• Journal of the Korean Wood Science and Technology
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• v.52 no.3
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• pp.205-220
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• 2024

Various polylactic acid (PLA) blends were reinforced with untreated or silane-treated micro-sized cellulose fiber (MCF), successfully prepared as 3D printing filaments and then printed using a fused filament fabrication (FFF) 3D printer. In this study, we focused on developing 3D-printed MCF/PLA composites through silane treatment of MCF and investigating the effect of silane treatment on the various properties of FFF 3D-printed composites. Fourier transform infrared spectra confirmed the increase in hydrophobic properties of silane-treated MCF by showing the new absorption peaks at 1,100 cm^-1, 1,030 cm^-1, and 815 cm^-1 representing C-NH₂, Si-O-Si, and Si-CH₂ bonds, respectively. In scanning electron microscope images of silane-treated MCF filled PLA composites, the improved interfacial adhesion between MCF and PLA matrix was observed. The mechanical properties of the 3D-printed MCF/PLA composites with silane-treated MCF were improved compared to those of the 3D-printed MCF/PLA composites with untreated MCF. In particular, the highest tensile and flexural modulus values were observed for S-MCF10 (5,784.77 MPa) and S-MCF5 (2,441.67 MPa), respectively. The thermal stability of silane-treated MCF was enhanced by delaying the initial thermal decomposition temperature compared to untreated MCF. The thermal decomposition temperature difference at T₉₅ was around 26℃. This study suggests that the effect of silane treatment on the 3D-printed MCF/PLA composites is effective and promising.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.29 no.1
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• pp.51-57
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• 2023

Because of the global pollution caused by plastic disposal, demand for eco-friendly transformation in the packaging industry is increased. As part of that, the utilization of polylactic acid (PLA) as a food packaging material is increased. However, it is necessary to improve the crystallinity of PLA by adding nucleating agents or to improve the modulus by adding fillers because of the excessive brittleness of the PLA matrix. Thus, the cellulose nanofiber (CNF) was fabricated and dried to obtain a powder form and applied to the CNF/PLA nanocomposite. The effect of CNF on the morphological, thermal, rheological, and dynamic mechanical properties of the composite was analyzed. We can confirm the impregnated CNF particle in the PLA matrix through the field emission scanning electron microscope (FE-SEM). Differential scanning calorimetry (DSC) analysis showed that the crystallinity of not annealed CNF/PLA nanocomposite was increased approximately 2 and 4 times in the 1st and 2nd cycle, respectively, with the shift to lower temperature of cold crystallization temperature (T_cc) in the 2nd cycle. Moreover, the crystallinity of annealed CNF/PLA nanocomposite increased by 13.4%, and shifted T_cc was confirmed.

• Proceedings of the PSK Conference
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• 2000.04a
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• pp.221.1-221.1
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• 2000

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.331-331
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• 2006

Polylactic acid (PLA) is a promising polymer because it can be derived from renewable resources and provides a biodegradable alternative to petrochemical based polymers. This research aims to synthesize PLA, through direct polycondensation and also tries to avoid the occurrence of separation by-product and the use of catalysts in the process. The polymerization of lactic acid was done at three different temperatures $150^{\circ}C,\;180^{\circ}C\;and\;200^{\circ}C$ for 90 h without catalysts and organic solvent. The proposed process provides results that are comparable to those that incorporate catalysts; during polymerization temperature was $180^{\circ}C$ the molecular weight of PLA obtained reached 42448 Da. The thermal properties of PLA analysis by Differential Scanning Calorimetry (DSC).

• Composites Research
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• v.24 no.4
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• pp.5-10
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• 2011

As environmental pollution getting worse, biodegradable materials have been drawn more attention than ever. In this study, polylactic acid (PLA)/carbon nanotubc (CNT) nanocomposites were manufactured via extrusion molding and injection molding, In order to change the crystallinity, annealing treatment was done for different time span, Crystallization kinetics of PLA was analyzed by differential scanning calorimeter (DSC), and it was confirmed that a proper amount of CNT can increase the crystallization rate of PLA. In addition, the presence of CNT significantly accelerates the hydrolytic degradation rate of PLA, however, it decreases with the increase of crystallinity. The reason is that degradation may occur in the PLA/CNT interface easily, and the molecular structure of the composite becomes dense with the increase of crystallinity.

• Composites Research
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• v.27 no.3
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• pp.96-102
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• 2014

In this study, we fabricated jute fiber reinforced polylactic acid (PLA) composite in the form of sandwich panel structure which includes core foam of chopped jute fiber reinforced PLA and outer skin layer of continuous glass fiber reinforced PLA. Flexural properties of the composite were assessed for different jute fiber weight fractions. Density of the core foam ranged from 0.31 to 0.67 $g/cm^3$ and void content fraction 0.51 to 0.71. The maximum flexural strength was 92.7 MPa at 12.5 wt.% of jute fiber content, and the maximum flexural modulus was 7.58 GPa at 30.0 wt.%. Cost analysis was also conducted. The cost to enhance the flexural strength of the applied structure was estimated to be $0.010USD/m^3/MPa$ for 12.5 wt.% fiber content.

• Applied Chemistry for Engineering
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• v.24 no.1
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• pp.104-111
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• 2013

Poymer blends of two degradable aliphatic polyesters, relatively expensive material polylactic acid (PLA) and relatively inexpensive material poly(butylene adipate-co-terephthalate) (PBAT), were used in this study. Three different kinds of modifiers were used with various amounts. Diisocyanate type methylenediphenyl 4,4'-diisocyanate (MDI) and hexamethylene diisocyanate (HDI) were used as modifiers and epoxy type coupling agents also used. The melt flow index (MFI) and dynamic viscoelasticity of various compositions of PLA/PBAT blends were studied. The mechanical property and morphology with respect to the fracture surface of PLA/PBAT blends were also investigated using tensile test and field emission scanning electronic microscopy, respectively. These tests were also used to verify the compatibility of PLA/PBAT and the effect of mechanical properties due to the use of modifiers. Tensile properties of PLA/PBAT blends modified with HDI were improved remarkably.

• Journal of Korean Neurosurgical Society
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• v.39 no.4
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• pp.286-291
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• 2006

Objective : We evaluate the effect of the copolymer-coated coils on immediate occlusion of the aneurysm, preventing rupture, and decreasing compaction or re-growth. Methods : Thirty-five aneurysms treated between September 2003 and December 2004 using Matrix detachable coil were reviewed. Study population consisted of 12 men and 23 women ranging in age from 34 to 75 years[mean, 55.1 years]. Twenty-two aneurysms were ruptured and 23 aneurysms were located in the anterior circulation. Follow-up angiography was obtained in 16 patients after 6 months from the procedure. Results : Initial complete occlusion was achieved in 17 aneurysms[48.6%], and the others remained as a residual neck in 8 aneurysms[22.8%] and residual sac in 10 aneurysms[28.6%]. Among these incompletely occluded aneurysms, 7 aneurysms were performed follow-up angiography. And 6 of them converted into complete occlusion. In the other hands, among 17 aneurysms achieved complete occlusion initially, 9 aneurysms were performed follow-up angiography. Recurrence due to coil compaction occurred in one aneurysm and the others maintained complete occlusion. There was one mortality case due to thromboembolic complication. Conclusion : In spite of difficulty in achieving complete occlusion with Matrix coil system, there is no rupture or re-rupture during follow-up period. Follow-up angiography shows many conversions of residual sac into complete occlusion. Embolization using Matrix coil system is safe and effective, but the effects of PGLA copolymer need further investigation.

• Journal of Veterinary Science
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• v.22 no.6
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• pp.76.1-76.15
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• 2021

Background: The development of a vaccine for Jembrana disease is needed to prevent losses in Indonesia's Bali cattle industry. A DNA vaccine model (pEGFP-C1-tat) that requires a functional delivery system will be developed. Polylactic-co-glycolic acid (PLGA) may have potential as a delivery system for the vaccine model. Objectives: This study aims to evaluate the in vitro potential of PLGA as a delivery system for pEGFP-C1-tat. Methods: Consensus and codon optimization for the tat gene was completed using a bioinformatic method, and the product was inserted into a pEGFP-C1 vector. Cloning of the pEGFP-C1-tat was successfully performed, and polymerase chain reaction (PCR) and restriction analysis confirmed DNA isolation. PLGA-pEGFP-C1-tat solutions were prepared for encapsulated formulation testing, physicochemical characterization, stability testing with DNase I, and cytotoxicity testing. The PLGA-pEGFP-C1-tat solutions were transfected in HeLa cells, and gene expression was observed by fluorescent microscopy and real-time PCR. Results: The successful acquisition of transformant bacteria was confirmed by PCR. The PLGA:DNA:polyvinyl alcohol ratio formulation with optimal encapsulation was 4%:0.5%:2%, physicochemical characterization of PLGA revealed a polydispersity index value of 0.246, a particle size of 925 nm, and a zeta potential value of -2.31 mV. PLGA succeeded in protecting pEGFP-C1-tat from enzymatic degradation, and the percentage viability from the cytotoxicity test of PLGA-pEGFP-C1-tat was 98.03%. The PLGA-pEGFP-C1-tat demonstrated luminescence of the EGFP-tat fusion protein and mRNA transcription was detected. Conclusions: PLGA has good potential as a delivery system for pEGFP-C1-tat.

• Journal of Veterinary Clinics
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• v.40 no.4
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• pp.268-275
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• 2023

In this paper, we designed 3D-printed orthopedic splint models for patient-specific external coaptation on fracture healing and analyzed the stability of the models through finite element method (FEM) analysis under compressive load conditions. Polylactic acid (PLA) and acrylonitrile-butadiene-styrene (ABS) based 3D splint models of the thicknesses 1, 3, 5 and 7 mm were designed, and Peak von Mises stress (PVMS) and maximum displacement (MD) of the models were analyzed by FEM under compressive loads of 50, 100, 150, and 200 N. The FEM results indicated that PVMS and MD values, regardless of material, had a negative correlation with the thickness of the models and a positive correlation with the compressive load. There was a risk of splint deformation under conditions more extreme than 100 N with 5 mm thickness. For successful clinical application of 3D-printed orthopedic splints in veterinary medicine, it is recommended that the splint should be produced not less than 5 mm thickness. Also, it is expected to be stable when the splint is applied to situations with a compressive load of 100 N or less. There is an advantage of overcoming the limitations of the existing bandage method through 3D-printing technology as well as verifying the stability through 3D modeling before application. Such 3D printing technology will be widely used in veterinary medicine and various fields as well as orthopedics.