Wood and olive kernel flour as reinforcement for itaconic acid-based UV-curing additive manufacturing material

Additive manufacturing allows for the fabrication of specialized parts with high individualization and opens up new fields of application. However, in many cases the performance of parts fabricated by additive manufacturing cannot compete with similar parts prepared by more classical manufacturing technologies like injection molding. One possibility to enhance the performance is the printing of composites, reinforced with fibers and/or particles. For thermoplastic matrices, the preparation and processing of composites with additive manufacturing techniques is quite straight-forward, utilizing for example fiber or particle filled filaments in fused filament fabrication. On the other hand, for techniques utilizing thermosetting matrices, such as stereolithography, the production of composites is more challenging. Fillers can sediment over the time of the printing process and that can lead to a heterogenous distribution of the particles in the printed parts. In this work, we present the use of wood and olive kernel flour as fillers in combination with bio-based UV-curable resins, to prepare biocomposites by means of UV-curing additive manufacturing. Up to 15 % of the bio-based fillers could be incorporated in the polymer matrix without agglomeration of the particles. In addition, the fillers enhanced the mechanical performance and the thermal stability, even at relatively low loadings. For example, the addition of only 0.5 wt% olive kernel flour resulted in an enhancement of the tensile modulus from 190 to 593 MPa. Therefore, these renewable fillers are promising candidates for the fabrication of composite materials with stereolithography techniques, as they enhance the thermomechanical properties of the printed parts while simultaneously increasing the overall bio-based content of that class of UV-curing materials.