Additive Manufacturing with Liquid Latex and Recycled End-of-Life Rubber

Abstract Elastomers and rubber are common industrial materials used for test objects, supporting parts, and many other commercial products. The industrial processing of these materials is currently dominated by injection molding, which reduces manufacturing costs and speeds up production. However, this manufacturing method does not permit personalization or customization and lacks the versatility of other techniques such as three-dimensional printing. Understandably, there has been a move toward additive manufacturing (AM) with elastomers. This work proposes a new approach to AM with liquid latex, using a drop-on-demand (DoD) based inkjet to fabricate latex patterns. The printhead actuator benefits from a higher material compatibility compared to conventional inkjet/extrusion-based printers, allowing the jetting of viscous fluids, as well as liquids with high solid loading. The setup allows printing with viscous liquid latex of a high solid content (60 wt. %). The process is controllable and reliable, making the printing of patterns possible. In addition, we explore printing with micronized rubber powder (MRP) made from end-of-life tires, to test solid-particle loading compatibility and as a novel method for rubber recycling. In this study, we demonstrate that large-scale DoD inkjet printing is capable of handling solid particle loadings of up to 10 wt. % in addition to the high solid content liquid latex. Moreover, multilayer objects were created from pure liquid latex, as well as from MRP/latex suspensions. Material characterization indicates that the stiffness of cured latex is not altered by the addition of MRP, but reduces the maximum elongation length from 750% to 430%. The results highlight the ability to print with both high particle loading and large particles. This explorative study demonstrates the potential of AM processes with liquid latex, as well as a new approach to tire rubber reuse.