• Macromolecular Research
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• 제17권11호
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• pp.919-925
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• 2009

The enzymatic polymerization of 12-hydroxystearic acid (12-HSA) was carried out with Lipase $CA^{(R)}$ in benzene to produce poly(12-hydroxystearate) (PHS) with a low molecular weight. When this polymerization was continued for a long reaction time, the PHS once formed was depolymerized into a cyclic diester, 13,16-dihexyl-1,14-dioxacyclohexacosane-2,15-dione (12-HSAD). Similar polymerization and depolymerization were observed when 12-hydroxyoleic acid (12-HOA) was treated with Lipase $CA^{(R)}$, whereas only polymerization occurred when 12-hydroxydodecanoic acid (12-HDA) was treated in a similar manner. The preferential formation of cyclic diesters for 12-HSA was attributed to the structural requirements due to the bulky n-hexyl side groups stemming from the ring systems.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 1999년도 추계학술발표대회 논문집
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• pp.36-39
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• 1999

Steel tire cords were coated via RF Plasma Polymerization of acetylene in order to enhance adhesion to rubber compounds. Adhesion of tire cords was measured by TACT as a function of plasma polymerization and argon etching conditions such as power, treatment time and chamber pressure. Tested tire cords were analysed by SEM to elucidate the adhesion mechanism. The highest adhesion values were obtained with argon etching condition at 90W, 10min, 30mtorr followed by acetylene plasma polymerization condition at 10W, 30sec., 30mtorr. In SEM analysis, the plasma polymerized tire cord at the optimized condition showed 100% rubber coverage as observed from brass-plated steel tire cords.

• Restorative Dentistry and Endodontics
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• 제29권2호
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• pp.191-199
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• 2004

The purposes of this study were to estimate the material properties of the recently developed domestic composite resins for core filling material (Chemical, Dual A, Dual B；Vericom, Korea) and to compare them with other marketed foreign products (CorePaste, Den-Mat, USA；Ti-Core, Essential Dental Systems, USA；Support. SCI-Pharm. USA). Six assessments were made：working time. setting time. depth of polymerization. flexural strength. bonding strength. and marginal leakage. All items were compared to ISO standards. All domestic products satisfied the minimum requirements from ISO standards (working time：above 90 seconds. setting time：within 5 minutes). and showed significantly higher flexural strength than Core Paste. Dual A and B could. especially. reduce the setting time to 60 seconds when cured with $600mW/cm^2$ light intensity. All experimental materials showed 6 mm depth of polymerization. Bond strengths of Ti-Core and Dual B materials were significantly higher than the other materials. Furthermore. three domestic products and Ti-Core could reduce the microleakage effectively.

• 대한화학회지
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• 제24권2호
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• pp.167-174
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• 1980

PPBC/KOH 촉매작용에 의한 2-pyrrolidone의 음이온중합에 있어서 PPBC/KOH 몰비, KOH의 농도 및 온도가 중합에 미치는 영향을 조사하였다. PPBC/KOH 몰비가 0.5일때 중합속도가 가장 빠르고 전환율도 가장 높았으며, 또 KOH 의 농도는 2몰%일때 가장 높은 전환율과 점도가 얻어졌다. $50^{\circ}C$에서의 중합은 $30^{\circ}C$에서의 중합보다 초기반응속도는 빠르나 시간이 경과할 수록 전환율과 점도가 오히려 낮아지는 경향이 관찰되었다. 최소자승법으로 계산하여 구한 중합속도상수$(k_p)$의 값은 $30^{\circ}C$일때 $22.4\;l/mole{\cdot}hr$ 였고 $50^{\circ}C$일때 $191.9\;l/mole{\cdot}hr$ 였다.

• Macromolecular Research
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• 제9권4호
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• pp.220-227
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• 2001

The polymerization of 1,6-heptadiyne was carried out by molybdenum and tungsten-based transition metal catalysts. This polymerization by MoCl$\_$5/ alone proceeded well to give a quantitative yield of polymer. The effect of monomer to catalyst mole ratio (M/C), initial monomer concentration ([M]$\_$0/), and the polymerization temperature for the cyclopolymerization of 1,6-heptadiyne was studied and discussed. The polymerization solution exhibited red color even after 30 min of polymerization time. The resulting polymers were mostly brown powders and mostly insoluble in any organic solvents although the polymerization proceeded in homogeneous manner in some cases. The polymer structure was characterized by various instrumental methods to have the conjugated polymer backbone structure carrying cyclic recurring unit. The thermal and morphological properties of the resulting poly(1,6-heptadiyne) were also discussed.

• 한국염색가공학회지
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• 제5권3호
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• pp.194-205
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• 1993

Plasma polymerization in prepared glow discharge was carried out to improve the bathochromic of dyed PET fabrics by using silicon containing vinyl monomer in plasma polymerization equipment which consists of a pair of electrodes was connected to the 13.56MHz RF generator. The optimum condition for the bathochromic effect was investigated on various plasma polymeriztion parameters. By plasma polymerization used silicon containing vinyl monomer, the bathochromic of dyed PET fabrics was very enhanced. The optimum conditions on this equipment were as follows ; electrode distance : 3cm, discharge output : 60W, gas pressure : 0.3 Torr, monomer flow rate : 30㎤/min. plasma polymerization time : 60sec. The apparent strength of plasma polymerized PET fabrics was increased about 40∼47% with decreasing about 3 of L value.

• 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.

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 1990년도 제2차 학술발표초록집
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• pp.8-8
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• 1990

A new method for the graft polymerization of acrylonitrile onto starch is presented. Graft polymerization of acrylonitrile onto starch and the subsequent hydrolysis in sodium hydroxide solution to prepare absorbents is well known. This process has been utilized to produce the commercial product, Super Slurper. In a typical batch process, ~5% starch in water mixture is gelatinized at $95^{\circ}C$ under stirring for 1 hour then cooled to room temperature. The graft polymerization itself is carried out for approximately 2 hours at $25~30^{\circ}C$ on the gelatinized starch by eerie ion initiation. In this study, graft polymerization of acrylonitrile onto starch via a reactive extrusion process which is a continuous, efficient process is described. Initial concentration of starch in water is 35% and the reaction temperatures are between $50~80^{\circ}C$. However, the most significant difference in the reactive extrusion process is the short time in which the graft polymerization takes place. Preliminary results on the properties of graft polymerization products obtained from the reactive extrusion process are compared to those obtained from the batch process as well as the absorbency of the hydrolyzed samples. Absorbent material has also been prepared by sequential grafting and saponification in the extruder followed by a 2 hour heat treatment of the extrudate in an air circulated oven at $100^{\circ}C$.

• 공업화학
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• 제8권6호
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• pp.886-892
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• 1997

Polystyrene latex를 제조하는 여러방법중에서 상업적으로는 유화중합기술이 가장 많이 사용되고 있다. 유화중합에서 사용되는 화학개시제가 환경오염 유발의 원인이 될 수 있을 뿐만 아니라 고분자 중합 방법도 전통적 기술을 벗어나는 다양한 공정의 개발이 필요하다. 따라서 본 연구에서는 화학 개시제를 초음파 에너지 효과로 대체하여 초음파 조사시에 나타나는 공동현상에 의한 자유 라디칼(free radical)을 생성시켜 polystyrene latex를 제조하였다. 제조된 polystyrene latex를 GPC로 분석한 결과 초음파 조사시간이 증가할수록 평균분자량은 증가하였으며 분산도는 감소하였다. 또한 계면활성제로 사용된 sodium dodecyl sulfate(SDS)의 농도가 증가할수록 중합도는 증가하였으며, SDS의 농도가 전체의 2wt.%이고 반응온도가 $40^{\circ}C$일 때 중합도는 $2.43{\times}10^4$으로 최대값을 나타내었다. 중합이 진행되는 동안 해중합이 동시에 발생하므로 평균분자량은 증가와 감소를 반복하는 경향을 나타내었으며, 초음파 조사시간과 계면활성제의 농도를 조절하므로써 분자량이 조절된 좁은 분자량 분포의 polystyrene latex를 제조할 수 있었다.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 1993년도 Fifth International Fuzzy Systems Association World Congress 93
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• pp.1106-1108
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• 1993

This paper deals with an industrial application of a fuzzy feedback combined learning control to an industrial batch free radical polymerization reactor. As a result, the plant has reduced the batch reaction time by 50 minute and stabilized both by 40 percent reduction of the standard deviations of product qualities, such as the total solid content and the graft gum, and by 45 percent reduction of the standard deviation of the batch reaction end time.