Dessorção iônica e degradação de filmes de polipirrol dopado com dodecilsulfato induzidas por elétrons de alta energia

Electron stimulated ion desorption (ESID) and degradation studies of polypyrrole doped with dodecylsulfate (PPy/DS) deposited on FTO were performed using time-of-flight mass spectrometry (TOF-MS) for ion analysis. The results suggest a strong contribution from fragments of the dodecylsulfate hydrocarbon chain to the mass spectra. In the 650-1500 eV energy range the ion yield curves show maxima at about 600, 1200 and 1400 eV, which can be related to carbon, nitrogen and oxygen-containing fragments, respectively, and interpreted in terms of the Auger Stimulated Ion Desorption (ASID) mechanism. Degradation studies indicate rapid loss of heavier hydrocarbons and an increase of bulk and substrate fragments. Some degradation profiles suggest formation of new species.

Análise dinâmico-mecânica: aplicações em filmes comestíveis

Edible films are thin materials based on biopolymers and food additives. The aim of this work is a review on the application of dynamic mechanical analysis in edible film technology. After a brief review of the linear visco-elasticity theory, a description of some practical aspects related to dynamic mechanical analysis, such as sample fixation and sample dehydration during analysis and types and modes of tests are presented. Thus, the use of temperature scanning analysis for glass transition and for plasticizer-biopolymer compatibility studies and frequency scanning tests, less common in edible film technology, are critically reviewed.

Obtenção de filmes finos de TiO2 nanoestruturado pelo método dos precursores poliméricos

This work focuses in optimizing setup for obtaining TiO2 thin films by polymeric precursor route due to its advantages on stoichiometric and morphological control. Precursor stoichiometry, synthesis pH, solids concentration and rotation speed at deposition were optimized evaluating thin films morphology and thickness. Thermogravimetry and RMN were applied for precursor's characterization and AFM, XRD and ellipsometry for thin films evaluation. Results showed successful attainment of homogeneous nanocrystalline anatase TiO2 thin films with outstanding control over morphological characteristics, mean grain size of 17 nm, packing densities between 57 and 75%, estimated surface areas of 90 m²/g and monolayers thickness within 20 and 128 nm.

Aplicação de espectroscopias raman e infravermelho na identificação e quantificação de plastificantes em filmes comerciais de PVC esticável

This paper reports the use of Raman and infrared techniques for the qualitative and quantitative analysis of plasticizers in polyvinylchloride (PVC) commercial films. FT-Raman marker bands were indentified for di-2-ethyl-hexyl adipate (DEHA) and di-2-ethyl-hexyl phthalate (DEHP), allowing for the rapid identification of these species in the commercial film. Quantitative analysis by FT-IR resulted in plasticizers concentrations ranging from 11 to 27% (w/w). Considering the little sample preparation and the low cost of the techniques, FT-IR and FT-Raman are viable techniques for a first assessment of plasticizers in commercial samples.

Preparação, caracterização e propriedades de filmes poliméricos com potencial aplicação no recobrimento de sementes

Films of sodium carboxymethyl cellulose, sodium alginate and their mixture were evaluated in terms of interactions between the polymers, morphology, water absorption and application as seed coatings. FTIR analysis suggested that only hydrophobic interactions occurred between the polymers. The coating of bean seeds was confirmed by microscopy, indicating the formation of dense and homogeneous films with 7 μm thickness. The obtained films did not affect the germination capacity of the seeds. In summary, the characteristics and properties of the films formed and the water absorption capacity, indicate that these systems are viable for use in seed coating processes.

Alteração do caráter hidrofílico de filmes de quitosana por tratamento de plasma de HMDS

Alteration in hydrophilicity feature of chitosan films by hexamethyldisilazane (HMDS) cold-plasma treatment is evaluated. All treated films were colorless and transparent with no apparent textural changes. The effect on surfaces was characterized through contact angle measurements, degree of swelling and water vapor permeation. A significant reduction in all of the hydrophilicity parameters was observed. It is assumed that the HMDS treatment forms nonpolar silicone type structures. The goal is to investigate the formation of a stable hydrophobic barrier in order to increase the chitosan films usefulness in packaging applications.

Comparação da labilidade de metais empregando voltametria, difusão em filmes finos por gradiente de concentração (DGT) e modelo computacional

Speciation of metals in a synthetic freshwater was comparatively evaluated using Anodic Stripping Voltammetry, Diffusive Gradients in Thin Films and a Chemical Equilibrium Model. The labile fractions of Cu and Zn quantified by DGT were similar to the ones measured by ASV. The labile species of Cd and Pb could not be determined by both experimental methods due to the formation of inert complexes with organic ligands in the sample. Despite the differences among the methods, the speciation results obtained by the use of DGT and ASV agreed well with predictions made by the chemical equilibrium model.

Filmes ultrafinos de ésteres de celulose: preparo, caracterização e imobilização de proteínas

In this study cellulose acetate butyrate (CAB) and carboxymehtylcellulose acetate butyrate (CMCAB) films adsorbed onto silicon wafers were characterized by means of ellipsometry, atomic force microscopy (AFM), sum frequency generation spectroscopy (SFG) and contact angle measurements. The adsorption behavior of lysozyme (LIS) or bovine serum albumin (BSA) onto CAB and CMCAB films was investigated. The amounts of adsorbed LIS or BSA onto CMCAB films were more pronounced than those onto CAB films due to the presence of carboxymethyl group in the CMCAB structure. Besides, the adsorption of BSA molecules on CMCAB films was more favored than that of LIS molecules. Antimicrobial effect of LIS bound to CAB or CMCAB layers was evaluated using Micrococcus luteus as substrate.

Influência do tipo de ácido e tempo de envelhecimento na atividade fotocatalítica de filmes finos de TiO2

TiO2 thin films were prepared by the sol-gel method using different acids (HCl and HAc), with a parallel evaluation of the gel ageing effects on the film properties. After the thermal treatments, the resulting materials were characterized through gravimetric analysis, UV-VIS spectrophotometry (from which optical parameters such as band gap was derived), XRD, morphological surface analysis (AFM) and photocatalytic activity. The majority of the obtained thin films parameters were similar independent of the acid type and the ageing time of the gel. Nevertheless, a visible effect of the surface morphology properties on the films and their photocatalytic activity was observed.

Filmes de amidos de mandioca modificados para recobrimento e conservação de uvas

In this article, films were produced with six types of cassava's starch mixed with gelatin and plasticized with sorbitol. These films were used in covering of grapes 'Benitaka' (Vitis vinifera L.) as biodegradable packaging. The acetylated starch film showed the best results in solubility, thickness and homogeneity, besides the less water loss the fruit, resulting in better coverage, increasing the shelf life fruits in 12 days. These results demonstrate the great potential of using films in food conservation, adding value to agricultural activity and helping to reduce non-biodegradable plastics in the environment.

Fotoeletrodegradação do corante AO7 utilizando filmes de nanocompósitos de ZnO-TiO2

The Zn-TiO2nanocomposite films were prepared by electrodeposition, using an acidic zinc sulphate solution with TiO2 nanoparticles in suspension. The as-deposited samples have been heated in air at 450 ºC for 6 h. The XRD and SEM analyses pointed out to the metal matrix conversion from Zn to ZnO and a rich morphology of needles-shaped grains. These materials were used on the photoelectrochemical degradation of AO7, which was efficiently degraded, with 40% of color removal, after 2 h period at 1.0 V, under white light irradiation. The apparent first order rate constant of the photoelectrodegradation reaction was 4.12 x 10-3 min-1.

Estudo comparativo da caracterização de filmes biodegradáveis de amido de mandioca contendo polpas de manga e de acerola

Most compounds reinforcements have been used to improve thermals, mechanical and barrier properties of biopolymers films, whose performance is usually poor when compared to those of synthetic polymers. Biodegradables films have been developed by adding mango and acerola pulps in different concentrations (0-17,1% w/w) as antioxidants active compounds to cassava starch based biodegradable films. The effect of pulps was studied in terms of tensile properties, water vapor permeability, DSC, among other analysis of the films. The study demonstrated that the properties of cassava starch biodegradable films can be significantly altered through of incorporation mango and acerola pulps.

Propriedades físicas de filmes biodegradáveis à base de amido de mandioca, álcool polivinílico e montmorilonita

The objective of this work was to manufacture biodegradable films based on cassava starch, polyvinyl alcohol (PVA) and sodium montmorillonite (Na-MMT), using glycerol as a plasticizer. These films were characterized according to their microstructure, optical, mechanical, and barrier properties. The combination of starch-PVA-MMT resulted in films with a more homogeneous surface than starch films. The introduction of PVA into the starch matrix led to the formation of films with lower water vapor permeability (WVP), higher tensile strength and greater elongation. MMT was exfoliated in the films, resulting in greater stability for different relative humidities, lower WVP, higher resistance and lower flexibility.

Caracterização físico-química de filmes comestíveis de amido adicionado de acerola (Malphigia emarginata D.C.)

Edibles films are an alternative to synthetic materials used for packing food products. Barbados cherry is rich in vitamin C and carotenoids. The aim of this study was to characterize and develop films by casting from cassava starch, lyophilized Barbados cherry pulp and glycerol. The films were characterized with respect to thickness, water vapor permeability (WVP), water solubility, vitamin C, carotene and mechanical properties. The interaction of pulp and glycerol reduced film thickness. An increase in pulp concentration up to 60% increased WVP but beyond this concentration reduced both WVP and solubility leading to an increased level of vitamin C and β carotene in the films.

Fatores que influenciam a formação da fase β-PbO2 em filmes eletrossintetizados galvanostaticamente sobre substrato de tecido de carbono

PbO2 films were electroformed onto carbon cloth substrates (twill woven type) in acid conditions using the nitrate precursor by changing the electrodeposition current density, temperature and pH, in order to optimize the formation of the β-PbO2 phase. The crystal structure and morphology of the PbO2 films were investigated using X-ray diffraction (XRD) and scanning electronic microscopy (SEM) techniques. The optimum conditions obtained for formation of the β-PbO2 were presented and discussed.