• Clean Technology
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• v.15 no.4
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• pp.245-252
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• 2009

Profiles development of melt spinning process of poly(lactic acid) (PLA) was simulated via a numerical method and the radial temperature distribution was calculated using finite difference method. The spinning speed ranged from 1 km/min to 5 km/min was analyzed and the effect of spinning conditions on the radial temperature distribution was investigated. At low spinning speed, the difference between PLA and poly(ethylene terephthalate) (PET) was relatively small. As the spinning speed increased, the difference in velocity profile became prominent. PLA showed a slower spinning speed than PET and solidified more slowly. The temperature difference between the core and surface of the PLA filament reached 4.6 K, which was less than that of PET filament with a difference of 10.4 K. The radial temperature difference increased with increasing the cooling-air velocity and the spinning temperature.

• Proceedings of the Korean Fiber Society Conference
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• 1999.04a
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• pp.257-260
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• 1999

• Macromolecular Research
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• v.9 no.5
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• pp.259-266
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• 2001

Multiblock copolymer was synthesized by the copolycondensation of oligo(L-lactic acid) prepared by thermal dehydration of L-lactic acid, Pluronic$\^$TM/(PN) and dodecanedioic acid as carboxyl/hydroxyl adjusting agent. This polycondensation proceeded by catalysis of stannous oxide to give the multiblock copolymers with high molecular weight and wide range of compositions. Polymer film was prepared by casting the chloroform solution of the multiblock copolymers having different composition. The multiblock copolymers having relatively high contents of poly(L-lactide) were melt spun into filaments which were subsequently drawn at 60$^{\circ}C$. The copolymer films and the filaments showed an improved flexibility due to the incorporation of the soft segments.

• Proceedings of the Korean Fiber Society Conference
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• 2007.11a
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• pp.235-236
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• 2007

• Proceedings of the Korean Fiber Society Conference
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• 1997.04a
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• pp.328-332
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• 1997

Hot stretching focused on the improvement of properties of poly(L-lactic acid) fiber. Some aliphatic polyesters are biodegradable under microbial attack and the new unique applications are expected. Generally, these materials have a somewhat low melting temperature and low mechanical properties compared with the aromatic polyesters. In this study, melt-spinning of poly(L-lactic acid) was conducted. We investigated effects of the stretching and the molecular orientation of aliphatic polyester fibers on the change of fine-structure. Glass transition temperature, molecular orientation and crystallinity increased according to the increase of stretching ratio.

• Korean Chemical Engineering Research
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• v.49 no.4
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• pp.438-442
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• 2011

Mechanical and morphological properties of poly(acrylonitrile-butadiene-styrene) (ABS) and poly(lactic acid) (PLA) blends containing compatibilizers were investigated. Poly(styrene-acrylonitrile)-g-maleic anhydride) (SAN-g-MAH), poly(ethylene-co-octene) rubber-maleic anhydride (EOR-MAH) and poly(ethylene-co-glycidyl methacrylate) (EGMA) were used as compatibilizers. Mechanical properties such as tensile, flexural and impact strengths of ABS/PLA (80/20, wt%) blends were found to be increased when the SAN-g-MAH, EOR-MAH and EGMA were used. The maximum values for mechanical properties of the ABS/PLA (80/20) blend were observed when SAN-g-MAH was used as a compatibilizer at the concentration of 3 phr. From morphological studies of the ABS/PLA (80/20) blends, PLA droplet size was decreased by the addition of the compatibilizers used in this study. From the results of mechanical and morphological properties of the ABS/PLA (80/20) blends, SAN-g-MAH (3 phr) was found to be the most effective compatibilizer among the compatibilizers used in this study.

• Archives of Craniofacial Surgery
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• v.17 no.1
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• pp.1-4
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• 2016

Absorbable plates are used widely for fixation of facial bone fractures. Compared to conventional titanium plating systems, absorbable plates have many favorable traits. They are not palpable after plate absorption, which obviates the need for plate removal. Absorbable plate-related infections are relatively uncommon at less than 5% of patients undergoing fixation of facial bone fractures. The plates are made from a mixture of poly-L-lactic acid and poly-DL-lactic acid or poly-DL-lactic acid and polyglycolic acid, and the ratio of these biodegradable polymers is used to control the longevity of the plates. Degradation rate of absorbable plate is closely related to the chance of infection. Low degradation is associated with increased accumulation of plate debris, which in turn can increase the chance of infection. Predisposing factors for absorbable plate-related infection include the presence of maxillary sinusitis, plate proximity to incision site, and use of tobacco and significant amount of alcohol. Using short screws in fixating maxillary fracture accompanied maxillary sinusitis will increase the rate of infection. Avoiding fixating plates near the incision site will also minimize infection. Close observation until complete absorption of the plate is crucial, especially those who are smokers or heavy alcoholics. The management of plate infection is varied depending on the clinical situation. Severe infections require plate removal. Wound culture and radiologic exam are essential in treatment planning.

• Korean Chemical Engineering Research
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• v.49 no.2
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• pp.206-210
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• 2011

We fabricated rod-like poly(lactic acid)(PLA) specimens through applying various methods of equal-channel angular extrusion(ECAE) process and investigated the change of thermal and mechanical properties of specimens before and after each ECAE process. Combining three re-injection routes(A, BC, and C) and three pass counts(1, 2 and 4) allowed us to fabricate 7 different PLA specimens. Thermal properties of each specimen were measured by both differential scanning calorimeter and thermo-gravimetric analyzer. Shear strains of each specimen with respect to applied loads were measured by indentation hardness tester. Field emmision scanning electron microscopy was used to observe internal microstructure of cross-section of each specimen. The observed microstructures qualitatively supported the explanation of hardness test results. Among 7 specimens, PLA-P2A showed the biggest shear strain probably due to its dense microstructure.

• Journal of Pharmaceutical Investigation
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• v.38 no.1
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• pp.63-72
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• 2008

Meloxicam-loaded microspheres were prepared with poly(D,L-lactic acid)(PLA) by a solvent-emulsion evaporation method. The morphology, particle size, drug loading capacity, drug entrapment efficiency (EE) and release patterns of drug were investigated in vitro. Various batches of micro spheres with different size and drug content were obtained by changing the ratio of meloxicam to $PLA^{\circ}{\AE}s$ with different molecular weight, PLA concentration in the dispersed phase and stirring rate. Meloxicam crystals on microsphere surface, which were released rapidly and could act as a loading dose, were observed with increasing drug content. The release rate was increased with increase in drug contents and decrease in the molecular weight of PLA. Microspheres prepared with smaller molecular weight produced faster drug release rate. The release rate of meloxicam for long-acting injectable delivery system in vitro, which would aid in predicting in vivo release profile, could be controlled by properly optimizing various factors affecting characteristics of microspheres. Blood concentration-time profile of meloxicam after intramuscular injection of meloxicam-loaded microspheres in rabbits showed possibility of long term application of this system in clinical settings.

• Korean Chemical Engineering Research
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• v.48 no.3
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• pp.342-349
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• 2010

Lactic acid is widely used in the food, chemical and pharmaceutical industries, and there is an increasing demand for lactic acid as the raw material of poly lactic acid(PLA), which is a biodegradable polymer. Lactic acid production has been changing over from production by synthesis to production by fermentation, since the fermentation process is more nature friendly and economic. However, the fermentation method generates excess water and impurities with high boilers. The presence of high boilers and non volatility of lactic acid makes the separation of lactic acid very difficult job. Also, the purification-separation process requires the many investment costs and energy costs. Reactive distillation concept was also introduced for the process, giving higher selectivity and yield compared to the convention method. We introduce a new highly integrated process, reactive diving wall column, to reduce the capital and energy cost for producing a pure lactic acid. The reactive dividing wall column combines reactive distillation and dividing wall column. We compared capital and energy consumption required for the purification of lactic acid the between the proposed design structures. And we examined the effect of major process variables on the process performance and determined optimal process.