Design and Additive Manufacturing of Polyethylene-Based Hierarchical Composites by Selective Laser Sintering

Selective laser sintering (SLS) is gaining increasing importance in polymer additive manufacturing. It has many unique advantages compared with extrusion or photopolymerization based technologies. However, one of the main challenges for SLS is the limited types of compatible polymer microparticles. This study develops a versatile material platform for the scalable synthesis of polyethylene (PE) and its composite microparticles for SLS 3D printing. The incorporation of metal oxide nanoparticles inside PE microparticles by in situ sol-gel chemistry as well as blending with carbon black for enhanced laser absorption is found to have significant impacts on the printability and physical properties of printed structures. Importantly, this study also demonstrates that post-printing processing can substantially enhance the mechanical properties and introduce new functionalities to 3D PE structures. Thermal annealing improves the mechanical strength and modulus by more than ten times. Electrochemical deposition of copper on the 3D PE composite structures significantly enhances the electrical conductivity and mechanical properties, which can be utilized to fabricate 3D hierarchical metallic structures with broad applications. A new type of polyethylene-based composite microparticle is developed and used for selective laser sintering 3D printing. The 3D-printed structures show excellent shape fidelity, tunable internal structure, and electrical conductivity. Their mechanical properties are significantly enhanced after post-printing thermal annealing. image