Influence of pre-drying the filament using different methods on the mechanical properties and microstructure of PLA, ABS, TPU and PETG thermoplastic polymers in additive

• Main Author: Husni, Siti Nur Hidayah
• Format: Thesis
• Language: English; English
• Published: 2022
• Subjects: T Technology (General); TS Manufactures
• Online Access: http://eprints.utem.edu.my/id/eprint/26804/1/Influence%20of%20pre-drying%20the%20filament%20using%20different%20methods%20on%20the%20mechanical%20properties.pdf; http://eprints.utem.edu.my/id/eprint/26804/2/Influence%20of%20pre-drying%20the%20filament%20using%20different%20methods%20on%20the%20mechanical%20properties.pdf; http://eprints.utem.edu.my/id/eprint/26804/; https://plh.utem.edu.my/cgi-bin/koha/opac-detail.pl?biblionumber=121768
• Institution: Universiti Teknikal Malaysia Melaka

Additive manufacturing (AM), also known as 3D printing, creates three-dimensional solid items from the CAD file. Fused Deposition Modelling (FDM) is one of the most widely used AM techniques because of its versatility and inexpensive cost. The FDM process creates 3D structures by extruding pre-heated thermoplastic polymers with a nozzle at predetermined process parameters. Filaments that contain moisture will interrupt the extrusion process, as the mass flow rate and humidity are correlated. Thermoplastic filaments are mostly hygroscopic and absorb moisture when exposed to a humid environment if not stored properly using dry cabinets. As a result, water absorbed in the plastic will rapidly expand, boil, and break as the filament is extruded. Hence, microstructure and mechanical performance can all be affected. Pre-drying the moisture-exposed used filament can theoretically eliminate the moisture, avoid unnecessary interruption during the printing, and simultaneously produce good quality 3D printer parts. In addition, density is a significant physical property related to the porosity of the microstructure. Generally, dense material exhibits a packed microstructure with limited porosity, and the pores in the microstructure are detrimental to the mechanical properties of specimens. Pre-dried filaments could improve the mechanical strength and reduce the porosity of the samples. In this study, a comparative study was made between the undried and pre-dried specimens (SUNLU dryer and oven). This study aimed to investigate two different drying methods of filaments before printing and to observe the influence of adopting those drying approaches on the mechanical properties, microstructure, and polymeric chain bonding. Thermoplastic polymers (ABS, PLA, TPU, PETG) were employed to see how moisture influences the 3D specimens. Hence, three conditions were established: (i) new filaments as the reference, (ii) used filaments stored in the vacuum bag with desiccant, and (iii) used filaments stored in an open environment and exposed to a humidifier for a variant of 48 hours, 96 hours and 150 hours. Shimazu AGS-X Universal Testing Machine (UTM), Scanning Electron Microscope (SEM) machine, densimeter, and Jasco FTIR machine are used. As a result, the tensile and flexural strength were improved after filament drying compared to the undried. Besides, the density was also improved, which was validated by the SEM images that show a smaller interlayer gap was found in the pre-dried specimen. In addition, the microstructure of the pre-dried specimen shows fewer voids, low incomplete fusion, and better layer formation. The chemical chain bonding of the sample was altered by humidity, and the pre-dried filaments showed almost no presence of water (H20). The absorption of the spectra is high in the O-H group, which was discharged when drying. Further investigations and improvements are needed to evaluate 3D printed part performance based on porosity characterization.