• Polymer(Korea)
• /
• v.27 no.3
• /
• pp.249-254
• /
• 2003

The variation of chemical structure and physical properties of crosslinked polyethylene (XLPE) during thermal aging process was investigated. The formation of carbonyl functional group resulting from thermal oxidation reaction of XLPE was monitored using X-ray photoelectron spectroscopy and near infrared (NIR) spectroscopy. It was observed that the intensity of carbonyl peak observed at 1715 nm linearly increased with aging time in NIR spectroscopy. The linear relationship between NIR peak absorbance and aging time confirmed that NIR spectroscopy might be used as a proper tool for monitoring the aging process of polymeric materials. Also the formation of crosslinks during the aging process was monitored using thermal mechanical analysis, stress-strain test, and Shore hardness test. The change in the physical properties, such as the increase in the glass transition temperature from 110 to 132$^{\circ}C$, the decrease in the strain from 265 to 110%, as well as the increase in the shore D hardness from 32 to 50, was observed during the aging process.

• Proceedings of the KSME Conference
• /
• 2008.11a
• /
• pp.1570-1574
• /
• 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.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.7 no.4
• /
• pp.26-33
• /
• 1993

The acoustic emission automatic detection system is developed to observe tree deterioration phenomena. Applying an alternating voltage of 15(kVnns) toXLPE tree specimens, many pulses of small amplitude are detected when the bush type tree developes branch type and a few pulses of high amplitude prcxluced as branch type propagated to bush type tree. Therefore, it is known that pulses having small amplitude operates as a destructive factor. It is observed that the skewness of the amplitude and the number of average pulses as distribution tendency of three dimension are characteristic quantity of AE pulses. As the trajectory of skewness is farther from the origin on the S-plane, it is more likely to breakdown.

• Resources Recycling
• /
• v.23 no.1
• /
• pp.48-57
• /
• 2014

In this study, we have investigated the influence of the nature of solvent on the grafting reaction of maleic anhydride onto polyethylene wax obtained as a by-product in a high density polyethylene plant. The results show that the grafting ratio in xylene as a solvent was higher than toluene. This is because xylene has excellent monomer solubility, swelling property and miscibility. It has been also observed that grafting degree shows an initial jump in percentage of grafting with increasing amount of solvent, from 0% v/w to 200% v/w giving maximum grafting in 200% v/w and then slightly decreases on further increase in the amount of solvent and becomes almost constant. It can be also seen that gel content was not formed under the use of solvent. It means that solvent prevented cross-linking reaction due to chain transfer reactions to solvent molecules. Studies of melt viscosity at $140^{\circ}C$ showed that viscosity increased after grafting of maleic anhydride onto polyethylene wax.

• Proceedings of the KIEE Conference
• /
• 1982.07a
• /
• pp.227-228
• /
• 1982

• Journal of Biomedical Engineering Research
• /
• v.20 no.1
• /
• pp.99-106
• /
• 1999

Ultra-high molecular weight polyethylene (UHMWPE) was crosslinked in the melt state to enhance wear resistance, Dicumyl peroxide (DCP) and triallyl cyanurate (TAC) was used as a crosslinking agent and a promoter, respectively. With increasing amount of DCP and TAC used, gel content of crosslinked UHMWPE (XUMPE) increased, while the melting temperature, crystallizaiton temperature, crystallinity, and tensile properties decreased. The results of pin-on-disk wear test and ball-on-disk test with small applied load showed reduced wear volumes of XUMPE from that of the unmodified UHMWPE. As the wear mechanism effected in the experimental condition of this study was thought to be deformation rather than adhesion or fatigue, a new parameter, the ratio of maximum contact stress to yield stress, was proposed to correlate well with observed wear resistance. In ball-on-disk wear test with larger applied load, XUMPE showed higher wear volumes than that of the unmodified UHMWPE which were accompanied with increased friction coefficients and surface roughness of the wear tracks. When contact stress was well above yield stress, the failure of XUMPE, as well as deformation, was thought to be much accelerated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1988.10a
• /
• pp.73-75
• /
• 1988

• Proceedings of the KIEE Conference
• /
• 2004.07c
• /
• pp.1652-1654
• /
• 2004

초고압 지중 케이블을 전기적, 기계적으로 연결하는 역할을 하는 중간 접속함은 미가교 폴리에틸렌을 사용하여 현장에서 가교시키는 TMJ(tape molded Joint), 에폭시와 EPDM고무의 복합 절연구조를 가지고 있는 PJ(Prefabricated Joint), 그리고 EPDM또는 실리콘 고무를 단독으로 사용하는 PMJ(Premolded Joint)로 대표된다. 그러나 TMJ는 현장에서 가교하는 방식으로 조립 후 품질을 파악하기가 쉽지 않으며 PJ는 공장에서 미리 성형한 제품을 현장에서 조립만 하면 되는 구조이나 그 부품의 수가 많고, 이종 계면을 가지고 있는 복합절연구조를 가지고 있어 최근에는 부품의 수도 적고 조립이 간편하며 이종 계변의 수를 최소화하여 전기적 안정성을 높인 조립형 접속함인 PMJ를 선호하는 경향을 보이고 있다. 본 논문에서는 PMJ용으로 사용되는 실리콘 고무의 절연과 반도전 계면에서의 접착력과 전기적 파괴 특성간의 상관 관계를 규명하였고 또한 실리콘 고무의 상온 및 고온에서의 AC 및 Impulse 전압의 특성 변화와 Impulse 전압의 극성효과에 대해 규명하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1999.05a
• /
• pp.173-176
• /
• 1999

Crosslinked Decree is an important 7actor to determine dielectric property of crosslinked polyethylene(XLPE) used for the insulation material in Power cables. Recently, though it is necessary to investigate electrical properties according to crosslinked degree as a Part of the whose characterization of cable. it is not examined closely. In this study. crosslinked degree of samples were measured according to temperature and holding time of crosslinking. electrical tree characteristics of these characteristics of these samples were analyzed by crosslinked degree and applied temperature that was chanced from normal temperature to operating temperature of power cables. As a result. when the crosslinked degree was low, dielectric properties were decreased and influence of temperature was increased. but the crosslinked degrees were high, initiation voltages of treeing were increased and dielectric properties were improved. It is proved that the optimum crosslinked degree was one of most important factor for aging time and residual lifetime of Power cable.

• Korean Journal of Materials Research
• /
• v.9 no.4
• /
• pp.398-403
• /
• 1999

Studies on the electrical treeing deterioration and dielectric breakdown phenomena in the polymeric insulator of polyethylene and epoxy resin were carried out. Block type samples with needle-plane electrode geometry were electrically stressed and the tree pattern from the needle tip was observed. In LDPE the density of electrical tree was very high and its pattern was bush type. For the case of XLPE, branched tree was observed. As temperature and SN content increased, the dielectric breakdown voltage decreased and the treeing phenomena became more complicated. Fan type cracks were observed around the conducting tree path in the brittle DGEBA/MDA system.