Influence of phosphorous acid concentration on the self-lubricating properties of electroformed Ni-P-PTFE ternary composites

Abstract

In micro-injection molding, polymer/mold interface adhesion may cause severe deformation or damage of micro features on the molded products. To reduce the interface adhesion and improve the molding quality of polymer microfluidic chip, Ni-P-PTFE (polytetrafluoroethylene) ternary composite was adopted to electroform mold insert with self-lubricating properties. The influence of phosphorous acid concentration on the composition and performance of Ni-P-PTFE composites was systematically investigated. Our results demonstrated that the content of P and PTFE particles in the composites raised with an increase in phosphorous acid concentration. Elevated phosphorous acid concentration adversely affected the current efficiency and slowed down the deposition rate, allowing sufficient contact time for PTFE to transfer and adsorb onto the electrode surface. The hardness of the deposited nickel increased from 310 HV to 510 HV in the Ni-P-PTFE composites. Furthermore, the Ni-P-PTFE composites demonstrated excellent self-lubricating properties, showcasing friction coefficients of 0.15 and 0.25 during the initial and steady stages, respectively, representing a notable reduction of 66.7 % and 64.3 % compared to pure nickel. This study provides a novel approach to fabricate molds with self-lubricating properties, which contributes to the high-precision injection molding of polymer-based micro devices.