• 한국세라믹학회지
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• 제22권6호
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• pp.15-20
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• 1985

In the course of cement hydration it was found that the addition of polyvinyl alcohol(contracted as PVA. here after) only in the cement paste could more influence on the set-retardation the depression of heat evol-ution rate than that of montmorillonit only or PVA-montmorillonie intercalation complex (PMIC) due to the effective adsorption of PVA on cement particles. The improved mechanical strength by addition of montmorillonite and PMIC was observed remarkably up to 0.05wt% due to the decrease of macro-pores caused by lowed viscosity or the acceleration of hydration reaction.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.28-31
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• 2004

This paper discusses the role of micro and macrofibers in the workability, compressive strength, and failure of cementitious composites. Workability(flow), compressive strength, splitting strength and fracture mechanism of hybrid fiber reinforced cement composites(HFRCC) have been investigated by means of Korean Standard (KS). The specific blend pursued in this investigation is a combination of polyvinyl alcohol(PVA) and steel cord. It was demonstrated that a hybrid combination of steel and PVA enhances fiber dispersion compared to only steel cord reinforced cement composites and that the brittle and wide cracking was much reduced in HFRCC as expected because in the matrix containing the PVA fiber around the steel cord, a multiple microcracking occurred and the steel cord could sufficiently work for bridging the cracked surface.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.29-32
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• 2005

An experimental investigation on the strength and behavior of High Performance Fiber Reinforced Cement Composite(HPFRCC) column with Polyvinyl alcohol(PVA) fibers under axial load have been carried out. The columns were subjected to monotonic axial compression until failure. The variables in this study are the combination ratio of PVA, and the volumetric ratio of transverse reinforcement. Test results showed that the fibers, when used in PVA2.0, could result in superior composite performance compared to their individual fiber reinforced cement composites.

• KSBB Journal
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• 제6권4호
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• pp.363-368
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• 1991

PVA degrading bacteria were isolated from water system, and identified as Pseudomonas cepacia and Pseudmonas pseudomallei, which were named as Pseudomonas sp. G5Y and Pseudomonas sp. PW. It was found out that those two kinds of bacteria have a symbiotic relationship to degrade PVA. For the mixed culture of these bacteria, the optimal conditions of pH, temperature, nitrogen source, and polymerization degree of PVA were found to be 7.5, $35^{\circ}C$, ammonium sulfate, and 500, respectively. Also, the growth of these bacteria was promoted by trace elements such as vitamin B1, B12, pyridoxine, and p-aminobenzoate, respectively. The specific growth rate of mixed bacteria was inhibited when the concentration of PVA was more than 20g/l. The substrate inhibition kinetics of the mixed culture was $${\mu}=\frac{0.065S}{2.56+S+(S^2/156}hr^{-1}$

• 한국전기전자재료학회논문지
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• 제22권2호
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• pp.114-118
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• 2009

PVA (polyvinyl alcohol) brush cleaning method is a typical cleaning method for semiconductor cleaning process especially post-CMP cleaning. PVA brush contacts with the wafer surface and abrasive particle, generating the contact rotational torque of the brush, which is the removal mechanism. The brush rotational torque can overcome theoretically the adhesion force generated between the abrasive particle and wafer by zeta potential. However, after CMP (chemical mechanical polishing) process, many particles remained on the wafer because the brush was contaminated in previous post-CMP cleaning step. The abrasive particle on the brush redeposits to the wafer. The level of the brush contamination increased according to the cleaning run time. After cleaning the brush, the level of wafer contamination dramatically decreased. Therefore, the brush cleanliness effect on the cleaning performance and it is important for the brush to be maintained clearly.

• Current Research on Agriculture and Life Sciences
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• 제31권4호
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• pp.250-255
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• 2013

As a renewable nanomaterial, cellulose nanocrystal (CNC) isolated from wood grants excellent mechanical properties in developing high performance nanocomposites. This study was undertaken to compare the reinforcing efficiency of two different CNCs, i.e., cellulose nanowhiskers (CNWs) and cellulose nanofibrils (CNFs) from hardwood bleached kraft pulp (HW-BKP) as reinforcing agent in polyvinyl alcohol (PVA)-based nanocomposite. The CNWs were isolated by sulfuric acid hydrolysis while the CNFs were isolated by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation. Based on measurements using transmission electron microscopy, the individual CNWs were about $6.96{\pm}0.87nm$ wide and $178{\pm}55nm$ long, while CNFs were $7.07{\pm}0.99nm$ wide. The incorporation of CNWs and CNFs into the PVA matrix at 5% and 1% levels, respectively, resulted in the maximum tensile strength, indicating different efficiencies of these CNCs in the nanocomposites. Therefore, these results suggest a relationship between the reinforcing potential of CNCs and their physical characteristics, such as their morphology, dimensions, and aspect ratio.

• 공업화학
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• 제26권6호
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• pp.706-713
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• 2015

그라파이트 폼이 polyvinyl alcohol-acrylic acid (PVA-AAc) 용액에 다양한 함량의 메조페이스 핏치(mesophase pitch, MP)를 첨가한 후 열처리를 통해 제조되었다. 그라파이트 폼의 공극 크기는 슬러리 농도(고분자 용액에 첨가된 메조페이스 핏치의 함량)에 따라 조절되며, 그 열 전도도 및 압축강도는 각각의 조건에서 형성된 그라파이트 폼의 공극률에 의해서 조절됨을 확인하였다. 본 실험에서 얻어진 그라파이트 폼은 공극률 0.69에서 $53.414{\pm}0.002W/mK$의 가장 높은 열전도도 및 $1.348{\pm}0.864MPa$의 압축강도 값을 나타내었다. 메조페이스 핏치 기반의 그라파이트 폼의 열전도도는 등방성 핏치 기반의 그라파이트 폼에 비하여 흑연화 구조의 발달로 인하여 그 값이 23배로 크게 증가되었다.

• 콘크리트학회논문집
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• 제24권2호
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• pp.121-127
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• 2012

지금까지 연구된 고인성 섬유 복합체의 주요 결합재는 시멘트이다. 이 연구의 목적은 시멘트를 전혀 사용하지 않은 고로슬래그 기반 알칼리 활성 모르타르와 PVA(polyvinyl alcohol) 섬유를 이용하여 고인성을 나타내는 복합체에 대한 가능성을 검토하는 것이다. 이를 위하여 알칼리 활성화제 종류에 따라 균일한 섬유 분산성을 확보하면서 섬유 혼합을 용이하게 하기 위한 적절한 모르타르의 유동성 및 점성을 갖는 두 가지 배합을 결정하였고, 복합체의 기본적인 성능을 평가하기 위하여 슬럼프 플로, 압축강도, 일축인장, 휨 실험을 수행하였다. 실험 결과 두 가지 배합의 슬럼프 플로는 평균 465 mm로 나타났고, 약 2% 정도의 인장 변형 성능과 다중 미세균열을 나타내는 것을 확인하였다. 이를 통하여 시멘트를 전혀 사용하지 않고도 변형률 경화 거동에 의한 고인성을 나타내는 섬유 복합체의 개발 가능성을 입증하였다.

• 한국미생물·생명공학회지
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• 제24권5호
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• pp.546-552
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• 1996

The applicability of chitosan, a biodegradable natural polymer, as the coating material to prevent the dispersal of the spores of the apple white rot agent Botryosphaeria dothidea, was investigated. The physical properties of mixed chitosan/polyvinyl alcohol(PVA) film showed the increased physical properties for film formation, such as tensil strength, elongation, and viscosity, compared to either chitosan or PVA film. The FT-IR spectra of chitosan/PVA film indicated that the film was formed by simple blending not by any new synthetic bond. The chitosan and chitosan/PVA film showed effective antifungal activity on B. dothidea. The formed films were well decomposed by ASTM strains used for biodegradability test, on the other hand, the PVA film could not be decomposed by above standard strains. The field test at apple orchard showed that the dispersal of B. dothidea spores could be effectively reduced by coated film, especially by chitosan/PVA film. The spore dispersal was reduced upto 97.0% by 1.0% chitosan/5.0% PVA film during 4 months.

• 한국건축시공학회지
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• 제23권4호
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• pp.337-348
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• 2023

본 연구의 목적은 고유동성이 부여된 일반강도 배합 콘크리트에 대하여 요변성을 부여하여 시공정밀도가 낮은 거푸집 틈새를 통해 누출될 수 있는 모르타르나 시멘트 페이스트의 양을 저감하는 것이다. 본 연구에서는 콘크리트에 요변성을 부여하기 위해 PVA와 붕사를 사용하였다. 이에 PVA와 붕사를 사용하는 방법에 대하여 각각의 수용액을 추가하고 치환하는 방법에 따라 요변성을 포함하는 콘크리트의 성능의 변화와 거푸집의 틈새를 모사한 누출 저감 성능을 평가하였다. 본 연구에서 진행된 실험의 조건에서는 PVA와 붕사를 추가하는 방법보다는 치환하는 방법이 추가적인 물의 사용을 억제하여 재료분리 저항성과 응결 지연에서 더 양호한 콘크리트 물성을 나타내었으며 요변성의 발현 및 거푸집 누출 방지에도 효과적인 것으로 나타났다. 특히, PVA 수용액 6%를 치환하였을 때 의미 있는 수준의 거푸집 누출 감소 효과를 얻을 수 있었다. 이를 통해 PVA와 붕사를 이용하여 콘크리트 배합에 대해 요변성을 부여할 수 있다고 판단하였다. 또한 거푸집의 시공정밀도가 다소 낮은 경우에도 PVA와 붕사를 사용하여 콘크리트에 요변성을 부여함으로써 시공 품질을 확보할 수 있을 것으로 기대한다.