The electrical, rheological properties and phase change behavior of polypropylene (PP)/ polystyrene (PS) blends filled with multi-walled carbon nanotube (MWNT) were investigated. Two kinds of masterbatch were used to prepare ternary blends of PP, PS, and MWNT, and the effects of the kinds of masterbatch were confirmed by phase morphology of ternary blends and the distribution of MWNT. From thermodynamic analysis, MWNT is expected to locate in PS phase and it shows a good agreement with the TEM observations. The ternary composites show the lowest conductive percolation threshold and fine morphologies when most MWNT particles are located at the interface. Time sweep test were carried out to monitor the phase coalescence of the ternary blends and MWNT migration and agglomeration in the PS phase during annealing. The enhancement of thermal properties of MWNT-filled blends was also investigated by DSC and TGA.

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Abstracts: Poly(ethylene-co-vinyl acetate) (EVA)/clay nanocomposites were prepared using a melt mixer and then crosslinked with electron beam irradiation. To improve the dispersion of clay in the EVA matrix, high-intensity ultrasound was imposed during mixing. The tensile strength increased and the elongation at break decreased with the irradiation dose, respectively. The tensile strength increased remarkably when ultrasound was applied for better dispersion. Thermogravimetric analysis (TGA) showed that the thermal stability of EVA/clay nanocomposites increased with the irradiation dose and the dispersity of clay. The improvement in the thermal and mechanical properties could be attributed to the enhanced dispersion of clay and the network formed by radiationinduced crosslinking.

The cure kinetics of the epoxy-layered, silicate nanocomposites were studied by differential scanning calorimetry under isothermal and dynamic conditions. The materials used in this study were o-cresol novolac epoxy resin and phenol novolac hardener, with organically modified layered silicates. Various kinetic parameters, including the reaction order, activation energy, and kinetic rate constants, were investigated, and the storage stability of the epoxy-layered silicate nanocomposites was measured. To synthesize the epoxy-layered silicate nanocomposites, the phenolic hardener underwent pre-intercalation by layered silicate. From the cure kinetics analyses, the organically modified layered silicate decreased the activation energy during cure reaction in the epoxy/phenolic hardener system. In addition, the storage stability of the nanocomposite with the pre-intercalated phenolic hardener was significantly increased compared to that of the nanocomposite with direct mixing of epoxy, phenolic hardener, and layered silicate. This was due to the protective effect of the reaction between onium ions and epoxide groups.

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Solution and melt viscoelastic properties of controlled microstructure poly(lactide) J. Rheol. 55, 987 (2011); 10.1122/1.3609853 Model linear metallocene-catalyzed polyolefins: Melt rheological behavior and molecular dynamicsAbstract. The chain structure of polymer molecules is an important characteristic of polymers. In the polymer industry, in-situ processing during polymerization or a post-processing is applied to alter the chain structure as an attempt to produce polymers with tailored properties. Among various methods to control the chain structure, ultrasound-induced polymer chain scission is a useful route which can either be used as a post-processing step or can be used during ultrasound-induced polymerization. In our previous studies, we intended to induce degradation of polymer melts in a sonicated intensive mixer and extruder By combining high intensity ultrasound which causes chain scission of polymer molecules and a multifunctional agent (MFA) having double bonds at its ends, we were able to modify the molecular structure of polycarbonate (PC) from linear to branched structure during melt processing. The three double bonds in chain ends of MFA were expected to act as sites for trapping macroradicals of PC during the course of ultrasound-assisted mixing process. The transformation of molecular structure of PC was confirmed by the measurements of rheological properties of the modified PC.