Aloña Retegi

Starch and cellulose nanocrystals together into thermoplastic starch bionanocomposites.

In the present work, thermoplastic maize starch based bionanocomposites were prepared as transparent films, plasticized with 35% of glycerol and reinforced with both waxy starch (WSNC) and cellulose nanocrystals (CNC), previously extracted by acidic hydrolysis. The influence of the nanofiller content was evaluated at 1 wt.%, 2.5 wt.% and 5 wt.% of WSNC. The effect of adding the two different nanoparticles at 1 wt.% was also investigated. As determined by tensile measurements, mechanical properties were improved at any composition of WSNC. Water vapour permeance values maintained constant, whereas barrier properties to oxygen reduced in a 70%, indicating the effectiveness of hydrogen bonding at the interphase. The use of CNC or CNC and WSNC upgraded mechanical results, but no significant differences in barrier properties were obtained. A homogeneous distribution of the nanofillers was demonstrated by atomic force microscopy, and a shift of the two relaxation peaks to higher temperatures was detected by dynamic mechanical analysis.

Sustainable optically transparent composites based on epoxidized soy-bean oil (ESO) matrix and high contents of bacterial cellulose (BC)

Production of transparent composites from totally renewable resources with extraordinary potential for different applications can be made possible using cellulose. Composites of epoxidized soybean oil (ESO)/bacterial cellulose (BC) nanofibers have been prepared with high fiber content. Due to the nano-order scale network-like structure of BC nanofibers, composite films present high transparency even at high BC content. Transparency of films has been analyzed by UV–visible spectroscopy observing that only 15% of matrix transmittance is lost in the nanocomposites. ESO/BC composites show better mechanical properties with increasing BC content. Composites combine high stiffness and good ductility due to the incorporation of BC network structure in ESO matrix.

Conductive properties of TiO2/bacterial cellulose hybrid fibres

Conductive properties of TiO(2) nanoparticles and TiO(2)/BC hybrid inorganic/organic fibres were investigated by electrostatic force microscopy (EFM). TiO(2)/BC hybrid composites were prepared based on bacterial cellulose produced by Gluconobacterxylinum, being the bacterial cellulose as a hydrophilic substrate for TiO(2) nanoparticles synthesized via sol-gel. Taken into account hydrophilic nature of the cellulose, TiO(2) nanoparticles were located on the surface of the fibres due to hydrogen bonding interactions. EFM was used to determine qualitatively conductive properties of TiO(2) nanoparticles and their TiO(2)/BC hybrid inorganic/organic fibres. Results indicate that TiO(2)/BC hybrid fibres respond to applied bias regardless of the sign of the applied voltage.

Design of reusable novel membranes based on bacterial cellulose and chitosan for the filtration of copper in wastewaters

This study has been carried out to design novel, environmentally friendly membranes by in situ and ex situ routes based on bacterial cellulose (BC) as a template for the chitosan (Ch) as functional entity for the elimination of copper in wastewaters. Two routes led to bionanocomposites with different aspect and physico-chemical properties. The mechanical behaviour in wet state, strongly related to crystallinity and water holding capacity, resulted to be very different depending on the preparation route although the Ch content was very similar: 35 and 37 wt% for the in situ and ex situ membranes, respectively. The morphological characterization suggested a better incorporation of the Ch into BC matrix through the in situ route. The cooper removal capacity of these membranes was analyzed and in situ prepared membrane showed the highest values, about 50%, for initial concentrations of 50 and 250 mg L-1. Moreover the reusability of the membranes was assessed. This is the first time that the whole 3D nano-network BC membrane is used to provide physical integrity for chitosan to develop eco-friendly membranes with potential applications in heavy metal removal.

By-products of the cider production: an alternative source of nutrients to produce bacterial cellulose

In the present work a culture process to produce bacterial cellulose (BC) using by-products of the cider production from the Basque Country was investigated. The apple pomace was mixed with sugar cane (AR/SC medium) and the mixture was found to be a potential carbon source for Gluconacetobacter medellinensis strain ID13488 since higher cellulose production was observed with respect to the commercial Hestrin and Shramm medium (H–S). The culture media were characterized in terms of pH, oxygen and sugars consumption. The expression level of the operon bcs (genes involved in BC biosynthesis) in apple residue containing medium respect to standard H–S medium was determined. It was found that in AR/SC medium the expression levels of bcsA gene, wich is the first gene of the bcs operon, was increased in 1.5-fold respect to the H–S media which correlates with the fact that BC production in AR/SC media is higher than in H–S media. The physico-chemical and mechanical properties, microstructure, crystallinity and water holding capacity of the biosynthesized BC membranes were analyzed and it was found that, in general, the BC obtained from AR/SC medium presented superior properties than that obtained from H–S medium. In this study an economic method for BC production is proposed with suitable properties for many applications.

¿Peligra la escultura del Peine del Viento por la fuerza del oleaje que lo azota? Diseño de un ABP orientado al aprendizaje activo en la formación de Arquitectos Técnicos

In this communication, the design of a PBL, Problem Based Learning, for the teaching of physical and mechanical properties of materials in the subject of Fundamentals of Materials I for a degree in Technical Arquitecture is presented. This new methodology of teaching orientated to the active learning was implemented in the academic course 2012/13. On the basis of the results obtained in the exams, we can confirm that the methodology is suitable and positive for the acquisition of the results of learning proposed for the subject.