Direct Extrusion 3D Printing for a Softer PLA-based Bio-polymer Composite in Pellet Form

Abstract

Fused deposition modelling is the most popular method of 3D printing with a variety of polymers, but the raw materials are commonly in the filament form. Research has demonstrated the ability to use pellets for this process, which are easier to produce than filaments. Apart from the savings on the pre-processing, the approach also combines the good attributes of both injection moulding and 3D printing and referred to as extrusion 3D printing. Direct printing of pellets is especially suited for thermosensitive polymers, with which, repeated or excessive heating may lead to degeneration. Also, polymers that are too soft do not qualify for filament-based extrusion. PLA is a popular choice for fused deposition modelling in the filament form but is often too brittle. A softer version of PLA composite based on PBAT and cellulose fibres is proposed here for 3D printing. Considering the lack of stiffness of the filaments, direct extrusion from pellet form is evaluated. Regardless of form, the polymer material system satisfied the stringent conditions of consolidation as dictated by the dynamic combination of extrusion and rasterised material deposition. Experimental evaluation based on meso-structural and mechanical property analyses indicate the new pellet-based material system to be suitable and to perform well. The novelty of the material and process combination is that the printed samples were actually comparable mechanically to the injection moulded counterparts, which is an extraordinary achievement, considering the shortcomings typical of material consolidation in additive manufacturing.