In this investigation, our aim was to evaluate the performance of a controlled release of malathion pesticide loaded in microspheres of pure polymers of poly(3-hydroxybutyrate) and poly(e-caprolactone) (PCL) and of blends of these polymers with compositions of 70/30, 80/20, 90/10, 95/5, and 97/3 w/w. Microspheres were obtained by an emulsion-evaporation method to load a model pesticide. Scanning electron microscopy and differential scanning calorimetry were used to characterize the effect of the pesticide on the morphology and particles size of the biodegradable microspheres. The interaction between the matrix and pesticide was determined by Fourier transform infrared spectroscopy. The test for controlled release was performed in an aqueous medium, and malathion was quantified by ultraviolet spectroscopy. The results show that the release of malathion was improved with the PCL content in the blends; this indicated the possibility of modulating the release of the pesticide in these biodegradable blends.

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In this study the effects of the dispersion of carboxylated single-walled carbon nanotubes (SWCNT-c) in epoxy matrices using two different routes were investigated. In the first route, SWCNT-c were dispersed in the resin using solvent and tip sonication. In the second route, SWCNT-c were dispersed in the hardener in two different ways: with and without solvent, but both with tip sonication. For comparison purposes, neat epoxy was also prepared using the same curing conditions. The samples were characterized via mechanical and dilatometric testing, raman and FTIR analyses, SEM images, and dilatometric tests. An increase of 88% was found for Young’s modulus in the route with dispersion in the resin aided by solvent. Dispersing the SWCNT-c into the hardener showed a significant increase in some mechanical properties, indicating that this is a possible route for preparing nanocomposites. In addition it was observed that all nanocomposites presented smaller volumetric expansion than neat epoxy.

In this study, carboxylated (SWCNT-c) and pristine (SWCNT) single-walled carbon nanotubes were randomly dispersed in a hardener prior to mixing it with an epoxy resin. The influence of several parameters on the dispersion process were investigated. The produced samples were characterized by infrared spectroscopy, differential scanning calorimetry, dilatometry, dynamic mechanical analysis, scanning electron microscopy and mechanical testing (tensile, flexural and microhardness). The results obtained with the nanocomposites with SWCNT-c suggested that the lowest time and amplitude of sonication improved the mechanical properties. The use of a solvent (acetone) was important to improve dispersion, ultimately increasing microhardness and Young's Modulus up to 32%. Nanocomposites with 0.25 wt. (%) SWCNT-c presented superior mechanical properties compared to those with 0.50 wt. (%) SWCNT. Two simple mathematical models (rule of mixtures and Halpin-Tsai) were used to predict Young's Modulus of the composites yielding results very close to the experimental ones.

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