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Cellulose is an abundant and sustainable material that is receiving more and more attention in different industries. In the context of additive manufacturing, it would be even more valuable. However, there are some challenges to overcome in processing cellulose-based materials. Therefore, this study used a new thermoplastic cellulose-based granulate to show its potential in filament extrusion and the fused filament fabrication printing process. Furthermore, the mechanical properties were investigated. It was shown that filaments with a suitable and uniform diameter could be produced. A parameter study for printing revealed that adhesion of the material on the bed and between layers was an issue but could be overcome with a suitable set of parameters. Tensile bars with different orientations of 0°, +/-45°, and 90° were printed and compared with injection-molded samples. It could be shown that different mechanisms (single strand breakage, shear failure) caused fracture for different printing orientations. In comparison with injection-molding, the printed parts showed lower mechanical properties (moduli of 74-95%, a tensile strength of 47-69%, and an elongation at break of 29-60%), but an improvement could be seen compared with earlier reported direct granule printing. The study showed that FFF is a suitable process for the new cellulose-based material to fabricate samples with good mechanical properties.

RESUMEN

Due to their light-weight and cost-effectiveness, cellular thermoplastic foams are considered as important engineering materials. On the other hand, additive manufacturing or 3D printing is one of the emerging and fastest growing manufacturing technologies due to its advantages such as design freedom and tool-less production. Nowadays, 3D printing of polymer compounds is mostly limited to manufacturing of solid parts. In this context, a merged foaming and printing technology can introduce a great alternative for the currently used foam manufacturing technologies such as foam injection molding. This perspective review article tackles the attempts taken toward initiating this novel technology to simultaneously foam and print thermoplastics. After explaining the basics of polymer foaming and additive manufacturing, this article classifies different attempts that have been made toward generating foamed printed structures while highlighting their challenges. These attempts are clustered into 1) architected porous structures, 2) syntactic foaming, 3) post-foaming of printed parts, and eventually 4) printing of blowing agents saturated filaments. Among these, the latest approach is the most practical route although it has not been thoroughly studied yet. A filament free approach that can be introduced as a potential strategy to unlock the difficulties to produce printed foam structures is also proposed.

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RESUMEN

This article summarizes the investigation of in-line particle characterization during high shear wet granulation (HSWG) using focused beam reflectance measurement (FBRM) for enhanced process understanding, which is part of an effort to develop this drug product within the framework of quality by design (QbD) and process analytical technology (PAT). Traditionally, the effectiveness of in-line monitoring of HSWG processes is hindered by wet and sticky material fouling the probe resulting in inconsistent and erroneous data collection. For this study, a FBRM C35 probe was used which incorporates a scraping mechanism to maintain a clean probe window ensuring consistent measurements throughout each batch. The evaluations were conducted on nine scale-up DOE development batches and eight clinical sub-lots. In the DOE campaign, the purpose of FBRM was used to study the impact of varying water amount and wet massing time on granule dimension and count during granulation, while batch-to-batch variation or batch reproducibility was evaluated under the same process conditions for the clinical batches. In addition, a preliminary investigation of the most optimal probe position was conducted. The results indicate that FBRM is capable of monitoring the rate and degree of change to granule dimension/count during HSWG, and could be a potential technique for granulation endpoint determination.

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