Studies on the phase separation of polyetherimide-modified epoxy resin, 3. Morphology development of the blend during curing

Abstract

SUMMARY Scanning electron microscopy (SEM) was used to trace the development of the morphology of polyetherimide-modified epoxy resins. On the basis of SEM results and the change of the glass transition temperature of the blends during curing, different phase formation processes were found and discussed. Regarding the low molecular weight polyetherimide-modified system, the phase separation follows a spinodal decomposition mechanism. However, the poor miscibility of high molecular weight polyetherimide with epoxy resin causes the PEI-rich phase to separate in an early stage of curing. As a result, the separated phase, about 10-20 pm in dimension with fine structure in it, is not the same as that observed in ordinary phase separation processes.

Polymerization-induced phase separation in polyethersulfone modified epoxy resin systems: effect of curing reaction mechanism

“…As a result, much work has been made to toughen highly crosslinked thermosetting polymers with high modulus, high glass transition temperature thermoplastics, such as polyethersulfone (PES) [1,2] , polysulfone (PSF) [3] , poly (ether ether ketone) (PEEK) [4] and polyetherimide (PEI) [5,6] . Since the mechanical properties of the materials are determined by their final morphologies, much work has been focused on mechanism study of phase separation and morphology control [7][8][9][10][11][12][13] . Effective improvement in toughness can only be obtained at high fractions of the engineering thermoplastic [14,15] , where the thermoplastic forms a continuous phase with the epoxy spherical domain, or the thermoplastic and epoxy form a bicontinuous phase structure.…”

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

“…[1][2][3] Aromatic polyimide, which has a high glass transition temperature and high mechanical and thermal stability, has been used as a toughener, [4][5][6][7][8] and the cure kinetics, domain structures, and phase separation mechanisms have been studied for several polyimide-toughened epoxies by varying curing temperature, [9,10] initial concentration, [11,12] and molecular weight. [13] Fluorinated polyimide, which has a low dielectric constant and generally high thermal stability even under oxygen atmosphere, is expected to be a useful toughener, but an epoxy resin toughened by fluorinated polyimide has not been studied so far within our knowledge. We studied the morphological structures of phase-separated domains at various initial polyimide concentrations.…”

Studies on the Phase Separation of Poly(ether imide)-Modified Epoxy Resin, 5. Phase Separation Behavior of a Quasi-Binary System

“…work, [7] it seemed that NG might be involved in the poly-(ether imide)-modified epoxy systems, together with SD. Meanwhile it is necessary to concentrate on the choice of experimental method because different investigating methods may produce different results.…”