Effects of crosslinkers, catalyst and filler on printability of silicone

Complex three-dimensional (3D) silicone structures with functional properties for medical applications can be produced using 3D printing technology. The printability of extrusion-based 3D silicone structure is dependent on precise control of silicone rheological behaviour, especially shear-thinning behaviour and static yield stress. However, the rheology behaviour of silicone elastomer limits its fabrication technique to the moulding process, which is more suited for mass production but not small batch production and prototyping. In this study, a custom condensation-cured room temperature vulcanisation (RTV-1) silicone is formulated for an extrusion-based 3D printer to tackle this problem. Pure silicone polymer lacks key rheology behaviours to ensure a successfully 3D print. The roles and impacts of crosslinkers, catalyst and filler (nano-silica) on the rheology properties of silicone were investigated. Through the rheology characterisation of the formulated silicone materials, the critical component in contributing to the success of extrusion-based silicone printing can be identified.