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Poly(phthalazinone ether ketone)s (PPEK) were used to toughen bismaleimide (BMI) resin composed of 4,4'-bis-maleimidodiphenyl methane (BMDM) and O,O-diallyl bisphenyl A (DABPA). Dynamic differential scanning cal-orimetry (DSC) of the blends was carried out for kinetic analysis of the curing reaction. The reaction activation energy indicated that the reaction mechanism remained the same even after the incorporation of PPEK. The reaction-induced phase separation process in BMI/ PPEK blends was investigated by optical microscopy (OM). The primary phase structure of the blends was fixed at the early stage of phase separation, and a secondary phase separation was observed as a result of the high viscosity of the blends. Scanning electron micro-scope (SEM) graphs showed that the morphology of the cured resin changed from a dispersed structure to a phase-inverted structure with the increase of PPEK content. Compared with the neat resin, the fracture toughness of the modified resin exhibits a moderate increase when PPEK was incorporated. Several toughening mechanisms, such as local plastic deformation, crack deflection, and branches, presumably took part in improving the toughness of BMI/PPEK blends on the basis of the morphology. POLYM. ENG. SCI., 49:2301-2308, 2009. [C] 2009 Society of Plastics Engineers, INTRODUCTION Bismaleimide (BMI) resins, as high-performance composite matrices, have been widely used in the aerospace field and electronic industry because of their good thermal stability, low water absorption, and good [...]

Nickel-coated multiwalled carbon nanotubes (Ni-MWNT) were prepared by electroless deposition with ultrasonic vibrations. The morphologies and components were characterized by scanning electron microscope and energy dispersive spectroscopy. Two types of fillers, multiwalled carbon nanotubes (MWNT) and Ni-MWNT, were blended with poly(phthalazinone ether sulfone ketone)s (PPESK) by the solution-mixing method, respectively. The electrical conductivity and microwave absorbing properties of the composites were investigated. The results show that Ni-MWNT/PPESK composites have relatively lower electrical resistivity values than MWNT/PPESK, and in both cases the decrease in electrical resistivity indicates a similar percolation transition behavior in the same MWNT content region. Moreover, as MWNT loading is 5 parts per hundred parts of resin (phr), Ni-MWNT/PPESK composite has the wider frequency region (9.5-13.5 GHz) of the reflection loss (RL) less than -10 dB and the lower minimum value of RL (-27.5 dB) compared with MWNT/PPESK. The better microwave absorption properties can be attributed to the improved dielectric and magnetic properties of the fillers. A good correlation between electrical conductivity and microwave absorption was found for MWNT/PPESK composites. In addition, tensile test and thermogravimetric analysis indicate that introducing Ni-MWNT into PPESK is favorable for the improvement of the mechanical properties and high temperature stability of the composites. POLYM. ENG. SCI., 48:1007-1014, 2008. © 2008 Society of Plastics Engineers, INTRODUCTION The development of microwave absorbing techniques continues to attract much attention because of the increasing environmental pollution from nonionizing microwave irradiation and the essential part of a stealth defense [...]