Óscar Sahuquillo

Mechanical properties and degradation studies of poly(mannitol sebacate)/cellulose nanocrystals nanocomposites

Polyesters based on polyols and sebacic acid, known as poly(polyol sebacate)s (PPS) are good candidates to develop degradable materials, due to their combination of flexibility and degradability, which are both useful properties in the context of soft-tissue engineering (Z. Sun, C. Chen, M. Sun, C. Ai, X. Lu, Y. Zheng, B. Yang and D. Dong, Biomaterials, 2009, 30, 5209, C. Sundback, J. Shyu, Y. Wang, W. Faquin, R. Langer, J. Vacanti and T. Hadlock, Biomaterials, 2005, 26, 5454, D. Motlagh, J. Yang, K. Lui, A. Webb and G. Ameer, Biomaterials, 2006, 27, 4315, A. Mahdavi, L. Ferreira, C. Sundback, J. W. Nichol, E. P. Chan, D. J. D. Carter, C. J. Bettinger, S. Patanavanich, L. Chignozha, E. Ben-Joseph, A. Galakatos, H. Pryor, I. Pomerantseva, P. T. Masiakos, W. Faquin, A. Zumbuehl, S. Hong, J. Borenstein, J. Vacanti, R. Langer and J. M. Karp, Proc. Natl. Acad. Sci. U. S. A., 2008, 105, 2307). However, PPS generally display poor mechanical properties, in particular a low modulus, that limit the true potential of these materials in the biomedical field. Here, we introduce an approach to obtain nanocomposites based on poly(mannitol sebacate) (PMS) matrices reinforced with cellulose nanocrystals (CNCs) in order to improve the application range of these materials. Different strategies were used based on varying the feed ratios between mannitol : sebacic acid (1 : 1 and 1 : 2), crosslinking conditions and CNCs content, resulting in different degrees of crosslinking and, therefore, mechanical and degradation behavior. All of the developed nanocomposites displayed the expected mass loss during the degradation studies in simulated body fluid (SBF) similar to the neat matrix, however, doubling the sebacic acid feed ratio or extending the curing temperature and time, resulted in higher mechanical properties, structural integrity, and shape stability during a degradation time lessening mass loss rate. Changing mannitol : sebacic acid reaction ratios from 1 : 1 to 1 : 2 and for low crosslinking degree neat samples, the Youngs modulus increases four-fold, while mass loss after 150 days of incubation is reduced by half. The Youngs modulus range obtained with this process covers the range of human elastic soft tissues to tough tissues (0.7–200 MPa).

Conductivity of composite membrane-based poly(ether-ether-ketone) sulfonated (SPEEK) nanofiber mats of varying thickness

Nanofiber mats of SPEEK70wt%–PVB30 wt% (polyvinyl butyral)-based composite membranes were prepared by varying the electrospinning time in order to obtain mats with different thicknesses. These mats were embedded in SPEEK65wt%–PVA35wt% (polyvinyl alcohol) polymer solution to fill the pores in the fibers. The obtained membranes with different mat thicknesses have been characterized by water uptake, ionic exchange capacity, scanning electron microscopy, mechanical properties and proton conductivity. Microtensile test studies reveal that the maximum tensile strength increases as the thickness of the SPEEK–PVB nanofiber mats increases, resulting in more flexible composite membranes compared to a pure SPEEK–PVA membrane obtained by casting. The proton conductivity occurs more easily through the nanofiber than through the matrix phase, and the best conductivity (0.038 S cm−1) was measured at 120 °C for the composite membrane of SPEEK–PVB nanofiber mats obtained after 12 hours of electrospinning time. This value suggests that our composite membranes have high potential to function in the temperature range between 100 and 140 °C without losing their strength and while maintaining their high proton conductivity, making them an excellent candidate for fuel cells that operate at intermediate temperatures.

Phosphoric Acid Doped Polybenzimidazole (PBI)/Zeolitic Imidazolate Framework Composite Membranes with Significantly Enhanced Proton Conductivity under Low Humidity Conditions

The preparation and characterization of composite polybenzimidazole (PBI) membranes containing zeolitic imidazolate framework 8 (ZIF-8) and zeolitic imidazolate framework 67 (ZIF-67) is reported. The phosphoric acid doped composite membranes display proton conductivity values that increase with increasing temperatures, maintaining their conductivity under anhydrous conditions. The addition of ZIF to the polymeric matrix enhances proton transport relative to the values observed for PBI and ZIFs alone. For example, the proton conductivity of PBI@ZIF-8 reaches 3.1 × 10−3 S·cm−1 at 200 °C and higher values were obtained for PBI@ZIF-67 membranes, with proton conductivities up to 4.1 × 10−2 S·cm−1. Interestingly, a composite membrane containing a 5 wt.% binary mixture of ZIF-8 and ZIF-67 yielded a proton conductivity of 9.2 × 10−2 S·cm−1, showing a synergistic effect on the proton conductivity.

Diseño de actividades y uso de la coevaluación para fomentar el desarrollo de competencias transversales en ingeniería mecánica y de materiales

En esta comunicacion se presentan las actividades de evaluacion desarrolladas en el marco de un Proyecto de Innovacion y Mejora Educativa, junto con algunos resultados preliminares. El principal objetivo de este proyecto es el diseno de actividades de evaluacion que fuercen a los estudiantes a desarrollar sus competencias transversales, al mismo tiempo que permitan a los profesores evaluar su desempeno en las competencias cientifico-tecnicas. Se emplea un enfoque de evaluacion formativa, de forma que las actividades de evaluacion sean utiles a los estudiantes para mejorar su aprendizaje. Palabras clave: competencias transversales, actividades de evaluacion, coevaluacion

Comparación de herramientas de evaluación de la competencia comunicación oral efectiva

El proyecto has sido financiado por el Vicerrectorado de Estudios, Calidad y Acreditacion de la Universitat Politecnica de Valencia a traves del programa PIME 2016-17 bajo la referencia A26.

Desarrollo de estrategias de evaluación de competencias transversales en asignaturas de ingeniería mecánica y de materiales

Por ultimo, los autores quieren agradecer la ayuda economica y el apoyo institucional recibidos de la Universitat Politecnica de Valencia a traves del proyecto PIME/2014/A/012/B.

Evaluación de competencias transversales en asignaturas relacionadas con Ingeniería Mecánica y de Materiales: Análisis y Resolución de Problemas, Aplicación y Pensamiento Práctico

Los autores quieren agradecer la ayuda economica y el apoyo institucional recibidos de la Universitat Politecnica de Valencia a traves del proyecto PIME/2014/A/012/B.

Propuesta de evaluación de las competencias de comunicación oral y escrita en asignaturas de Ingeniería Mecánica y Ciencia de Materiales

Los autores agradencen la financiacion recibida de la Universitat Politecnica de Valencia a traves del proyecto PIME/2014/A/012/B.