Synthesis of Silver Nanocomposites for Stereolithography: In Situ Formation of Nanoparticles.

Additive Manufacturing (AM) offers remarkable advantages in relation to traditional methods used to obtain solid structures, such as the capability to obtain customized complex geometries adapted to individual requirements. The design of novel nanocomposites suitable for AM is an excellent strategy to widen the application field of these techniques. In this work, we report on the fabrication of metal/polymer nanocomposites with enhanced optical/electrical behaviour for stereolithography (SLA). In particular, we analyse the in situ generation of Ag nanoparticles (NPs) from Ag precursors (AgNO and AgClO) within acrylic resins via SLA. Transmission electron microscopy (TEM) analysis confirmed the formation of Ag NPs smaller than 5 nm in all nanocomposites, providing optical activity to the materials. A high density of Ag NPs with a good distribution through the material for the larger concentration of AgClO precursor tested was observed, in contrast to the isolated agglomerations found when the precursor amount was reduced to 0.1%. A significant reduction in the electrical resistivity up to four orders of magnitude was found for this material compared to the unfilled resin. However, consumption of part of the photoinitiator in the formation process of the Ag NPs contributed to a reduction in the polymerization degree of the resin and, consequently, degraded the mechanical properties of the nanocomposites. Experiments with longer curing times showed that, for the higher AgClO concentrations tested, post-curing times of 300 min allowed an 80% degree of polymerization to be achieved. These conditions turned these materials into promising candidates to obtain solid structures with multifunctional properties.