High-performance nano-PTFE reinforced nickel mold for defect-free micro injection molding of surface micro structures

Abstract

Interest in electroformed nickel (Ni) molds has continued increasing due to their high precision, low cost and high surface finish. Nevertheless, pure Ni molds still rely on extra surface treatments employing release agents to achieve defects-free demolding and meanwhile, mitigate the residual contamination. To address these issues, lubricant-retaining Ni mold was achieved by doping low surface tension polytetrafluoroethylene (PTFE) nano-fillers into the Ni matrix via electrodeposition. The introduction of surfactant mixtures facilitated the successful incorporation of PTFE into the Ni matrix, causing them to perfectly integrate and form as a whole. Such mold exhibited excellent mechanical performance with the enhanced hardness of 452 HV (2.3-fold increase), low surface roughness of 23 nm in S_a and low surface energy of 28.1 mJ/m² (33.6% decrease), resulting in a maximum reduction of 28.6% in demolding force. This Ni-PTFE mold can withstand more than 1 500 demolding cycles without the need for additional demolding agents or the removal of residual contaminants. Importantly, no PTFE nanoparticles were detected on the produced cyclic-olefin-copolymer (COC) chips, as confirmed by energy dispersive X-ray spectroscopy analysis and Raman spectroscopy, confirming no contamination to the polymer and no lubrication degradation of such mold. Polymer chips produced from such mold displayed well-defined structures and excellent biocompatibility, rendering them suitable for microfluidic applications. Finally, this facile and cost-effective method enables creating a reusable, high-resolution mold with low surface energy, ensuring defects-free demolding for the mass production of polymer parts.

Keywords

Polytetrafluoroethylene (PTFE) nano-filler / Lubrication / Electroforming / Mold / Micro injection molding

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Funding

Science Foundation Ireland(22/RP-2TF/10466)

Enterprise IRELAND(CF-2021-1635-P)

China Sponsorship Council(202008300010)

University College Dublin

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