…expelled and resulted to a three-layered structure formation, as the previous work reported. 6,19,20 At even lower or higher PSF contents, the slow dynamic property of PSF also played a great role in the phase separation process, which will be discussed in the following section. Phase separation process of w = 0.10 and 0.20 was measured in situ by TRLS, and the observed information was presented in Figure 2.…”

“…21À24 A three-layered structure thus formed has been reported in the previous work, where mobility of the components was compared and a speculation of the layered structure formation and phase separation kinetics was proposed. 6,19,20 In this study, more detailed and systematic experimental results on the kinetics at various thermoplastic concentrations and curing temperatures will be presented. Theory of viscoelastic phase separation is used to explain such a phase separation process, and the dynamic asymmetry between the components and the influence on phase separation mechanism will be discussed.…”

“…Reaction-induced phase separation (RIPS) in epoxy/thermoplastic blend has been extensively studied due to the importance in the toughening application such as for the continuous fiber composites and also for the fundamental interest. − In an initially homogeneous epoxy/thermoplastic blend, molecular weight of epoxy increases with the curing reaction; thus, the entropy of mixing decreases. Therefore, the concentration fluctuation gradually increases, and eventually the phase separation is induced. , With different thermoplastics (TP) and curing agents used, the competition between reaction and phase separation has been qualitatively considered. − Various morphological structures, namely, sea–island, bicontinuous, or double-phase and nodular structure, have been observed in the order of increasing thermoplastic weight fraction w .…”

Compatibilized the thermosetting blend of epoxy and redistributed low molecular weight poly(phenylene oxide) with triallylisocyanurate

“…One of the most commonly investigated methods to improve the dielectric properties of epoxy resin is to blend it with other high performance materials. The blends of epoxy resin with several polymers such as poly(phenylene oxide) (PPO), [4][5][6][7] cyanate ester (CE), 8,9 and polyimide (PI) 10,11 have been studied. PPO has a low dielectric constant and loss, as well as excellent mechanical properties, high dimensional stability and low moisture uptake.…”

Reactive blend of epoxy‐novolac resin and epoxide‐terminated low‐molecular‐weight poly(phenylene oxide)

“…Polymer blending has been a feasible and convenient way to improve the physical properties of epoxy resins. Epoxy resins have been blended with several polymers such as poly(phenylene oxide) (PPO),5−16 cyanate ester (CE),17−19 and polyimide 20,21. Among them, PPO has the good heat‐resistant property, high dimensional stability, low moisture uptake, low flammability, as well as the excellent electrical properties such as low dielectric constant and dissipation factor 5,6.…”