• Title, Summary, Keyword: Crosslinking Density

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Study on the Crosslinking Characteristics of LDPE and LLDPE by $\gamma$-Ray Irradiation ($\gamma$-선 조사에 의한 LDPE, LLDPE의 가교특성에 관한 연구)

  • 김정일;박성현;강필현;노영창
    • Polymer Korea
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    • v.25 no.5
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    • pp.657-664
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    • 2001
  • In this study. the effects of ${\gamma}$-irradiation on the crosslinking of low density poly ethylene (LLDPE) and linear low density polyethylene (LLDPE) containing crosslinking agents were investigated to find the degree of crosslinking in the polymer. The LDPE and LLDPE specimens were prepared by blending crosslinking agents with each polymers, and by hot-press-molding into a sheet at 13$0^{\circ}C$. The ${\gamma}$-irradiation was conducted at 50 to 150 kGy in nitrogen. The crosslinking percentage in these specimens was measured in relation to the irradiation dose and the type of crosslinking agents. The mechanical properties, thermal properties and crystallinity of specimens were examined as a function of irradiation dose as well. It was found that the degree of crosslinking of the irradiated specimens was increased with increasing irradiation dose and by the addition of crosslinking agents. The mechanical properties and thermal properties of specimens were improved in proportion to an increase in the degree of crosslinking. The crystallinity of original resin was decreased with increasing crosslinking density.

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Poly(vinyl alcohol) Membranes Containing Sulfonic Acid Groups for Direct Methanol Fuel Cell Application (설폰산기를 함유한 PVA막의 직접 메탄올 연료전지 응용)

  • Lee Young Moo;Lee Sun Yong
    • Membrane Journal
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    • v.14 no.3
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    • pp.240-249
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    • 2004
  • Crosslinked PVA membranes were achieved by esterification between the hydroxyl groups of PVA and carboxyl group of sulfosuccinic acid (SSA). SSA containing sulfonic group was used as a chemical crosslinking agent as well as a donor of fixed anionic group ($-SO_3$H). The crosslinking density of membranes was controlled by SSA content and calculated using polar and non-polar solvent. The crosslinking density measured by using non-polar solvent such as xylene and benzene increases with SSA content. However, using the polar solvent such as water and methanol, the crosslinking density increases up to SSA content of 20 wt% and above the content decrease due to sulfonic acid groups. The crosslinked PVA membranes were studied in relation with water diffusion coefficient and mechanical property as well as proton conductivity and methanol permeability as a function of crosslinking density. These properties were all dependent on the effect of SSA content.

Characteristics of Heat Shrinkable High Density Polyethylene Crosslinked by ${\gamma}$-Irradiation

  • Kang, Phil-Hyun;Nho, Young-Chang
    • Nuclear Engineering and Technology
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    • v.33 no.2
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    • pp.184-191
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    • 2001
  • The effects of ${\gamma}$-irradiation on the crosslinking of high density polyethylene (HDPE) was investigated for the purpose of obtaining a suitable formulation for heat shrinkable materials. In this study the HDPE specimens were prepared by blending with cross linking agents and pressed into a 0.2 mm sheet at 18$0^{\circ}C$. ${\gamma}$-irradiation was conducted at 40 to 100 kGy in nitrogen. The heat shrinkable property and thermal mechanical property of the HDPE sheets have been investigated. It was found that the degree of crosslinking of the irradiated HDPE samples were increased with irradiation dose. Compared with the HDPE containing triallylisocyanurate, the HDPE containing trimethylol propane triacrylate shows a slight increase in crosslinking density. The heat transformation and dimension change of HDPE decreased with increasing radiation dose. The heat shrinkage of the samples increased with increasing annealing temperatures. The thermal resistance of HDPE increased upon the crosslinking of HDPE.

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Studies on the Crosslinking Density and Reinforcement of Rubber Compounds by Cure System (가황조건별 배합고무의 가교밀도와 고무보강성에 관한 연구)

  • Park, Nam-Cook;Lee, Seog
    • Elastomers and Composites
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    • v.33 no.5
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    • pp.315-323
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    • 1998
  • The purpose of this study was to investigate the crosslinking density and reinforcement of rubber compounds with various carbon black loadings, cure systems and cure temperatures. Bound rubber content increased with volume fraction of carbon black in rubber compounds, but total crosslinking density decreased with increasing the bound rubber content. Rate constant of cure reaction was changed significantly by cure system and cure temperature, especially it showed strong dependence on the cure temperature. High activation energys of cure reaction were shown in the rubber compound with high loading of carbon black under EC system and in the rubber compound with low loading of carbon black under CC system. High total crosslinking density of vulcanized compounds appeared in the rubber compound with low loading of carbon black and CC system among cure systems. Typical change of total crosslinking density by EC system was not shown. The highest elastic constant by Mooney-Rivlin equation was shown in the rubber compound with low loading of carbon black and SEC system. Modulus increased as increasing the loading of carbon black in the rubber compounds and showed the order of SEC, CC, and EC system for cure system.

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Effect of Co-agent on Cure, Mechanical Properties of NBR Compounds in Peroxide System

  • Seo, Eun Ho;Kim, Gi Hong;Kim, Do Young;Lee, Dong Won;Seo, Kwan Ho
    • Elastomers and Composites
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    • v.52 no.3
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    • pp.187-193
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    • 2017
  • In this study, the effect of the cure, mechanical properties, and oil resistance of NBR (acrylonitrile-butadiene rubber)/peroxide compounds were investigated for various co-agents. NBR compounds were characterized using a swelling test, a rheometer (MDR), and a compression set test. Mechanical properties were tested with original compounds, heated in air and exposed to the ASTM No.1, IRM 903 oil. NBR compounds were prepared using peroxide as the crosslinking agent. Trimethylolpropane trimethacrylate (TMPTMA), triallyl isocyanurate (TAIC), and 1,2-polybutadiene (HVPBD) were used as co-agents. The NBR compounds containing TMPTMA and HVPBD lowered the scorch time, while the addition of TAIC did not significantly change the scorch time. NBR compounds containing TMPTMA increased the crosslinking density, while the addition of TAIC and HVPBD lowered the crosslinking density. Moreover, the addition of TMPTMA improved the oil resistance of the NBR compound.

Variations of the Electrical Treeing and Breakdown Characteristics on LDPE Due to Gamma-ray Irradiation

  • Lee, Chung;Ryu, Boo-Hyung
    • International Journal of Safety
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    • v.8 no.1
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    • pp.14-17
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    • 2009
  • The $Co^{60}$ $\gamma$-ray irradiation effects on the electrical and thermal characteristics of low density polyethylene crosslinked by Dicumyl peroxide (DCP) were investigated. We experimented on electrical properties as following; electrical tree inception and growing type for applying AC step voltage, AC breakdown strength, volume resistivity with increasing dosage. Also, chemical analyses were performed TGA, gel fraction. These electrical properties changed depending upon its crosslinking degree and byproducts from crosslinking reactions. Crosslinking reactions were considered causing by $\gamma$-ray irradiation and DCP had contained in low density polyethylene.

Studios on the Thermal Properties of Silane Crosslinked Polyethylene Prepared by Various Crosslinking Conditions (Silane 가교 PE의 가교조건에 따른 열적특성 변화에 관한 연구)

  • Sohn, Ho-Soung;Suh, Kyung-Do
    • Applied Chemistry for Engineering
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    • v.5 no.6
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    • pp.1036-1043
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    • 1994
  • The silane crosslinking method was applied for the crosslinking of polyethylene (PE). Crosslinking of PE was performed by, first grafting vinyltrimethoxysilane(VTMOS) to the main chain of PE using an extruder at $200{\sim}210^{\circ}C$, followed by exposure to three different silane crosslinking conditions (1. immersed in $80^{\circ}C$ water, 2. at $80^{\circ}C$ air forced convection oven, 3. exposed to air at room temperature ). The thermal characteristic changes of PE resins with respect to the silane crosslinking conditions were studied by measuring the crystalline melting temperature, density and crosslinking reaction rate. Because silane crosslinking was carried out at solid state, crystalline melting temperature, crystallinity, crystal growth rate, crosslinking reaction rate and the change in the density of silane crosslinked PE were affected by crosslinking condition and the type of base resin. The properties of silane crosslinked PE were different from those of Peroxide crosslinked PE which was crosslinked at the molten state. It was found, from the result of DSC analysis, that silane crosslinked linear low density polyethylene(LLDPE) crosslinked at room temperature had no secondary melting peak because the crosslinking reaction proceeds slowly as the crystalline grows. After crystallization, the melting point of PE was lowered by crystalline interruption of crosslinked site.

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Preparation and Characterization of Emulsified Chlorosulfonated Polyethylene Rubber (CSM) (유화 Chlorosulfonated Polyethylene Rubber (CSM)의 제조 및 특성 연구)

  • Choi, Seo-Young;Lee, Eun-Kyoung;Choi, Kyo-Chang
    • Elastomers and Composites
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    • v.40 no.1
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    • pp.12-21
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    • 2005
  • In this work, magnesium carbonate and calcium hydroxide as metallic crosslinking agent were added to chlorosulfonated polyethylene rubber (CSM) emulsion to enhance the mechanical properties of emulsion film such as tensile strength, elongation at break, and tear strength and crosslinking density, thermal features, and surface energy were also investigated. Crosslinking density of the CSM emulsion film with increasing the amount of magnesium carbonate and calcium hydroxide increased, leading to the enhancement of water resistance. It was shown that compared with calcium hydroxide, magnesium carbonate had a little higher crosslinking density and $T_g$ value. The surface energy and mechanical characteristics of the CSM emulsion film, however, showed somewhat different behaviors. The highest surface energy, tensile strength, and tear strength were observed when 0.75% for magnesium carbonate and 1.0% for calcium hydroxide were added respectively. Therefore, it can be concluded that as metallic crosslinking agent to improve water resistance and mechanical properties of the CSM emulsion, magnesium carbonate is more preferable to calcium hydroxide.

Enhancement of Physical Properties in Partially Crosslinked Waste High Density Polyethylene (재활용 고밀도 폴리에틸렌의 가교에 의한 물성 향상 연구)

  • Lee, Jong-Rok;Lee, Dong-Gun;Hong, Soon-Man;Kang, Ho-Jong
    • Polymer Korea
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    • v.31 no.1
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    • pp.25-30
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    • 2007
  • The characteristics of crosslinking and physical properties in partially crosslinked waste high density polyethylene (HDPE) were studied by introducing reactive melt processing with perbutyl peroxide (PBP). It was found that impurities in waste HDPE affected the crosslinking kinetics. Decrease in density and heat of fusion were observed in partially crosslinked HDPE while its melt viscosity increased. It was explained that impurities in waste HDPE enhanced the crosslinking compared to pure HDPE As a result, dramatic mechanical property improvement was achieved in the waste HDPE by crosslinking reaction.

Crosslinking Characteristics of High Density Polyethylene by Reactive Melt Processing (반응 용융 가공에 의한 고밀도 폴리에틸렌의 가교 특성 연구)

  • Lee Jong Rok;Lee Dong Gun;Hong Soon Man;Kang Ho-Jong
    • Polymer Korea
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    • v.29 no.4
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    • pp.385-391
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    • 2005
  • Reactive melt processing has been carried out to investigate crosslinking characteristics of high density polyethylene OTDPE) with dicummyl peroxide (DCP) and perbutyle peroxide (PBP). The increase of torque in the internal mixer indicated that the crosslinking in HDPE has been occurred by peroxides. As a result, the substantial decrease of density, melting temperature, and melt enthalpy were found while the melt viscosity increased in partially crosslinked HDPE. In the mechanical properties of partially crosslinked HDPE, the increase of maximum strength and the decrease in elongation at break were clearly noticed and these were more pronounced when PBP was applied as a crosslinking agent. It seems that the maximum strength was obtained with reactive processing temperature at $150^{circ}C$, however, the mixing time did not affect to the strength of partially crosslinked HDPE.