Influence of Humidity on the Tensile Strength of 3D Printed PLA Filament

Abstract

Polylactic acid (PLA) filament is sensitive to humidity due to its hygroscopic properties, resulting in poor printing quality. Many studies focus on the effect of process parameters on the 3D printed part; however, the influence of humidity on the printing quality is less explored. Moisture can influence the mechanical properties of 3D printed parts due to the water’s existence, altering the polymer chain’s bonding, resulting in a lower mechanical strength. This study investigates the effect of humidity on the tensile strength of 3D printed PLA specimens exposed to various humidity conditions. Three conditional settings were established; a new PLA roll acts as the reference, used PLA roll stored in the vacuum bag with desiccant, and used PLA roll stored in an open environment, exposed with the humidifier for 24–150 h. As a result, the moisture decreases the tensile strength and increases the plastic region. The presence of moisture causes a plasticizing effect of the polymer, which increases its deformability while lowering its rigidity as the moisture changes the polymer’s molecular structure. Humidity expands the interlayer gap, promoting enhancement in the fracture strain due to increased macromolecules deformation space. However, the used PLA filament stored in a vacuum bag with some desiccants shows an equivalent tensile strength with the reference specimen. To conclude, humidity influences the tensile strength and should be controlled for a good printing quality of PLA parts. Therefore, it is recommended that all 3d printer users seal the used PLA filament in a vacuum bag with some dehumidifying agents as an alternative to the drying cabinet.