Surface texture and thermo-mechanical properties of material extruded and ironed polylactic acid

This work investigates the effects of the ironing process on physical properties of material extruded polylactic acid (PLA). Polylactic acid is an exceedingly popular biodegradable polymer commonly used in material extrusion 3D printing. As a promising alternative to petroleum based polymers, PLA has found use in the medical, textile, and packaging industries due to its biocompatibility, renewability, and good mechanical properties. Several process parameters in the material extrusion printing technique can alter physical characteristics of a part such as, print speed, extrusion (nozzle) temperature, layer thickness, and infill density; which have led to several studies on 3D printed PLA. Albeit, the surface texture and viscoelasticity of 3D printed and ironed PLA has yet to be reported upon. This study utilizes a fractional factorial design as the basis for an experimental design, in order to correlate the impacts these process parameters have on the surface morphology and viscoelasticity of 3D printed and ironed PLA. In this study, samples were produced using the material extrusion additive manufacturing process with PLA as the feedstock material. Twenty-seven iterations were 3D printed; each with varying process parameters dictated by the fractional factorial design. The (1) surface morphology, (2) surface roughness, and (3) thermo-mechanical (visco-elastic) properties of these samples were investigated to report on the effect of the ironing process. The surface texture was observed to produce a more uniform and smoother surface when ironed. Additionally, the storage modulus and glass transition temperature of the 3D printed and ironed PLA is shown to be dependent on the process parameters mentioned above. Parametric control of physical characteristics of 3D printed materials can benefit the research and development of existing materials, improving the additive manufacturing process, and can be applied to a wide range of engineering applications. This study contributes to understanding the control of the abovementioned material properties through process parameter modification.