Polypropylene powder and sisal fibers were oxygen plasma treated, and the mechanical properties of their composites were tested. Two main effects were investigated: the incorporation of oxygen polar groups in the polypropylene surface and the surface degradation and chain scission of both polypropylene and sisal fibers. Prior to these treatments, three reactor configurations were tested to invesbgate the best condition for both effects to occur in PP films. Results showed that polypropylene-cellulose adhesion forces are about an order of magnitude higher for PP f i l m treatments at 13.56 MHZ than at 40 kHz owing to much hgher chain scission at lower frequencies, although it probably also occurs at high frequency and high power. Polypropylene powder treated with oxygen plasmas in optimum conditions for polar group incorporation did not result in improvement in any composite mechanical property, probably owing to the polymer meltmg. Sisal fibers and PP powder treated in conditions of surface degradation did not improve flexural or tensile properties but resulted in higher impact resistance, comparable to the improvement obtained with the addition of compatibilizer.

The effect of the filler content and size, as well as accelerated aging on the mechanical properties of polypropylene composites reinforced with woodflour (WF/PP) were evaluated. The composites were prepared by the extrusion of polypropylene with woodflour (Pinus elliotti) based on following ratios: 15, 25 and 40 wt% with two different granulometries. The specimens were injection molded according to ASTM standards. The composite properties did not show significant differences as a function of the filler granulometry. We also observed that by increasing the filler content, both the mechanical properties and the melt flow index (MFI) decreased, and the elasticity modulus, hardness and density increased. Concerning the accelerated aging, the composite presented a reduction in tensile properties. The results showed that the composite properties are extremely favorable when compared to other commercial systems reinforced by inorganic fillers

Pyrrolo-[3,2-b]pyrroles represent a class of promising materials for application in organic electronics with interesting optoelectronic properties and great synthesis versatility, but yields obtained from varied synthetic routes are still very low, hindering their effective application for industrial purposes. In this report, we present a method for the synthesis of tetraaryl-1,4-dihydropyrrolo-[3,2-b]pyrrole derivatives by multicomponent reactions employing niobium pentachloride as a catalyst. The optical characterization of the products is also presented. Electronic structure calculations were performed to help the interpretation of the synthesis process, as well as the optical properties of the systems. Excellent yields and low reaction times were obtained, indicating that NbCl 5 is an efficient catalyst for such systems. The products show promising properties for optoelectronic applications that can be adjusted by the choice of benzaldehyde derivatives used in the synthesis.

The effect of molecular weight, particle number density, and charge ratio on the colloidal behavior of positively charged polystyrene particles (PSA) in the presence of the natural polyanion carboxymethyl cellulose (CMC) was investigated by zeta potential and light scattering measurements. For low ionic strength, a phase diagram with three distinct regimes was proposed. Flocculation is favored for R values close to 1, where R is the ratio of the total negative charge (N tn ) to the total positive charge (N tp ). Colloidal stabilization is achieved in the R range of 2.5-200 and with polyelectrolytes chain length smaller than the critical chain length (L crit ), which is the contour length corresponding to the particle mean perimeter. For R values larger than 200, isolated particles and/or doublets are present in the dispersion and with polyelectrolytes chain length smaller than L crit , whereas doublets and/or aggregates are observed when the polyelectrolytes chain length is larger than L crit . The effect of the particle number density on the colloidal stabilization was weak. The adsorption behavior of CMC onto PSA particles was not comparable to that of CMC onto PSA films.

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