This work studies the possibility of reusing flexible postconsumed polyurethane foams modified by grafting with polystyrene as a sorbent material for the mitigation of oil spills. Different foams were evaluated via crude oil sorption and retention experiments, density, and morphological analyses. The foams with the best performance were chemically modified by grafting with polystyrene under different conditions (initiator concentration, styrene volume, and reaction time) in a system initiated by oxi-reduction of Ce(IV) from an amoniacal ceric nitrate solution. A three-level factorial design was used to study the influence of the variables. The foams were characterized via spectroscopy (XPS/ESCA and infrared) and water and oil sorption. Foam modification via grafting with polystyrene showed to be a viable alternative to increase its oil sorption ability.
Este trabalho descreve a importância e a conveniência dos procedimentos multivariados de otimização experimental, destacando as vantagens e aplicações dos sistemas de planejamento fatorial que permitem avaliar simultaneamente o efeito de um grande número de variáveis, a partir de um reduzido número de experimentos. Por meio de um exemplo prático é apresentada uma discussão do efeito da interação entre as variáveis e o estabelecimento de ótimos verdadeiros na otimização de parâmetros experimentais envolvidos na fotopolimerização do metacrilato de metila (MMA) comercial, na forma de oligômero, denominado "cola BERKEL", por radiação UV. Aspectos relativos ao desenho experimental e à interpretação de resultados também são apresentados. PALAVRAS-CHAVE: Planejamento fatorial; análise multivariada; fotopolimerização; metacrilato de metila (MMA).
ABSTRACT:This paper describes both the value and the role of multivariated methods of experimental procedure in scientific research. It is highlighted the advantages of factorial design systems which let simulate simultaneously several variables concerned a studied system, reducing the number of experiments of the research. The impact of these variables on the photopolymerization system is discussed upon the photocure of oligo(methyl methacrylate) (MMA), commercially called Berkel glue B 20, initiated by an UV light source. As feedback of the system it was measured the quantity of oligomer converted to polymer (in weight), finding the polymerization rate (in percent). Aspects related to the experimental design and the interpretations of results are also presented. KEY-WORDS: Factorial design; multivariate analysis; photopolymerization; methyl methacrylate (MMA).
Microparticles of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and poly(ε-caprolactone) (PCL) containing resveratrol were successfully prepared by simple emulsion/solvent evaporation. All formulations showed suitable encapsulation efficiency values higher than 80%. PHBV microparticles revealed spherical shape with rough surface and presence of pores. PCL microparticles were spherically shaped with smooth surface. Fourier-transformed infrared spectra demonstrated no chemical bond between resveratrol and polymers. X-ray powder diffraction patterns and differential scanning calorimetry analyses indicated that microencapsulation led to drug amorphization. These PHBV/PCL microparticles delayed the dissolution profile of resveratrol. Release profiles were better fitted to biexponential equation. The hypochlorous-acid-scavenging activity and 2,2-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation discoloration assay confirmed that the antioxidant activity of PHBV/PCL microparticles was kept, but was dependent on the microparticle morphology and dissolution profile. Resveratrol-loaded PHBV/PCL microparticles showed no cytotoxic effect on red blood cells.
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