Jun Cui

On polyetherimide modified bismaleimide resins, 1 : Effect of the chemical backbone of polyetherimide

Four kinds of polyetherimides with different diamines were prepared and used to improve the toughness of bismaleimide resins composed of bis(4-maleimidediphenyl)methane and o,o-diallyl bisphenol A. Dynamic mechanical analysis and scanning electron microscopy were used to characterize the phase structure of the modified resins. The modified resins display different phase morphologies depending on the polyetherimide backbone structure. The results indicate that the degree of phase separation leads to different morphologies and toughening. The fracture energy (G IC ) was increased by 300% with the PIM modified system.

Studies on the phase separation of polyetherimide modified tetrafunctional epoxy resin. II. Effects of the molecular weight

ABSTRACT The effects of molecular weight on the phase separation of phenyl-terminated polyetherirnide (P-PEI) modified tetraglycidyl-4,4′-di-aminodiphenylmethane (TGDDM) diaminodiphenylsulfone (DDS) systems were investigated by using Differential Scanning Calorimetry (DSC), Time-resolved Light Scattering (TRLS) and Scanning Electron Microscope (SEM). The P-PEI modified systems showed faster cure rate than the neat epoxy resin. An increase of the molecular weight of P-PEI raised the cure rate of the modified systems and changed the morphology from polyetherimide-rich domain in the low molecular weight P-PEI modified system to polyetherimide-epoxy co-continuous phase structure in the high molecular weight ones. The phase separation of high molecular weight P-PEI modified systems may proceed as a two stage process and result in the epoxy-rich spherical domains dispersed in the P-PEI-rich matrix.

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

In this work we present a quasi-binary system for the study of reaction-induced phase separation. Differential scanning calorimetry (DSC) shows that the reaction mechanism of epoxy resin cured by C11Z-CNS imidazole is simple without being affected by the addiction of poly(ether imide) (PEI). The phase structure of interconnected globules was observed by scanning electron microscopy (SEM), and the phase separation is driven by spinodal decomposition as introduced by synchrotron radiation small-angle X-ray scattering (SR-SAXS).

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

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 PEl-rich phase to separate in an early stage of curing. As a result, the separated phase, about 10-20 μm in dimension with fine structure in it, is not the same as that observed in ordinary phase separation processes.

Effect of hydroxyl-terminated polyethersulfone on the phase separation of polyetherimide-modified epoxy resin

Hydroxyl-terminated polyethersulfone (HPES) is added as a second toughener to a polyetherimide (PEI)-modified epoxy resin, and phase separation initiated by curing is studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and time-resolved light scattering (TRLS). SEM shows that, by addind HPES with a higher molecular weight, phase inversion can be observed at different temperatures, and the dispersed particles show a bimodal size distribution. THe TRLS experiment reveals that the peak scattering vector q m shifts towards a smaller angle or towards a larger angle, depending on the molecular weight of HPES added. The TEM experiment shows that, at an early stage of phase separation, dissimilar morphologies are observed when HPES of different molecular weights is added. The rheometry and TRLS results indicate that the morphology is pinned up by the low mobility of the two components before gelation or vitrification.

Studies on the phase separation of a polyetherimide-modified epoxy resin, 4. Kinetic effect on the phase separation mechanism of a blend at different cure rates

Keeping the same thermodynamics of the blend, the kinetic effect on the pase separation mechanism of polyetherimide modified epoxy resin systems was studied. With the changes of cure rates phase separation in the reacted blends takes place. The process of phase separation is traced by time-resolved light scattering (TRLSand the final morphology is observed by scanning electron microscopy (SEM). The early stage of phase separation is analyzed using Cahns linearized theory, while the scaling postulate is tested in the late stage. The effect of the competition between thermodynamics and kinetics on phase separation mechanism is discussed.

Studies on the Phase Separation of Polyetherimide Modified Tetrafunctional Epoxy Resin. III. Morphology Development of the Blend During Curing

ABSTRACT Using scanning electron microscope (SEM), differential scanning calorimetry (DSC) and time-resolved light scattering (TRLS) methods, the morphology development of novel polyetherimide modified tetreglycidyl-4,4′-diaminodiphenylmethane (TGDDM) epoxy resin was investigated. The phase separation took place early in the blend and morphology was fixed in the first 10 minutes of curing. Then, the diffusion of the epoxy and the polyetherimide molecules still existed till the final stage of curing.