강인한 바이오필터설계를 위한 바이오필터모델: 1. 바이오필터 담체의 흡착거동

Dynamic Adsorption; Adsorption Behavior; Biofilter-Medium; GAC; Compost

The adsorption and desorption behavior of biofilter-medium was investigated on the performance of an adsorption column. Continuous flow-isothermal adsorption experiments were performed to treat waste air containing such a VOC as ethanol under the same condition of > 90% relative humidity as the condition of the feed to a biofilter process. In case of feeding waste air containing ethanol of 1,000 ppmv (or 2,050 mg ethanol/m3) to the adsorption system at the rate of 2 L/min, the onsets of its breakthrough and reaching the state of dynamic equilibrium at the exit had been delayed 10 and 3 times, respectively, later than those at the 1st stage sampling port. Moreover, in case of 2,000 ppmv (or 4,100 mg ethanol /m3), they had been delayed 9 and 3 times,respectively. Thus, regardless of feeding concentration, the ratios of delaying period were observed to be quite consistent each other at the exit of the adsorption column. With regard to the period of desorption, the ratios of delaying period were consistent each other to be 1.5 for both cases. In addition, the effect of microbial activity and sterilization-process was studied on adsorption equilibrium. The ethanol concentration in the vapor phase of vials packed with sterilized granular activated carbon (GAC) was quite consistent to that with unsterilized GAC. However, the ethanol concentrations in the vapor phase of vials packed with unsterilized compost and the unsterilized mixture of GAC and compost were higher than those with sterilized compost and the sterilized mixture of GAC and compost, respectively.

강인한 바이오필터설계를 위한 바이오필터모델: 2. 동적 바이오필터모델

Dynamic Biofilter Model; Robust Biofilter Design; Thiele Modulus; Biofilter Medium

A dynamic biofilter model was suggested to integrate the effect of biofilter-medium adsorption capacity on the removal efficiency of volatile organic compound (VOC) contained in waste air. In particular, the suggested biofilter model is composed of four components such as biofilm, gas phase, sorption volume and adsorption phase and is capable of predicting the unsteady behavior of biofilter-operation. The process-lumping model previously suggested was limited in the application for the treatment of waste air since it was derived under the assumption that the adsorbed amount of VOC equilibrated with biofilter-media would be proportional to the concentration of dissolved VOC in the sorption volume of biofilter-media. Therefore a Freundlich adsorption isotherm was integrated into a robust biofilter process-lumping model applicable to a wide range of VOC concentration. The values of model parameters related to biofilter-medium adsorption were obtained from the dynamic adsorption column experiments in the preceding article and literature survey. Furthermore a separate biofilter experiment was conducted to treat waste air containing ethanol and the experimental result was compared with the model predictions with various values of Thiele modulus (φ). The obtained value of Thiele modulus (φ) was close to 0.03.

Improvement of bacterial cellulose production in Acetobacter xylinum using byproduct produced by Gluconacetobacter hansenii

Bacterial Cellulose; Acetobacter xylinum; Gluconacetobacter hansenii; Water Soluble Oligosaccharides; Characterization

A single sugar α-linked glucuronic acid based oligosaccharide (SSGO) is water soluble oligosaccharides (WSOS) obtained by Gluconacetobacter hansenii PJK (KCTC 10505BP) as a byproduct during bacterial cellulose (BC) production. In this study, SSGO was used for the improvement of BC production by the vinegar bacterium, Acetobacter xylinum, which produces heteropolysaccharides as a byproduct. The addition of 1.0% SSGO to the chemically defined medium (CDM) resulted in an 89.3% increase in BC production by A. xylinum after 15 days of cultivation under static condition, and a 52.3% increase in BC production by G. hansenii. Both the dry cell weight and live cell density of A. xylinum increased 50% with the addition of 1.0% SSGO. SSGO successfully improved BC production by A. xylinum.

고무사출성형의 적정설계

Rubber Injection Molding; C. V. Joint Boots; Crack; Process simulation; Weld and Meld Line; Air Trap; Curing

The optimum mold design and the optimum process condition were constructed upon executing process simulation of rubber injection molding with the commercial CAE program of MOLDFLOW (Ver. 5.2) in order to solve the process-problems of K company relating to cracks, which occurs at the inner cavity wall of C. V. joint boots. As a result it was confirmed that the real cracks occurs at the exactly same position of the cavity as exhibits the defects of weld and meld line and unsatisfactory curing according to the result of simulation. In order to prevent the occurrence of weld and meld line at the defect-position, the location of gate was altered to the optimum position of the cavity. Consequently the filling pattern was established to minimize the degree of the melt-fronts confronting or the melt-flows melding to prevent the occurrence of weld and meld line at the defect-position. It was observed that both gate-positions to maximize the degree of the formation of weld and meld line and air traps are located, respectively, in opposite direction each other with reference to the optimum gate position. In addition, the temperature of mold was raised by 10 o℃ and maintained at 170 ℃ for satisfactory curing.

Highly improved adsorption selectivity of L-phenylalanine imprinted polymeric submicron/nanoscale beads prepared by modified suspension polymerization

Molecularly Imprinted Submicron/Nanoscale Beads; Modified Suspension Polymerization; FE-SEM; FT-IR; 13C CP-MAS NMR

Molecularly imprinted polymer (MIP) submicron/nanoscale beads selective for L-Phenylalanine (L-Phe) and D-Phe as well as non-imprinted beads were prepared by modified suspension polymerization involving agitation of the reaction mixture at high rotation speed under safe radical conditions. The effects of pH, template and concentration of racemate solution on the performance of the phenylalanine (Phe) imprinted polymeric submicron/nanoscale beads were studied. L-Phe-imprinted submicron/nanoscale beads prepared for the first time by modified suspension polymerization showed enhanced adsorption capacity and selectivity over those of D-Phe imprinted and non-imprinted beads. Maximum adsorption capacity, 0.35 mg/g, and selectivity, 1.62, of L-Phe imprinted submicron/nanoscale beads were higher than the adsorption capacities, 0.30 and 0.19 mg/g, and selectivities, 1.59 and 1.02, of D-Phe imprinted and nonimprinted submicron/nanoscale beads, respectively. FE-SEM analyses revealed that L- and D-Phe imprinted beads were larger (100 nm-1.5 μm) than non-imprinted nanobeads (100-800 nm). 13C CP-MAS NMR spectroscopy helped in correlating the bead sizes and the extent of reaction during polymerization. Similarly, FT-IR study was used for evaluation of structural characteristics of the prepared Phe-imprinted and non-imprinted beads. The preparation of Phe-imprinted submicron/nanoscale beads with improved adsorption and separation properties and the study of effect of template on the size and performance of the prepared beads are suitable from both economical and research point of view in MIP field.

Effect of chitosan penetration on physico-chemical and mechanical properties of bacterial cellulose

Bacterial Cellulose; Chitosan; Composites; Physico-mechanical Properties

Bacterial cellulose-chitosan composites (BC-Ch) were prepared in order to obtain the BC-Ch composites with improved physico-mechanical characteristics. BC sheets were immersed in a Ch solution hoping that the Ch penetrates into the BC sheet. Ch penetration was observed according to variations in temperature, operation mode and treatment time. The morphological changes due to enhanced penetration were observed through FE-SEM, FT-IR and XRD analysis. FE-SEM analyses confirmed the formation of three dimensional multilayered structures in BC-Ch, whose thickness increased with Ch penetration. The FT-IR analysis showed intermolecular hydrogen bonding interaction between the BC and Ch molecules. XRD results revealed a slight decrease in the crystallinity index of the BC-Ch composites compared to pure BC. The mechanical properties, water holding capacity (WHC) and water release rate (WRR) of the BC-Ch composites were significantly improved compared to pure BC. The superior mechanical properties, WHC and water release rate would make the BC-Ch composites suitable for wound dressing and other biomedical applications.

방진고무사출성형의 적정설계

Rubber Injection Molding; Process Simulation; Optimum Process Condition; Air Trap; Short-Shot

The optimum mold design and the optimum process condition were constructed upon executing process simulation of rubber injection molding with the commercial CAE program of MOLDFLOW(Ver. 5.2) in order to solve the process-problems of K company relating to air-traps and short-shots. The former occurs at the cavity edge of torquerod-bush and the latter takes place for the injection molding of dynamic dampers. As a result the process problem relating to air traps was solved by optimizing edge-angle and the number of gates to prevent the flow congestion of flowfront and to make the flow-front movement unaffected by congestion. For dynamic dampers of K company the unmolded flaw caused by their unfilled cavity was corrected by installing the air-vent at the confronting locations of both upstream and downstream of flow-front where air traps frequently occur. Besides the unmolded flaws were rectified by altering the position of gate from the upper to the middle or by increasing the number of gates. Thus the process problems of K company relating to air-traps and short-shots of torque-rod-bush and dynamic dampers, respectively, were solved by proper altering of mold design with process simulation of rubber injection molding.

하이브리드시스템을 이용한 악취폐가스 처리

Hybrid Process; Waste-Air; Biofilter; Photocatalytic Reactor; Humidifier; Fluidized Aerobic Reactor; Anoxic Reactor

In this research hydrogen sulfide, ammonia and toluene were designated as the representative source of malodor and VOC, respectively, frequently generated at the compost manufacturing factory and publicly owned facilities. The optimum operating condition to treat the waste air(2 L/min) containing malodor was constructed using photocatalytic reactor/biofilter process with humidifier composed of fluidized aerobic anf anoxic reactor. The ammonia(300 ppmv) of fed-waste air was removed by 22, 55 and 23% at the stage of photocatalytic reactor, humidifier and biofilter, respectively. The toluene(100 ppmv) of fed-waste air was removed by 20, 10 and 70% at the stage of photocatalytic reactor, humidifier and biofilter, respectively. Therefore the water-soluble ammonia and the water-insoluble toluene were treated mainly at the stage of humidifier and biofilter, respectively. In addition, hydrogen sulfide(10 ppmv) was almost treated at the stage of photocatalytic reactor and its negligible trace was absorbed in humidifier so that it was not detected before biofilter process. The nitrate concentration of the process water from anoxic reactor was found lower by 3 ppm than that from fluidized aerobic reactor. Besides, the dissolved ammonia-nitrogen concentration of the process water from humidifier remained at the high value of 1,500-2,000 ppm, which may be attributed to the existence of ammonium chloride and other source of ammonium nitrogen.

Surface hydrophobicity alteration of fractionated paraffin wax, crude by-product polyolefin wax and their blend

Crude By-product Polyolefin Wax; Commercial Paraffin Wax; Blend; Surface Hydrophobicity; Diffusivity; Surface Enrichment

The surface compositions of crude by-product polyolefin wax (wax K) from a naphtha cracking unit, fractionated commercial paraffin wax (wax J) and their blend (wax M) were compared, under various conditions, by using FT-IR. Then a practical criterion was theoretically derived by back-of-the-envelope-calculation to estimate the diffusivity for the surface enrichment of hydrophilic functional groups. The hydrophobicity in terms of chemical structure and functional groups was altered by changing the environment as well as by blending wax K with wax J. The surface properties of wax J and wax M turned out more hydrophobic than that of wax K within the experimental period of water-submerged condition, even though the structure and functional groups on the surfaces of all waxes under ambient atmospheric condition are extremely similar. Thus the blend of wax M behaved unlike wax K but similarly to wax J in terms of alteration of hydrophobicity. Such values of diffusivity as 1.35×10^(-11) cm2/s and 1.96×110^(-11) cm2/s are established for wax J and wax M, respectively, under 1 day water-submerged condition. Furthermore, under 1 week watersubmerged condition, the values of their diffusivity for wax J, wax K and wax M are estimated as 3.06×10^(-12) cm2/s, 7.23×10^(-11) cm2/s and 1.50×10^(-11) cm2/s, respectively. The obtained values of diffusivity are consistent, in terms of the order of magnitude, with the value of diffusion coefficient of 5.75×10^(-11) cm2/s obtained, using a very complicated empirical-formula, by Chen et al. for the investigation of surface-modifier enrichment. Thus, the suggested criterion may be very useful and practically applied to clarify the process of surface enrichment from general polymer-blends.

Comparison of thermal properties of crude by-product polyolefin wax, fractionated paraffin wax and their blend

Crude By-product Polyolefin Wax; Commercial Paraffin Wax; Blend; Molecular Weight Distribution; Melting-temperature Shift; Degree of Crystallization; Co-crystallization

The molecular weight and thermal properties of unfractionated by-product polyolefin wax (wax K) from a naphtha cracking unit, fractionated commercial paraffin wax (wax J) and their blend (wax M) were evaluated and were compared with each other using differential scanning calorimetry (DSC), normal and high-temperature gel permeation chromatography (GPC), and wide-angle X-ray diffraction (WAXD). Such properties as molecular weight distribution, melting temperature and degree of crystallization were altered by blending wax K with wax J. By blending with two parts of wax K and one part of wax J to prepare wax M, Mw of wax K was shifted, by half, to that of wax J in order to approach that of wax M, whereas the Mn of wax K remains almost unaltered to become that of wax M. In particular the effect of blending of wax K and wax J turned out co-crystallization for the sharper lower-melting-temperature endothermic peak of the blend, indicating narrower molecular distribution, than that of wax K at the melting temperature shifted even below that of wax J. The total degree of crystallinity for the blend, wax M, turns out less than that before blending wax K with wax J, which may be attributed to the effect of co-crystallization due to blending.

악취제거를 위하여 분리한 황화합물 산화균주의 배양특성

Sulfur Compound-Oxidizing Strains; Isolation; Identification; Malodor; Hydrogen Sulfide; Incubation Characteristics

Both strains of KD-1212 and DAH-1056 were isolated and identified from animal manure-contaminated soil by screening bacterial strains for the removal of sulfur compound-malodor with such substrate as sodium thiosulfate or free sulfur. Then the characteristics on the incubation of these microbes were observed under various incubating-condition such as pH, temperature, aerobic or anaerobic, substrate(sulfur compound) concentration, nitrogen and carbon source and rotating speed for mixing, and the optimum incubating condition was established. The optimum pHs of KD-1212 and DAH-1056 were 7.0 and 4.0, respectively, and their optimum temperatures were in the range of 30~35 ℃. Another autotrophic strain, ED-1138, was isolated from contaminated soil. The strain DAH-1056 excelled a strain Thiobacillus sp. IW in eliminating hydrogen sulfide during the process of malodor-biofiltration with a fixed strain. The characteristics on the incubation of strain KD-1212 were observed under various substrate-concentrations, nitrogen and carbon sources. KD-1212 favored glucose and maltose, and yeast extract as carbon sources and nitrogen source, respectively. The optimum concentrations of substrate and nitrogen source were 25 mM of sodium thiosulfate and 0.5% yeast extract, respectively for the growth of strain KD-1212.

원심 임펠러가 장착된 발효조에서 G. hansenii에 의한 미생물셀룰로오스 생산

Bacterial Cellulose; Gluconacetobacter hansenii PJK; Water Soluble Oligosaccharides; Turbine Impeller; Inclined Centrifugal Impeller; Centrifugal Impeller; Volumetric Oxygen Transfer Coefficient

In order to improve the bacterial cellulose(BC) production yield, centrifugal and inclined centrifugal impellers were developed. A 6 flat-blade turbine impeller was used as a control system. The flow pattern in the fermenter and volumetric oxygen transfer coefficient(kLa) of these fermentation systems were studied. Fermentations were carried out for the production of BC by G. hansenii PJK in a 2-L jar fermenter equipped with new impellers. Liquid medium was circulated from the bottom, through the cylinder of the impeller and to the wall. The volumetric oxygen transfer coefficients, kLa, of inclined centrifugal and centrifugal impeller systems at 100 rpm were 23 and 15% of the conventional turbine impeller system, respectively. However, the conversion of microbial cells to cellulose non-producing mutant decreased and this results in the increase in BC production at low rotating speed of impellers.

Production of bacterial cellulose in static conditions by a simple fed-batch cultivation strategy

Bacterial Cellulose; Gluconacetobacter hansenii PJK; Fed-batch Cultivation; Static Culture Conditions; Water Soluble Oligosaccharides

The current study investigated fed-batch cultivation for the increased productivity of bacterial cellulose (BC) sheets by Gluconacetobacter hansenii PJK in static conditions using chemically defined medium and waste from beer fermentation broth. Fermentations were carried out in a 3 L jar fermenter without any impeller for 30 days. In the proposed fed-batch cultivation, 500 mL of the medium was initially inoculated with pre-culture in a jar fermenter while a fresh medium was fed periodically. BC production was also done by using batch cultivation which was used as a control for comparison. The results obtained revealed an overall of 2-3 times increase in BC production in fedbatch cultivation compared to batch cultivation after 30 days of cultivation. During these experiments, it was found that waste from beer fermentation broth is a superior medium for the BC production using fed-batch cultivation. The production of water soluble oligosaccharides as useful by-products was also monitored during these investigations. Fed-batch cultivation and waste from beer fermentation was also found superior for the production of these by-products. According to literature search and to the best of our knowledge, it is the first report of using fed-batch cultivation for BC production in static conditions.

Preparation of D-phenylalanine imprinted microbeads by the modified suspension polymerization using a magnetic impeller

Molecularly Imprinted Polymeric Microbead; Phenylalanine; Modified Suspension Polymerization; Enantioselective Separation; Molecular Recognition; Impeller

Molecularly imprinted polymeric microbeads (MIPMs) were prepared by using a magnetic impeller by the modified suspension polymerization method with D-phenylalanine (Phe) as the water-soluble template without derivatization, methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the cross-linker, toluene as the porogen, polyvinyl alcohol as the stabilizer, and sodium dodecyl sulfate as the surfactant. The mean diameter of MIPMs decreased from 12.45 μm to 8.86 μm by using a simple magnetic impeller instead of a conventional simple straight-blade turbine impeller during suspension polymerization. The adsorption selectivity of MIPMs prepared with a magnetic impeller was much improved as compared to the adsorption selectivity of MIPMs prepared with a conventional simple straight-blade turbine impeller. The adsorption selectivity of MIPMs changed from reversed adsorption (less than 1) to positive (higher than 1) as the washing time increased after suspension polymerization.

Metal recovery by aged beads prepared using cell-suspension from the waste of beer fermentation broth

Biosorption of Heavy Metals; S. cerevisiae; Cell Immobilized Bead; Cell Suspension; Waste of Beer Fermentation Broth

Lead, copper, and cadmium were adsorbed onto aged calcium alginate beads containing cell-suspension from the waste of beer fermentation broth. Beads prepared by adding 0.6% (w/v) sodium alginate into the cell suspension from the waste of beer fermentation broth and making the cell suspension drop into the 1% (w/v) calcium alginate solution were stored in the 1% (w/v) calcium chloride solution for 1 year. The specific metal uptake of the aged cell-suspension immobilized bead was 312 mg Pb^(2+), 158 mg Cu^(2+), and 112 mg Cd^(2+)/g bead dry weight at pH 7.5 of the metal solution, respectively. The relation between the specific metal uptake by the aged cell-suspension immobilized beads and the equilibrium metal concentration was nonlinearly regressed and well described by the Freundlich isotherm. The specific cadmium uptake capacity of aged cell-suspension immobilized beads was between the specific cadmium uptake capacities of commercial beads Duolite GT-73 and Amberite IRA-400 and higher than those of the fresh Saccharomyces cerevisiae ATCC 834 and Saccharomyces cerevisiae ATCC 24858 immobilized beads.

연료전지 스택 가스켓용 불소고무에 있어 충전제 종류에 따른 영향

fuel cell; gasket; filler

The rubber was compounded with carbon black and silica series-filler to examine the effects of the various rubber fillers on a gasket material’s suitability and fuel cell stack conclusion. The evaluation of a long term heat resistance and oil resistance of the mixed rubber material was performed considering at the drive environment of PEMFC. Test results of compression set for the most influencing property of gasket showed that it was about less than 15% at long term of up to 1000 h. In this experiment, FEM analysis is carried out about the rubber material’s properties depending on each filler and the stress which is produced when a gasket is contracted by using various filler. Sealing force was expected to maximum 2.5 MPa from minimum 0.2 MPa by using FEM (finite element method) at stacking gasket to gasket.

바이오필터설계를 위한 바이오필터 담체의 흡착 특성

Adsorption; Biofilter Media; Ethanol; Process-Lumping Biofilter Model

Freundlich isothermal adsorption parameters, applicable to such biofilter-model as process-lumping model(Lim’s model), for sterilized granular activated carbon(GAC), sterilized compost and sterilized equal volume mixture of GAC and compost were obtained and were compared each other, assuming that adsorbents are enclosed by water layer, in order to construct robust process-lumping biofilter model effective for wide-range of hydrophilic volatile organic compounds(VOC). In this investigation 0.04, 0.08, 0.12, 0.16, 0.2, 0.4, 0.8 and 1.0ml of ethanol were added to three kinds of adsorbent-media and were placed at 30°… under the wet condition of the media, which was the same as biofilter operating condition, until the adsorption reached the condition of equilibrium before each adsorbed amount of ethanol was obtained. Then adsorption capacity parameters(K) and adsorption exponents of Freundlich adsorption isotherm equation, which simulates the adsorbed amount of ethanol equilibrated with the ethanol concentration of the condensed water in the pore of the media, were constructed for sterilized granular activated carbon(GAC), sterilized compost and sterilized equal volume mixture of GAC and compost as (0.7566 and 5.070×10-7 mg-ethanol/mgmedia/(mg-ethanol/m3)0.7566), (0.8827 and 1.000×10-8 mg-ethanol/mgmedia/(mg-ethanol/m3)0.8827) and (0.5688 and 5.243×10-6 mg-ethanol/mgmedia/(mg-ethanol/m3)0.5688), respectively. These Freundlich isothermal adsorption parameters were applicable to the adsorption characteristics of biofilter media enclosed with bio-layer. The order of magnitude of the ratio of ethanol-air/water partition coefficient and toluene-air/water partition coefficient was almost consistent to that of ethanol-adsorbed amounts in this experiment with compost and in the investigation of Delhomenie et al. on toluene-adsorption to wet compost.

Production of bacterial cellulose by a static cultivation using the waste from beer culture broth

Bacterial Cellulose; Gluconacetobacter hansenii PJK; Waste from Beer Fermentation Broth; Static Cultivation; Water Soluble Oligosaccharide

Bacterial cellulose (BC) was produced by using the waste from beer culture fermentation instead of a chemically defined medium. Static cultivation was superior to the shaking cultivation on the basis of the BC production. The amount of BC produced during 120 hrs of cultivation using the waste from beer fermentation broth (WBFB) by a static cultivation was 4.52 g/L on the dry weight basis and much higher than 0.45 g/L produced from a Buffered Schramm and Hestrin (BSH) chemically-defined medium. The addition of 1% industrial-grade glucose to WBCB increased the production of bacterial cellulose from 8.46 to 13.95 g/L after 336 hrs of cultivation. Water soluble oligosaccharide (WSOS), the by-product obtained during BC cultivation increased to 5.05 g/L at 192 hrs of cultivation and then decreased to 2.18 g/L at 336 hrs.

Functional biopolymers produced by biochemical technology considering applications in food engineering

Microbial Exopolysaccharides; Foods Industry; Dextran; Xanthan; Bacterial Cellulose; Gellan; Curdlan; Pullulan

Polysaccharides are widely used in foods as thickening, gelling, stabilizing, emulsifying, and water-binding agents. The majority of the polysaccharides currently employed in the food industry are derived from plants and seaweeds. Recently, microbial polysaccharides have emerged as an important set of biothickeners for foods. These biopolymers have overcome to great extent the flaws associated with the plants and seaweeds polysaccharides. This relatively new class of biopolymers has unique rheological properties because of their potential of forming very viscous solutions at low concentrations and pseudoplastic nature. This review deals with the current applications of these microbial biopolymers in the food industry with a special focus on the commonly used important exopolysaccharides in this area.

Production of bacterial cellulose by Gluconacetobacter hansenii using a novel bioreactor equipped with a spin filter

Bacterial Cellulose; Gluconacetobacter hansenii PJK; Cel-Mutants; Spin Filter

In order to improve bacterial cellulose (BC) production yield by increasing the cell density, a new fermentation system using a spin filter was developed and its performance characteristics were tested. Fermentations were carried out in a fermenter equipped with a 6 flat-blade turbine impeller and a spin filter consisting of a cylinder surrounded by stainless steel mesh and whose stainless steel bottom was attached to the agitator shaft. This new fermentation assembly was tested under different experimental conditions for BC production by Gluconacetobacter hansenii PJK. In periodical perfusion culture without pH control, the BC production and the total cell mass increased with the culture time to 3.07 and 5.65 g/L, respectively, at 140 h of cultivation. The BC production was also tested at adjusted pH and pH 5 was found optimum for maximum BC production. At pH 5, in periodical perfusion culture, the BC production and the total cell mass reached to 4.57 and 11.52 g/L, respectively, after 140 h of cultivation. This amount of BC production was 2.9 times higher than that obtained in a conventional jar fermenter. The productivity improved and was 0.044 g/L·h at 68 h of cultivation.

Synthesis and Photoalignment of Soluble Polyimides Containing Photoreactive 2-Styrylpyridine Derivatives as Side Groups

soluble polyimide; 2-styrylpyridine; dichroic ration; liquid crystal

We describe the synthesis and characterization of soluble photoreactive polyimides. The precursor of the polyimides was prepared from 4,4'-(2,2,2-trifluoro-1-phenylethylidene)diphthalic anhydride and 3,3'-hydroxy-4,4'-diaminobiphenyl. The photoreactive polyimides (PI-SP6 and PI-SP12) were then prepared by the polymer reaction of the hydroxyl groups in the precursor polymer with 2[2-{4-(w-hydroxyalky-loxy)phenyl}ethenyl]pyridines as photoreactive 2- styrylpyridine derivatives (alkyl: hexyl and dodecyl). The photoreactive polymers and the precursor polyimide showed their initial decompositions at temperatures of 350 and 480 ℃, respectively. These polymers were soluble in various polar organic solvents and their thin films were easily formed by solution casting. The normalized absorbances of the photoreactive polymers in the film state decreased to ca. 74% at a 2.0 J/cm2 exposure dose. Transmittances of their films were ca. 90% at room temperature and ca. 85% at 200℃. These results indicate that the polyimides are photoreactive polymers exhibiting good photosensitivity and high optical transparency. The dichroic ratios of PI-SP6 and PI-SP12 were observed to be 0.019 and 0.030 at a 0.1 J/cm2 exposure dose; these values indicate that the polymers show the effect of alkylene spacer length on the photoalignment. The liquid crystal in the film cells of the polymers was oriented perpendicularly to the electric vector of the linear polarized UV light. These photoalignment results are discussed in light of the differences between the structures of the photoreactive polyimides obtained in this study and those in a previous report.

맥주발효 폐액을 이용한 미생물 셀룰로오스 생산

Bacterial Cellulose; Glucuronacetobacter Hansenii Pjk; Beer Fermentation Broth

Bacterial cellulose (BC) was produced by Gluconacetobacter hansenii PJK (KCTC 10505 BP) strains using the waste of beer fermentation broth. It contained more C and N than a basal medium with a small amount of Sand more than 4％ ethanol. The amount of BC produced in a shaking culture using the waste of beer fermentation broth was nearly the same as that of a basal medium. The production of BC decreased in a shear stress field in a jar fermenter although the conversion of cellulose producing (Cel+) cells to non-cellulose producing (Cel.) mutants was not severe.This study showed that the waste of beer fermentation broth is an inexpensive carbon, nitrogen source with ethanol and thus a worthy substitute for the conventional medium for BC production.

Transient behavior of biofilter inoculated with Thiobacillus sp. IW to treat waste-air containing hydrogen sulfide

Biofilter; Hydrogen Sulfide; Transient Behavior; Removal Efficiency; Elimination Capacity

Hydrogen sulfide is heavier than air and is colorless, toxic and flammable, the gas odor threshold of which is about 0.47 ppbv, which causes nuisance odor at concentrations as low as about 8ppbv and corrosion problems in sewer systems. The transient behavior of biofilter packed with mixed media (of granular activated carbon and compost) inoculated with a pure culture of Thiobacillus sp. IW was observed at a height of four sampling ports to treat wasteair containing hydrogen sulfide in this investigation, which shall be used as control to be compared with the performance of a biofilter-involved integrated system for the treatment of waste-air containing hydrogen sulfide in a subsequent investigation. Unlike the previous studies of the other investigators, various process conditions were applied to successive biofilter runs in order to monitor and correlate each corresponding unsteady behavior of the biofilter at the height of each sampling port. During 10 days (20 times) after start-up of a biofilter hydrogen sulfide was continuously adsorbed on the media and that the adsorption of hydrogen sulfide was under way since the inlet loads of 1st and 2nd stage operations were very low. Afterwards it was obvious that the breakthrough curves at the 1st, 2nd, 3rd and 4th (exit) sampling ports responded rapidly to the change of operating conditions of a biofilter so that the breakthrough curve at each sampling port responded rapidly to approach a new state of saturation, which suggests that the adsorption capacity of biofilter-media may be relatively small or its affinity to hydrogen sulfide may be relatively high, compared to such volatile organic compound as ethanol. Up to the 3rd stage of operation the removal efficiency continued to be nearly 100%. However it began to decrease as inlet load increased. At the end of last stage of the biofilterrun removal efficiency was decreased and maintained at 94%. The maximum elimination capacity was observed to be ca. 95 g/m3/h, which was higher than that of the biofiltration-work of any other previous investigator except for that of the biofiltration-work with use of each of two inorganic packing materials (porous ceramics, calcinated and formed obsidian).

Effect of Temperature on the Performance of a Biofilter Inoculated with Pseudomonas putida to Treat Waste-Air Containing Ethanol

Biofilter; Waste-Air; VOC; Ethanol; Optimum Operating Temperature; Optimum Incubation Temperature; Pseudomonas putida

The microbes of Pseudomonas putida (KCTC1768) were fixed on the biofilter-packing media comprising an equivolume mixture of granular activated carbon (GAC) and compost, by recycling the liquid medium containing incubated Pseudomonas putida (KCTC1768). A biofilter experiment was performed to observe its transient behavior under the operating condition of 2,180 ppmv of ethanol-inlet concentration and 158 g/m3/h of ethanol-inlet load for the five consecutive temperature-stages of operation ranging from 25 ℃ to 40 ℃. For the five temperaturestages of operation their removal efficiencies were measured and were compared with each other. The optimum operating temperature of the biofilter turned out to be ca. 30 ℃, which was consistent with the previous experimental result of Lim and Park. However, the optimum incubation-temperatures of Pseudomonas putida (KCTC1768) and the equivalent (i.e., NCIMB8858) were announced to be of 26 ℃ and 25 ℃ by Korea Collection for Type Cultures (KCTC) and National Collections of Industrial, Food and Marine Bacteria (NCIMB), respectively. It was also confirmed by the experiment in which the microbes were incubated in the same liquid medium as in the previous work of Lim and Park at temperature ranging from 20 ℃ to 40 ℃ and their growth rates were subsequently measured. Thus, the optimum operating temperature of a biofilter inoculated with Pseudomonas putida (KCTC1768) was proved to be 30 ℃, which was higher than its optimum incubation-temperature by ca. 5 ℃.

Characteristics of Selective Adsorption Using D-Phenylalanine Imprinted Terpolymer Beads

Molecularly Imprinted Polymer; Phenylalanine; Bead; Wet-phase Inversion Method; Repeated Batch

A D-Phenylalanine (Phe) imprinted terpolymer, Polyacrylonitrile-Poly(acrylic acid)-Poly(acryl amide) (Poly(AN-AA-AAm)) bead was prepared by the wet-phase inversion method. Acrylamide (AAm) and acrylic acid (AA) were used as the functional monomer and acrylonitrile (AN) was used as a physical cross linker. The characteristics of selective adsorption by the D-Phe imprinted terpolymer beads were investigated at high concentrations of Phe racemate solution, 1 g Phe/L, and 10 g Phe/L. The adsorption selectivity of the D-Phe imprinted terpolymer beads prepared by an in-situ implanting method reached 0.82 and 0.8 at 1.0 g and 10 g Phe/L racemate solution, respectively, and almost all of the adsorbed D-Phe and about 43% of the adsorbed L-Phe were desorbed by 4% acetic acid. The uptake capacities of the terpolymer beads were maintained for several repeated batches.

The Treatment of Waste-air Containing Mixed Solvent using a Biofilter 2. Treatment of Waste-air Containing Ethanol and Toluene in a Biofilter

Biofilter; Mixed Solvent; Degree of Interference; Solubility of Hydrophobic VOC; Hydrophilic Co-feed

An experiment for five stages of a biofilter-run was performed to investigate the effect of hydrophilic ethanol and hydrophobic toluene on the biodegradation of hydrophobic toluene and hydrophilic ethanol, respectively, when waste-air containing toluene and ethanol was treated by a biofilter. Removal efficiencies of toluene and ethanol began to decrease when inlet load surpassed 90 g/m3/h and 100 g/m3/h consistent with maximum elimination capacities of toluene and ethanol, respectively. At the end of the biofilter-run, removal efficiencies for toluene and ethanol were decreased and maintained at 65% and 40%, respectively. The concentration of toluene at 1st sampling port was raised by factor of two in the 3rd stage of the biofilter run when the inlet load of ethanol co-feed was increased by 1.5 times, while the process conditions of toluene were maintained the same as those of the 2nd stage of biofilter-run. According to the result of Mohseni and Allen, it may be interpreted that removal efficiency of hydrophobic toluene was affected by the presence of hydrophilic ethanol when high load of hydrophobic toluene was applied like that of the 1st sampling port of the biofilter. However it was not the case when a low load of hydrophobic toluene was applied like those of the 2nd, 3rd and 4th sampling ports since hydrophobicity of toluene is much less that of α-pinene. Thus, it may be suggested that biodegradation of hydrophobic VOC was interfered by hydrophilic VOC dissolved in the biolayer and the degree of interference was proportional to the inlet load of hydrophobic VOC as well as that of hydrophilic VOC and was inversely proportional to the solubility of hydrophobic VOC. However, it was inferred that the existence of hydrophobic toluene from waste-air can hardly inversely hinder the removal of hydrophilic ethanol in the biofilter when timeevolutions of hydrophilic ethanol concentrations of this experiment were compared with those of the previous experiment of biofilter to treat waste-air containing ethanol only.

Treatment of Mixed Solvent Vapors with Hybrid System Composed of Biofilter and Photo-catalytic Reactor

Hybrid System; Photo-catalytic Process; Biofilter; Toluene; Ethanol; Transient Behavior; Removal Efficiency; Elimination Capacity

The transient behavior of a hybrid system composed of biofilter and photo-catalytic reactor was observed at the height of each sampling port to treat waste-air containing ethanol. The biofilter packed with mixed media (of granular activated carbon and compost) was inoculated with a pure culture of Burkholderia cepacia G4 and Pseudomonas putida, while a photo-catalytic reactor was composed of 15W UV-A lamps and annular pyrex tubes packed with glass beads coated with sol type of TiO2 before calcination. The maximum elimination capacities of toluene and ethanol turned out to be 130 g/m3/h and 230 g/m3/h, respectively, which were greater by 40 g/m3/h and 130 g/m3/h, respectively, than those from the experiments performed with a biofilter only. Thus, the maximum elimination capacities for toluene and ethanol increased by 44% and 130%, respectively, by use of a hybrid system. The photo-catalytic process contributed to the maximum elimination capacities of hybrid system on toluene and ethanol by 30.8% and 56.5%, respectively, which contributions for the elimination capacities on toluene and ethanol were allocated indirectly by 25.4% and 44.3% as well as directly by 5.4% and 12.2%, respectively. Direct contributions of photo-catalytic process were 17.5% and 21.5% to the increments of the elimination capacities on toluene and ethanol, respectively, while its indirect contributions were 82.5% and 78.5% to those on toluene and ethanol, respectively.

Gas Flow Direction Under Heterogeneous Geometry Composed of a Pipe and a Cavity of Two Square-Flat Plates in Gas Assisted Injection Molding

gas assisted injection molding; rule qf thumb; preferred direction qfgas; least resistance to initial-resin velocity; heterogeneous geometry

The novel unsteady mass (and momentum-) balance equations as well as the resistance to the initial velocity of a Newtonian fluid were proposed as rule of thumbs to predict the direction of gas flow in gas assisted injection molding (GAIM). Such configuration was adopted as that a pipe was connected vertically to a cavity formed between two parallel plates and gas was injected at the point above where two cavities filled with melt polymer resin were connected. Upon performing the simulation with various thickness of a cavity formed between two parallel plates and fixed diameter of a pipe using commercial software (MOLDFLOW) the results of simulation were compared with those of not only the ratios of the resistances to the initial velocity but also predicted-unsteady trajectories of gas penetration in GAIM by the suggested novel unsteady mass (and momentum-) balance equations to check the precision of predicted trajectories by these suggested flow models as well as the consistency of their predicted directions. In case of such a heterogeneous geometry as the combination of both a pipe and the cavity between two square flat plates (SFP), once the initial direction of most gas entered into cavities was determined to the side of two SFP since the value of the ratio of resistances became less than unity, the ultimate gas flow direction was decisively determined to that side due to geometrical reasons. However, in the reverse or the other cases, one should compare the effect of the ratio of resistances with the geometric effect of a fan-shaped cavity together with the loss of moving mass of melt polymer due to the formation of coated layer at the surface of the mold, which was treated in the unsteady model-predictions of the length of gas penetration using the proposed novel flow models. Consequently the values from the proposed novel flow models were excellently consistent with those from the simulation results while those of the ratio of resistances were fairly consistent with those from the simulation-results.

Flow Directions in Gas Assisted Injection Molding When Cavities of Square Flat Plates and Pipes are Involved 1. Theory of Flow Model and Its Criterion

Gas Assisted Injection Molding; Rule of Thumb; Preferred Direction of Gas; The Least Resistance to Initialresin Velocity

In such a complex situation as the cavity of two square plates connected to cavities composed of four pipes with same length and different diameter connected in series and parallel, the resistance of cavity of two square plates should be combined with that of pipes to determine the gas direction in gas assisted injection molding (GAIM). The flow model of Newtonian fluid was previously suggested under the fan-shaped geometry incuding relatively thin cavity of two square plates when pv_rH/μ(H/R₀)≪1, (H/R₀)²1/θ²≪1 and (H/R₀)²≪1. However, one may frequently encounter the problem of relatively thick fan-shaped cavity between two square plates where (H/R₀)² is around 10^-1 and θ² is the order of one. The rule of thumb containing a first order-approximated flow model by perturbation technique was introduced to show, in qualitative way, whether the resistance of the relatively thick cavity of two square plates may affect the gas direction in GAIM under the fore-said geometry. Subsequently, various simulations were performed under the conditions that all dimensions of cavity of two square plates and pipes were fixed except for the diameters of pipes. The results of simulation were compared with the results of the rule of thumb (RT1) containing the approximated flow model as well as those of another rule of thumb (RT2) without the resistance of the relatively thick cavity of two square plates. The results of simulations were generally consistent with the former in qualitative way to determine gas directions in gas assisted injection molding even though a relatively large value of 0.36 was applied as the value of ε to describe a relatively thick cavity of two square plates. In addition, the situation was treated when cavities of pipes and runners were involved in configuration. The rule of thumb was used for the ratio of initial velocities to be recalculated at the first coming change of diameters when the ratio was close to unity and it was quite consistent to the results of simulation.

Flow Directions in Gas Assisted Injection Molding When Cavities of Square Flat Plates and Pipes are Involved 2. Development of Time-dependent Flow Model

Gas Assisted Injection Molding; Rule of Thumb; Preferred Direction of Gas; The Least Resistance to Initialresin Velocity

For such conditions that (H/R₀)² is replaced by ε (that is the order of 10^-1) and θ² is the order of one, the rule of thumb for an approximated flow model was introduced in part 1 of the paper to show, in qualitative way, whether the resistance of the relatively thick cavity of two square plates might affect the gas direction in GAIM under the aforesaid geometry. Subsequently, various simulations were performed by using Moldflow (version of MPI 4.0) under the conditions that all dimensions of cavity of two square plates and pipes were fixed except for the diameters of pipes, and the results of simulation were compared with the results of a rule of thumb (RT1) containing the approximated flow model as well as those of another rule of thumb (RT2) without the resistance of the relatively thick cavity of two square plates. There were some exceptional cases where RT1 or RT2 were not consistent with the simulation results (i.e., flow directions). Thus such a developed model as time-dependent model was required to describe transient behavior of the interface between gas phase and resin phase instead of comparison of initial velocities in upper side and lower side of the configuration, which was proposed and utilized to compare with the results of Moldflow in this 2^nd part of the paper. The predictions of the developed flow model were so quite consistent with the results of simulation that the proposed time-dependent flow model may be referred to describe very well the transient behavior of the movement of the interface of gas and melt-resin in the cavities. In addition, a timedependent model was also established and was used to compare with the results of Moldflow when cavities of pipes and runners were involved in configuration. It is amazing that the proposed developed model was able to predict exactly the cross-over between the trajectories of interface of upper and lower side, and it is also surprising to describe the time dependent behavior so well that the result of the predictions by the developed model were quite consistent to the results of simulation by Moldflow.

The Treatment of Waste-air Containing Mixed Solvent using a Biofilter: 1. Transient Behavior of Biofilter to Treat Waste-air Containing Ethanol

Biofilter; Ethanol; Transient Behavior; Removal Efficiency; Elimination Capacity

Transient behavior of a biofilter packed with mixed media (of granular activated carbon and compost) inoculated with a pure culture of Pseudomonas putida was observed at the height of each sampling port to treat wasteair containing ethanol. In addition, flooding effects of an excess supply of buffer solution was observed at each sampling port of the biofilter until it recovered the status prior to the flooding. Unlike previous investigations, various process conditions were applied to successive biofilter runs in order to monitor the corresponding unsteady behavior of the biofilter in this work. In early stage of biofilter run the removal efficiency of ethanol maintained almost 100%. However, it began to decrease when inlet load surpassed 100 g/m³/h consistent with maximum elimination capacity. At the end of biofilter-run removal efficiency was decreased and maintained at 40%. The results of this work were compared to those of such biofiltration studies as the work of Christen et al. from the point of view that pure cultures of microorganism were used in both works. Except for the period of flooding effect of the 2nd stage, the inlet load and removal efficiency continued at 105.5 g/m³/h and 95%, respectively, while they were 93.7 g/m³/h and 95%, respectively, according to the result of Christine et al.. Removal efficiency remained at 90% for the beginning period of 3 days of the 3rd stage, and it gradually decreased to 60% for remaining 5 days of the stage with an inlet load of 158.26 g/m³/h, which may be interpreted as better than the result of Christine et al. Their result was that the removal efficiency on the inlet load of 154 g/m³/h of ethanol was continued to be 60% for 6 days of a separate biofilter run and decreased to 40% later. Thus, with similar inlet loads of ethanol, removal efficiency of this work was equivalent to or higher than that of Christine et al..

Separation of Phenylalanine by Ultrafiltration Using D-Phe Imprinted Polyacrylonitrile-Poly(acrylic acid)-Poly(acryl amide) Terpolymer Membrane

Molecularly Imprinted Polymer; Phenylalanine; Membrane; Wet Phase Inversion Method; Ultrafiltration

A D-phenylalanine (D-Phe) imprinted terpolymer P(AN-AA-AAm)membrane was prepared by the wet phase inversion method. Acrylamide (AAm) and acrylic acid (AA) were used as the functional monomer and acrylonitrile (AN) was used as a physical cross linker. The template molecules from the membrane matrix increased the population of free COOH groups and reduced that of dimerized COOH groups in the membrane matrix, which is an indirect evidence of the formation of recognition sites. The adsorption selectivity of the D-Phe imprinted tepolymer membrane prepared by in-situ implanting method was 0.37 at pH 2 after 3 h batch adsorption using 100 mg Phe/l recemate solution and reached nearly 1 after 24 h. In the ultrafiltration process, the permselectivity was 0.38 at pH 2 after 2.5 min. Separation of D-Phe from the racemate solution was demonstrated by a repeated ultrafiltration batch work.

Flow Direction When Fan Shaped Geometry is Applied in Gas-Assisted Injection Molding: 1. Flow Model Theory and its Criteria for Predicting Flow Directions

Fan-shaped Geometry; Direction of Gas Flow; Gas-Assisted Injection Molding; Gas Penetration Length; A Rule of Thumb; Simulation

In part 1 of this paper a qualitative analytical method to predict the preferred gas flow direction in gasassisted injection molding (GAIM), which involves flow through panel-areas of various fan-shaped geometries, and the criteria to apply the method were presented with appropriate assumptions. Then the definition of a resistance to initial velocity was proposed as a rule of thumb, by which the gas directions of GAIM were predicted under various fan-shaped geometries. Upon performing the simulation on them with commercial software (MOLDFLOW), we compared the ratio of simulated gas penetration lengths to both directions with the predicted ratio of resistances as well as the predicted direction of the gas flow in GAIM using the suggested rule of thumb herein presented. The predictions with the suggested rule of thumb were generally quite consistent with the results of simulation (MOLDFLOW). However the discrepancy between the ratio of gas penetration lengths and the ratio of resistances was observed to increase as the ratio more{(H/R₀)(one-side)/less(H/R₀)(the other-side)}of the values of H/R₀ on both sides of fan-shaped cavities became bigger even though the suggested rule of thumb was assumed adequate to use until the case met the condition of (H/R₀)² 1/θ² << 1 and (H/R₀)² << 1. Nevertheless, the suggested rule of thumb was still effective as far as the direction of gas flow was concerned.

Flow Direction When Fan Shaped Geometry is Applied in Gas-Assisted Injection Molding: 2. Development of Flow Model and its Predictions

Gas-Assisted Injection Molding; Rule of Thumb; Preferred Direction of Gas; Novel Flow Model; Trajectory of Gas Flow; Gas Penetration

In part 2 of the paper simplified unsteady-mass (and momentum-) balance equations of melt polymer resin in the cavities of GAIM were proposed, as a time-dependent rule of thumb, to constitute a novel flow model in GAIM under the configuration of two fan-shaped geometries connected with a gas nozzle. Upon performing a simulation on them with commercial software (MOLDFLOW), we compared the time evolution of simulated gas penetration lengths with the those of unsteady trajectory on the gas flow in GAIM by the suggested novel flow model in the fan-shaped cavities in order to check the precision of model-predicted gas penetration lengths as well as the consistency of its predicted direction. The results by the suggested novel flow model were satisfactory to fit the trajectory simulated with commercial software (MOLDFLOW).

인슐린을 고정화한 폴리우레탄 막의 제조 및 섬유아세포와의 상호작용

insulin; polyurethane; fibroblasts; surface modification; proliferation

Polyurethanes containing L-lysine segments in the main chain (PULL) were synthesized from 4, 4′-diphenymethyl diisocynate, poly(tetramethylene glycol), and z-lysine oligomer as a chain extender. Insulinimmobilized polyurethanes (PULL-In) were prepared by a coupling reaction of PULL surface amino groups with insulins. The amount of immobilized insulin was about 0.30 nmol/cm², as determined by Bradford method. The interactions of NIH/3T3 fibroblasts with surface-modified PULLs were investigated using ³H-thymidine incoporation and optical microscopy. The cell growth rate on PULL-In film was higher than those on other substrates. The cell proliferation by the immobilized insulin was almost same as that by the free one.

광반응 곁사슬기로서 4-스티릴피리딘유도체를 가지는 용해성 폴리이미드의 합성과 광배향

soluble polyimide film; liquid crystal; photoalignment; photoreactivity; 4-styrylpyridine

Soluble aromatic polyimides bearing 4-(4-oxyalkyleneoxystryl)-pyridines (ethylene and hexylene) as photoreactive side groups were synthesized and characterized. The photoreactive polymers were soluble in various polar organic solvents and their films were easily formed by solution casting. The photoreactivities of the polymers in the film state were approximately 64% at an exposure energy of 1.5 J/cm². Transmittances of the polymer films were about 85% after annealing at 200 ℃. Therefore, these polymers can be evaluated to be photoreactive polyimides with good transparency and solubility. The dichroic ratios of the polymers with ethylene and hexylene groups as the alkylene spacers were 0.023 and 0.026, respectively. The order parameters of 4'-pentyl-4-biphenylcarbonitrile as a liquid crystal (LC) in the film cells of the former and latter polymers were 0.50 and 0.52, respectively. These results indicate that the polymers show the effect of alkylene spacer on the photoalignments the LC in the film cells of the polymers was perpendicularly oriented to the electric vector of the linear polarized UV light (LPUVL).

Ester/Imide 조성이 Poly(ester-imide) 경화물의 열적 특성에 미치는 영향

poly(ester-imide); curing; freeman-carroll equation; varnish

The poly (ester-imide) copolymers were synthesized from N,N'-(4,4'-diphenyl methane) bistrimellitimide (DIDa), dimethyl terephthalate (DMT), ethylene golycol, and 1,3,5-tris-(2-hydroxy ethyl) isocyanurate. DIDa monomers were synthesized from solution-condensation polymerization of trimellitic anhydride and methylene dianiline. Compositions of copolymers were controlled by various ratios of DIDa/DMT from 100:0 to 0:100. The synthesized copolymers were cured by reactions with the isocyanate compounds. The structures of DIDa and those copolymers were confirmed by elementary analysis and spectroscopy. From the GPC data, it was found that weight average molecular weights of copolymers were below 3000, and the copolymerization behavior showed 4 or 5 types. The investigation of the thermal stabilities of the cured copolymers were carried out with the data from DSC and TGA analyses by using Freeman-Carroll equation. From the results, it was found that the thermal stabilities of the cured copolymers were increased with increasing DIDa contents.

Adsorption Selectivity of Phenylalanine Imprinted Polymer Prepared by the Wet Phase Inversion Method

Molecularly Imprinted Polymer; Macrovoids; Phenylalanine; pH Dependency

A phenylalanine (Phe) imprinted polymer was prepared by the wet phase inversion method to investigate the optimum preparation condition which endows the polymer matrix with prominent adsorption selectivity. The addition of a large amount of porogen (dimethyl sulfoxide: DMSO) was needed to form macrovoids in the polymer matrix. For the high adsorption selectivity of the polymer matrix, a complex between functional monomers and a template molecule must be formed before the copolymerization of acrylonitrile (AN: crosslinker) and acrylic acid (AA: functional monomer). The formation of a phenyl group in the polymer matrix by the coupling reaction between DPhe and AA seemed to cause the reverse adsorption selectivity of the polymer matrix. The adsorption selectivity of the Phe imprinted polymer was dependent on the pH of the racemate solution. The adsorption selectivity of the D-Phe imprinted polymer prepared by the post implanting method reached 11 at pH 2 and showed a reverse adsorption selectivity at pH 4 and 6.

Annual Variation of Fresh Water Quality in the Gachang Dam Reservoir

Algae Population; Freshwater; Gachang Dam; Total Nitrogen; Total Phosphorus

This paper investigated the relationship between the annual variation of the algae population and the physicochemical properties of the water reservoired in the Gachang Dam in the hopes of serving as a guideline in the production of a clean water supply to regions of the city of Taegu. Summer thermal stratification was formed in the freshwater reservoired in the Gachang Dam and thus dissolved oxygen (DO) decreased according to the depth of the water. The pH of epilimnion was much higher than that of hypolimnion in summer because of the difference in the photosynthesis rate of algae. In July, at the beginning of the rainy season, the amount of total nitrogen (T-N) in the freshwater reached a maximum of 1.92 mg/L without an increase in the amount of total phosphorus (T-P). In August, the concentration of T-P in the freshwater increased steeply and reached 0.12 mg/L. Aulacoseira spp. (diatoms) were predominantly distributed in the freshwater throughout the year and Synedra and Asterionella (diatoms) predominantly populated in the spring. However, Anabaena and Microcystis (blue-green algae), which caused malodor and a bad taste, flourished predominantly in epilimnion in August when the temperature of the water at the surface region increased to the maximum and the concentration of T-P was sufficiently high.

Prediction of Gas Flow Directions in Gas Assisted Injection Molding When Cavities and Runners Are Involved

Gas Assisted Injection Molding; Rule of Thumb; Preferred Direction of Gas; The Least Resistance to Initial-Resin Velocity

In the prediction of gas flow-direction for gas-assisted injection molding (GAIM), the statement “Gas goes to the direction of the last area to fill with resin” has been accepted as a correct one. When there exists more than one area to fill with resin, a mold design engineer for GAIM technologies has to determine to which direction gas goes that commercial software for GAIM (e.g., Moldflow) may be utilized for its mold design. However commercial software is generally expensive and is sometimes hard to become familiar with. As a rule of thumb, it is suggested that the resistance to the initial velocity of melt polymer at the nearest geometry to a gas injection point should be used as its criterion since gas goes in the direction of least resistance to initial resin-velocity. Neither the flow rate nor the resistance to flow rate can be a criterion in the prediction. Thus the statement “Gas goes to the direction of the least resistance to flow rates” should be corrected to “More flow rate goes to the direction of the least resistance to flow rates.” The rule of thumb suggested in this paper was verified by using commercial software, Moldflow, in the prediction of gas flow directions in GAIM under geometries where cavities and runners were involved. When the ratio of initial resin-velocity is so close to unity it is proposed as the adapted rule of thumb to calculate new emerging resinvelocities and resistances to resin-velocity at the first coming change of diameters in series of pipes and to compare those for upper and lower sides each other to predict the gas direction. Thus the judgment as to which point is the point where gas starts to choose a preferred direction is very important in the prediction.

Biofilter Modeling for Waste Air Treatment: Comparisons of Inherent Characteristics of Biofilter Models

Biofilter; Modeling; Adsorption; Biofilm; Sorption Volume

The types of biofilter modeling may be primarily classified in accordance with whether a biofilm is differentiated from other phases in each model. It may be a secondary classification with regard to biofilter-modeling whether sorption volume and/or adsorption are adopted as reservoirs or not. Thirdly, biofilter models are classified as to whether adsorption is assumed to exist through gas phase and/or a biofilm. Among all the biofilter-models of previous investigators all model-components including gas phase, a biofilm, sorption volume and adsorption surface are considered only in the model of Lim. Since his model does not require a numerical solution but an algebraic solution to describe the concentration of organic pollutants in waste-air-streams along the height of a biofilter even under unsteady-state conditions, it satisfies the condition of simplicity that is one of the important model requirements. In spite of its simplicity, Lim’s model predictions are fairly good to fit Hodge and Devinny’s experimental data.

보호된 이소시아네이트기와 불소화 알킬기를 가지는 아크릴계 고분자의 합성과 특성

protected isocyanate group; fluoroalkyl group; water repellent polyacrylate derivative; reactivity ratio; contact angle

The copolymerizations of 2-fluorohexylethyl acrylate (FA) with 2-(o-(1-'methylpropylidenamino)carboxyl amino) ethyl methacrylate (MEM) with different molar ratios of the two monomers were carried out in methyl ethyl ketone using α,α',-azobisisobutyronitrile as an initiator to synthesize water repellent polyacrylate derivatives with protected isocyanate groups. The contents of FA and MEM in the copolymers were analyzed by NMR. The monomer reactivity ratios of MEM (1) and FA (2) were determined by Kelen-Tudos plot as follows : r₁=1.59 and r₂=0.50. The number-average molecular weights of the copolymers were in the range of 39400 to 72400 and the polydispersity indexes were about 1.5. The protected isocyanate groups in the copolymers were converted into isocyanate groups above 150 ℃. The contact angle of the copolymer with 65 mol% of FA for water was about 95 °.

항균제로서 8-히드록시퀴놀린의 moiety를 가지는 아크릴고분자의 합성과 특성

acrylic siging agent; microbicidal activity; release; 8-hydroxyquinoline

8-Quinolinyl acrylate and monomers of ethyl acrylate, methyl methacrylate, and acrylic acid were radically copolymerized in order to prepare an acrylic sizing agent with microbicidal activity. The yield and the molecular weight of the polymer increased with increasing the polymerization time. The number-average molecular weight was in the range of 26000 to 42000, and the polydispersity was in the range of 3.0 to 4.2. The glass transition temperature was at around 36 ℃, and the initial decomposition temperature was around 250 ℃. The release rate of 8-hydroxyquinoline from the polymer increased with increasing pH of the release medium. This result was attributed to the enhanced proton dissociation of carboxyl group of the acrylic acid unit in the polymer. The polymer was excellent for reducing microbial activity of the E.Coli.

Characteristics of Phenylalanine Imprinted Membrane Prepared by the Wet Phase Inversion Method

Molecularly Imprinted Membrane; Adsorption Selectivity; Phenylalanine

A phenylalanine imprinted membrane without a sponge layer containing macrovoids was prepared by the wet phase inversion method. The structure of the phenylalanine imprinted membrane prepared by an in-situ implanting procedure was denser than that of the membrane prepared by post implanting. Consecutive washings with distilled water and acetic acid solution removed nearly all of the template molecules from the membrane prepared by the post implanting procedure, although much of the template molecules remained in the membrane prepared by in-situ implanting. The removal of the template molecules from the membrane increased the population of the free COOH groups but reduced that of the dimerized COOH groups in the membrane. A D-Phenylalanine imprinted membrane prepared by post implanting selectively adsorbed D-phenylalanine from a racemate solution, where the adsorption selectivity reached 4.79. A D-phenylalanine imprinted membrane prepared by in-situ implanting exhibited an inverse adsorption affinity.

Metal Recovery Using Immobilized Cell Suspension from a Brewery

Biosorption of Heavy Metals; S. cerevisiae; Brewery; Cell Suspension; Bead

Lead, copper, and cadmium were adsorbed onto calcium alginate beads containing the cell suspension discarded from a brewery. In the cell suspension, there were many cells under lysis. The cell-suspension immobilized beads were prepared by adding 0.6% (w/v) sodium alginate into the cell suspension from the brewery and then making the cell suspension fall dropwise into the swirling 1% (w/v) calcium alginate solution. The dry weight of insoluble solid in the cell suspension was 96 g dry weight/l and the dry density of the bead containing cell suspension was 140 g dry weight/l of the bead. The specific metal uptake of the cell-suspension immobilized bead was 23.7 mg Pb2+, 14.3 mg Cu2+, and 13.4 mg Cd2+/g bead dry weight, respectively. The cell-suspension immobilized beads retained the initial metal-uptake capacity after 20 repeated batches of adsorption and desorption, but the fraction of metal desorbed from the beads by 1M HCl solution was only 70% of the adsorbed metal. The beads, which had been contained for 14 successive days in the 0.5% (w/v) CaCl2 solution at 4 oC just after 20 cycles of adsorption/desorption, retained the initial metal-uptake capacity after 30 repeated cycles, and more than 90% of the copper and cadmium adsorbed on the beads was desorbed by the 1 M HCl solution.

A Phenomenological Model for Linear Viscoelasticity of Monodisperse Linear Polymers

monodisperse polymers; linear viscoelasticity; molecular weight

Although the reptational model of Doi and Edwards gives a successful description of viscoelasticity of flexible linear polymers, the success is restricted to the terminal region.1 There have been several attempts to modify the Doi-Edwards model to describe wider range of time or frequency.2-6 This paper suggests a simple phenomenological model which can describe wider range of molecular weight than such molecular models can. Although our model is a phenomenological one, it is practical and convenient to predict the effect of molecular weight distribution on linear viscoelastic data because of its simple mathematical form.

항균제로서 m-크레졸의 Moiety를 가지는 고분자의 합성과 특성

microbicide; m-cresyl acrylate; terpolymerization; release

By the reaction of m-cresol as a microbicide with acryloyl chloride m-cresyl acrylate (CA) was synthesized, and polymers with the moiety of m-cresol were prepared by the radical terpolymerization of CA-methylmethacrylate-acrylic acid. The contents of CA unit in the polymers were found to be 4.7 mol% and 10.1 mol% from their nuclear magnetic resonance spectra. The number-average molecular weights of the polymers were in the range of 12000 to 15000. Through the hydrolysis of the polymers m-cresol was released. The release rate of the microbicide increased with increasing pH of the release medium. This result can be attributed to enhanced proton dissociation of carboxyl group of the acrylic acid unit in the polymers. These polymers showed microbicidal activities for S. aureus as a positive microbe and E. coli as a negative microbe.

폐수처리용 페타이어 담체의 제조 및 특성

Media; Waste-Tire-Powder; Waste-Water Treatment; Adsorbents; Ammonium Ion

For recycling waste-tires the process conditions to prepare the media of waste-tire-powder for the fluidized treatment of waste-water were optimized by the analysis of their physical properties. The optimum ratio(w/w) of waste-tire-powder to EVA(ethyl vinyl acetate) binder to prepare waste-tire-powder media turned out to be 4 to 1 and their porosity was 0.74. Various adsorbents were applied to the surface of the prepared media, after which they were used in the treatment of waste-water so that their removal rates of ammonium ion were evaluated under 5 modes of different operating conditions such as temperature and C/N ratios and were compared each other. At 20 ℃ the ammonium ion removal rates of 5 modes were similar regardless of adsorbents applied to the surface of the prepared media. In the meantime, at 10 ℃ the ammonium ion removal rates of the media with coconut- or coal-based activated carbon were shown to be higher by more than 1.5 times than those of the media with synthetic calcium silicate.

Synthesis of Poly(phenylene-co-biphenylene sulfide) and Its Blend with Bisphenol A Polysulfone

PPS; copolymer; blend; PSF; partial miscibility

A series of poly(phenylene-co-biphenylene sulfide)s (PPBS) were prepared by substituting parts of phenylene units of poly(phenylene sulfide) (PPS) with more rigid biphenylene units. A copolymer was blended with bisphenol A polysulfone (PSF), and drawn to prepare a in situ composite. Dynamic mechanical observation suggested the immiscibility of PSF/PPS blend and the partial miscibility of the PSF/PPBS blend. PPBS appeared to be a better rheology modifier and reinforcing agent than PPS, which is observed in the melt viscosity and the tensile tests. SEM micrographs of the blends show smaller and more uniform domains in PSF/PPBS blends than in PSF/PPS blends. In drawn blends PPBS appeared to form better-defined fibrils with higher aspect ratios than PPS in PSF. As a result PSF/PPBS blend showed higher level of tensile modulus and yield stress over the PSF/PPS blend.

Plasma Display Panel용 순수 현상형 감광성 격벽 Paste 및 Photolithography 공정 특성

plasma display panel(PDP); photosensitive barrier rib paste; photolithography; barrier rib

Barrier ribs for the plasma display panel (PDP) are commonly utilized to have uniform height and width and to prevent optical crosstalk between adjacent cells. The basic requirements for such barriers are uniform height and shape, low outgassing rate and low porosity, high aspect ratio, fine resolution, and so on. In this study, an attempt was made to demonstrate the possibility of using a photolithography method in manufacturing the barrier ribs. The barrier rib paste was prepared by first dissolving hydroxypropyl cellulose in 3-methoxy-3-methyl butanol (3MMB), forming 20 wt% solution. To this solution, a mixture of EB600/PETA at 50/50 wt%, HSP 188 as the photoinitiator, and barrier rib powder were added. Then the mixture was throughly mixed in a three-roll mill. The effect of the component and concentration of photosensitive barrier paste on the photolithographic process was studied. After optimization of the paste formulation and photolithographic process, the resulting barrier ribs showed height of 110 μm, width of 80 μm and pitch of 420 μm.

Seed 중합에 의한 Carboxylated NBR계 Composite Latex의 합성 및 물성

carboxylated NBR latices; seed emulsion polymerization; co-monomer; coagulum; neutralization

In order to improve the stability and compatibility of NBR latex with other filler and resin, carboxylated NBR latices were synthesized by seed emulsion polymerization. The reaction conditions studied include type and amount of emulsifier, partial neutralization of acrylic monomer, the ratio of acrylic monomer in the acrylic type co-monomer, and the NBR core/shell weight ratio. Sulfonate type emulsifiers such sodium dodecyl sulfonate was found to minimize the coagulum formation in seed emulsion polymerization compared with carboxylate type or non-ion type emulsifiers. As the degree of neutralization and the amount of acrylic acid monomer were increased, the stability and particle size of the final latices increased. As the core/shell weight ratio was decreased to about 1 : 0.2, the final latices showed smaller particle size and less coagulum formation.

Production of L-Phenylacetylcarbinol (L-PAC) by Encapsulated Saccharomyces cerevisiae Cells

L-phenylacetylcarbinol; L-PAC; Benzaldehyde; Saccharomyces cerevisiae

In the present study, benzaldehyde was converted by both the free cells Saccharomyces cerevisiae (ATCC 834) and those immobilized in the calcium alginate liquid-core capsule into L-PAC during anaerobic fermentation in a medium containing benzaldehyde. In a free cells survey, skipping aerobic adaptation before anaerobic fermentation caused all of benzaldehyde to be converted by 220 g (wet weight) of cells in 100 mL of the medium even at a higher concentration of 8 g/L benzaldehyde. The yield of L-PAC based on the moles of converted benzaldehyde increased as the amount of benzaldehyde dose was increased. The encapsulation protected cells effectively from the toxicity of benzaldehyde. Even a small quantity, 1.1 g (dry weight), of encapsulated cells in 100 mL of the medium containing 0.6% benzaldehyde converted more than 95% of the benzaldehyde, and the corresponding yield of L-PAC was about 40%. The production of L-PAC by the encapsulated cells depended on the pH of the medium. The conversion of benzaldehyde decreased slightly, but yield of L-PAC increased as the pH of the broth solution was fixed at a lower value. Biotransformation in a small side reactor of the batch system caused higher yield of L-PAC than that in the batch reactor containing the same quantity of encapsulated cells during the first 4 hours of fermentation.

Synthesis and Thermal Properties of Poly(phenylene sulfide-co-phenylene sulfide ketone)

Poly(phenylene sulfide-co-phenylene sulfide ketone)s; PPS/SK Copolymer; Thermal Properties

Poly(phenylene sulfide-co-phenylene sulfide ketone)s (PPS/SK) were synthesized from p-dichlorobenzene (DCB)/4,4'-dichlorobenzophenone (DCBP) and p-dibromobenzene (DBB) /DCBP monomer pairs using sodium sulfide trihydrate (Na2S · 3H2O) in N-methyl-2-pyrrolidinone (NMP) solvent. The yield and molecular weight of the PPS/SK copolymers were higher with the DBB/DCBP/Na2S monomers. The copolymer composition and molecular weight of the PPS/SK copolymers were determined by an elemental (C, H, S) analysis and high temperature (210 ℃) GPC with 1-chloronaphthalene as an eluent, respectively. The molecular weight of the PPS/SK copolymers showed a maximum value at a feed ratio of [DBB]/[DCBP] = 70/30 mol%. The plot of the T(g)'s of the PPS/SK copolymers relative to the copolymer content of the DCBP repeat unit matched well with Fox equation. As the content of the DCBP unit increased in the PPS/SK copolymers, the T(g) of the PPS/SK copolymer also increased. The PPS/SK copolymers exhibited T(m)'s with all compositions at a 20 ℃/min scan rate for the DSC measurement. The eutectic point appeared to be 267.2 ℃ with 29.8 mol% DCBP units in the copolymers.

아크릴계 응집제 라텍스의 합성 및 이를 이용한 NBR 라텍스의 고형분 향상

Agglomeration latex; High solid content latex; Stability of latex; NBR latex

In order to increase the solid content of NBR latex while maintaining latex stability, an acrylate type agglomeration lattices were synthesized. Seeded emulsion polymerization was used to get agglomeration latices. As the amount of emulsifier increased and that of potassium persulfate initiator decreased, the particle size of agglomerating latices increased. The addition of electrolytes, such as KCl and K2CO3, also increased the particle size of agglomeration latex. NBR latex after agglomeration process exhibited increased of particle sizes with bimodal distribution. While NBR base latex itself could be concentrated up to 45 wt% solid content, the NBR latex with added agglomeration latex could be concentrated up to 54 wt% without loosing latex stability.

개시제 및 촉진제 함량 변화에 따른 불포화 폴리에스테르의 경화 거동

Unsaturated polyester; Activation energy; Reaction rate equation

The activation energy has been quantified with initiator and accelerator content. From this result, the optimum condition of initiator and accelerator contents was determined. In this initiator and accelerator contents, unsaturated polyester (UP) was cured isothermally and the conversion rate was obtained. Reaction rate equation was used for obtaining reaction order. Calculated value was obtained from this reaction order, and it was compared with experimental value. Curing reaction of UP was satisfactory with n-order reaction and average reaction order value was about 1.38. In addition, the effect or initiator and accelerator contents on the mechanical properties was investigated by measuring glass transition temperature and hardness. The plasticizer effect was confirmed by the excessive initiator content.

Biphenylrl를 포함하는 공액 공중합체의 합성 및 전계발광 특성

light-emitting diode; conjugated polymer; α-elimination; honer-emmons reaction

Poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene)(MEH-PPV) and poly(2-methoxy-5-(2-ethylhexyl-oxy)-1,4-phenylene vinylene-co-1,1''-biphenyl-4,4''-ylene vinylene) [poly(MEHPV-co-BPV)] with a different feed ratio of biphenyl group in the main chain were synthesized by α-elimination reaction. Poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene-alt-1,1''-biphenyl-4,4''-ylene vinylene) [poly(MEHPV-alt-BPV)], which has alternating repeat unit, and poly(1,8-octanedioxy-2-methoxy-1,4-phenylene-1,2-ethenylene-1,1''-biphenyl-4,4''-ylene-1,2-ethenylene-3-methoxy-1,4-phenylene) [poly(BFMP8-BPV)] and poly(1,12-dodecaedioxy-s-methoxy-1,4-phenylene-1,2-ethenylene-1,1''-biphenyl4,4''-ylene-1,2-ethenylene-3-methoxy-1,4-phenylene)[poly(BFMP12-BPV)] containing both conjugated and non-conjugated group in the main chain were synthesized by the Honer-Emmons were examined. The solubility of poly(MEHPV-co-BPV)s in common organic solvents decreased rapidly with the increasing amount of BPV units in the copolymer. Emission spectrum of poly(MEHPV-co-BPV)s had two peaks corresponding to MEPHV(586 nm) and BPV(469, 495 nm) moiety, respctively. However, LED fabricated with poly(MEHPV-alt-BPV)showed relatively sharp single peak(544 nm) in the middle of the two peaks.

고분자 반응을 이용한 Maleimide계 비선형 광학 고분자의 합성 및 전기광학 특성

nonlinear optical polymer; maleimide copolymer; nlo properties; nlo polymer system

Novel polymers which exhibit non-linear optical (NLO) properties have been synthesized and their electro-optic properties were examined. Poly (α-methylstyrene-co-hydroxphenyl maleimide) (MSHM) and poly (α-methylstyrene-co-4-carboxyphenyl maleimide) (MSCM) substrate polymers were obtained readily by free radical polymerization. Introduction of DR1 chromophore to substrate polymer was conducted by using Mitsunobu reaction. The degree of substitution of DR1 into the MSHM, MSCM substrate polymer was found to be 9403 mol% and 33.0 mol%, respectively. The glass transition temperature (Tg) of NLO polymer was in the range of Tg=185-217℃. The electro-optic coefficient(r33) of NLO polymer was determined with an experimental setup capable of the real-time measurement while varying the poling field and temperature. The NLO polymer, MSHM-DR exhibited higher r33 values than MSCM-DR due to the increased substitution of the DR1 chromophores. MSHM-DR had a maximum r33 value of 26pm/V at 135MV/m poling field with a 632.8 nm light source.

Polymerization of Ethylene Initiated with Trisiloxane-bridged Heterometallic Dinuclear Metallocene

The new trisiloxane-bridged heterometallic dinuclear metallocenes, hexamethyltrisiloxanediy-1(cyclopentadienyltitanium trichloride) (cyclopentadienylidenyl zirconium dichloride), Cl₂Ti-Cp(CH₃)₂Si-O-Si(CH₃) ₂-O-Si(CH₃)₂-Cp-ZrIndCl₂ (1) and hexamethyltrisiloxanediyl(cyclopentadienylindenylhafnium dichloride) (cyclopentadienylindenyl zirconium dichloride), Cl₂lndHf-Cp(CH₃₂Si-O-Si(CH₃) ₂-O-Si(CH₃)₂-Cp-ZrlndCl₂ (2) connecting two dissinilar metallocenes were synthesized and used for ethylene polymerization in the presence of modified methylaluminoxane (MMAO) cocatalyst. The catalytic activity of heterometallic dinuclear metallocenes, 1 and 2 was lower than that of corresponding mononuclear metallocene as well as two physically mixed catalysts. CpTiCl₃/Cp₂ZrCl₂ and Cp₂HfCl₂ZrCl₂. On the ofther hand, MWDof PE obtained with 1 and 2 remarkably broader (M_w/M_n became up to 9.4)than those of PEs prepared with the corresponding mononuclear metallocenes and mixed catalysts. With analysis by GPC and CFC, it was found that PE produced by the heterometallic dinuclear metallocenes exhibited the definite bimodal GPC curves that should cause the brodening of MWD.