3D printing refers to any technology for manufacturing a real object by laminating proper materials according to three-dimensional design data. It is a technology to design an object to be a virtual object through a three-dimensional digital drawing, ...
3D printing refers to any technology for manufacturing a real object by laminating proper materials according to three-dimensional design data. It is a technology to design an object to be a virtual object through a three-dimensional digital drawing, and then stack each material along a design shape in a very thin section to form an object. Therefore, it's getting great attention nowadays as a very efficient technical alternative for a model that is difficult to implement with a conventional manufacturing method or a product that can be produced only through a complicated and numerous process. There are many ways to execute 3D printing technology. Among them, the most widely used methods are a fused deposition modeling (FDM) in which thermoplastic resins are melted and laminated, and a digital light processing (DLP), which selectively cures photo curable resins by irradiating light energy source in a short wavelength band. However, conventional materials used in these methods need to be developed and supplemented in terms of range, usability, and the physical properties of the end products. In addition, the research is not only needed to improve various functionalities of 3D printed object, but the approaches on plastic wastes used in FDM and DLP is also necessary in view of environmental pollution which is a significant part of modern society.
In this study, bioplastics and wood-derived cellulose resources (i.e., wood flour and cellulose nanocrystals) were used to develop the novel materials used for 3D printing, and composites were prepared using functional fillers (i.e., nanoclay and nano-CaCO3) and evaluated for various properties.
For the filament form material used in the FDM, wood flour was added based on PLA, a representative bioplastic, and optimize 3D printing parameters according to the amount of wood flour addition, and composites were manufactured to evaluate various properties. The morphological properties were investigated to determine the mechanism of voids generation in 3D printed object by the addition of wood flour, and its effects on the mechanical properties. In addition, by examining the biological degradation properties according to the addition of wood flour of bioplastics/wood flour composite material by microorganisms, it was confirmed that it represents a better eco-friendly properties according to the amount of wood flour added.
Based on the experimental results, the optimum amount of wood flour (20 wt%) was selected for PLA polymer, and the possibility of introducing 3D printing of PBAT, another bioplastic, was investigated according to the optimized 3D printing parameters. The morphological and mechanical properties according to the PBAT additions were investigated, and the results showed that the thermal stability was significantly improved by the addition of PBAT. Therefore, filament manufactured from PLA and PBAT, which are eco-friendly bioplastics, and wood flour, which is a natural and sustainable resource, is highly applicable as a new resource-cycling material for FDM 3D printing. In addition, wood flour incorporation induced the cost-effectiveness, and visual appearance in terms of external aesthetics is successfully improved.
The composite material of cellulose nanocrystals and functional fillers was prepared by 3D printing on the liquid photocurable resin used in the DLP, and various properties were analyzed. The influence to morphological characteristics and mechanical strength of composites was investigated by examining the mechanism of freezing behavior of CNC according to the lyophilization concentration of CNC added to the composites, and the pretreatment process step for the addition of CNC and inorganic fillers to the photocurable resin was established. The optimum amount of CNC addition was investigated by analyzing the mechanical and morphological properties according to the concentration of CNC addition. In addition, the composites were fabricated to show better physical properties through the addition of nanoclay and nano calcium carbonate. Through the research of manufactured composites not only studied the utilization of wood-derived cellulose resources, but also showed better mechanical properties compared to conventional photocurable resins, and therefore, it can be applied as a functional new material applicable to DLP 3D printing.
The results obtained through the above studies are considered to be precedence study that uses various forest resources for FDM and DLP 3D printing materials to build a basic property information, and develop eco-friendly materials with better properties that can be applied to 3D printing. It is expected that this will lay the foundation for future research on 3D printing materials.