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Blends of two semicrystalline polymers, poly(l-lactic acid) (PLLA) and poly-p-dioxanone (PPD) have been prepared by solvent casting in different compositions. Thermal, morphological, and mechanical properties of the blends were studied using modulated differential scanning calorimetry, wide-angle X-ray diffractometry, scanning electron microscopy (SEM), polarizing light microscopy (PLM), and tensile tests. Thermal analysis showed two glass transition temperatures nearly constant and equal to the values of the homopolymers and constant values of melting temperature (T m ) for all blend compositions, suggesting that both polymers are immiscible. The PLM and SEM observations validated these results, and showed the different morphology obtained by changing the composition of the blend. The blends 40/60, 50/50, and 60/40 presented a clearly macroseparated system, while the 20/80 and 80/20 blends presented better homogeneity, probably due to the low amount of one component in the other. It was found by PLM that PPD is able to crystallize according to a spherulitic morphology when its content is above 40%. Under this content, the crystallization of PPD is hardly observed. The blend 20/80 is more flexible, and tough material and neck formation during elongation is also observed, due to PPD, which may act as a plasticizer.

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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