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Lightweight, renewable origin, mild processing, and facile recyclability make thermoplastics the circular construction materials of choice. However, in additive manufacturing (AM), known as 3D printing, mass adoption of thermoplastics lags behind. Upon heating into the melt, particles or filaments fuse first in 2D and successively in 3D, realizing unprecedented geometrical freedom. Despite a scientific understanding of fusion, industrial consortium experts are still confronted with inferior mechanical properties of fused weld interfaces in reality. Exemplary is early mechanical failure in patient-specific and biodegradable medical devices based on Corbion’s poly(lactides), and more technical constructs based on Mitsubishi’s poly(ethylene terephthalate), PET. The origin lies in contradictory low rate of polymer diffusion and entangling, and too high rate of crystallization that is needed to compensate insufficient entangling.
Knowing that Zuyd University in close collaboration with Maastricht University has eliminated these contradictory time-scales for PLA-based systems, Corbion and Mitsubishi contacted Zuyd with the question to address and solve their problem. In previous research it has been shown that interfacial co-crystallization of alternating depositioned opposite stereo-specific PLA grades resulted in strengthening of the interface.
To promote mass adoption of thermoplastics AM industries, the innovation question has been phrased as follows: What is a technically scalable route to induce toughness in additively manufactured thermoplastics?
High mechanical performance translates into an intrinsic brittle to tough transition of stereocomplex reinforced AM products, focusing on fused deposition modeling. Taking the professional request on biocompatibility, engineering performance and scalability into account, the strategies in lowering the yield stress and/or increasing the network strength comprise (i) biobased and biocompatible plasticizers for stereocomplexed poly(lactide), (ii) interfacial co-crystallization of intrinsically tough polyester based materials formulations, and (iii) in-situ interfacial transesterification of recycled PET formulations.