Gizilene M. Carvalho

Cassava starch films containing acetylated starch nanoparticles as reinforcement: Physical and mechanical characterization

This paper reports the use of acetylated starch nanoparticles (NPAac) as reinforcement in thermoplastic starch films. NPAac with an average size of approximately 500 nm were obtained by nanoprecipitation. Fourier transform infrared (FTIR) and thermogravimetric analysis (TGA) indicated that NPAac are more thermally stable and essentially amorphous when compared with acetylated starch. Thermoplastic starch films with different proportions of NPAac (0.5, 1.0, 1.5, 10.0%, w/w) were obtained and characterized by scanning electron microscopy (SEM), water vapor permeability (WVP), adsorption isotherms, TGA and mechanical tests. The inclusion of reinforcement caused changes in film properties: WVP was lowered by 41% for film with 1.5% (w/w) of NPAac and moisture adsorption by 33% for film with 10% (w/w) of NPAac; and the Youngs modulus and thermal stability were increased by 162% and 15%, respectively, for film with 0.5% (w/w) of NPAac compared to the starch film without the addition of NPAac.

Physical and structural characterisation of starch/polyester blends with tartaric acid

Starch/PBAT blends were produced by reactive extrusion with tartaric acid (TA) as an additive. The effects of TA, glycerol and starch+PBAT on the mechanical, optical and structural properties of the films were evaluated, with formulations based in a constrained mixture design. Tartaric acid acts as a compatibiliser and promotes the acid hydrolysis of starch chains. These two functions explain the observed film resistance and opacity. TA reduced the weight loss in water. Scanning electron microscopy (SEM) images showed that TA reduces the interfacial tension between the polymeric phases, resulting in more homogeneous films. Nuclear magnetic resonance ((13)C CPMAS) and Fourier transform infrared spectroscopy (FT-IR) suggest that tartaric acid is able to react with the hydroxyl groups of the starch by esterification/transesterification reactions, confirming its role as a compatibiliser. The addition of TA results in materials with better properties that are suitable for use in food packaging.

ISOLATION AND CHARACTERIZATION OF NANOFIBRILLATED CELLULOSE FROM OAT HULLS

The objectives of this work were to investigate the microstructure, crystallinity and thermal stability of nanofibrillated cellulose obtained from oat hulls using bleaching and acid hydrolysis at a mild temperature (45 oC) followed by ultrasonication. The oat hulls were bleached with peracetic acid, and after bleaching, the compact structure around the cellulosic fibers was removed, and the bundles became individualized. The extraction time (30 or 60 min) did not affect the properties of the nanofibrillated cellulose, which presented a higher crystallinity index and thermal stability than the raw material (oat hulls). The nanocellulose formed interconnected webs of tiny fibers with diameters of 70-100 nm and lengths of several micrometers, producing nanofibers with a relatively high aspect ratio, thus indicating that these materials are suitable for polymer reinforcement.

Nanocellulose Produced from Rice Hulls and its Effect on the Properties of Biodegradable Starch Films

Rice hull is a residue from agro-industry that can be used to produce nanocellulose. We produced nanocellulose from rice hulls through bleaching (with a 5% NaOH solution followed by a peracetic acid solution) and acid hydrolysis at a mild temperature (45oC) followed by ultrasonication. We investigated the microstructure, crystallinity and thermal stability of these materials and studied their effects on the properties of starch films. After bleaching, the compact structure around the cellulosic fibers was removed, and the lignin content of the residue decreased from 7.22 to 4.22%. The obtained nanocellulose presented a higher crystallinity (up 70%), higher thermal stability than the raw material and lignin contents below 0.35%. The nanocellulose formed interconnected webs of tiny fibers (< 100 nm in diameter), which decreased the opacity, water vapor permeability and improved the mechanical properties when added as reinforcement in the starch films.

Oat fibers modification by reactive extrusion with alkaline hydrogen peroxide

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.