Desenvolupament de nous materials basats en alúmina per a fabricació additiva mitjançant estereolitografia

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Abstract

Stereolithography (SLA) consists of the photopolymerization of a liquid resin in layers through selective irradiation of the area forming part of the 3D object. Two technologies based on SLA are used in this thesis; SLA based on a Digital Light Processing (DLP) projection system and a second, which uses a UV LED source and a Liquid-Crystal Display (LCD) masking system.

Despite SLA having been developed for printing objects from photosensitive polymers, it is also used to obtain composite and ceramic materials. In the case of composite materials, the final piece is obtained directly. For ceramic materials, much more concentrated suspensions are required. The polymer acts as a binder, which will be removed during the debinding and sintering process to obtain the final ceramic piece. However, there are some difficulties associated with this technology. The SLA requires very fluid suspensions, which allow a good levelling and correct flow of the suspension. On the contrary, ceramic processing needs suspensions with very high concentrations to ensure the correct densification of the piece and avoid cracks.

In this work, PEG 200 has been incorporated as a non-reactive diluent to improve the removal of the organic part. A stable suspension of 77.5% alumina by weight has been achieved, printable by SLA-DLP and can be thermally treated to obtain a ceramic piece with faster heating rates than usual. Regarding the development of composite materials, great interest in this field is generated due to the low mechanical properties presented by acrylic resins. This lack of properties limits their widespread use. In this sense, this thesis aims to formulate and characterize different alumina ceramic suspensions with little concentration in particles, to obtain composite materials with improved properties compared to the base resin. Suspensions of different alumina have been obtained with a maximum concentration of 15% by weight of ceramic powder, which has higher elastic moduli than base resin in the range between 5 and 10% alumina. Additionally, dual epoxy-acrylic systems have been studied as a base resin for incorporating reinforcement particles.