Toca-Toca: ejemplos sencillos para conceptos complejos en asignaturas de ciencia y tecnología de materiales

En las asignaturas de tipo “Fundamentos de Ciencia de los Materiales” es habitual encontrar que la propuesta de temario es muy extensa y que en ella se introducen un gran número de conceptos, que van desde las bases físico-químicas de la estructura de la materia, hasta el comportamiento macroscópico de la misma, como son los fenómenos de fractura y fallo por corrosión. Es una situación común que el estudiantado considere esta diversidad de contenidos como un problema, atendiendo a la dificultad para asimilar tal cantidad de conceptos, a menudo sin vínculos concretos y reales que permitan afianzar los modelos y asimilar los contenidos con coherencia. La consecuencia general de este fenómeno, es que la asignatura de materiales se pueda percibir como dificultosa y/o aburrida, a lo que se asociaría una baja tasa de superación. En este trabajo se presenta una colección de recursos demostrativos, para su uso y aplicación en las aulas, que faciliten e ilustren algunos conceptos, habituales en asignaturas básicas de materiales. Estos ejemplos tienen la particularidad de ser “próximos”, con objetos cotidianos o no excesivamente “exclusivos”, de modo que el alumnado puede interaccionar con ellos y “tocarlos”, llevando la experiencia sensorial a otros sentidos, además de la vista y el oído, para que permanezcan en la memoria el tiempo suficiente hasta que se puedan vincular con otro concepto o ejemplo

Development of control strategies for bacteria and fungi associated with a micropropagated new cultivar of orange-fleshed sweet potato (Ipomoea batatas cv. Agrosavia–Aurora)

Vegetative propagation of sweet potato lead to the accumulation of diseases from generation to generation, which represents a threat to both productivity and conservation of genetic resources. In vitro techniques can help to overcome phytosanitary problems by applying plant material cleaning strategies. The objective of this study was to develop in vitro micropropagation strategies for the production of high-quality plant material of an orange-fleshed variety of sweet potato recently released in Colombia. Molecular identification of contaminating microorganisms was performed by sequencing the 16S rRNA gene for bacteria and ITS for fungi. Five disinfection protocols were evaluated, three of which were previously developed for sweet potato and included disinfection with 0.5, 1, and 2% sodium hypochlorite respectively, while two protocols are proposed in this work and included washing with povidone-iodine, disinfection with sodium hypochlorite 2%; one of these two new protocols also contains acetic acid and quaternary ammonium. For the evaluation of the viability of in vitro plants after disinfection, they were acclimatized in a greenhouse, reintroduced, and a molecular testing by PCR of 16S rRNA gene and ITS was carried out to verify the phytosanitary status of the material. The contaminating microorganisms found were filamentous fungi of the genera Fusarium, Sarocladium, Cladosporium and Aspergillus, yeasts of the genera Pseudozyma and Moesziomyces, and the actinobacterium Curtobacterium sp. The results indicated that washing with povidone-iodine and disinfection with 2% sodium hypochlorite, acetic acid and quaternary ammonium was the most efficient disinfection protocol, reducing the number of contaminated cultures by up to 10% and eradicating 70% of contaminants. The in vitro plants established in the greenhouse remained healthy and, after reintroduction, the molecular test for bacteria and fungi was negative. These results allowed the generation of an optimized protocol that can be incorporated into the in vitro micropropagation process to generate contamination-free sweet potato seeds

Toughness Enhancement of Commercial Poly (Hydroxybutyrate-co-Valerate) (PHBV) by Blending with a Thermoplastic Polyurethane (TPU)

Poly(hydroxyl butyrate-co-valerate) (PHBV) is a biopolymer synthesized by microorganisms that is fully biodegradable with improved thermal and tensile properties with respect to some commodity plastics. However, it presents an intrinsic brittleness that limits its potential application in replacing plastics in packaging applications. Films made of blends of PHBV with different contents of thermoplastic polyurethane (TPU) were prepared by single screw extruder and their fracture toughness behavior was assessed by means of the essential work of fracture (EWF) Method. As the crack propagation was not always stable, a partition method has been used to compare all formulations and to relate results with the morphology of the blends. Indeed, fully characterization of the different PHBV/TPU blends showed that PHBV was incompatible with TPU. The blends showed an improvement of the toughness fracture, finding a maximum with intermediate TPU contents.Financial support for this research from Ministerio de Economía y Competitivi dad (project AGL2015-63855-C2-2-R (MINECO/FEDER) and Pla de Promoció de la Investigació de la Universitat Jaume I (PREDOC/2012/32 and E-2015-22) is gratefully acknowledged

Estimating the benefits of dedicated unloading bays by field experimentation

In most dense urban environments in emerging markets, retail deliveries are very fragmented to thousands of nanostores. It is not uncommon for a delivery route to include more than 60 stops. Unloading bays are often blocked by regular traffic. Due to the complex urban environment, it is difficult to estimate the benefits of making unloading bays available. In this study, we conduct a field experiment in an urban field lab of one square kilometer in the downtown of Querétaro, Mexico. During the treatment period of one week, we obtain help from the local traffic police to keep the unloading bays available for unloading only. Using advanced GPS devices and extensive manual field observations, we are able to capture the change in driver behavior and the direct efficiency increases. We find a high efficiency gain, not only in travel time (39%) but also – remarkably – in the total time parked (17%). Corrected for other effects, we estimate a gain of about 44% in total time per delivery. Apart from the insights on unloading benefits, we also provide insights into the method of field experimentation in such a complex environment

Mejora de la termoconformabilidad del PHBV mediante mezclas biodegradables con poliuretano

Actas del Congreso publicadas por ed. Compobell. ISBN 978-84-942655-8-7Mezclas de poli (3-hidroxibutirato-co-3-hidroxivalerato) (PHBV) y poliuretano termoplástico (TPU) se obtuvieron mediante extrusión con el objetivo de mejorar la procesabilidad del PHBV. La morfología, las propiedades mecánicas y la termoconformabilidad del PHBV se han evaluado observándose un aumento en la elongación a rotura y una mejora en el termoconformado del PHBV.A number of samples of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and thermoplastic polyurethane (TPU) were obtained through extrusion, with the aim of improving the processability of PHBV. The relevant assessment of PHBV’s morphology, mechanic properties, and thermoformability has been carried out, observing an increase in elongation at break and an improvement in the thermoforming of PHBV.Ministerio de Economía y Competitividad (proyecto MAT2012-38947-C02-01), Generalitat Valenciana (GV/2014/123) y Pla de Promoció de la Investigació de la Universitat Jaume I (PREDOC/2012/32)

Mejora de las propiedades mecánicas y compatibilidad de mezclas de PHBV/PLA con plastificantes comerciales de origen bio

Actas del Congreso publicadas por ed. Compobell. ISBN 978-84-942655-8-7Mezclas de poli (3-hidroxibutirato-co-3-hidroxivalerato) (PHBV) y ácido poliláctico (PLA) se prepararon con un plastificante comercial funcionalizado de origen bio. La morfología obtenida, así como las propiedades mecánicas y dinamo-mecánicas de probetas inyectadas se ha evaluado observándose una mejora en la compatibilidad del PHBV y el PLA y un aumento en la deformación a rotura en tracción.A number of samples of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and polylactic acid (PLA) were treated with a commercial funcionalised bio plasticiser. The relevant assessment was made on the morphology and both the mechanic and dynamo-mechanic properties obtained in the injected test tubes. An improvement in terms of compatibility between PHBV and PLA has been observed, as well as an increase in strain at break in tensile testing.Ministerio de Economía y Competitividad (proyecto MAT2012-38947-C02-01) y Pla de Promoció de la Investigació de la Universitat Jaume I (PREDOC / 2012/32

Void Content Minimization in Vacuum Infusion (VI) via Effective Degassing

This paper addresses the major concern which component porosity represents in Vacuum Infusion (VI) manufacturing due to resin gelation at pressures close to absolute vacuum. Degassing is a fundamental step to minimize or even avoid resin outgassing and enhance dissolution of voids created during preform impregnation. The efficacy of different degassing procedures based on vacuum degassing, and assisted by adding a nucleation medium, High Speed (HS) resin stirring and/or later pressurization during different time intervals have been analyzed in terms of final void content is studied. Through a rigorous and careful design of the manufacturing process, outgassing effects on final void content were isolated from the rest of porosity causes and specimens with two clearly identifiable regions in terms of porosity were manufactured to facilitate its analysis. Maximum void content was kept under 4% and porous area size was reduced by 72% with respect to conventional vacuum degassing when resin was stirred at HS; therefore, highlighting the importance of enhancing bubble formation during degassing

Effect of the Purification Treatment on the Valorization of Natural Cellulosic Residues as Fillers in PHB-Based Composites for Short Shelf Life Applications

This is a pre-print of an article published in Waste and Biomass Valorization. The final authenticated version is available online at: https://doi.org/10.1007/s12649-020-01192-1In this work the effect of a combined NaOH + peracetic acid (PAA) purification treatment on the valorization of almond shell (AS) and rice husk (RH) lignocellulosic residues as fillers in PHB-based composites for short shelf life applications has been studied. The efficiency of the treatment at removing the non-cellulosic components of the fibers has been evaluated by SEM, FTIR, WAXS and TGA taking a commercial cellulose as reference. The influence of the untreated and treated fibers on the morphology, thermal, crystallization, tensile properties, fracture toughness and dynamo mechanical behavior of the PHB/fiber composites has been studied. The treatment has demonstrated its ability at removing the lignin, hemicelluloses and waxes allowing the obtention of fibers with relative crystallinity, thermal stability and composition similar to the commercial cellulose. The different agro-food based lignocellulosic residues used resulted in two suitable reinforcing fillers for a PHB matrix. Hence, composites prepared with the treated fibers presented better thermal and mechanical performance than those prepared with the untreated ones. Therefore, the so-obtained purified residue fibers are comparable to a pure cellulose as a filler for PHB composites

Electric Conductivity Study of Porous Polyvinyl Alcohol/Graphene/Clay Aerogels: Effect of Compression

In this work, poly(vinyl alcohol) (PVOH)/graphene (GN) oxide/clay aerogels were prepared using montmorillonite (MMT) and kaolinite (KLT) as fillers. This work paves the way for the development of aerogels filled with MMT or KLT with high conductivity. The mechanical properties of the polymer/clay aerogels are enhanced by incorporating GN into these systems. These composite materials have an enhanced thermal stability, and the combination of PVOH and GN leads to interconnected channels which favored the conductivity when a clay (MMT or KLT) is added to the mixed PVOH/GN matrix. However, after compressing the samples, the conductivities drastically decreased. These results show that the design of solid MMT/GN and KLT/GN composites as aerogels allows maximizing the space utilization of the electrode volume to achieve unhindered ion transport, which seems contrary to the general design principle of electrode materials where a suitable porous structure is desired, such as in our uncompressed samples. These findings also demonstrate the potential of these materials in electrodes, sensors, batteries, pressure-sensing applications, and supercapacitors.Financial support for this research from Ministerio de Economía y Competitividad (project AGL2015-63855-C2-2-R) (MINECO/FEDER) is gratefully acknowledged.The authors acknowledge the Servei Central d’Instrumentació Científica (SCIC-UJI) and Servei Central de Suport a la Investigació Experimental (SCSIE-UV) from Universitat Jaume I and Universitat de València, respectively, for the use of instruments and staff assistance. Authors would like to acknowledge José Ortega and Raquel Oliver for experimental support

Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate)/ Purifi ed Cellulose Fiber Composites by Melt Blending: Characterization and Degradation in Composting Conditions

Novel biodegradable composites based on poly(3-hydroxybutirate-co-3-hydroxyvalerate) (PHBV) and different contents of purifi ed alpha-cellulose fi bers (3, 10, 25 and 45%) were prepared by melt blending and characterized. The composites were characterized by scanning electron microscopy (SEM), wide-angle X-ray scattering (WAXS) experiments, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanic analysis (DMA) and Shore D hardness measurements. Disintegrability under composting conditions was studied according to the ISO 20200 standard. Morphological results showed that high dispersion of the fi bers was achieved during mixing. Good adhesion on the fi ber-matrix interface was also detected by SEM. The addition of low and medium cellulose contents did not result in lower thermal resistance with respect to the neat PHBV. A reinforcing effect of the cellulose fi bers was detected in all samples, this effect being more pronounced at high temperatures. The composting results show that the addition of the fi bers did not affect the disintegrability of the PHBV, and thus compostable “green” low-cost PHBV/cellulose composites can be obtained