Electrospun nanofibers were prepared from mixed solutions of partially hydrolyzed poly(vinyl alcohol) (PVA) and medium molar mass chitosan (CS) at different solution compositions, at 15 and 20 kV. The mats were visualized by scanning electron microscopy (SEM), and the average diameters of nanofibers were determined. Three of these solutions were chosen for further studies, to elucidate the influence of CS on the mats properties. Electrospinning at 15 kV had a higher tendency to produce nanofibers free of defects, in which the diameters (157 to 189 nm) were not affected significantly by the total concentration and solution composition. Polymer interactions between the components were supported by infrared spectroscopy, thermogravimetry and dynamic mechanical analysis (DMA). The effect of CS composition was evidenced by DMA and tensile tests techniques. Immersion in water led to the breakage of nanofibers and flower-like morphologies.

Melt blending of 1:1 poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and glycerol-plasticized starch (TPS) was performed in the presence of an organically-modified montmorillonite, incorporated at 2.5, 5, 7.5 and 10 wt% amounts. Scanning electron micrographs (SEM) revealed the role of the organoclay as a compatibilizing agent for the immiscible blend. The blends were also characterized by X-ray diffraction (XRD), tensile tests, humidity absorption and soil burial biodegradation tests. The results indicated improved properties of the hybrid materials in relation to TPS alone, with a faster biodegradation rate than PHBV.

The use of biopolymers for the development of oxygen carriers has been extensively investigated. In this work, three different ABA triblock copolymers were synthesized and used to encapsulate purified bovine hemoglobin, using a double emulsion technique. The effect of polymer composition, homogenization velocity, and addition of a surfactant, on the protein entrapment was evaluated. These copolymers, which have a hydrophilic block, achieved higher values of encapsulation efficiency than the corresponding homopolymers. The increase in homogenization strength also promoted an increase in encapsulation efficiency. Capsules formation occurred even in the absence of PVA.

Liquid polybutadiene (PBLH) was modified with maleic anhydride (MA). The material (PBLHM) was characterized and used to prepare hybrid materials by blending with glycerol-plasticized cassava starch (TPS) and an organophilic clay at 5 wt% content. Processing was performed by extrusion under mild conditions and led to TPS/PBLHM/clay hybrids, at 95/5 to 85/15 TPS/PBLHM compositions, which were characterized by contact angle measurements, X-ray diffraction and mechanical analysis. The results revealed a reduction in the hydrophilicity and the reinforcement of the hybrid materials. Biodegradability tests showed that the addition of clay and of PBLHM led to materials with high biodegradability.

Amidos termoplásticos plastificados com glicerol (TPS), e reforçados com bentonita cálcica, foram preparados por extrusão. A morfologia dos materiais extrusados foi analisada por microscopia eletrônica de varredura. Foram avaliados os efeitos do teor de argila e do teor de glicerol sobre as propriedades físicas dos materiais. Os resultados de difração de raios X mostraram que o aumento no teor de glicerol contribuiu para o aumento da cristalinidade do tipo B. A adição da argila levou a materiais híbridos com propriedades melhoradas em relação ao TPS sozinho, mesmo após o envelhecimento sob condições de umidade relativa do ar de 80% durante 90 dias. A difração de raios X também permitiu a avaliação da intercalação da argila na matriz de amido, antes e após o condicionamento. Resultados de testes mecânicos sob tensão uniaxial sugeriram um alto grau de exfoliação.

Glycerol-plasticized corn starch materials (TPS), reinforced with calcium bentonite, were prepared by melt extrusion. Scanning electron microscopy was used to visualize extrudates morphology. The effects of clay content and of glycerol content on physical properties of extrudates were evaluated. As determined by X-ray diffraction, the increase in glycerol content led to materials with higher B-type crystallinity. Addition of clay resulted in hybrid materials with improved properties in relation to TPS alone, even after conditioning at a high relative humidity for 90 days. X-Ray diffraction was also used to evaluate clay intercalation within the polymeric matrix, before and after conditioning. Results from tensile tests suggested a high degree of exfoliation.

Chitosan/gelatin microparticles were prepared by complex coacervation. Three chitosan (CH) samples, with different acetylation degrees and intrinsic viscosities, were used together with commercial gelatin (G) samples. Microparticles formation was investigated at various CH/G ratios, within the pH range of 3.5 to 6.0. Reactions were carried out at 40 and 60 ºC, for 2, 4, and 6 hours. Turbidity measurements performed at 633 nm were used to monitor the process. The resulting curves revealed maximum values, which were correlated to the glucosamine content of CH samples. After isolation, yields were determined, and the microparticles were characterized by infrared spectroscopy (FTIR) and thermogravimetry (TGA). Both techniques evidenced the formation of coacervate microparticles. The highest yields in microparticles were determined for the system comprising the CH sample with the lowest degree of acetylation and intrinsic viscosity, and the gelatin sample with the lowest bloom strength.

Nanoesferas de carbono foram produzidas a partir de resíduos de petróleo, obtidos da produção de piches pela destilação de óleos decantados, pela técnica de deposição química de vapor a 1200 °C, sem catalisadores, em um processo contínuo. Três resíduos foram selecionados de forma a representar a faixa de propriedades tipicamente encontradas para este material. Nitrogênio e argônio foram empregados como gases de arraste. As nanoesferas obtidas apresentaram propriedades semelhantes para os três resíduos diferentes, sendo a influência do precursor menos significativa que a do gás de arraste empregado. Os rendimentos obtidos, na faixa de 40-50%, e a baixa sensibilidade do processo à composição do precursor indicam que o processo é adequado à utilização industrial.

Carbon nanospheres were produced from petroleum residues obtained in the production of petroleum pitches by distillation of decant oils, using chemical vapor deposition at 1200 °C, without catalysts and in a continuous process. Three residues were selected to represent the typical variability in the properties of this material. Nitrogen and argon were used as carrier gases. The three residues yielded nanospheres of similar properties, which were more influenced by the nature of the carrier gas. The mass yields of 40-50% and the low dependence on precursor composition indicate that the process is suitable for large scale industrial use.

A obtenção de piches mesofásicos para a produção de fibras de carbono de alta performance foi investigada por meio de tratamento térmico de três piches de petróleo, em dois estágios em um reator com agitação magnética e capacidade de 700 g. O primeiro estágio consistiu de um pré-tratamento sob agitação e atmosfera de nitrogênio a 0,9 MPa, a 390, 410 e 430 °C, durante três horas. No segundo estágio, o tratamento térmico foi realizado por mais três horas, sob pressão atmosférica. Durante os experimentos, amostras foram recolhidas e analisadas por meio de medidas de solubilidade em tolueno e quinolina, ponto de amolecimento e o percentual de mesofase. Foi verificado que, para todos os piches produzidos, nas temperaturas de 390 e 410 °C a variação dos parâmetros físico-químicos foi muito pequena e que os tratamentos térmicos no patamar de 430 °C produziram piches com pontos de amolecimento acima de 300 °C, e percentual de mesofase próximo a 70%.

Mesophase pitches, precursors of high-performance carbon fibers, were prepared from petroleum pitch by a two-stage heat treatment, in a reactor capable of heat treating 700 g of petroleum pitch under stirring. The process consisted of a pretreatment under pressure at 390, 410 and 430 °C under nitrogen atmosphere, at 0.9 MPa, for three hours, as the first stage, followed by another heat treatment under atmospheric pressure, as the second stage. To study the properties of the petroleum pitch samples, during the experiment, they were removed from the system. Quinoline insolubles, toluene insolubles, mesophase content and softening point of the samples were used to follow the pyrolysis process. The results revealed slight variations in the properties for the pitches produced at 390 and 410 °C. However, the pitch samples produced at 430 °C had softening points higher than 300 °C, and mesophase contents of around 70%.

A galactomanana de Prosopis juliflora (PJ) foi obtida por extração em água, a 50 °C, a partir de sementes moídas. As suas características estruturais e as propriedades em solução foram comparadas com as de uma amostra comercial de goma guar (GG). Após degradação parcial, as amostras resultantes foram submetidas à espectroscopia de 13C RMN. As razões manose/galactose de PJ (M/G = 1,64) e de GG (M/G = 1,85) foram determinadas a partir das áreas relativas aos picos atribuídos a C-1. A expansão das linhas do C-4 revelaram diferenças na estrutura fina das duas galactomananas. A viscosidade intrínseca determinada para a amostra de GG, [eta] = 10,3 dL g-1, foi ligeiramente maior do que a determinada para a PJ, [eta] = 9,4 dL g-1. Experimentos dinâmicos realizados nas mesmas concentrações mostraram comportamentos viscoelásticos similares para as duas gomas. Nenhum aumento no módulo de armazenamento (G<FONT FACE=Symbol>¢)</FONT> foi observado para misturas kapa-carragenana/PJ em 0,1 mol L-1 KCl em uma concentração total de 1,0 g L-1, em relação à kapa-carragenana sozinha. Géis fortes, obtidos pela mistura de kapa-carragenana e PJ ou GG em 0,25 mol L-1 KCl em uma concentração total de 10 g L-1 apresentaram propriedades mecânicas similares.

The galactomannan from Prosopis juliflora (PJ galactomannan) was extracted from milled seeds in water at 50 ºC. Its structural and solution properties were characterised in comparison with a commercial sample of guar gum (GG galactomannan). After partial degradation, the resulting samples were submitted to 13C-NMR spectroscopy. The mannose to galactose (M/G) ratios of PJ (M/G = 1.64) and GG (M/G = 1.85) galactomannans were estimated from the relative peak areas of the corresponding C-1 lines. Expansion of the C-4 lines revealed differences in the fine structure of the two galactomannans. The intrinsic viscosity determined for the GG sample, [eta] = 10.3 dL g-1, was slightly higher than that determined for PJ galactomannan, [eta] = 9.4 dL g-1. Dynamic experiments carried out at the same concentrations showed similar viscoelastic behaviours for the two gums. No enhancement in the storage modulus (G<FONT FACE=Symbol>¢</FONT>) was observed for kappa-carrageenan/PJ mixed solution in 0.1 mol L-1 KCl at 1.0 g L-1 total polymer concentration, in relation to kappa-carrageenan alone. Self-supporting gels obtained by mixing kappa-carrageenan and PJ or GG galactomannans in 0.25 mol L-1 KCl at 10 g L-1 total polymer concentration displayed similar mechanical properties.

O efeito das variáveis de extrusão de misturas de farinha de arroz polido (FAP) e de bagaço de jabuticaba (FBJ) foi estudado em função das características de adsorção de água e da estabilidade dos produtos extrusados (FME). A metodologia de superfície de resposta (MSR) do tipo 2³ foi usada para a obtenção de um modelo matemático preditivo para a estabilidade das farinhas. O desenho experimental foi elaborado para verificar o efeito de dois níveis de substituição de FBJ como fonte de fibra (15 e 25%), dois níveis de velocidade de rotação do parafuso (100 e 200 rpm) e duas condições de aquecimento na 3ª zona do extrusor (120 e 180ºC), originando oito tratamentos. As características de adsorção de água das FAP, FBJ e de suas misturas foram comparadas e estudadas por meio de isotermas de adsorção expressas como atividades de água (A W), que variaram de 0,113 a 0,973, a temperatura de 25ºC. Os dados experimentais das isotermas foram ajustados a modelos matemáticos de GAB, o que originou o coeficiente Xm (umidade de equilíbrio na monocamada) aplicada à MSR como variável resposta para avaliar a estabilidade das farinhas extrusadas. Os resultados obtidos permitiram verificar a importância das três variáveis durante o processo de extrusão. As curvas das isotermas apresentaram características de superfícies hidrofílicas de forma sigmoidal do tipo II. A região de umidade intermediária das isotermas revelou que a FAP adsorve maior quantidade de água por unidade de A W, seguida pelas misturas extrusadas. A FBJ mostrou ser menos higroscópica neste caso. Quanto à estabilidade das misturas extrusadas, as três variáveis de extrusão foram significativas, verificando-se um aumento com o aumento da FBJ e com o aumento da temperatura, enquanto que houve um decréscimo com a velocidade de rotação, porém, de menor efeito. A combinação de valores elevados de temperatura e porcentagem de FBJ aumentou a estabilidade das farinhas extrusadas.

It was studied the effect of extrusion variables on the water absorption characteristics of pre-gelatinized flours (FME) resulting from the extrusion of white rice (FAP) and jabuticaba (Myrciaria jaboticaba) dried bagasse flour (FBJ). Response surface methodology (RSM) type 2³ was used as a predictive mathematical model to evaluate the flour stability. The experimental design was used to study the effect of two levels of FBJ replacement as a fiber source (15 and 25%), two levels of screw speed (100 and 200 rpm) and two temperatures of the 3rd heating zone (120 and 180ºC) resulting in eight treatments. The water absorption of FME, FAP and FBJ were compared by analysing the absorption isotherms water activity (Aw), which varied from 0.113 to 0.973 at 25ºC. The isotherms experimental data were adjusted to GAB mathematical model, which generated the Xm (equilibrium moisture of the monolayer) coefficient applied to RSM as a variable response to evaluate the stability of the pre-gelatinized flours. The results showed the importance of the three variables during the extrusion process. The isotherms curves presented a typical surface hydrophilic characteristic having a sigmoidal type II shape. The region of intermediate moisture revealed that FAP adsorbed higher water content per unit of Aw, followed by FME. FBJ showed the lowest hygroscopic character. Concerning the stability of pre-gelatinized flour, the three extrusion variables were statiscally significant. The stability increased with the increase of FBJ flour content and also with the extruder temperature, whereas it decreased as the screw speed reduced, although with lower effect. The combination of high temperature and FBJ content improves the stability of the extruded flours.

Medidas reólogicas sob cisalhamento oscilatório foram realizadas em reômetro de tensão e deformação controladas com suspensões de concentrado de proteínas do soro do leite (WPC) a 10% (m/m) em água e a diferentes condições de pH (pH 4,0, 4,6 e 7,0). O processo de gelificação induzida pelo calor foi investigado, assim como as propriedades viscoelásticas dos géis formados a 80°C e daqueles formados após o decréscimo da temperatura a 20°C. Foi verificado que, em presença de teores significativos de sais, procedentes do próprio soro, a concentração usada nos experimentos foi suficiente para a formação de géis macroscópicos, e que o pH exerce papel importante na formação e na natureza estrutural dos géis.

Rheological measurements have been carried out in a controlled stress and strain rheometer on a whey proteins concentrate (WPC) at 10% (w/w) in water and at different pH conditions (pH 4.0, 4.6 and 7.0). The heat-induced gelation process was investigated, as well as the viscoelastic properties of the gels formed at 80°C and those formed after decreasing the temperature to 20°C. The results indicated that, in the presence of significant contents of salts from the whey sample, the concentration used in the experiments was sufficient for the formation of macroscopic gels, and that the pH exerts an important role on the formation and on the structural nature of the gels.

Aging of cornstarch films prepared by casting was investigated. Water and glycerol-plasticized cornstarch films were stored at 50% relative humidity over a period of 330 days. Aging was followed by X-ray diffraction (XRD) and atomic force microscopy (AFM). XRD spectra indicated development of B-type crystallinity even for fresh films and that the crystallinity index increased from 0.06 to 0.28 as a function of storage time. AFM images of 270-day-old films revealed that the general morphology and the overall roughness have not changed due to aging. AFM phase contrast images at higher magnification showed an increasing number of ordered domains at the surface of these films, which may be attributed to recrystallization of amylose. No morphological change was observed at least at the surface of the granular region, which is enriched in amylopectin.

Misturas de amido de milho e água nas proporções 70:30, 80:20 e 90:10% (p/p) foram submetidas a processamento a 90°C, sob diferentes velocidades de rotação (20, 40, 80 e 100rpm), em câmara de mistura Rheomix 600 equipada com rotores do tipo "roller". A influência do teor de água e da velocidade de rotação dos rotores no processamento do amido de milho foi investigada por meio de curvas de torque e de temperatura fornecidas pelo reômetro de torque Rheocord 9000. Análises em Analisador Rápido de Viscosidade e por microscopia óptica de luz polarizada foram realizadas, a fim de complementar as informações registradas pelas curvas de torque e de temperatura. Os resultados mostraram que o teor de água e a rotação empregada no processamento exercem influência significativa nas características do amido processado. Os menores teores de água (10 e 20% p/p) e as velocidades de rotação mais elevadas (80 e 100rpm) contribuíram para a maior degradação do amido. Nas misturas com teor de água de 30% (p/p), sob as velocidades de rotação empregadas, a função plastificante da água contribuiu para minimizar o efeito do cisalhamento, já que a degradação do amido não foi observada. Nesses casos, a estrutura granular do amido foi preservada em grande parte durante o processamento.

Corn starch/water mixtures at compositions of 70:30, 80:20 and 90:10 (w/w %) were submitted to processing at 90ºC and different rates (20, 40, 80 and 100rpm) in an internal mixer (Rheomix 600), equipped with counter-rotating roller type rotors. The effect of the water content and of the rotation rate on the starch processing was investigated by torque and temperature curves given by the in-line Rheocord 9000 torque rheometer. Viscosity measurements, carried out in a Rapid Visco Analyser (RVA), and optical microscopy analysis were performed on the processed samples to complement the rheometry data. The results indicated that the water content and the rotation rate had a significant effect on the characteristics of the processed starch samples. For compositions with 10 and 20% (w/w) water contents and processed at 80 and 100rpm, degradation was observed at a larger extent. For compositions in which water had been added at a 30% (w/w) content, its plastifying property contributed to minimize degradation caused by mechanical and thermal inputs. In these cases, the granular structure of starch was largely preserved.

Devido ao baixo custo de produção e excelente biodegradabilidade, o amido constitui-se em matéria-prima promissora para a produção de plásticos biodegradáveis. No entanto, a grande hidrofilicidade dos filmes à base de amido representa uma séria limitação tecnológica à sua comercialização, uma vez que as propriedades dos filmes são afetadas pela variação da umidade relativa do ar durante a sua estocagem ou o seu uso. Neste trabalho, filmes de amido termoplástico foram recobertos com uma fina camada protetora polimérica gerada por intermédio da tecnologia de plasma frio. 1-Buteno e 1,3-butadieno foram utilizados como monômeros para a polimerização por plasma. Os filmes recobertos apresentaram uma redução de até 80% na absorção de água e aumento do ângulo de contato em relação à água. Estes resultados indicaram uma redução significativa na natureza hidrofílica do material à base de amido após o recobrimento.

Due to low cost and excellent biodegradability, the use of starch as a raw material for bioplastic production is growing in interest. However, the properties of starch-based materials are affected by relative humidity during their use and storage due to their hydrophilic character. In this work, thermoplastic cornstarch films were coated by cold plasma technology with a protective thin layer in order to reduce water sensitivity. 1-Butene and 1,3-butadiene were used as monomers for plasma polymerization. Coated films presented a reduction of water absorption up to 80% an increase in contact angle related to water. These results indicated that the coating process reduced significantly the hydrophilic nature of the starch-based materials.

Os processos de gelatinização e de extrusão de amido de milho foram estudados. Calorimetria diferencial de varredura e miscroscopia óptica foram utilizadas na determinação da temperatura de gelatinização, T(G), em função do grau de umidade. Misturado a plastificantes, o amido foi processado em extrusoras mono- e dupla-rosca para obtenção de termoplásticos. As propriedades mecânicas dos filmes obtidos por processamento em extrusora dupla-rosca foram investigadas. A análise termo-dinâmico-mecânica do filme de amido termoplástico com 33% (p/p) de plastificantes revela a presença de duas transições distintas, atribuídas às transições das duas macromoléculas constituintes do amido.

The gelatinization and extrusion processes of corn starch were studied. Differential scanning calorimetry and optical microscopy were used to determine the gelatinization temperature, as a function of the water content. Plasticized corn starch was processed in single- and twin-screw extruders to produce thermoplastic materials. The mechanical properties of the films obtained in the twin-screw extruder were evaluated. The thermo-dynamical-mechanical analysis of the thermoplastic starch with 33% (w/w) plasticizers showed two transitions, attributed to the starch constituents.