The barrier and mechanical properties of polymer matrices are affected by the polymer crystallization kinetics and the incorporation of nanoparticles can modify the nucleation density as well as the rate and mechanism of crystallization. In this study, a nanocomposite of poly(lactic acid) (PLA) containing cellulose nanocrystals (CNC) was prepared in order to evaluate the effect of the CNC content on the crystallization kinetics of the polymer matrix. Dimethylformamide, a solvent of PLA, was used to replace the aqueous medium for the dispersion of the CNC, to facilitate the preparation of PLA films with dispersed CNC. Higher levels of CNC in the films induced an increase in the crystallization rate and reduced the degree of crystallinity without affecting the dimensions of the crystal lattice. In conclusion, the incorporation of CNC into PLA influences the crystallization kinetics, which significantly affects the PLA processing conditions.

<p>In recent decades, starch has been studied as a raw material due to low production costs. The limitations associated with starch being highly permeable to water vapor and its mechanical properties being dependent on the relative humidity have been investigated. The proprieties of thermoplastic starch/poly(lactic acid) (TPS/PLA) blends have been studied by researchers, as well as the incorporation of compatibilizers to improve the interfacial interaction between the blend components. The purpose of this study was to evaluate the effect of maleic anhydride (MA) as a compatibilizer and a plasticizer. The blends were prepared in a torque rheometer through different mixture processes. Blends prepared with grafted MA showed interfacial adhesion and small domains of PLA in the TPS matrix, due to the use of MA as a compatibilizer. The presence of free MA in the TPS/PLA blends affected the mechanical and thermal properties, suggesting a plasticizer effect.</p>

Blendas de poli(ácido láctico)(PLA) e amido termoplástico (TPS) foram preparadas por extrusão e moldagem por compressão utilizando 0,1, 0,2 e 0,3 g de PLA per g de TPS. O TPS foi obtido por extrusão utilizando 0,25 e 0,30 g de glicerol por g de amido. Foram avaliadas as propriedades mecânicas e de barreira ao vapor de água, e determinadas as isotermas de sorção de umidade. A morfologia dos materiais foi avaliada através de microscopia eletrônica de varredura e as propriedades térmicas dos polímeros puros e das blendas, através de calorimetria diferencial de varredura (DSC). A microscopia e os resultados de DSC indicaram a imiscibilidade da blenda e a presença de duas fases. Nas blendas contendo 20% e 30% de PLA observou-se um aumento da tensão de ruptura e do módulo elástico. A blenda contendo 30% de PLA apresentou uma redução da permeabilidade ao vapor de água, comportamento associado à redução do coeficiente de difusão observada nesta amostra.

Blends of poly(lactic acid) (PLA)/thermoplastic starch (TPS) were prepared by extrusion and thermopressing, with proportions of 0.1, 0.2 and 0.3 g of PLA per g TPS. Thermoplastic starch was obtained from the extrusion of 0.30 g or 0.25 g of glycerol per g of starch. The mechanical properties and water vapor permeability were tested and water sorption isotherms were obtained. The morphological characteristics of the samples were observed through scanning electron microscopy (SEM) and the thermal properties of the pure polymers and the blends by differential scanning calorimetry (DSC). The SEM and DSC results indicated the immiscibility of the TPS/PLA blends and the presence of two phases. For blends with 20% and 30% of PLA increases in the tensile strength and modulus were observed. The lowest water vapor permeability was observed for the blend with 30% of PLA, which is related to the lowest diffusion coefficient value observed for this sample.

Biodegradable films of thermoplastic starch and poly (butylene adipate co-terephthalate) (PBAT) containing fatty acids were characterized thermally and with infrared and Raman spectroscopies. The symmetrical character of the benzene ring in PBAT provided a means to illustrate the difference between these spectroscopic techniques, because a band appeared in the Raman spectrum but not in the infrared. The thermal analysis showed three degradation stages related to fatty acids, starch and PBAT. The incorporation of saturated fatty acids with different molecular mass (caproic, lauric and stearic) did not change the nature of the chemical bonds among the components in the blends of starch, PBAT and glycerol, according to the thermal analysis, infrared and Raman spectroscopies.

This paper describes the synthesis of asymmetric polymer membranes used for the production of drinking water. Filtration of water through the membranes is an alternative method for water treatment, where the membrane acts as a selective barrier which blocks the passage of some components. Water samples for this study were inoculated with 10(7) to 10(8) colony forming units (CFU) of Escherichia coli per ml. The process used was phase inversion, and the membranes were prepared beginning with polymer solutions, including polysulfone and polyvinylidene fluoride. In both cases polymethyl methacrylate was added to the polymeric solutions, using N,N-dimethylformamide as solvent. Some of the membranes prepared achieved bacterial removal of 99 to 100%, at a flow of 300 L/h m²

En este trabajo se presenta un estudio sobre la síntesis de membranas poliméricas asimétricas para la producción de agua potable. La filtración usando membranas es un proceso alternativo para el tratamiento de aguas, donde la membrana actúa como una barrera selectiva que bloquea el pasaje de algunos componentes. En este trabajo algunas muestras de agua fueron infectadas con 10(7) a 10(8) unidades formadoras de colonias (UFC) por ml con la bacteria Escherichia coli. El proceso utilizado fue la inversión de fases y las membranas fueron preparadas a partir de soluciones poliméricas, con polisulfona y con fluoruro de polivinilideno. En ambos casos, se agregó poli metacrilato de metilo a las soluciones poliméricas, usando N,N-dimetilformamida como solvente. Algunas membranas removieron entre 99 y 100% de las colonias bacterianas, con un flujo de 300 L/h m²