Binder Development for Indirect SLS of Non Metallics

In this work, a binder system for non metallics such as graphite has been developed and tested. A graphite-phenolic mixture was used for making bipolar plates using SLS. Phenolic resin melts (~90°C) instead of cross-linking (~165°C) in the SLS machine. During post processing in a furnace, the SLS parts slumped due to remelting of phenolic resin with no other binder present to hold the powder together. To prevent this slumping and to increase the green strength of the SLS parts, a new binder system was developed with Nylon/11 added. Nylon/11 has a melting point of ~185°C and is able to hold the SLS part together until the phenolic can cross link, preventing slumping. Single layer scan experiments with different compositions and SLS parameters were run to identify optimum composition and SLS parameters. Three point bend specimens were prepared with 70 wt. % Graphite-25 wt. % Phenolic- 5 wt. % Nylon/11 and 70 wt. % Graphite-20 wt. % Phenolic- 10 wt. % Nylon/11, tested and compared to graphite-phenolic parts. No significant increase in green strength was attained with Nylon/11 addition.