• Journal of the Korean Wood Science and Technology
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• v.33 no.4 s.132
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• pp.60-65
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• 2005

This study was carried out to investigate the sheet properties of Indian mallow Hanji, made by different pulping methods, such as alkali and sulfomethylated pulpings, and different stock compositions, various mixing ratios of bast fiber and wood core fibers. Indian mallow Hanjis made with 60% of woody core pulps were shown better Chinese ink spreading distance than those of the others. The Chinese ink spreading distance of the Indian mallow Hanjis made from bast fiber pulp only were unsuitable for Hwaseonji. The Chinese ink spreading distance of Indian mallow Hanji was closely related to the mixing ratio of long fiber and short fiber. Especially sulfomethylated pulping method was superior to alkali pulping method.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.31 no.1
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• pp.31-38
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• 1999

Adsorption of polymeric flocculants and dry strength agents onto the surface of papermaking fibers is critical for their effective utilization since the polymeric substances not adsorbed on fibers or fines keep recirculating in the papermaking system to cause various operational difficulties and loss of raw materials. Problems associated with the unadsorbed polymeric substances generate great attention because unprecedent interests in utilization of recycled papers and papermaking system closure. In this study, to understand the effects of recycling on the adsorption propensity of cationic polyacryamide (PAM) dry strength resin onto hardwood bleached kraft pulp fibers and fines a systematic approach was followed. Never dried bleached hardwood kraft pulp was recycled in two different ways. In mode one recycling experiment never dried pulp was beaten then recycled three times by employing simple drying and disintegrating steps. In mode two recycling experiment beating of the recycled pulp was carried out after each recycling step. Adsorption of cationic PAM on fibers and fines was evaluated employing Kjeldahl nitrogen analysis method. The influence of recycling on water retention value, carboxyl content, sheet density and tensile strength of the pulp was examined. As the number of recycling increased, water retention value of the fiber was reduced due to hornification and this in turn caused a decrease in adsorption of cationic PAM. On the other hand, the carboxyl content of the recycled fibers increased because of the oxidation of fibers occurred during drying, and this caused an increase in adsorption of cationic PAM. Because of these two opposing factors the adsorption of the cationic PAM on the recycled fibers decreased and then increased slightly at third recycling step. Increase of PAM adsorption, however, did not provide did not provide and strength improvement for the recycled pulp fibers indicating greater influence of the honification on interfiber bonding.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2000.11a
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• pp.138-138
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• 2000

국내의 백상지 공정은 공정에 투입되는 청수의 양을 줄이면서 동시에 폐수 배출 양을 감 소시키기 위해 많은 노력을 하고 있다. 공정으로 유입되는 청수의 양과 처리된 폐수의 양을 줄이기 위한 방법으로 PDFCpolydisk filter)를 도입하여 백수를 여과하여 showertf sealing 에 재사용하고 있으며 공정수 재활용에 따른 유기 물질과 무기물질의 계 내로의 축적을 방 지하기 위한 효과적인 폐수 처리방법을 모색하고 있다. 일반적으로 청수를 백수로 대체할 경우 공정 백수 내에 TDSCtotal dissolved solid), T TSSCtotal suspended solid), CODCchemical oxygen demand), 전기 전도도와 칼숨 경 도 등이 증가되며 음이온성 저해 물질Canionic trash)이 증가하여 보류 및 지력증강용 첨가제의 효율 을 떨어뜨릴 뿐만 아니라 마모, 슬라엄, 펠트 막힘 등의 문제를 유발하게 된다고 알려져 있다. 청수를 백수로 대체함에 따라 생기는 이러한 문제를 해결하면서 효율적인 청수 절약 방안 을 세우기 위해서는 무엇보다도 문제를 유발하는 원인 물질의 축적 양을 예측하는 것이 중 요하다고 판단된다. 본 연구는 백상지 공정의 폐쇄화 수준이 높아짐에 따른 공정 백수 내의 유기물질의 축적 현상을 분석하는 것올 목적으로 하였다. 이를 위해 산화전분을 유기물질의 대표하는 물질로 설정하였다. 이는 백상파지와 함께 초지계 내로 유업되는 산화전분은 파지의 4%를 차지할 정도로 유입량이 많을 뿐만 아니라 음이온성을 띄고 있어서 지료에 홉착율이 낮고 양이온성 고분자의 효율을 저해하며 슬라임의 원인이 되기도 하는 물질이기 때문이다. 산화전분의 축적 현상을 분석하기 위하여 pilot 설비 상세 설계도를 참고하여 하루 생산량 이 16 T/D이고 백상파지만이 파지로 유입되는 백상지 생산 공정을 모델로하였으며, 산화전 분의 홉착과 용출 모델을 만들어 상용 시율레이터를 이용하여 시율레이션 프로그램을 작성 하였다. 시률레이션 프로그램에서는 장섬유 미세섬유, 충전제를 지료 구성 성분으로 설정하였고 O Orccotoma 등이 사용한 일과 보류도 모델을 응용하여 보류도 모델올 만들었다. 산화전분은 백상파지에 포함된 형태로만 초지계 내로 유입되며 백상파지가 해리되는 과정에서 완전히 백수에 용출되었다가 지료 구성 성분에 홉착되는 것으로 가정하였다. 지료 홉착된 산화전분 의 양은 용존 산화전분 총량에 비례하는 것으로 가정하였으며, 이 때 이 비례상수를 전분 홉착율이라 정의하였다. 시율레이션 결과, 공정 폐쇄화가 진행됨에 따라 백수 내의 산화 전분 농도는 증가하게 되 며, 폐쇄화 수준이 높아질수록 백수 내 전분 농도의 증가량은 더 높아졌다. 백수 내의 전분 농도의 증가량은 백상파지 첨가량이 증가할수록, 표면 사이징 양이 증가할수록 커졌다.

• Polymer(Korea)
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• v.25 no.1
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• pp.122-132
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• 2001

Thermoplastic film infusion process was investigated by using a rubber tool, which intrinsically contains a thermally-expandable characteristic and effectively compensates for the pressure loss caused by thermoplastic polymer infusion. Increasing temperature up to the melting temperature of matrix, the polymer melt subsequently infused into the dry fabric, but the pressure was successfully sustained by the rubber tool. Even with the decreased resin volume, the rubber tool produced sufficiently high elastic force for continuous resin infusion. Combining D'Arcy's law with the compressibility of rubber tool and elastic fiber bed, a film infusion model was developed to predict the resin infusion rate and pressure change as a function of time. In addition, the film infusion process without the rubber tool was viewed and analyzed by a compression process of the elastic fiber bed and viscous resin melt. The compressibility of fiber bed was experimentally measured and the multiple-step resin infusion was well described by the developed model equations.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.38 no.4
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• pp.300-306
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• 2002

In this paper the failure mechanisms and Charpy impact tests of carbon fiber polypropylene composites have been studied in the temperature range -5$0^{\circ}C$ to 6$0^{\circ}C$ and 3 different supported length of specimen (span length). There are significant effects of temperature and span length on impact fracture toughness, which shows a peak at ambient temperature and decrease as temperature is reduced. Fracture toughness shows a maximum at span length s=20mm. Failure mechanisms are characterized based on SEM examination, which is correlated the measured fracture toughness. Mafor mechansms of this composites can be classified as fiber matrix debonding, delamination, fiber pull-out and matrix deformation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.12
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• pp.837-842
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• 2015

In this study, the characteristics of electrostatic attenuation in plain shape glass filament sample (0.29 mm thickness, cross section of $12.25cm^2$, $16cm^2$, $20.25cm^2$) for insulator has been measured at temperature of $5^{\circ}C{\sim}38^{\circ}C$, humidity of 50%~90%. The results of this study are as follows. In case of samples that the cross section is $12.25cm^2$, $16cm^2$, $20.25cm^2$ at humidity of 50%~90%, it found that the electrification voltage of electrostatic increased with increasing temperature, with a return to decrease at $20^{\circ}C$. In case of samples that the cross section is $12.25cm^2$, $16cm^2$, $20.25cm^2$ at temperature of $5^{\circ}C{\sim}38^{\circ}C$, it found that the electrification voltage of electrostatic decreased with increasing humidity. In case of the sample at temperature of $20^{\circ}C$ and humidity of 65%, 75%, it found that the electrification voltage of electrostatic increased with increasing cross section. In case of the sample at humidity of 65% and cross section of $12.25cm^2$, the time that it takes to reduce electrification voltage of electrostatic in half decreased to 0.912s, 0.736s, 0.673s with increasing temperature to $10^{\circ}C$ $20^{\circ}C$, $30^{\circ}C$.

• Journal of the Korean Electrochemical Society
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• v.18 no.3
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• pp.115-120
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• 2015

The mechanical and electrochemical properties of poly(ethylene oxide) (PEO)-coated Rayon separator were characterized using potassium polyacrylate (PAAK)-KOH electrolyte. The supercapacitive properties of activated carbon supercapacitor adopting the Rayon/PEO separator and PAAK-KOH electrolyte was also tested. As the PEO content increased, the mechanical strength increased. Room-temperature ionic conductivity of over $10^{-2}S\;cm^{-1}$ was obtained at the PEO content lower than 5 wt.%, applicable to a supercapacitor. As a result, the specific capacitance at $1000mV\;s^{-1}$ of the activated carbon supercapacitor adopting the Rayon/PEO separator and PAAK-KOH electrolyte was highly stable after 1000th cycle. This was due to high rate-capability provided by the fact that PEO coating could fix the entanglements among fiber filaments of Rayon.

• Composites Research
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• v.31 no.6
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• pp.317-322
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• 2018

In various industry, the composite is tried to be applied to products and thermoplastic based composite is in the spotlight because this composite can be recycled. The use of continuous fiber thermoplastic (CFT) method increased gradually than long fiber thermoplastic (LFT). In this study, tensile, flexural, and impact test of different array types of glass fiber (GF)/thermoplastic composites were performed to compare with GF array. Impregnation property between GF mat and thermoplastic was determined using computed tomography (CT). At CFT method, thermoplastic film is not wet into GF roving and many voids are appeared into composite. This phenomenon affects to decrease mechanical properties. Plain pattern GF mat was the best mechanical and impregnation properties that distance between two roving was set closely to $100{\mu}m$.

• Composites Research
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• v.33 no.6
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• pp.383-389
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• 2020

Thermoplastic composite is introduced to design an automotive door impact beam, and the manufacturing process is demonstrated. The safety regulation for vehicles has been steadily tightened, and weight-reduction has become a mandatory factor in the automotive industry. Hence, both high-performance and lightweight are demanded for automotive components. The aim of the present study is to develop an automotive door impact beam using fiber-reinforced thermoplastic composites to reduce the weight of the impact beam while increasing its mechanical performance. A new production method which combines continuous fiber-reinforced composite and LFT(Long Fiber-reinforced Thermoplastic) is implemented by using insert injection molding process. The mechanical performance of the composite impact beam was evaluated using 3-point bending tests. Thermoplastic composite will expand its application range to various automotive components due to its light-weight design capability and high productivity.

• Composites Research
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• v.35 no.1
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• pp.38-41
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• 2022

In this study, the strain rate dependent tensile and compressive properties of PP-LGF and TPO was investigated under the high strain rate by using the Split Hopkinson Pressure Bar (SHPB). The SHPB is the most widely used apparatus to characterize dynamic mechanical behavior of materials at high strain rates between 100 s^-1 and 10,000 s^-1. The SHPB test is based on the wave propagation theory which was developed to give the stress, strain and strain rate in the specimen using the strains measured in the incident and transmission bars. In addition, to verify the strain data obtained from SHPB, the specimen was photographed with a high-speed camera and compared with the strain data obtained through the Digital Image Correlation (DIC).