Showing papers by "Rosario Benavente published in 2020"

Study of the matrix-filler interface in PLA/Mg composites manufactured by Material Extrusion using a colloidal feedstock

Abstract: The aim of this paper is to investigate the evolution of a matrix-filler interface during the processing of novel composites formed by a matrix of polylactic acid (PLA) and Mg particles, when they are manufactured by Materials Extrusion. The particles addition to the PLA was carried out through the preparation of a Magnesium stable suspension in the polymer solution. To improve the Mg dispersion, the surfaces of the particles were previously modified by the adsorption of dispersants, namely Polyethylenimine (PEI) and Cetyltrimethylammonium bromide (CTAB) in aqueous suspension. The physical and mechanical characterization of PLA/Mg composites show that the Mg surface modification is the key to its successful dispersion due to the formation of ionic interactions between the dispersants and the matrix. This is favoured by the seeding effect of the PEI-modified Mg particles over the PLA re-precipitation during the composite shaping. Moreover, a PEI-PLA covalent bond appeared in the printed scaffolds as a consequence of the temperature applied (165 °C) during extrusion and printing. Consequently, the matrix-filler strengthened interface improved the extrusion process and permits the printing of 3D customized pieces. At the same time, particle agglomeration and the nozzle blocking is prevented.

In Vitro Degradation of Plasticized PLA Electrospun Fiber Mats: Morphological, Thermal and Crystalline Evolution.

Abstract: In the present work, fiber mats of poly(lactic acid), PLA, plasticized by different amounts of oligomer lactic acid, OLA, were obtained by electrospinning in order to investigate their long term hydrolytic degradation. This was performed in a simulated body fluid for up to 352 days, until the complete degradation of the samples is reached. The evolution of the plasticized electrospun mats was followed in terms of morphological, thermal, chemical and crystalline changes. Mass variation and water uptake of PLA-based electrospun mats, together with pH stability of the immersion media, were also studied during the in vitro test. The results showed that the addition of OLA increases the hydrolytic degradation rate of PLA electrospun fiber mats. Moreover, by adding different amounts of OLA, the time of degradation of the electrospun fiber mats can be modulated over the course of a year. Effectively, by increasing the amount of OLA, the diameter of the electrospun fibers decreases more rapidly during degradation. On the other hand, the degree of crystallinity and the dimension of the α crystals of the electrospun fiber mats are highly affected not only by the presence but also by the amount of OLA during the whole process.

New approach to improve polymer-Mg interface in biodegradable PLA/Mg composites through particle surface modification

Abstract: PLA/Mg composites have been successfully proposed as biodegradable and fully bioabsorbable materials for bone repair. The present work claims the benefits of Mg particles modification throughout the adsorption of surface modifiers in the in vitro biodegradation behavior of PLA/Mg composites. Additionally, the mixture of PLA with Mg particles in a colloidal suspension replaces the thermal-melting extrusion mixing, preventing the drawbacks associated to the thermal degradation of the polymer during processing. To fulfill this requirement it is necessary to improve the interaction particle-liquid medium for the hydrophilic surface of Mg particles and the organic solvent of PLA, which will provide the maximum dispersion of the Mg in the composite. In this sense, surfaces of Mg particles were modified by the adsorption of two different stabilizers, a surfactant as cetyltrimethylammonium bromide (CTAB) and a polyelectrolyte as polyethylenimine (PEI). The colloidal and chemical stability of Mg was studied in terms of Mg2+ dissolution, zeta-potential and rheology. A chemically stable suspension of modified Mg particles was mixed with the PLA solution in THF, and the mixture was used as feedstock to prepare films by tape casting. The characterization of the composites shows that particle surface modification determines Mg corrosion and hence governs the composite biodegradation.

Potential Applications of Magnesium-Based Polymeric Nanocomposites Obtained by Electrospinning Technique.

Abstract: In the last few decades, the development of new electrospun materials with different morphologies and advanced multifunctional properties are strongly consolidated. There are several reviews that describe the processing, use and characterization of electrospun nanocomposites, however, based on our knowledge, no review on electrospun nanocomposites reinforced with nanoparticles (NPs) based on magnesium, Mg-based NPs, are reported. Therefore, in the present review, we focus attention on the fabrication of these promising electrospun materials and their potential applications. Firstly, the electrospinning technique and its main processing window-parameters are described, as well as some post-processing methods used to obtain Mg-based materials. Then, the applications of Mg-based electrospun nanocomposites in different fields are pointed out, thus taking into account the current trend in developing inorganic-organic nanocomposites to gradually satisfy the challenges that the industry generates. Mg-based electrospun nanocomposites are becoming an attractive field of research for environmental remediation (waste-water cleaning and air filtration) as well as for novel technical textiles. However, the mayor application of Mg-based electrospun materials is in the biomedical field, as pointed out. Therefore, this review aims to clarify the tendency in using electrospinning technique and Mg-based nanoparticles to huge development at industrial level in the near future.

Identification of Additives in Polypropylene and Their Degradation under Solar Exposure Studied by Gas Chromatography-Mass Spectrometry.

Abstract: Additives are absolutely essential in the development of commercial polymeric materials. Accordingly, an exhaustive control of composition and evolution in these additives over time is necessary to...

Influence of ABS Type and Compatibilizer on the Thermal and Mechanical Properties of PC/ABS Blends

Abstract: The present work aimed to study the influence of ABS type and compatibilizer on the thermal and mechanical properties of PC/ABS blends. For that, blends of PC with two types of ABS, with d...

Comparative studies of the mechanical and thermal properties of clay / copolymer nanocomposites synthesized by two in-situ methods and solution blending method

Abstract: In this study, copolymer/clay nanocomposites were prepared by two different methodologies, the in-situ method and solution blending method. Comparative analyses of mechanical and thermal properties of the nanocomposites fabricated by the two different methods were performed. The solution blending method was found to be an efficient technique to obtain nanocomposites with uniform dispersion of the organoclay loading of up to 10 wt%, simple and fast. On the other hand, the in-situ method produced nanocomposites with good exfoliation and high thermal stability, whereas solution blending method produced materials with good mechanical properties compounds in the nano/clay intercalation and high thermal stability.

Bis‐β‐(diketonates) Zn(II) complexes substituted with thiophene: Electropolymerization, homogeneous and heterogeneous catalysis for ring opening polymerization of lactide

Abstract: The authors acknowledge the financial support from FON-DECYT Postdoctoral project 3160673 (D.M.G.), FONDEQUIP(EQM130154), the Vicerrectoria de Investigacion y EstudiosAvanzados, Pontificia Universidad Catolica de Valparaiso, Chile and FONDEQUIP (EQM-150106) of Universidad de Santiago de Chile. J. O. thanks CONICYT (Chile) for a doctoral fellowship N21171363. R. B. (Spain) thank the financial support from MINECO grant number MAT2016-79869-C2-1-P (AEI/FEDER, UE