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The fused filament fabrication (FFF) process is characterized by fast local temperature decrease. Such characteristic usually leads to lower crystallinity degree in final printed parts when semi-crystalline polymers are used. By melt-compounding poly(lactic acid) (PLA) with its nucleating agent Talc, filaments of PLA/Talc composite were produced and used in FFF. Through investigations in static/dynamic mechanical and thermal properties, and morphology, the influence of Talc on the PLA based composite in FFF are revealed: after melt compounding with Talc, PLA matrix can crystallize considerably during fast cooling in FFF; as a consequence, final parts exhibited higher degree of crystallinity than the case of neat PLA; furthermore, melt crystallization process releases heat, promoting coalescence between adjacent layers, and ultimately contributes to higher parts stiffness and better mechanical integrity. This paper presents a first example in which in-situ melt crystallization is recovered for semi-crystalline polymers during FFF via composition modification. With this example, an increase in crystallinity from 3.6% to 12% can lead to 15% increase in flexural modulus for FFF printed parts. Research results also provide insights in material property reinforcement, heat treatment on finished parts, and explorations in other semi-crystalline materials in FFF.
Yu et al. (Mon,) studied this question.