• Korean Chemical Engineering Research
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• 제46권5호
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• pp.938-944
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• 2008

고분자 분산형 액정 표시 소자(PDLC)에 사용되는 pre-polymer인 PN393에 다량으로 함유된 반응성 모노머 2-ethylhexyl acrylate(EHA)를 비닐에테르 계열의 모노머인 butanediol vinyl ether(BDVE)로 대체하여 제작된 PDLC 셀의 전기 광학적 특성 변화를 알아보았다. BDVE 함량 30 wt%까지는 액정방울의 크기가 작아졌으나, 그 이상의 조성(40 wt%)인 경우, 더 이상의 액정방울크기 변화는 관찰되지 않았다. 명암비, 응답속도는 상용화된 PN393를 적용한 경우보다 각각 490%, 15%로 성능이 향상되었으나, 동작전압은 약 60% 증가하는 것으로 확인되었다. 전기광학적 특성 변화를 $0{\sim}60^{\circ}C$ 온도범위에서 관찰한 결과, 응답속도와 동작전압의 온도안정성은 향상되었으나, 명암비 성능은 온도증가에 따라 열화되는 것으로 확인되었다.

• 한국염색가공학회지
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• 제31권2호
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• pp.88-97
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• 2019

In this study, when printed on a nylon material, the color strength and fastness are lower than that of a polyester material, and the nylon material shrinks due to heat and pressure, resulting in poor design and poor compatibility. To overcome this problem, we investigated the possibility of transfer DTP by adding pre-treatment process to nylon transfer DTP process. For the basic study of pre-treatment preparation, we used pure nylon material which is not compounded and dispersion ink and transfer paper applied to existing PET transfer DTP. Pre-treatment preparations were classified into three types of acryl-base polymer and pre-treated with nylon and then applied to transfer DTP to confirm their color strength and fastness. The color strength of the pre-treated nylon material increased and poly-methyl-acrylate amulsion pre-treatment showed the best color at $210^{\circ}C$, 1.5m/min and 0.3MPa. The nylon material pre-treated with washing, friction, and light fastness was judged to be more excellent and stable.

• Carbon letters
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• 제9권4호
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• pp.308-315
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• 2008

In the present study, fast isothermal stabilization processes for rayon precursor fabrics were performed at $350^{\circ}C$ and $400^{\circ}C$ within 3 minutes and the chemical and physical characteristics of the stabilized fabrics were investigated. In addition, rayon precursor fabrics were pre-treated with three different phosphorous-based flame retardants and then stabilized. The effect of flame retardants on the chemical composition, thermal shrinkage, weight change, thermal stability and XRD results was examined, comparing with those of the precursor fabrics. The result showed that the stabilization of rayon fabrics was most effective as the stabilization temperature was $350^{\circ}C$, the stabilization time was 3 min, and the pre-treatment with phosphoric acid of 1 vol%. The carbon contents of stabilized rayon fabrics were increased with increasing stabilization temperature and time, whereas the oxygen contents were decreased. Also, it is likely that the pre-treatment with phosphoric acid plays a role in retarding the change of chemical structure of rayon fabric. The XRD result was quite consistent with the result showing the effect of phosphoric acid on the chemical composition, thermal shrinkage and weight reduction of rayon fabric.

• Macromolecular Research
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• 제13권3호
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• pp.206-211
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• 2005

Multi-walled carbon nanotubes (MWNTs) pre-treated by concentrated mixed acid or oxidized at high temperature were melt mixed with poly(methyl methacrylate) (PMMA) using a twin screw extruder. The morphologies and electrical properties of the MWNT/PMMA composites were investigated. The thermally treated MWNTs (t-MWNTs) were well dispersed, whereas the acid treated MWNTs (a-MWNTs) were highly entangled, forming large-sized clusters. The resulting electrical properties of the composites were analyzed in terms of the carbon nanotube (CNT) dispersion. The experimental percolation threshold was estimated to be $3 wt\%$ of t-MWNTs, but no percolation occurred at similar concentrations in the a-MWNT composites, due to the poor dispersion in the matrix.

• Elastomers and Composites
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• 제53권2호
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• pp.67-74
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• 2018

Magneto-rheological elastomers (MREs) are smart materials in which the inherent stiffness and damping properties can be changed by the influence of an external magnetic field. The magneto-rheological (MR) effect depends on the orientation characteristics of the dispersed magneto-responsible particles (MRPs) in the matrix. In this study, natural rubber (NR) and ethylene propylene diene rubber (EPDM) were blended and used as a matrix of an MRE. EPDM was pre-cured before blending with NR. The Mooney viscosity, curing characteristics, and mechanical properties were analyzed with various pre-curing conditions of EPDM and the NR/EPDM blend. The results show that excellent mechanical properties of the NR/EPDM blend-based MRE were obtained when the pre-curing time of EPDM was 60 min. The aging property of the NR-based MRE was improved by the introduction of pre-cured EPDM. Also, the anisotropic MRE showed a higher MR effect than that of the isotropic MRE.

• Carbon letters
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• 제12권3호
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• pp.131-137
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• 2011

Kenaf fibers, cellulose-based natural fibers, were used as precursor for preparing kenafbased carbon fibers. The effects of carbonization temperature ($700^{\circ}C$ to $1100^{\circ}C$) and chemical pre-treatment (NaOH and $NH_4Cl$) at various concentrations on the thermal change, chemical composition and fiber morphology of kenaf-based carbon fibers were investigated. Remarkable weight loss and longitudinal shrinkage were found to occur during the thermal conversion from kenaf precursor to kenaf-based carbon fiber, depending on the carbonization temperature. It was noted that the alkali pre-treatment of kenaf with NaOH played a role in reducing the weight loss and the longitudinal shrinkage and also in increasing the carbon content of kenaf-based carbon fibers. The number and size of the cells and the fiber diameter were reduced with increasing carbonization temperature. Morphological observations implied that the micrometer-sized cells were combined or fused and then re-organized with the neighboring cells during the carbonization process. By the pre-treatment of kenaf with 10 and 15 wt% NaOH solutions and the subsequent carbonization process, the inner cells completely disappeared through the transverse direction of the kenaf fiber, resulting in the fiber densification. It was noticeable that the alkali pre-treatment of the kenaf fibers prior to carbonization contributed to the forming of kenaf-based carbon fibers.

• 한국염색가공학회지
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• 제29권3호
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• pp.122-130
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• 2017

In the direct digital textile printing process, the pre-treatment process is an essential condition for products by forming a clear pattern by sticking and penetration of DTP dye without spreading on the fabric. Recently, pre-treatment agent is changing from high viscosity to low viscosity in order to reduce defects of fabric during pre-treatment process. In this study, pre-treatment agent of acrylic polymer with low viscosity(less than 50cps) was prepared according to the solid content of the polymer, pre-treated on the cotton fabric, and direct DTP printing was performed to compare the color and sharpness. As a result, it showed high color at a viscosity of 50cps or less. When the solid content of the polyacrylic acid having a high molecular weight(A1) was 2.5wt%, when the solid content of the polyacrylic acid having a low molecular weight(A2) was 1 - 1.5wt%, the color was the best. And when the solid content of A1 and A2 was 1.5wt%, the degree of spreading was small and A1 was superior to A2 at the sharpness.

• Macromolecular Research
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• 제13권5호
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• pp.367-372
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• 2005

As a preliminary work for the preparation of nylon 6/c1ay nanocomposites by reactive extrusion, nylon 6/c1ay nanocomposites were prepared by anionic polymerization in a flask. In order to investigate the effect of the intercalation of clay layers, the clay feeding times, such as in pre-mixing where the clay was fed before initiation of polymerization and in after-mixing method where the clay was fed after initiation of polymerization, were changed. The appearance of the WAXD peak of nanocomposites prepared by the pre-mixing method was obvious and the tensile strength was decreased compared with that of pure nylon 6, which indicates that the clay layers were not dispersed and distributed. During the preparation of the nanocomposites by the after-mixing method, disordering of the clay layers was observed with increasing clay addition time and was suspected to result from the rapid polymerization of nylon 6 within the clay layers.

• Advances in environmental research
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• 제8권1호
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• pp.71-84
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• 2019

Effective waterproofing of structures was a compulsory constraint to avoid leaks and dampness or humidity in walls, ceilings, roofs underground tank and underground room. Traditionally used methods of roof waterproofing were bitumen with tinny seared clay tiles are very troublesome, overwhelming time and involving high labor cost. These waterproofing methods are not allocation the purpose due to their intrinsic disadvantages. Prepackaged polymer modified slurries (PPPMS) are now attainment the vogue and easy to use, easily available in the market, cheaper in cost and more workable than the traditional methods of waterproofing. An experimental study has shown that prepackaged polymer modified slurries (PPPMS) are superior in cost and performance to as a roof water proof coatings. Bituminous coatings were mixed with water and different combination of prepackaged polymer modified slurries and primer respectively, to find optimum coverage underneath worst atmospheric conditions. Every specimen of different proportioned was applied on plane roofs and through the passage of time, their performance was checked, assessed and associated with each other. The roof of approximately 40000 ft² area of prepackaged polymer modified slurries was used will give us hundred percent result (no water seepage or no water absorption) therefore no complaints as compare to roofs area of approximately 24000 ft² bituminous coating was used for waterproofing they have shown the result of 30 to 40 percent water seepage. This result shows that prepackaged polymer modified slurries were two times cheaper than bituminous coating. Comparing an equal number of surfaces coated with a polymer modified prepackaged mortar and bitumen the prepackaged polymer modified slurries (PPPMS) showed excellent performance, ease of application and low bitumen coating cost.

• 한국구조물진단유지관리공학회 논문집
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• 제9권4호
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• pp.235-242
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• 2005

본 연구는 프리웨팅 스프레이 공법에 사용되는 폴리머 시멘트 모르타르의 성능을 평가한 것이다. 프리웨팅 스프레이 공법은 손상된 콘크리트 구조물을 보수하기 위한 것으로서 분진 및 리바운드 발생량을 줄이기 위해 분말재료에 미리 소량의 물을 첨가한 후 분사 직전에 노즐에서 정량의 물이 다시 혼합되어 분사되는 획기적인 보수 방식이다. 시험결과 프리웨팅 스프레이 공법에 사용되는 폴리머 시멘트 모르타르인 TS 100의 압축강도, 휨강도 및 부착강도 같은 물리 성능은 기존의 다른 보수용 모르타르에 비해 우수한 것으로 나타났으며, 또한 염소이온 침투저항성, 중성화 저항성, 내약품성 및 동결융해 저항성 같은 내구 성능도 우수한 것으로 나타났다.