Abstract Modification of composite components has been proposed as a tool to improve their functional properties. The present work studied crosslinking of a starch/oat hull mixture by reactive extrusion with sodium trimetaphosphate (STMP), for application in composites with polylactic acid (PLA). The treated mixture was characterized regarding degree of substitution, FT-IR, and thermal properties. The native and modified mixtures were processed by injection molding, together with PLA and glycerol. The microstructure, mechanical properties, shrinkage, density, and thermal properties of the composites were determined. The FT-IR results, increase in phosphorus content and thermal stability after starch/fiber mixture treatment with STMP suggested the occurrence of crosslinking. Better interfacial adhesion between oat hulls and the polymeric matrix was observed in electron micrographs of the composites containing the modified components. Slight decreases in tensile strength and modulus were observed in the modified composites, suggesting that extrusion and subsequent milling may have broken some structures/linkages.

Abstract This work investigated the influence of microcrystalline cellulose (MCC) in thermoplastic starch/poly (butylene adipate-co-terephthalate) films produced by blown extrusion, using different MCC contents (4, 7 and 10 g.100 g-1). The films were characterised for their mechanical, structural and barrier properties. Increasing fibres concentration reduced the tensile strength (6.9 to 4.6 MPa), the elongation at break (568 to 147%) and weight loss in water (12.8 to 11.1%) of the films. The rigidity of the films increased from 19.8 MPa (without MCC) to 79.2 MPa in the samples with 10 g.100 g-1 of MCC. SEM images showed the occurrence of some agglomerates in this sample. The water vapour permeability of the films was not affected by the presence of MCC. The production of starch/PBAT/MCC films by blown extrusion was successful; however some adjustments are necessary to improve the dispersion of the particles at the polymeric matrix.

Abstract The modification of lignocellulosic fibers can enhance their interaction with other materials and alkaline hydrogen peroxide (AHP) is a reagent widely used to promote such modification. This work aimed to modify oat hulls fibers by reactive extrusion using AHP (7 g 100 g-1 of hulls). The modified oat hulls displayed performances comparable to those observed by other researchers using conventional AHP method (without extrusion). The AHP treated oat hulls showed increased luminosity compared to the extruded ones. Fourier transform infrared spectroscopy showed differences between the modified and unmodified structures. The removal of surface compounds resulted in a more open morphology, with greater surface area and greater porosity. Reactive extrusion can be an alternative method for fiber modification with several advantages, such as short processing time and no wastewater generation.

AbstractThe demand for renewably sourced biodegradable materials has increased the need to produce materials that combine appropriate functional properties at competitive costs. Thermoplastic starch and polyester blends are an interesting alternative to current materials due to the low cost of starch and the functional properties and processability of the resulting blends. Producing thermoplastic starch (TPS) requires using a plasticiser at concentrations between 20 and 30%wt (in relation to starch). Glycerol is the most common plasticiser due to its high plasticising capacity and thermal stability at processing temperatures. The objective of this study was to evaluate glycerol waste from the biodiesel industry, with different degrees of purification, as plasticisers for TPS / poly (butylene adipate-co-terephthalate) (PBAT) blends. Different purities of glycerol produced films with similar mechanical, optical and barrier properties to those made with purified glycerol (99.7%). Therefore, crude glycerol is a renewable alternative plasticiser that reduces the cost of plasticisation by 6-fold.

The mechanical, viscoelastic and structural properties of starch/ poly (butylene adipate co-terephthalate) (PBAT) blown films produced by reactive extrusion were evaluated using citric acid (CA) and maleic anhydride (MA) as compatibilizers. Scanning electron microscopy images showed more homogeneous structure when CA and MA were included in the formulation. The tensile strength (MPa) was improved with the inclusion of the highest proportion of both compatibilizers (1.5 %wt). A larger elastic component with values between 0.42-0.45 for the degree of solidity (1-c1) was observed for the intermediate concentration of compatibilizers. A high level of glycerol (10 %wt) results in films with increased % elongation. Three partially miscible phases were observed in the blends. Biodegradable films of starch/PBAT with better properties could be produced by one-step reactive extrusion using CA and/or MA as compatibilizers.

O objetivo deste estudo foi investigar o efeito combinado de inulina, amido e leite nas características texturais de géis e de propriedades de pastas empregando o planejamento experimental de misturas. Foram avaliados o perfil viscoamilográfico e a firmeza dos géis. Em todos os parâmetros avaliados, os modelos ajustados mostraram-se influenciados pela presença de inulina, amido e leite, assim como de algumas interações desses ingredientes. A viscosidade máxima e a viscosidade final foram influenciadas positivamente pela concentração de amido e negativamente pelas interações deste com leite e com inulina. A firmeza dos géis aumentou com o aumento do teor de amido, mas a interação amido-inulina foi antagônica, contribuindo para diminuir essa característica. O efeito da interação entre amido e inulina pode ser explicado pelo fato de que a inulina possui maior afinidade pela água, em relação ao amido, ou, ainda, por agir como diluente, fazendo com que haja menor contato entre os grânulos e/ou cadeias de amido. A partir dos resultados encontrados neste estudo, verifica-se que a inclusão da inulina em sistemas amido-leite pode influenciar nas características texturais e de viscosidade, possivelmente refletindo-se nas características sensoriais. Com isso, a avaliação das interações com outros ingredientes da formulação torna-se essencial.

The objective of this work was to investigate the combined effect of milk, starch and inulin on the textural characteristics of gels and on the pasting properties, using an experimental mixture design. Gel firmness and the amylographic profile were evaluated. For all the parameters evaluated, the fitted models were shown to be influenced by the presence of inulin, starch and milk, as also some of the interactions between the ingredients. The maximum viscosity and final viscosity were positively influenced by the starch concentration and negatively by interactions between the starch and the milk and inulin. Gel firmness increased with increase in starch concentration but the starch / inulin interaction was antagonic, contributing to a decrease in this characteristic. The effect of the starch / inulin interaction could be explained by the higher water affinity of inulin as compared to that of starch, or because it acts as a diluent, decreasing the interaction between the starch granules and/ or chains. From the results found in this study it appears that the inclusion of inulin in milk-starch systems could influence the viscosity and textural characteristics and possibly reflect on the sensory characteristics. Thus, an evaluation of the interactions with the other ingredients of the formulation is essential.