The additive manufacturing (AM) is a class of near-net shape technology in which a part is generated from 3D model data by adding material. Nowadays, these techniques allow the direct production of metal, ceramic and polymer components with complex shapes which are very difficult to fabricate using conventional forming methods. Among these techniques, fused deposition modeling (FDM) is an additive manufacturing (AM) method which can be employed for producing porous ceramic parts. During forming, specific polymer-based systems containing ceramic particles, soften and melt to build the object layer by layer in which particles are embedded. For this reason, the interaction between soften/molten polymers and ceramic particles play an important role to ensure the homogeneity of the mixture and avoid segregation during the forming process, although this aspect has not been widely reported.
In this work, porous structures developed from novel thermoplastic-ceramic systems via FDM were obtained taking into account data on wettability of soften/melted polymers on ceramic particles, granulometric/morphological characteristics of the ceramic powder and physical properties of the polymers. Commercially available submicrometer alumina powder was employed as ceramic material and characterized by particle size distribution (dynamic light scattering method), density (Arquimedes method), specific surface (BET) and SEM. Four different commercial polymers (PP, PLA, ABS and PA) were characterized by DSC, melt index and molecular weight measurements, and evaluated in order to design a starting polymer-based system to be used in the processing of porous structures by FDM. Wettability of soften/melted polymers on alumina substrates prepared by uniaxial pressing was evaluated by contact angle measuring and subsequent calculation of work of adhesion. The effect of adding oleyl alcohol (1-5 wt%) to alumina powder in order to modify the surface energy of particles was evaluated by measuring the same parameters. Based on properties of materials, especially the polymer-ceramic surface interaction, the main polymer component of the starting system was selected. Mixtures of PA pellets and alumina powder, besides organic additives as oleyl alcohol, were used to obtain compound filaments and controlled porous structures.