Influence of the viscosity of poly(methyl methacrylate) on the cellular structure of nanocellular materials

Three different grades of poly(methyl methacrylate) (PMMA) with different rheological properties are used for the production of nanocellular materials using gas dissolution foaming. The influences of both the viscosity of the different polymers and the processing parameters on the final cellular structure are studied using a wide range of saturation and foaming conditions. Foaming conditions affect similarly all cellular materials. It is found that an increase of the foaming temperature results in less dense nanocellular materials, with higher cell nucleation densities. In addition, it is demonstrated that a lower viscosity leads to cellular polymers with a lower relative density but larger cell sizes and smaller cell nucleation densities, these differences being more noticeable for the conditions in which low solubilities are reached. It is possible to produce nanocellular materials with relative densities of 0.24 combined with cell sizes of 75 nm and cell nucleation densities of 1015 nuclei cm−3 using the PMMA with the lowest viscosity. In contrast, minimum cell sizes of around 14 nm and maximum cell nucleation densities of 3.5 × 1016 nuclei cm−3 with relative densities of 0.4 are obtained with the most viscous one. © 2019 Society of Chemical Industr

Gas dissolution foaming as a novel approach for the production of lightweight biocomposites of PHB/natural fibre fabrics

Producción CientíficaThe aim of this study is to propose and explore a novel approach for the production of cellular lightweight natural fibre, nonwoven, fabric-reinforced biocomposites by means of gas dissolution foaming from composite precursors of polyhydroxybutyrate-based matrix and flax fabric reinforcement. The main challenge is the development of a regular cellular structure in the polymeric matrix to reach a weight reduction while keeping a good fibre-matrix stress transfer and adhesion. The viability of the process is evaluated through the analysis of the cellular structure and morphology of the composites. The effect of matrix modification, nonwoven treatment, expansion temperature, and expansion pressure on the density and cellular structure of the cellular composites is evaluated. It was found that the nonwoven fabric plays a key role in the formation of a uniform cellular morphology, although limiting the maximum expansion ratio of the composites. Cellular composites with a significant reduction of weight (relative densities in the range 0.4–0.5) were successfully obtained.Ministerio de Educación y Formación Profesional (grants FPU12/05869 and EST14/00273)Ministerio de Economía, Industria y Competitividad - Fondo Europeo de Desarrollo Regional (grants BIA2014-59399-R and MAT2015-69234-R)Junta de Castilla y Leon (grant VA011U16

Considerations about aging and quality of live

El envejecimiento es individual, es el resultado de la combinación de nuestra carga genética y la forma de adaptarnos al teatro de nuestra vida. La adaptación satisfactoria, la alta autoestima, la libertad, la felicidad, el bienestar guardan una relación con la buena calidad de vida en general. Los factores que consideramos mas importantes para una buena calidad de vida en la vejez serían: el grado de funcionalidad física, psíquica y social, la muerte de un miembro de la pareja y el estado de salud percibida.The way one ages is always personal. It is the result of one's own genetic load together with his/her adaptation to the life stage. A satisfactory adaptation, self-respect, freedom, happiness and wellbeing, bear a strong relationship to the quality of life in general terms. Factors we consider essential for good quality of life in old age (elderly) are: physical, psychical and social fitness; a long and happy partnership with a loved-one, and self-perception of the state of one's health. A good financial situation in old age, could sometimes be less significant, if compared with their former times in life when they have lived with more limited resources. It is not so important either when there is a social support such as NHS and/or certain bonuses which guaranty satisfaction for their basic needs such as food, clothing and housing for life

Special Issue. Higher education: A fundamental intangible capital towards a sustainable future

Peer Reviewe

Low density polyethylene/silica nanocomposite foams. Relationship between chemical composition, particle dispersion, cellular structure and physical properties

Postprint (author's final draft

“La importancia de la Gestión de la Experiencia del Consumidor en el sector del lujo”.

El aumento de la digitalización de la industria de la moda, el crecimiento de la competitividad del mercado, y la existencia de un consumidor más exigente e informado saturado del marketing tradicional, ha dado lugar a un marketing enfocado en la creación de experiencias. El objetivo principal de mi trabajo es analizar la Experiencia del Consumidor en el ámbito de la industria del lujo. En este trabajo se estudiarán las características únicas del lujo y a sus consumidores. Por otro lado, estudiaremos el termino gestión de la experiencia del consumidor, de donde viene y sus últimas aplicaciones. También tendré en cuenta el factor actual de la pandemia del Covid-19. Intentaremos explicar cómo se debe de aplicar este enfoque de marketing específico en el mundo del lujo. Tras el trabajo teórico, realizaré una serie de entrevistas en profundidad a dos perfiles dentro del mundo del lujo: el consumidor y los expertos. Los resultados obtenidos en las entrevistas serán de gran ayuda ya que se harán a perfiles muy concretos, tendrán la libertad de expresarse y surgirán nuevas preguntas.<br /

A scatter search heuristic for the optimal location, sizing and contract pricing of distributed generation in electric distribution systems

ABSTRACT: In this paper we present a scatter search (SS) heuristic for the optimal location, sizing and contract pricing of distributed generation (DG) in electric distribution systems. The proposed optimization approach considers the interaction of two agents: (i) the potential investor and owner of the DG, and (ii) the Distribution Company (DisCo) in charge of the operation of the network. The DG owner seeks to maximize his profits from selling energy to the DisCo, while the DisCo aims at minimizing the cost of serving the network demand, while meeting network constraints. To serve the expected demand the DisCo is able to purchase energy, through long-term bilateral contracts, from the wholesale electricity market and from the DG units within the network. The interaction of both agents leads to a bilevel programming problem that we solve through a SS heuristic. Computational experiments show that SS outperforms a genetic algorithm hybridized with local search both in terms of solution quality and computational time

Nanocellular Polymers with a Gradient Cellular Structure Based on Poly(methyl methacrylate)/Thermoplastic Polyurethane Blends Produced by Gas Dissolution Foaming

Graded structures and nanocellular polymers are two examples of advanced cellular morphologies. In this work, a methodology to obtain low-density graded nanocellular polymers based on poly(methyl methacrylate) (PMMA)/ thermoplastic polyurethane (TPU) blends produced by gas dissolution foaming is reported. A systematic study of the effect of the processing condition is presented. Results show that the melt-blending results in a solid nanostructured material formed by nanometric TPU domains. The PMMA/ TPU foamed samples show a gradient cellular structure, with a homogeneous nanocellular core. In the core, the TPU domains act as nucleating sites, enhancing nucleation compared to pure PMMA and allowing the change from a microcellular to a nanocellular structure. Nonetheless, the outer region shows a gradient of cell sizes from nano- to micron-sized cells. This gradient structure is attributed to a non-constant pressure profile in the samples due to gas desorption before foaming. The nucleation in the PMMA/ TPU increases as the saturation pressure increases. Regarding the effect of the foaming conditions, it is proved that it is necessary to have a fine control to avoid degeneration of the cellular materials. Graded nanocellular polymers with relative densities of 0.16–0.30 and cell sizes ranging 310–480 nm (in the nanocellular core) are obtained