• Journal of Pharmaceutical Investigation
• /
• v.21 no.2
• /
• pp.91-95
• /
• 1991

Polyethylene glycol, polypropylene glycol and block copolymer of ethylene glycol and propylene glycol were crosslinked by triisocyanate to form water swellable, rubbery polymer. The equilibrium swelling of the hydrogels ranged from 3% to 60% according to the hydrophobic-hydrophilic properties of the prepolymers. Model drugs, sodium salicylate and prednisolone were incorporated in the polymer matrices by swelling loading. Physical properties of the drugs affected the drug release mechanisms due to the change in the swelling behaviors of the polymeric devices. Zero order release was observed in the case of relatively hydrophobic polymer matrices.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.24 no.4 s.175
• /
• pp.824-829
• /
• 2000

The industries use polymer materials for many purposes because they have many merits. But these materials' costs take up too much proportion in overall cost of products that use these materials as their major material. So it is very economical for polymer industries to reduce these costs. Microcellular foaming process appeared in 1980's to solve this problem and it proved to be quite successful. This process uses inert gases such as CO2, N2. As these gases are dissolved into polymer matrices. many properties are changed. Glass transition temperature is one of these properties. DSC, DMA are devices that measures this temperature, but these are not sufficient to measure the temperature of polymer containing gas. In this paper, we devised a new tester that uses magnetism. We used this device to acquire data of the change of glass transition temperature and made Cha-Yoon model that can predict the change of glass transition temperature. Using this model, the change of this temperature can be estimated as a function of weight gain of gas. Cha-Yoon model proved that Chow's model is inappropriate to predict the change of glass transition temperature of polymer matrices containing gas.

• Journal of the Optical Society of Korea
• /
• v.10 no.1
• /
• pp.1-10
• /
• 2006

Optical transparency and high diffraction efficiency are two essential factors for high performance of the photopolymer. Optical transparency mainly depends on the miscibility between polymer binder and photopolymerized polymer, while diffraction efficiency depends on the refractive index modulation between polymer binder and photopolymerized polymer. For most of organic materials, the large refractive index difference between two polymers accompanies large structural difference that leads to the poor miscibility and thus poor optical quality via light scattering. Therefore, it is difficult to design a high-performance photopolymer satisfying both requirements. In this work, first, we prepared a new phase-stable photopolymer (PMMA) with large refractive index modulation and investigated the optical properties. Our photopolymer is based on modified poly (methyl methacrylate) as a polymer binder, acryl amide as a photopolymerizable monomer, triethanolamine as initiator, and yellow eosin as a photosensitizer at 532 nm. Diffraction efficiency over 85% and optical transmittance over 90% were obtained for the photopolymer. Second, Organic-inorganic nanocomposite films were prepared by dispersing an aromatic methacrylic monomer and a photo- initiator in organic-inorganic hybrid sol-gel matrices. The film properties could be controlled by optimizing the content of an organically modified silica precursor (TSPEG) in the sol-gel matrices. The photopolymer film modified with the organic chain (TSPEG) showed high diffraction efficiency (> 90%) under an optimized condition. High diffraction efficiency could be ascribed to the fast diffusion and efficient polymerization of monomers under interference light to generate refractive index modulation. The TSPEG modified photopolymer film could be successfully used for holographic memory.

• Journal of Adhesion and Interface
• /
• v.3 no.4
• /
• pp.44-52
• /
• 2002

Composite materials are created by combining two or more component to achieve desired properties which could not be obtained with the separate components. The use of reinforcing fillers, which can reduce material costs and improve certain properties, is increasing in thermoplastic polymer composites. Currently, various inorganic fillers such as talc, mica, clay, glass fiber and calcium carbonate are being incorporated into thermoplastic composites. Nevertheless, lignocellulose fibers have drawn attention due to their abundant availability, low cost and renewable nature. In recent, interest has grown in composites made from lignocellulose fiber in thermoplastic polymer matrices, particularly for low cost/high volume applications. In addition to high specific properties, lignocellulose fibers offer a number of benefits for lignocellulose fiber/thermoplastic polymer composites. These include low hardness, which minimize abrasion of the equipment during processing, relatively low density, biodegradability, and low cost on a unit-volume basis. In spite of the advantage mentioned above, the use of lignocellulose fibers in thermoplastic polymer composites has been plagued by difficulties in obtaining good dispersion and strong interfacial adhesion because lignocellulose fiber is hydrophilic and thermoplastic polymer is hydrophobic. The application of lignocellulose fibers as reinforcements in composite materials requires, just as for glass-fiber reinforced composites, a strong adhesion between the fiber and the matrix regardless of whether a traditional polymer matrix, a biodegradable polymer matrix or cement is used. Further this article gives a survey about physical and chemical treatment methods which improve the fiber matrix adhesion, their results and effects on the physical properties of composites. Coupling agents in lignocellulose fiber and polymer composites play a very important role in improving the compatibility and adhesion between polar lignocellulose fiber and non-polar polymeric matrices. In this article, we also review various kinds of coupling agent and interfacial mechanism or phenomena between lignocellulose fiber and thermoplastic polymer.

• Proceedings of the KIEE Conference
• /
• 1993.07b
• /
• pp.1122-1124
• /
• 1993

In this study, piezoceramics/polymer composites with 3-3 connectivity were made by BURPS(Burnout Plastic Sphere) technique with PZT ceramics and PVA sphere. And physical and dielectric properties dependent on the PVA wt.% were investigated. The density of porous piezoceramic and pieaoceramic/polymer composites were decreased almost linearly with increasing the PVA wt.%.

• Archives of Pharmacal Research
• /
• v.26 no.1
• /
• pp.76-82
• /
• 2003

Drug releasing porous poly($\varepsilon$-caprolactone) (PCL)-chitosan matrices were fabricated for bone regenerative therapy. Porous matrices made of biodegradable polymers have been playing a crucial role as bone substitutes and as tissue-engineered scaffolds in bone regenerative therapy. The matrices provided mechanical support for the developing tissue and enhanced tissue formation by releasing active agent in controlled manner. Chitosan was employed to enhance hydrophilicity and biocompatibility of the PCL matrices. PDGF-BB was incorporated into PCL-chitosan matrices to induce enhanced bone regeneration efficacy. PCL-chitosan matrices retained a porous structure with a 100-200 $\mu$m pore diameter that was suitable for cellular migration and osteoid ingrowth. $NaHCO_3$ as a porogen was incorporated 5% ratio to polymer weight to form highly porous scaffolds. PDGF-BB was released from PCL-chitosan matrices maintaining therapeutic concentration for 4 week. High osteoblasts attachment level and proliferation was observed from PCL-chitosan matrices. Scanning electron microscopic examination indicated that cultured osteoblasts showed round form and spread pseudopods after 1 day and showed broad cytoplasmic extension after 14 days. PCL-chitosan matrices promoted bone regeneration and PDGF-BB loaded matrices obtained enhanced bone formation in rat calvarial defect. These results suggested that the PDGF-BB releasing PCL-chitosan porous matrices may be potentially used as tissue engineering scaffolds or bone substitutes with high bone regenerative efficacy.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2004.10a
• /
• pp.491-495
• /
• 2004

The industries use polymer materials for many purposes for they have many merits. The costs of these materials take up too great a proportion of the overall cost of products that use these materials as their major material. It is advantage for polymer industries to reduce these costs. The microcellular foaming process was developed in the early 1980s to solve this problem and proved to be quite successful. Microcellular foaming process uses inert gases such as $CO_2$, $N_2$. As these gases solve into polymer matrices, many properties are changed. The microcellular foaming process makes the glass transition temperature of polymers to low, and diminish the residual stress of polymer matrices. Besides, the microcellular foaming process has several merits, impact strength elevation, thermal insulation, noise insulation, and raw material saving etc. This characteristic of microcellular foaming process has influenced by cell morphology. The cell morphology means cell size and cell density. The cell morphology has influenced by many factors. The examples of factor are pressure drop rate, foaming temperature, foaming time, saturation pressure, saturation time etc. Among their factors, pressure drop rate is the most important factor for cell morphology in microcellular foaming injection molding process. This paper describes about the cell morphology change in accordance with the pressure drop rate of microcellular foaming injection molding process.

• Journal of the Korean institute of surface engineering
• /
• v.29 no.4
• /
• pp.229-237
• /
• 1996

Porous matrices for PAFC were prepared with chemically synthesized polyaniline powders. Phosphoric acid doped polyaniline showed decreasing electric conductivities as the temperature increased. Above $100^{\circ}C$, it showed negligible conductivities. It was stable in phosphoric acid up to $250^{\circ}C$. SiC powders or SiC whiskers were added to polyaniline to decrease the thermal expansion of polyaniline. 10% of polytetrafluoroethylene(PTFE) was also added as a binder. The bubble pressures and wettabilities of matrices were investigated and compared with the porosities measured by porosimeter. Based on these data, the optimum manufacturing condition was determined. The bubble pressure of the matrix made by adding 25w/o SiC whiskers was 345mmHg, the wettability was 235w/o, and the porosity was 83%. In the unit cell operation, the performances of polyaniline matrices were as good as those of SiC matrices. This result suggested that polyaniline can be a possible candidate for the matrix material of PAFC.

• Journal of Pharmaceutical Investigation
• /
• v.32 no.4
• /
• pp.327-330
• /
• 2002

Alginate based polymeric matrices were designed for controlled release and stabilization of cefaclor in gastrointestinal fluid. Cefaclor is known to be acid stable and subjected to be degraded at neutral and alkaline pHs. In order to achieve an effective release profile of cefaclor in gastrointestinal tract, a particular strategy in dosage form design should be required from the view point of maintaining its activity. The amphiphilic nature of cefaclor allowed its controlled release using ionic polymers based on ionic interaction between the drug and polymers. The thrust of this study was to develop a technique that delivers cefaclor keeping effective release rate in the intestinal tract. Considering the fast degradation of cefaclor in the intestinal fluid, the matrices were designed to release surplus amount of cefaclor. The alginate based matrices demonstrated increase in release rate in the simulated intestinal fluid, which was favorable to compensate the degraded portion of cefaclor. In addition, stabilization of cefaclor in the intestinal fluid was obtained by employing citric acid that provides an local acidic environment. The matrices might be valuably used for the development of an oral cefaclor dosage form.

• Bulletin of the Korean Chemical Society
• /
• v.34 no.6
• /
• pp.1708-1714
• /
• 2013

Polyhexamethylene guanidine (PHMG) polymers used as an active ingredient in an antibacterial humidifier disinfectant were reported to cause harm to the human health when inhaled, although physical contact with this material was known to present low toxicity to humans. It is therefore necessary to develop an optimal analysis method which enables detection and analysis of PHMG polymers. MALDI-TOF investigations of PHMG are performed with a variety of matrices, and it is found that CHCA and 2,5-DHB are excellent matrices which well reflects the polymer population even at high mass. For the provided PHMG sample, the number-average ($M_n$) and weight-average ($M_w$) molecular masses were determined to be 744.8 and 810.7, respectively, when the CHCA was used as a matrix. The rank of the matrices in terms of averaged molecular weight was CHCA ~2,5-DHB > 5-NSA > DHAP, THAP > ATT > IAA ~ super-DHB ~ HABA. In addition, PSD of the PHMG oligomer ions exhibited a few unique fragmenation characteristics. The formation of a- and c-type fragments was the major fragmentation pathway, and the 25-Da loss peaks generally accompanied a- and c-type fragments.