• Journal of the Korean Wood Science and Technology
• /
• v.37 no.5
• /
• pp.426-433
• /
• 2009

This study investigates the tensile and morphological properties of nanocomposites prepared from poly(lactic acid) (PLA), wood flour (WF) and montmorillonite (MMT) by melt compounding with a twin screw extruder. In order to enhance the mechanical properties of PLA/WF composites, maleic anhydride grafted PLA (MAPLA) is synthesized as a compatibilizer. MAPLA prepared in the laboratory is characterized using FT-IR (Fourier transformed infrared spectroscopy). From the results of X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis for nanocomposites, we confirmed that silicate layers of MMT are intercalated and partially exfoliated. When 2 wt% MAPLA is added, the tensile strength and modulus of PLA/WF/MAPLA composites were higher than those of the PLA/WF composite. The addition of MMT increases the tensile modulus of PLA/WF/MAPLA composites but decreases the tensile strength.

• Journal of the Korean Wood Science and Technology
• /
• v.37 no.5
• /
• pp.434-439
• /
• 2009

This study investigates the thermal properties of nanocomposites prepared from poly(lactic acid) (PLA), wood flour (WF) and montmorillonite (MMT) by melt compounding with a twin screw extruder. In order to enhance the mechanical properties of PLA/WF composites, maleic anhydride grafted PLA (MAPLA) is synthesized as a compatibilizer. MAPLA prepared in the laboratory is characterized using FR-IR. From SEM microphotographs, the presence of MAPLA has a positive effect on the mechanical properties of WF-reinforced PLA composites. The addition of WF/MAPLA into neat PLA increased the glass transition temperature ($T_g$). The addition of 1 to 5 wt% MMT into PLA/WF/MAPLA composite decreases the $T_g$. The cold crystallization temperature ($T_{cc}$) was decreased by the addition of MMT. The MMT could act as effective nucleating sites of PLA crystallization. The thermal stability evaluated by thermogravimetric analysis (TGA) is improved with the contents of MMT up to 3 wt%.

• Archives of Pharmacal Research
• /
• v.19 no.1
• /
• pp.30-35
• /
• 1996

Poly(l-lactic acid)(PLLA) microspheres loaded with ampicillin sodium (AMP-Na_, .betha.-lactam antibiotic, were prepared by a w/o/w multiple emulsion-solvent evaporation method. The amounts of each component in three phases (inner water phase, organic phase, and outer water phase) wre carefully examined in the preparation of PLLA microspheres. The stirring rate, another preparation parameter, was also investigated for study on the effect of mechanical stress on the drug loading and morphology of PLLA microspheres. Most of the preparation parameters had a great influence on the drug loading, surface morphology and size distribution of PLLA microspheres. PLLA microspheres with 15.89 w/w% drug loading were subjected to the in vitro release experimet. The release of ampicillin sodium was constant at a rate of 1.68 $mug/ml/day$ per 1 mg of microspheres for 18 days initial burst effect.

• Bulletin of the Korean Chemical Society
• /
• v.33 no.7
• /
• pp.2295-2298
• /
• 2012

We describe herein a three-dimensionally diverse micropatterning of poly(lactic acid), as a biopolymer, using 1-butyl-3-methylimidazolium-based room-temperature ionic liquids (bmim-based RTILs), [bmim]X (X = $SbF_6$, $PF_6$, $NTf_2$, Cl). Utilizing the hydrophobic bmim-based RTILs, [bmim]X (X = $SbF_6$, $PF_6$, $NTf_2$) and a phase separation technique, we were able to produce white and opaque membranes with a three-dimensional structure closely packed with particles ($10-50{\mu}m$ in diameter). The particlulate structure, made by the assistance of [bmim]$NTf_2$ and DCM, interestingly transformed to a fibrous structure by using a cosolvent, e.g., DCM/$CF_3CH_2OH$. When we used an increased amount of [bmim]$NTf_2$, the particles were effectively detached and macrosized ($100-500{\mu}m$ in diameter) and the oval-shaped beads were obtained in a powder form. By varying the counter-anion type of the imidazolium-based RTIL, for example from $NTf_2^-$ to $Cl^-$, the particulate 3D-morphology was once more transformed to a porous structure. These reserch results could be potentially useful, as a method to fabricate particulate scaffolds, fibrous or porous scaffolds, and beads as a biopolymer device in diverse fields including drug delivery, tissue regeneration, and biomedical engineering.

• Macromolecular Research
• /
• v.15 no.3
• /
• pp.238-243
• /
• 2007

Nanofibers were prepared by electrospinning a solution of poly(lactic-co-glycolic acid) (PLGA) and their mean diameter was 340 nm. The PLGA nanofibers were treated with a plasma in the presence of either oxygen or ammonia gas to change their surface characteristics. The hydrophilicity of the electrospun PLGA nanofibers was significantly increased by the gas plasma treatment, as confirmed by contact angle measurements. XPS analysis demonstrated that the chemical composition of the PLGA nanofiber surface was influenced by the plasma treatment, resulting in an increase in the number of polar groups, which contributed to the enhanced surface hydrophilicity. The degradation behavior of the PLGA nanofibers was accelerated by the plasma treatment, and the adhesion and proliferation of mouse fibroblasts on the plasma-treated nanofibers were significantly enhanced. This approach to controlling the surface characteristics of nanofibers prepared from biocompatible polymers could be useful in the development of novel polymeric scaffolds for tissue engineering.

• Polymer(Korea)
• /
• v.34 no.4
• /
• pp.381-385
• /
• 2010

Aiphatic diester monomer, 3-[(benzyloxycarbonylamino)butyl]-1,4-dioxane-2,5-dione (BABD), was synthesized with the N-$\varepsilon$-benzyloxy-carbonyl-L-lysine as starting material. This monomer was synthesized to add the functionality to poly(lactic acid)s. BABD unit was successfully incorporated into the PLLA chain which was confirmed by $^1H$ NMR. The copolymer composition could be controlled by the feed ratios of monomer. The $M_n$ of this resultant polymer is expected to reach high molecular weight after the purification of monomer and optimization of polymerization time, though the polymer showed relatively low degree of polymerization ($M_n$＝3300). The copolymer is expected to possess the enhanced hydrophilicity and the possibility of chemical modification on amino group.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
• /
• v.28 no.2
• /
• pp.89-95
• /
• 2022

The goal of this study was to evaluate the effect of spent coffee grounds (SCG) biofiller on the morphological, thermal, mechanical and hydrolytic degradation characteristics of poly(lactic acid) (PLA) based biocomposites. The PLA-based biocomposite films were fabricated by using a high-viscosity kneading and hot-pressing machine. The PLA/SCG biocomposites were analyzed with SEM, DSC, TGA, UTM and hydrolytic degradation test. Aggregation in the PLA matrix is a result of increasing SCG concentrations. In the thermal properties, it was described that the cold crystallization temperature (T_cc) decreased as SCG was added to PLA. When SCG was incorporated to PLA, the degradation onset temperature (T_onset) revealed a diminish. The elastic modulus increased while tensile strength of PLA diminished as SCG was applied. Through hydrolysis analysis, the decomposition of PLA was accelerated with the addition of SCG. This research confirmed the possibility of devloping an eco-friendly packaging material with high degradability as SCG hasten the breakdown of PLA.

• Proceedings of the Korean Fiber Society Conference
• /
• 2002.04a
• /
• pp.49-52
• /
• 2002

합성 고분자의 생분해는 환경 보존이라는 측면에서 중요시 되고 있으며 봉합사나 bone fixation, 그리고 implant와 같은 의학적 응용면에서도 상당한 관심의 대상이 되어오고 있다 glycolic acid, L-lactic acid, $\varepsilon$-caprolactone에 근거하는 지방족 폴리에스터는 생분해성 봉합사로서 응용되고 있으나 여전히 열적, 기계적 가공특성과 같은 적정특성들이 부족하다.$^1$ 한편 폴리아마이드는 유사한 구조를 갖는 폴리에스터와 비교할 때에 상대적으로 높은 유리전이온도와 높은 융점을 가지고 있는 반면 높은 흡습성으로 인한 물성저하가 야기될 수 있다. (중략)

• Journal of the Korean Applied Science and Technology
• /
• v.34 no.3
• /
• pp.643-649
• /
• 2017

Biodegradable enzymes such as lipase and proteinase can hydrolyze not only fatty acid esters and triglycerides, but also aliphatic polyesters. We measured the biodegradability that biodegradable enzymes have an important role in the degradation of natural aliphatic poly material such as PLA, corn starch, and polyethylene glycol in the natural environment. However, we investigated on the biodegradability of PLA, PLA and Polyethylene acrylate blended, and PLAcoPolyethylene polymerized with PLA graft copolymer Polyethylene glycol acrylate. When prepared biodegradable polymers. the Mechanical properties of them were measured on Biodegradability, thermal properties, real time in-situ electrical monitoring of polymers resin. Therefore BOD and biodegradation of PLAcoPolyethylene was graft copolymerized with PLA and polyethylene acrylate were measured at a lower rate than the other samples.

• Polymer(Korea)
• /
• v.36 no.6
• /
• pp.745-755
• /
• 2012

Two types of polymers were tested in this study; poly(ethylene terephthalate) (PET) as a synthetic example and poly(lactic acid) (PLA) as a natural polymer. DSC analyses showed that the use of nanofiller increased the degree of crystallinity ($X_c$) of both PET and PLA polymers, but the effect was more noticeable on PET nanocomposites. The crystallization of PLA and PET nanocomposites occurred at higher temperatures in comparison to neat polymers. According to dynamic mechanical-thermal analysis (DMTA), the damping factor of PET/$TiO_2$ nanoparticles decreased compared to the neat matrix, but for PLA nanocomposites the opposite trend was observed. Results of the mechanical test showed that for both PET and PLA nanocomposites, the most successful toughening effect was observed at 3 wt% loading of $TiO_2$ nanoparticles. SEM micrographs revealed uniform distribution of $TiO_2$ nanoparticles at 1 and 3 wt% loading levels. The results of WAXD spectra explained that the polymorphs of PLA and PET was not affected by $TiO_2$ nanoparticles. UV-visible spectra showed that $TiO_2$ nanocomposite films had high ultraviolet shielding compared to neat polymer, but there was significant reduction in transparency.