• Polymer(Korea)
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• v.34 no.5
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• pp.485-489
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• 2010

Poly(lactic acid)(PLA) has been modified by electron radiation in the presence of 5 phr glycidyl methacrylate (GMA) to enhance the melt strength of PLA. The modified PLA was prepared by varying the dose of irradiation and was characterized by observing the thermal properties, the melt viscoelastic properties and the gel fraction. The irradiated PLA with 300 kGy in the presence of 5 phr GMA showed drastically improved complex viscosity and storage modulus properties: a complex viscosity of about 210 times higher and a storage modulus of 14500 times higher than those of virgin PLA when measured at a frequency of 0.1 rad/s. Gel fraction study revealed that a branching reaction was more dominant than a crosslinking reaction when the PLA was irradiated with less than 200 kGy.

• Journal of the Korean Wood Science and Technology
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• v.46 no.1
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• pp.107-113
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• 2018

In this study, the 3D printer filaments were manufactured by using the representative eco-friendly material, bio-composite. Bio-composites were made by incorporating biodegradable polymer of poly lactic acid (PLA) as the matrix and bamboo flour as the filler. The bamboos which were used in this experiment are Phyllostachys bambusoides, Phyllostachys nigra var. henonis, and Phyllostachys pubescen grown in Damyang district in Korea, and the mixture ratio between bamboo flour and PLA were set 10/90, 20/80, 30/70 by weight standard. Also, tensile strength of bamboo/PLA bio-composites manufactured with three kinds of bamboo were estimated and compared. In this result, the highest estimated bio-composites was Phyllostachys bambusoides flour/PLA which mixture ratio was 10/90, that is, it was the most suitable bamboo/PLA bio-composites for manufacturing 3D printer filament.

• Journal of Adhesion and Interface
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• v.9 no.4
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• pp.1-11
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• 2008

In the present study, kenaf fibers were treated with sodium hydroxide using soaking and ultrasonic methods prior to biocomposite processing, respectively. The effect of alkali treatment on the kenaf-PLA interfacial adhesion and mechanical and thermal characteristics of kenaf/poly(lactic acid) biocomposites was investigated in terms of their interfacial shear strength, flexural properties, dynamic mechanical properties and thermal stability and also microscopic observations of kenaf fibers and the composite fracture surfaces. As a result, use of both soaking and ultrasonic methods for treating kenaf fiber surfaces played a role in increasing the fiber-matrix adhesion and the mechanical properties of the biocomposites. Their characteristics depended not only on the fiber surface treatment method but also on the treatment condition like alkali concentration and treatment time.

• Korean Chemical Engineering Research
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• v.46 no.1
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• pp.124-130
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• 2008

In order to fabricate a modified poly (lactic acid) (PLA) for applications requiring high melt strength, a PLA has been irradiated in the presence of functional monomer of glycidyl methacrylate (GMA). Samples were prepared with various contents of GMA and irradiation dosages, and were characterized by observing their thermal and melt viscoelastic properties and gel faction. The complex viscosity and storage modulus of the modified PLA without GMA were lower than those of the original PLA. Those of the modified PLA decreased with increasing dosage. In the case of the modified PLA containing 0.1 phr or 0.3 phr of GMA, their changing tendency with dosage was similar to the irradiated PLA without GMA. However, the 5 kGy irradiated PLA containing 0.5 phr of GMA showed the greatly enhanced complex viscosity and storage modulus, which were about 3 and 10 times higher than those of the original PLA at a frequency of 0.1 rad/s, respectively.

• Journal of Industrial and Engineering Chemistry
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• v.67
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• pp.244-254
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• 2018

Surface modified poly ${\text\tiny{L}}$-lactic acid (PLLA) samples with hydroxyapatite (HA), heparin and bone morphogenetic protein-2 (BMP-2) mediated by polydopamine (pDA) coating (PLLA/pDA/HA/Hep/BMP-2) were prepared, and their effects on the enhancements of bone formation and osseointegration were evaluated in vitro and in vivo as compared to PLLA, PLLA/pDA/HA, and PLLA/pDA/Hep/BMP-2. The changes in surface chemical compositions, morphologies and wettabilities were observed by X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) and water contact angle measurements. Pre-coating of HA particles with pDA provided uniform and homogeneous anchoring of particles to PLLA surface. In addition, the strong ionic interaction between heparin and pDA led PLLA surface readily heparinized for loading of BMP-2. In vitro experiments revealed that the levels of alkaline phosphatase (ALP) activity, calcium deposition, and osteocalcin (OCN) gene expression were higher in MG-63 human osteosarcoma cell lines grown on PLLA/pDA/HA/Hep/BMP-2 than on control PLLA, PLLA/pDA/HA, and PLLA/pDA/Hep/BMP-2. In vivo studies using micro-computed tomography (micro-CT) also showed that PLLA/pDA/HA/Hep/BMP-2 screw exhibited greatest value of bone volume (BV) and bone volume/tissue volume (BV/TV) among samples. Histological evaluations with H&E and Von Kossa staining demonstrated that a combination of HA and BMP-2 contributed to the strong osseointegration.

• Korean Chemical Engineering Research
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• v.58 no.1
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• pp.36-43
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• 2020

A biliant stent was fabricated using a magnesium alloy wire, a biodegradable metal. In order to control the fast decomposition and corrosion of magnesium alloys in vivo, magnesium alloy wires were coated with biodegradable polymers such as polycaprolactone (PCL), poly(propylene carbonate) (PPC), poly (L-lactic acid) (PLLA), and poly (D, L-lactide-co-glycolide) (PLGA). In the case of PPC, which is a surface erosion polymer, there is no crack or peeling compared to other polymers (PCL, PLLA, and PLGA) that exhibit bulk erosion behavior. Also, the effect of biodegradable polymer coating on the axial force, which is the mechanical property of magnesium alloy stents, was investigated. Stents coated with most biodegradable polymers (PCL, PLLA, PLGA) increased axial forces compared to the uncoated stent, reducing the flexibility of the stent. However, the stent coated with PPC showed the axial force similar to uncoated stent, which did not reduce the flexibility. From the above results, PPC is considered to be the most efficient biodegradable polymer.

• Microbiology and Biotechnology Letters
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• v.26 no.1
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• pp.55-60
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• 1998

For an ideal extractive bioconversion in aqueous two-phase systems, the product has to be preferentially partitioned into the phase opposite to the one in which the biocatalyst is located. Partitioning behaviors of Lactobacillus helveticus IAM 11090 and lactic acid in aqueous two-phase systems composed a polycation, poly(ethylenimine) (PEI), and an uncharged polymer (hydroxyethyl)cellulose (HEC) were investigated. L. helveticus cells were preferentially partitioned to the HEC-rich top phase while about 85% of lactic acid was partitioned to the PEI-rich bottom phase. These results indicate that extraction of charged, low molecular weight products in an aqueous two-phase systems can be promoted by using an oppositely charged polymer as one of the phase-forming polymer. By the ideal partitioning of the cells and lactic acid, an aqueous PEI/HEC two-phase system can be used as a potential system for the extractive lactic acid fermentation of cheese whey.

• Elastomers and Composites
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• v.46 no.3
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• pp.195-203
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• 2011

Eco-friendly materials or bio-composites were made with poly(lactic acid) (PLA) as matrix polymer and kenaf fibers as filler. Also, acetylated kenaf fibers and compatibilizer were adopted in order to improve the interfacial adhesion between fiber and polymer. In this study, the effect of chemical modification and compatibilizer on the mechanical-viscoelastic and morphology properties of the bio-composites was discussed. The hydrophobic fibers by acetylation were known to show better interfacial bonding with the matrix polymer and resulted in improved performance and morphology. Viscoelastic property and glass transition temperature, however, were not nearly enhanced.

• Polymer(Korea)
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• v.37 no.6
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• pp.669-676
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• 2013

Demineralized bone particle (DBP) is a biomaterial used widely in the field of tissue engineering. In this study, in order to study the effect of DBP/poly(lactic-co-glycolic acid) (PLGA) scaffold on disc regeneration in vivo environment, we prepared the porous DBP/PLGA hybrid scaffold. Disc defect was induced by removing the nucleus pulposus tissue after incision the annulus fibrosus tissue in half and scaffolds were transplanted. After 1, 2 and 3 months later, the extracted discs were confirmed by collagen synthesis and glycosaminoglycan (sGAG). We conducted histology (H&E, Safranin-O, Alcian blue, Type I Collagen, Type II Collagen). From the results, it was confirmed that collagen and sGAG content were high in DBP/PLGA scaffold, and the regeneration of intervertebral disc was possible.

• Archives of Pharmacal Research
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• v.9 no.2
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• pp.63-73
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• 1986

The use of biodegradable polymetric materials as drug carriers is a relatively new dimension in polymeric drug delivery systems. A number of biodegradable or bioerodible polymers, such as poly(lactic/glycolic acid) copolymer, poly($\alpha$-amino acid), polyanhydride, and poly (ortho ester) are currently being investigated for this purpose. These polymers are useful for matrix and reservoir-type delivery devices. In addition, when chemical functional groups are introduced to the biodegradable polymer backdone, such as poly (N-(2-hydroxypropyl) methacrylamide), the therapeutic agent can be covalently bound directly or via spacer to the backbone polymer. These polymer/drug conjugates represent another new dimension in biodegradable polymeric drug delivery systems. In addition, examples of biodegradable polymeric durg delivery systems currently being investigated will be discussed for the purpose of demonstrarting the potential importance of this new field.