• Title/Summary/Keyword: Irradiation crosslinking

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Changes in the Chemical Structure and the Thermal/Physical Properties of Fluoropolymer Films Induced by Gamma Irradiation under Various Environments (다양한 환경에서 감마선으로 조사된 불소고분자 필름들의 구조 및 열적/물성 변화)

  • Choi, Ji Sun;Sohn, Joon-Yong;Shin, Junhwa
    • Polymer(Korea)
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    • v.38 no.4
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    • pp.457-463
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    • 2014
  • In this study, the changes in the chemical structure and the physical property of fluoropolymer films (PTFE, FEP, PFA, PVDF, and ETFE) induced by $Co^{60}$ gamma ray in air, $N_2$, and vacuum environments were investigated. FTIR spectra of the irradiated fluoropolymers indicate that the oxidation proceeded by the reaction of radicals generated by irradiation with oxygen in air. The changes in the heat of fusion and the degree of crystallinity of the irradiated fluoropolymers were investigated using DSC and the results indicate that the scission and crosslinking reactions of the irradiated fluoropolymers were largely influenced by the chemical structure. It was also found that the mechanical property of the irradiated fluoropolymer films under an air atmosphere was significantly decreased.

Radiation Effects on Electrical Treeing Characteristics of Low Density Polyethylene (저밀도 폴리에틸렌의 방사선 조사에 따른 전기 트리 특성 변화)

  • Lee, Chung;Shin, Hee-Kyung;Kim, Ki-Yup;Park, Soo-Gil;Ryu, Boo-Hyung
    • Proceedings of the KIEE Conference
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    • 1999.07d
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    • pp.1992-1994
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    • 1999
  • Dicumyl peroxide (DCP) is used for crosslinking agent in general. And the correlation between polyethylene and DCP is significant in particular radiation environment. On this paper, The effects on $Co^{60}{\gamma}$-ray irradiation of polyethylene doped 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, capacitance and dissipation factor at high frequency as increasing dosage. Also, chemical analysis was performed TGA, gel content.

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A Study to Improve the Interface Strength of Composite Materials by the Radiation of Ultrasonic Energy (초음파 조사에 의한 복합재료의 계면특성의 보강 개선에 관한 연구 (II))

  • Lee, Sang-Kook;Jhqun, Choon-Saing;Kim, Ik-Nyon
    • Proceedings of the KIEE Conference
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    • 1988.11a
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    • pp.179-182
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    • 1988
  • This study is to investigate the adhesive strength of composite material's interface on the experimental methode of tree growth in the material. The results are as fellows 1) The irradiations of ultrasonic energy cause the mechanical vibration in the polymer composite materials of fluid state, so then bring about physical dispersion and heat form inorganic materials, being supposed to produce chemical crosslinking reaction, decreasing of voids between filler and matrix. 2) The characterics of the breakdown are increased by using coupling agent in the composite material. 3) As the intensity of ultrasonic energy and its irradiated time are larger, the tree inception and break-down voltages increase and the tree growing is slower. so we obtain that the interface adhesive force tan be strengthened by the irradiation of ultrasonic energy.

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Effect of Stereoregularity on the Properties of Syndiotacticity-Rich Ultrahigh Molecular Weight Poly(vinyl alcohol)/Dimethylsu1foxide/Water Gel

  • Park, Jin-Hyun;Lyoo, Won-Seok;Ko, Sohk-Won
    • Proceedings of the Korean Fiber Society Conference
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    • 1998.10a
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    • pp.13-16
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    • 1998
  • Poly(vinyl alcohol) (PVA) gels are easily formed via physical pathway. Most PVA solutions including PVA/water solution are well known to form thermally reversible gels at low temperature but these gels showed poor mechanical properties. In order to overcome this weak point, transparent crosslinked PVA hydrogels were prepared by electron beam irradiation or by chemical process with crosslinking agents or additives. (omitted)

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Relationship between Crosslinking Processes and Mechanical Properties of UHMWPE for Artificial Joint (인공관절용 초고분자량폴리에틸렌의 가교결합 공정변수와 기계적 특성과의 상관관계)

  • Kim, H.M.;Kim, S.K.;Lee, J.D.;Yun, I.S.
    • Proceedings of the KSME Conference
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    • 2008.11a
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    • pp.1570-1574
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    • 2008
  • Various mechanical test were conducted on conventional and crosslinked ultra-high molecular weight polyethylene(UHMWPE) all prepared from the same lot of medical grade GUR 1050 for artificial joint. The conventional materials were not irradiated and treated by heating. The cosslinked materials were irradiated with $25kGy{\sim}200kGy$ by gamma-ray andthen annealed or remelted. Gamma-ray irradiation and heat treatment process were found to significantly impact the crystallinity, and hence the mechanical behavior, of the highly crosslinked UHMWPE. The radiation dose and heating conditions were key predictors of the uniaxial yielding, plastic flow, and failure properties of conventional and highly crosslinked UHMWPE. The correlation model from experiments would be the basic information to enhance the were resistance of artificial joint liner.

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Deposition of Copper Film on Polytetrafluoroethylene (PTFE) Modified by 1 keV Ion Irradiation (1 keV $Ar^+$이온빔으로 개질된 polytetrafluoroethylene (PTFE) 위의 구리 박막 증착)

  • Cho, Jun-Sik;Yoon, Ki-hyun;Koh, Seok-Keun
    • Korean Journal of Materials Research
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    • v.10 no.1
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    • pp.77-82
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    • 2000
  • A surface of polytetrafluoroethylene(PTFE) was modified with changing ion doses by 1 keV $Ar^+$ ion irradiation and Cu films having thickness $5000\;{\AA}$ were deposited on the modified PTFE. The SEM study showed that the surface texture of modified PTFE was in the form of cones whose height increased depending on ion doses. Through XPS spectra, it was found that the intensity of F ls peaks decreased with ion doses by preferential sputtering of F atoms and the C-C and / or C-F chains were formed by the crosslinking in the newly unstable chains. Cu films were deposited uniformly along the filaments formed on the modified PTFE. In x-ray diffraction (XRD) spectra of deposited Cu films on modified PTFE, a preferred orientation along (111) and (200) planes was found and the peak intensity of (111) plane increased as surface roughness of modified PTFE increased. The resistivity of Cu films was changed from $2.7{\mu}{\Omega}cm$ of unmodified PTFE to $4.3{\mu}{\Omega}cm$ of modified PTFE at ion dose of $1{\times}10^{16}/\textrm{cm}^2$ and the abrupt increase of resistivity in the modified PTFE at ion dose of $1{\times}10^{17}/\textrm{cm}^2$ was due to being cut off the film which resulted from the increased surface roughness.

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Preparation and Characterization of Polyvinylpyrrolidone/${\kappa}$-Carrageenan/Hexanediol Hydrogel by Gamma-ray Irradiation (감마선을 이용한 폴리비닐피롤리돈/카파-카라기난/1,2-헥산디올 하이드로젤의 제조 및 특성)

  • Han, Il-Soo;Lim, Youn-Mook;Gwon, Hui-Jeong;Park, Jong-Seok;Nho, Young-Chang
    • Polymer(Korea)
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    • v.35 no.1
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    • pp.13-16
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    • 2011
  • In this study, the hydrogels composed of polyvinylpyrrolidone (PVP), ${\kappa}$-carrageenan (${\kappa}C$), and 1,2-hexanediol (HD) were prepared by ${\gamma}$-ray irradiation. The radiation dose was 25 kGy and the concentration of ${\kappa}C$ was 3 wt%. The physical properties of the hydrogels were investigated as a function of the concentrations of PVP and HD. The gel content and the tensile strength increased with increasing PVP concentration due to the crosslinking between the pyrrolidone molecules and decreased with increasing HD concentration. The degree of swelling was inversely proportional to the gel content because the highly crosslinked hydrogels had a tighter structure, hence reducing their water absorption. The antibacterial tests indicated that the hydrogels containing HD had antibacterial activity.

Electrical Properties of Nanostructured Carbon Black-filled HDPE Composites: Effect of Electron Beam Irradiation on PTC Characteristics (나노구조 카본블랙/HDPE 복합재료의 전기적 특성: 전자선 조사에 의한 PTC 특성변화)

  • 박수진;송수완;서민강;이재락
    • Composites Research
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    • v.16 no.1
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    • pp.19-25
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    • 2003
  • In this paper, electrical properties of nanostructured carbon blacks (CB)-filled high density polyethylene (HDPE) composites were investigated as a function of temperature, which were prepared by the conventional melt-mixing method. The composites were irradiated with electron beam in a dosage of 30∼150 kGy to enhance an electronical reproducibility and to reduce a negative temperature coefficient (NTC) phenomenon. And, gel contents (%) of irradiated CB/HDPE composites were estimated by solvent extraction method. From the experimental results. the positive temperature coefficient (PTC) intensity of the composites was strongly depended on the CB content and particle size. And, the increase of gel contents (%) and disappearance of NTC behavior of the composites were identified at a dosage of 60 kGy. It was also found that the electron beam irradiation made an improvement of electrical reproducibility of the composites. This result was probably due to the reduction of the freedom of CB movement at above the melting temperature of the polymer crystalline, resulting in increasing the crosslinking structure of the composites.

Preparation and Characterization of Gelatin Scaffold Containing Microorganism Fermented Cellulose (미생물 발효 셀룰로오스와 젤라틴을 함유한 조직공학적 세포지지체의 제조 및 특성)

  • Lim, Youn-Mook;Kim, Mi-Yeong;Gwon, Hui-Jeong;Park, Jong-Seok;Nho, Young-Chang;Lee, Byeon-Heon;Lee, Jong-Dae;Song, Sung-Gi;Kim, Sung-Ho;Choi, Young-Hun;Lee, Sun-Yi
    • Journal of Radiation Industry
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    • v.4 no.4
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    • pp.373-379
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    • 2010
  • Cellulose, chitin, chitosan and hyaluronic acid are well known as polysaccharides. These polysaccharides have many effects on cell growth and differentiation. Cell activation increases with increasing the polysaccharides concentration. In this study, gelatin scaffold containing microorganism fermented cellulose, citrus gel were prepared by using irradiation technique. Physical properties of the scaffolds were investigated as a function of the concentrations of gelatin and citrus gel and the cell attachment, cell morphology and inflammation of the scaffolds also were characterized for regeneration of skin tissue.

Investigation on glass transition temperature of low density polyethylene by the characteristics of temperature dependent linear expansion (선팽창 온도특성에 의한 저밀도 폴리에틸렌의 유리 천이온도에 대한 고찰)

  • 김봉흡;강도열;김재환
    • 전기의세계
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    • v.30 no.7
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    • pp.441-447
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    • 1981
  • As a preceeding work for the study on dielectric characterstics of a kind of low density polyethylene introduced morphological change by mechanical method, glass transition temperature which is regarded as a macroscopic aspect for relaxation of molecular chain segments has been observed by means of temperature dependent dilatometric measurement. The origina specimen clearly shows two knees which correspond to two peaks (.gamma. and .betha. peak) in the intenal friction measurement, suggesting the existence of separated glass transition temperatures at 150.deg.k and 260.deg.k respectively. On the specimen irradiated to 100 Mrad both glass transition temperatures tend to shift towards high temperature sides because of crosslinking by irradiation. furthemore an evidence can be seen that radiation effect, even in amorphous phase, is also slelctive depending on slight morphological differences. The specimen extended to four times in length shows a peculiar nature such as negative linear thermal expansion coefficient increasing with temperature between 220.deg.k and ambient temperature and that this fact is interpreted by considering that c axis of the lattice aligns along the extended direction by drawing, further c axis inherently possesses the characteristics of negative linear thermal expansion coefficient. For the observations that the relatively small positive linear expansion on the specimen extended to ca. two times as well as the part below 220.deg.k of the specimen extended to four times, it is considered for the reason of the facts that the incompletely oriented region indicated as the middle part of Peterlin's model tends to restore partially to orginal arrangement-a kind of phase transition-as increasing with temperature.

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