• Membrane Journal
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• v.9 no.4
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• pp.221-229
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• 1999

The nominal pore size 0.2 ${\mu}m polytetrafluroethylene(PTFE, Satorius Co,) membrane was used for the filtration of 0.1 wt% kaolin, bentonite, yeast, and starch solution, respectively. After filtration, the membrane was cleaned and the pore size was measured by liquid displacement method(LDMl using water/iso-butanol system. The pore size for new PTFE membrane evaluated by LDM was comparable with those of which were measured by mercury porosimetry and scanning electron microscope. The membrane pores were severely fouled, and constricted to below 0.3 ${\mu}m in the cases of bentonite and starch solution which contained smaller particles than pores. However, in the case of kaolin - solution, only some parts of membrane pores above 0.35 ${\mu}m were slightly fouled. Hence, the phenomena of membrane fouling could be identified quantitatively by the evaluation of pore size using LDM.

• Elastomers and Composites
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• v.42 no.3
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• pp.137-142
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• 2007

In the performance test of polytetrafluoroethylene (PTFE) membrane, melting temperature and crystallinity were $344.1^{\circ}C$ and 42.5%, respectively, according to TGA and DSC analysis. These values were similar to those of commercially available GE Osmonics PTFE membrane. The average of pore size was observed $0.716{\mu}m$ and the average flow rate was 1.570 LMH. These are slightly higher values than those of GE Osmonics sample. The filtering efficiency rate was 30.5%.

• Journal of Periodontal and Implant Science
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• v.26 no.1
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• pp.47-67
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• 1996

The purpose of this study was to observe the effect of $Biocoral^R$ graft and bioglass 45S5 graft in combination with ePTFE membrane in periodontal osseous defects for new bone formation. Nine healthy dogs were used. Under general anesthesia, 3-wall defects were created on the mesial and distal surfaces of the maxillary right canines, the mesials of the maxillary right second premolars, the distals of the mandibular right canines and the mesials of the mandibular right third premolars. To induce periodontitis, a silicone rubber, $Provil^R$ light body, was injected under pressure into the defects. Ninety days later, $Provil^R$was removed and followed by thorough root planing. The followings were then applied in the mesial and distal defects of the maxillary right canines, the mesials of the maxillary right second premolars, the distals of the mandibular right canines and the mesials of the mandibular right third premolars by random selections : 1) ePTFE membrane only application, 2) $Biocoral^R$ graft, 3) $Biocoral^R$ graft and ePTFE membrane application, 4)Bioglass 45S5 graft, 5) Bioglass 45S5 graft and ePTFE membrane application. The membranes were removed 1 month later. The dogs were sacrified at 1, 2 and 3 months following the graft, and block sections were made, demineralized, embedded, stained and examined by light microscope and transmission electron microscope. On the sections from teeth treated with ePTFE membrane only, the defect demonstrated extensive connnective tissue and alveolar bone regeneration. The $Biocoral^R$ graft group demonstrated extensive bone regeneration compared with ePTFE membrane only group. In the $Biocoral^R$ graft plus ePTFE membrane group, regeneration of new alveolus and crest occurred within the defect. As the experimental period lengthened, bone regeneration was increased and bone bridge was formed among the graft particles. The but bioglass 45S5 graft group demonstrated extensive bone regeneration but the amount of new bone was less than that of the $Biocoral^R$ graft group. For the bioglass 45S5 graft plus ePTFE membrane group, the amount of new bone was also increased. As the experimental period lengthened, bone regeneration was increased. Multinucleated giant cells, fibroblasts and macrophages were observed. As the bone formation was increased, the number of such cells was decreased. In conclusion, the $Biocoral^R$ was found better than the bioglass 45S5 for new bone formation, and the use of ePTFE membrane alone or with $Biocoral^R$/bioglass 45S5 can be supported as potential methods of promoting bone formation.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.4 s.121
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• pp.342-349
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• 2007

Following the 2002 World-Cup held in Korea, studies have been actively conducted on plans to utilize all-weather stadiums of fine figures, where large-scale spaces are available for various utilizations. In Japan, dome-type stadiums have been built and are utilizing across the whole nation not only for sports events but also variety of other large-scale events. PTFE(poly tetra fluoro ethylene) is one of the membrane material mainly used for the outer ceiling surface of membrane structures. However, there has not been enough research on the acoustical properties of PTFE membrane material which has been widely used in the multi-purpose stadiums. In this study, air permeability values and sound absorption coefficient of PTFE membrane materials were measured and evaluated in the gymnasium. From the results of measurements of sound absorption coefficient and air permeability of inner membrane materials, it was found that the sound absorption coefficient was good in the air permeability range of $5{\sim}15\;cc/cm^2/s$. Also the relation ship between air permeability and sound absorption coefficient was very high and the sound absorption coefficient was the highest in the range of $6{\sim}9\;cc/cm^2/s$. Secondly, an analysis on the measurements sound absorption characteristics of inner membrane material reveals that the overall sound absorption coefficient was stabilized(higher than 0.5 throughout the whole frequency bands) when the air space behind the membrane material was deeper than 600 mm. When PTFE sound absorptive membrane material was installed in the ceiling of gymnasium, it was confirmed that sound absorptive membrane material can reduce reverberation and increase speech intelligibility in the gymnasium.

• Journal of Periodontal and Implant Science
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• v.35 no.2
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• pp.491-510
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• 2005

This study was performed to evaluate the effect of inorganic polyphosphate on bone formation in the calvaria of rabbit in the procedure of guided bone regeneration with bovine cancellous bone graft and titanium reinforced expanded polytetrafluoroethylene(TR-ePTFE) membrane. The rabbits were divided into four groups. Control group I used only TR-ePTFE membrane, control group II used TR-ePTFE membrane and deproteinized bovine bone mineral soaked in saline, experimental group III and IV used TR-ePTFE membrane and deproteinized bovine bone mineral soaked in 1% or 2% inorganic polyphosphate respectively. After decortication in the calvaria, GBR procedure was performed on 12 rabbits with titanium reinforced ePTFE membrane filled with deproteinized bovine bone mineral soaked in saline or inorganic polyphosphate. The animals were sacrificed at 2 weeks, 4 weeks, and 8 weeks after the surgery. Decalcified and non-decalcified specimens were processed for histologic and immunohistochemistric analysis. 1. Titanium reinforced ePTFE(TR-ePTFE) membrane showed good spacemaking and cell occlusiveness capability, but it showed poor wound stabilization. 2. The deproteinized bovine bone mineral did not promote bone regeneration, but it acted as a space filler. 3. There was no complete resorption of the deproteinized bovine bone mineral within 8 weeks. 4. 1% inorganic polyphosphate did not promote bone formation, but 2% inorganic polyphosphate promoted bone formation. Within the above results, 2% inorganic polyphosphate could be used effectively for bone regeneration.

• Membrane Journal
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• v.31 no.5
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• pp.351-362
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• 2021

All-vanadium redox flow battery (VRFB) is one of the promising high-capacity energy storage technologies. The ion-exchange membrane (IEM) is a key component influencing the charge-discharge performance and durability of VRFB. In this study, a pore-filled anion-exchange membrane (PFAEM) was fabricated by filling the pores of porous polytetrafluoroethylene (PTFE) support with excellent physical and chemical stability to compensate for the shortcomings of the existing hydrocarbon-based IEMs. The use of a thin porous PTFE support significantly lowered the electrical resistance, and the use of the PTFE support and the introduction of a fluorine moiety into the filling ionomer significantly improved the oxidation stability of the membrane. As a result of the evaluation of the charge-discharge performance, the higher the current efficiency was seen by increasing the fluorine content in the PFAEM, and the superior voltage and energy efficiencies were shown owing to the lower electrical resistance compared to the commercial membrane. In addition, it was confirmed that the use of a hydrophobic PTFE support is more preferable in terms of oxidation stability and charge-discharge performance.

• Journal of Sensor Science and Technology
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• v.29 no.2
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• pp.89-92
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• 2020

Polytetrafluoroethylene (PTFE) fibers are widely used in the textile industry, filter media, membrane distillation, electronic appliances, and construction. In this study, PTFE-polyethylene oxide (PEO) fibrous membranes were fabricated by emulsion electrospinning; subsequently, pure PTFE nanofibers were obtained via sintering. PTFE-PEO electrospinning solutions were prepared using different weight ratios to determine the optimized condition. As the ratio of the PEO increased, the fiber structure improved. Scanning electron microscopy and Fourier-transform infrared spectroscopy observations indicate that PEO is removed and PTFE fused gradually to form bonds among them during sintering. The obtained pristine PTFE membrane demonstrated hydrophobicity at 143.6° water contact angle and oleophilicity at 0° oil contact angle, which is known to be utilized for oil/water separation. A simple separation experiment was performed to remove oil droplets from water. The PTFE membrane exhibited good chemical stability and a high surface-area-to-volume nanofiber ratio. These excellent properties suggest that it is applicable to oil/water separation in harsh chemical environments.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.5
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• pp.353-358
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• 2011

In this study, ammonia removal characteristics in membrane contactor system under various operating conditions were evaluated. The mass transfer coefficient was used to quantitatively compare the effect of various operation conditions on ammonia removal efficiency. Effective removal of ammonia was possible with the tubular PTFE membrane contactor system at all tested conditions. Among the various operation parameters, contact time and solution pH showed significant effect on ammonia removal mechanism. Overall ammonia removal rate was not significantly affected by influent suspended solution concentration unlike other pressure driven membrane filtration processes. Also the osmotic distillation phenomena which deteriorate the mass transfer efficiency can be minimized by preheating of strip solution. Membrane contactor system can be a possible alternative to treat high strength nitrogen wastewater by optimizing operation conditions such as stripping solution flow rate, influent wastewater temperature, and influent pH.

• Membrane Journal
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• v.33 no.2
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• pp.53-60
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• 2023

Mechanical energy can be harvested by triboelectric nanogenerators (TENG) from biological and environmental systems. In wearable electronics, TENG has a lot of significance as biomechanical energy can be harvested from the motion of humans, which is applied in vibrational sensors. Wearable TENG is prone to moisture and polytetrafluoroethylene (PTFE) is an excellent hydrophobic material used in these applications. The presence of highly electronegative fluorine atoms leads to very low surface energy. At the same time, the performance of the device increases due to the efficient capture of the electrons on the microporous membrane surface. This similar behavior occurs with polyvinylidene fluoride (PVDF) due to the presence of fluoride atoms, which is relatively less as compared to PTFE.

• Journal of Periodontal and Implant Science
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• v.38 no.sup2
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• pp.325-334
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• 2008

Purpose: The carrier used as delivery agent for bone morphogenetic proteins(BMPs) should also act as a scaffold for new bone formation. Moreover, bone formation should be predictable in terms of the volume and shape. This study examined the osteogenic effect of macroporous biphasic calcium phosphate (MBCP) block combined with ePTFE membrane as a carrier for recombinant human bone morphogenetic proteins (rhBMP-2). In addition, the additive effect of ePTFE membrane on bone formation was evaluated. Materials and Methods: Eight-millimeter critical sized calvarial defects were created surgically in 28 male Sprague-Dawley rats. The animals were divided into 2 groups containing 14 animals each. The defects were treated with either rhBMP-2/MBCP block (rhBMP-2/MBCP group) or rhBMP-2/MBCP block/ePTFE membrane (rhBMP-2/MBCP/ePTFE group). A disc-shaped MBCP block (3 mm height and 8 mm diameter) was used as the carrier for the rhBMP-2 and ePTFE membrane was used to cover the rhBMP-2/MBCP block. The histologic and histometric parameters were used to evaluate the defects after 2- or 8-week healing period (7 animals/group/healing interval). Results: The level of bone formation in the defects of both groups was significantly higher at 8 weeks than that at 2 weeks (P < 0.05). The ePTFE membrane has no additional effect compared with the rhBMP-2/MBCP block only. However, at 8 weeks, rhBMP-2/MBCP/ePTFE group showed more even bone formation on the top of the MBCP block than the rhBMP-2/MBCP group. Conclusion: These results suggest that the ePTFE membrane has no additive effect on bone formation when a MBCP block is used as a carrier for rhBMP-2.