Design and Fabrication of a New Filament, PLA with PTFE as Fillers, for Water Repellent Surfaces

Abstract

The use of additive manufacturing by fused deposition is a versatile, cost-effective and simple prototyping and manufacturing technique that is generating and accelerating a revolution in equipment and filaments. However, materials are limited to a small number of polymers. It is a scientific challenge to bring new characteristics and properties to the parts obtained. In this work, a new filament has been designed with the combination of PLA (poly lactic acid) as matrix and PTFE (polytetrafluoroethylene) as filler. This filament has improved the water repellency of the parts obtained. Cleaning, demoulding, anti-adherence, anti-frost, anti-humidity and anti-bacterial applications can be deployed with this new filament. Extruded filaments have been obtained with PLA beads and PTFE micropowder. Flat test tubes have been produced with this filament. The experiments included PTFE fillers (1% to 40% by weight). The surfaces have been characterised by sliding angle (SA) and static contact angle (CA) tests, surface roughness (Sa and Sz), flatness error and % water adsorption. The results indicate, as expected, that the higher the fluoropolymer content, the higher the hydrophobicity, reaching values of 125° for CA and 9° for SA, and the % adsorption decreases. In terms of roughness, the surfaces are less rough when the PTFE load increases. On the other hand, the flatness is a property strongly affected by the % PTFE load and at values higher than 15% it produces intense warping and deformation of the specimens. Finally, the PTFE loading thresholds in the PLA matrix have been obtained below which the wettability and dimensional reproduction properties are balanced and optimal.