This study investigates the effects of process parameters on the quality of products fabricated by fused deposition modeling (FDM), such as surface roughness and tensile strength. Polylactic acid (PLA) samples were built on a FDM machine at various layer thicknesses, nozzle temperature and deposition head velocity. The effect of cooling the samples during the process was also considered. The experimental study was performed according to a mixed type Taguchi L16 orthogonal array. The effectiveness of each parameter was also discussed by an analysis of variance (ANOVA). The tensile strength results were compatible with the optical images of the fracture surfaces while the surface roughness results were compatible with the surface topography of the parts along the thickness. The two dominant quality characteristics were found to be layer thickness and deposition head velocity. Lower layer thickness values yielded higher tensile strength and lower surface roughness. Use of a cooling fan and nozzle temperature were found to be the least effective parameters. Finally, the results indicated that tensile strength and surface quality of the FDM samples improved about 25 %, and 12 %, respectively at optimal process conditions.
This study presents the improvement of mechanical properties and cell viability of polylactic acid/halloysite nanotube (PLA/HNT) scaffolds that were fabricated by foam injection molding. In this regard, firstly PLA and HNT were compounded on a twin screw extruder by melt mixing method within the HNT loadings of 1, 3, 5 wt%. Then, neat PLA and PLA/HNT pellets were foam injected molded to obtain tensile test samples. The mechanical properties of the scaffolds were determined by tensile test and methyl-thiazol-tetrazolium technique was used for determination of cell viability. The results have shown that the scaffold with 3 wt% of HNT addition gave the highest mechanical strength among the fabricated scaffolds with 124.2% and 79.2% of increments in tensile strength and elongation, respectively. Also, 3 wt% of HNT demonstrated the highest cell viability among the obtained scaffolds due to its improved scaffold morphology. K E Y W O R D Scell viability, foam injection molding, halloysite nanotube, mechanical strength, polylactide, scaffold
One of the important process parameters affecting the tensile strength and build time of the part is the build orientation. Therefore, in this study, FDM 3D-printed PLA parts were fabricated at different build orientations to examine the effects of build orientation on the tensile properties and build time of material. In this regard, three build orientations and three print angles were examined. According to results, tensile strength decreased when the build orientation of the parts was aligned from flat to upright direction and 0° to 90° printing angle. For upright build orientation, 36% less tensile strength was obtained compared to the flat ones because of the fracture mode and the loading direction. In terms of build time, build time increased as the build orientation changed from flat to upright. Therefore, the build orientation had a big impact on the tensile properties and build time of the parts produced using FDM. The findings of this study will contribute to the literature on proper build orientations and print angles.
In this study, multifunctional polymer nanocomposite scaffolds were fabricated by the fused deposition method (FDM) for biomedical applications. First, halloysite nanotube reinforced (1–5 wt%) polylactic acid filaments were prepared by melt mixing process. For the selected compositions, HNT was loaded with metformin (MET) by electrostatic interactions. The characterization of the scaffolds was observed by Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. The morphology of the nanocomposite scaffolds was investigated by scanning electron microscope. Mechanical behavior of the scaffolds was determined by tensile, compression, and three‐point flexural tests. It has been seen that 3%wt of HNT loading showed 124%, 145%, and 41% increments in tensile, compression, and three‐point flexural strength of the scaffolds, respectively. In‐vitro drug release and cell viability of the scaffolds were also examined. According to the cell viability result, a better cell proliferation regimen was achieved in all HNT‐containing groups without any cytotoxicity effect. Also, approximately 50% of the total drug was released from the scaffolds at the end of 120 h. Finally, it has been seen that the developed scaffolds show promise for bone regeneration and replacement of bone.
Homogenous dispersion of the nano particles in the polymer matrix is a key factor in order to achieve enhanced properties of the polymer nanocomposites. Dispersion or exfoliation of nano clay is difficult in the matrix during melt mixing. In this study, dispersion of nano montmorillonite (MMT) in polypropylene (PP) was done by using chemical foaming agent during melt mixing process. Chemical foaming agent (CFA) added (1 %wt.) PP/MMT nanocomposites were prepared on twin screw extruder. Then, injection molding was done to the granulated nanocomposites in order to obtain tensile test samples. Thermal test and morphological investigations were done. Tensile test was applied to observe the difference in mechanical strength of the nanocomposites depending on the presence of the foaming agent during melt mixing process. The results have shown that, dispersion of MMT enhanced in the matrix due to addition of chemical foaming agent. This brought improved tensile strength about 19% for the PP/MMT nanocomposites within same concentrations of nano filler.
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