Vicent Fombuena

Surface modification of polypropylene substrates by UV photografting of methyl methacrylate (MMA) for improved surface wettability

Despite polypropylene is one of the most used commodity plastics, its adhesion properties are remarkably restricted by its non-polar nature which leads to low wetting properties and, consequently, poor adhesion behavior. We report the use of ultraviolet photografting process of methyl methacrylate (MMA) monomer as an efficient chemical treatment for surface activation of polypropylene. Contact angle measurements are used for evaluating changes in polypropylene wetting properties together with surface free energy calculations. Chemical changes are showed in terms of the exposure time to UV radiation. Scanning electron microscopy has been used to evaluate topography changes in a qualitative way; atomic force microscopy has been used for a quantitative evaluation of surface changes in terms of roughness. The use of Fourier transformed infrared spectroscopy has revealed the nature of the chemical changes induced by the photografting process of MMA.

Optimization of atmospheric plasma treatment of LDPE films: influence on adhesive properties and ageing behavior

One of the major disadvantages of low density polyethylene (LDPE) films is their poor adhesive properties. Therefore, LDPE films have been treated with atmospheric pressure air plasma in order to improve their surface properties. So as to simulate the possible conditions in an industrial process, the samples have been treated with two different sample distances (6 and 10 mm), and treatment rates between 100 and 1000 mm s−1. The different sample distances are the distance of the sample from the plasma source. The variation of the surface properties and adhesion characteristics of the films were investigated for different aging times after plasma exposure (up to 21 days) using contact angle measurement, atomic force microscopy, weight loss measurements and shear test. Results show that the treatment increases the polar component () and these changes improve adhesive properties of the material. After the twenty-first day, the ageing process causes a decrease of wettability and adhesive properties of the LDPE films (up to 60%).

Improvement of mechanical and biological properties of Polycaprolactone loaded with Hydroxyapatite and Halloysite Nanotubes

Hydroxyapatite (HA) and Halloysite nanotubes (HNTs) percentages have been optimized in Polycaprolactone (PCL) polymeric matrices to improve mechanical, thermal and biological properties of the composites, thus, to be applied in bone tissue engineering or as fixation plates. Addition of HA guarantees a proper compatibility with human bone due to its osteoconductive and osteoinductive properties, facilitating bone regeneration in tissue engineering applications. Addition of HNTs ensures the presence of tubular structures for subsequent drug loading in their lumen, of molecules such as curcumin, acting as controlled drug delivery systems. The addition of 20% of HA and different amounts of HNTs leads to a substantial improvement in mechanical properties with values of flexural strength up to 40% over raw PCL, with an increase in degradation temperature. DMA analyses showed stability in mechanical and thermal properties, having as a result a potential composite to be used as tissue engineering scaffold or resorbable fixation plate.

Manufacturing and Characterization of Composite Fibreboards with Posidonia oceanica Wastes with an Environmentally-Friendly Binder from Epoxy Resin

Highly environmentally-friendly fibreboards were manufactured by hot-press moulding using Posidonia ocaeanica wastes and a partially biobased epoxy resin as binder. Fibreboards with a constant fibre content of 70 wt % were successfully manufactured by thermo-compression. The effects of a conventional alkali treatment were compared to the synergistic effects that additional silanization with two silanes (amino and glycidyl) can exert on the mechanical and thermo-mechanical properties of fibreboards. The results revealed a remarkable improvement of the mechanical properties with the combination of the alkali treatment followed by the silanization. Scanning electron microscopy also revealed increased resin-fibre interactions due to the synergistic effect of both amino- and glycidyl-silanes. These fibreboards represent a formaldehyde-free solution and can positively contribute to sustainable development as the lignocellulosic component is a waste and the binder resin is partially biobased.

Improvement of the T‐peel Strength of Polypropylene Adhesion Joints by Surface Photografting Pre‐Treatment with Methyl Methacrylate

Although polypropylene is one of the most used polymers at industrial level due to good balanced properties, it presents some restrictions in applications that require good adhesion properties as well as coating and painting. These restrictions are related to its non polar nature which leads to low wetting properties. So that, in most cases, it is necessary a previous surface pre‐treatment in order to improve adhesion properties. These surface treatments could be physical or chemical. Among the wide variety of physical processes, plasma technologies are useful from both technical and environmental points of view. If we take into account economic considerations, chemical processes are interesting due to low cost equipment and procedures. In particular, we have used photografting of methyl methacrylate (MMA) monomer on polypropylene substrates with UV radiation and initiators. This process is useful to promote chemical modification of polypropylene surface by grafting MMA monomers into polypropylene polymer...

Disintegration in Compost Conditions and Water Uptake of Green Composites from Poly(Lactic Acid) and Hazelnut Shell Flour

Green composites of poly(lactic acid)-PLA and hazelnut shell flour (HSF) with and without epoxidized linseed oil (ELO) as plasticizer/compatibilizer were subjected to different aging conditions such as water uptake by immersion and disintegration in compost soil. The effect of the hydrolytic degradation was analyzed by measuring the weight gain as a function of the immersion time in water and calculating the corresponding diffusion coefficients. As expected, the water diffusion coefficient increases with HSF content while no remarkable change is obtained for plasticized compositions with ELO. Differential scanning calorimetry reveals a noticeable increase in crystallinity after the degradation process by water immersion. Degradation in controlled compost soil was followed thorough measurements of weight changes. In general, the weight change for a particular degradation time is lower as the HSF content increases. In addition, presence of ELO as plasticizer/compatibilizer delays the degradation process in compost soil. Scanning electron microscopy highlighted a noticeable deterioration of aged samples after 2 weeks with multiple crack formation and high surface abrasion due to microbial activity after 4 weeks.

Utilización de técnicas Kanban para la gestión de tesis doctorales

The development of a doctoral thesis is a team work to be done by the doctorate and his supervisors. A huge list of jobs have to be faced by both. So, communication and coordination between them is mandatory in order an adequate support and track of the doctorate work is provided. This job presents how Kanban technique is applied in the development of a doctoral thesis. The Kanban techniques allow to organize tasks through boards, in a very visual and simple way which facilitates the communication between doctorate and the directors. Recently web and mobile applications that implement Kanban techniques have appeared. These applications allow a dalily collaboration in the thesis, they allow to assign tasks, to know the state of its progress, to hold conversations, to provide constant feedback and finally to see which tasks have already been completed. In a short time, a large part of emails, telephone conversations and chats to notify the status of a task have been eliminated. In a short time, a large part of emails, phone conversations and chats to notify the status of a task have been eliminated.

Incorporación de la aplicación Kahoot! para la evaluación de las prácticas de la asignatura de “Ciencia de Materiales”

Resumen Durante la realizacion de las practicas de laboratorio de la asignatura de “Ciencia de Materiales” en el Grado de Ingenieria Quimica se ha incorporado el uso de la aplicacion multiplataforma Kahoot! para su evaluacion. Con la incorporacion de esta aplicacion se consigue incrementar la atencion del alumno de forma efectiva y dinamica durante el desarrollo de las mismas. Ademas la aplicacion permite tanto la participacion individual como el debate entre los propios alumnos de manera dinamica y entretenida, mejorando la colaboracion y la atencion del alumno en el transcurso de las practicas. Con la implementacion de la aplicacion multiplataforma Kahoot! se fomenta la atencion y participacion del alumnado en las clases practicas de una forma muy efectiva. Palabras clave: gamificacion, metodologia, aplicaciones, Kahoot!, juego, competicion, formacion, evaluacion, dispositivo movil.

Improvement of adhesion properties of low density polyethylene (LDPE) substrate using atmospheric plasma

In this work we have used atmospheric plasma technology on polyethylene surface with different treatment conditions. These modify surface pre‐treatments on polyethylene, thus having a positive effect on overall surface activity of polymer surface and, consequently, adhesion properties can be remarkably improved. We have evaluated the influence of the nozzle/substrate distance and atmospheric plasma speed on wettability changes and adhesion properties. Wettability changes have been studied by contact angle measurements and subsequent surface energy calculation. Mechanical characterization of adhesion joints has been carried out in two different ways: peel and shear tensile test. The overall results show a remarkable increase in mechanical properties of adhesion joints for low nozzle/substrate distances and low speed. So plasma atmospheric technology is highly useful to increase adhesion properties of polypropylene.