RT Dissertation/Thesis
T1 Procesado por técnicas coloidales y caracterización de materiales polímero/Mg para aplicaciones en la industria biomédica
A1 Ferrández Montero, Ana
AB During recent years, PLA / Mg composite materials have emerged as new bioabsorbablebiomaterials for osteosynthesis applications. It has been proposed that the incorporationof Mg particles into a matrix based on a biodegradable polymer can address, on the onehand, the lack of bioactivity and the low mechanical properties of the polymers and, onthe other, the high rate of degradation or corrosion of Mg and its alloys. Many methodsfor the preparation of polymer/bioinorganic material have been reported, some typicalexamples are extrusion mixing, compression molding and solvent casting. Themanufacture challenge of these materials is to achieve a particle homogeneousdispersion in the final PLA structure.This work reports on a novel processing route that is based on a colloidal mixture of Mgpowder and PLA aimed to prevent the drawbacks associated to the polymer degradationduring the mixing step of conventional thermoplastic routes and increase the maximumload achieved (10% by mass) during conventional routes. To fulfill this requirement itwas necessary to improve the PLA-Mg interaction, as well as to increase the dispersionof the Mg in the final mixture through the surface modification of particles. Mg wasmodified by the adsorption of two different stabilizers, a surfactant (CTAB) and apolyelectrolyte (PEI). The dispersed and chemically stable suspension of modified Mgparticles was mixed with the PLA solution in THF, and was used as feedstock materialto obtain tapes, by tape casting, and granules, by drying the mixture under reducedpressure conditions. Besides, these granules were used as feedstock for furthermanufacturing of bulk cylinders by compression moulding and 3D printing scaffolds byFused Deposition Moulding (FDM).The results show that, in the tapes, particle surface modification is directly associatedwith good load dispersion through interactions between groups present in the PLA andin the stabilizers either by the formation of hydrogen bonds or by ionic and electrostaticinteractions. In the case of granules and compression moulding cylinders it is observeda covalent bond between PEI and PLA, which is produced by the temperature appliedduring processing.Mechanical behaviour was evaluated in terms of nanoindentation, mechanodynamicsand tensile properties for tapes, and compression for compression moulding cylinders.In the case of tapes, a Mg reinforcement effect in the matrix is observed at the proximityof the particles. Young’s module and strength improve in tapes with up to 10 wt.% ofMg. At higher particle content, tensile mechanical improvement could not be verifieddue to fragilization of the materials. The thermopressed composites present a moreevident improvement in the mechanical properties under compression with respect tothe neat polymer, observing an increase of 10% in the elastic modulus for compositeswith 30 wt.% of Mg.Regarding in vitro behavior, degradation and viability tests were carried out to verifythat the new processing defined does not affect the biocompatibility and viability ofPLA/Mg composites. The hydrogen release test shows that no material exceeds theamount tolerable by the human body, although the release is not proportional to theload, which is associated with a process of autocatalytic degradation. In the case oftapes, materials processed with modified Mg particles with PEI release less hydrogenthan those modified with CTAB. Concerning biological tests, it is proved that thereleased components during the degradation of the composite do not producecytotoxicity at the cellular level with fibroblastic cells (MEF) or stromal cells (ST-2).Finally, the direct tests carried out on the composite tapes allow concluding that for allthe materials, except for the sample with 50 wt.% Mg, there is a significant increase incell viability in comparison with the polymer matrix.
YR 2018
FD 2018-09
LK https://hdl.handle.net/10016/27714
UL https://hdl.handle.net/10016/27714
LA spa
NO Mención Internacional en el título de doctor
NO El autor agradece a la CAM el proyecto: MULTIMAT Challenge: Materiales Multifuncionales para retos de la Sociedad: S2013/MIT-2862.En el cual se engloba esta tesis doctoral, y a Jecs Trust, de la Sociedad Europea de Cerámica (ECERS), por la financiación que me permitió realizar mi estancia en el extranjero.Este proyecto se encuadra dentro de los objetivos de los proyectos: MAT2015-63974-C4-1, MAT2016-79869-C2-1-P, MAT2015-70780-C4-1-P, M-ERA.NET-2016: PCIN-2017-036
DS e-Archivo
RD 27 jul. 2024