Abstract
본 연구에서는 UVB-313(자외선 파장 290-315 nm) 노출 하에 smooth HDPE 지오멤브레인과 flexible PP 지오멤브레인에 대한 자외선 노출의 영향을 평가하였다. 인장특성, 용융지수, 표준 및 고압 산화유도시간 및 FTIR/ATR 결과들을 고찰하였다. 노출된 지오멤브레인 시료의 인장특성은 변하지 않았지만, HDPE 지오멤브레인보다 flexible PP 지오멤브레인의 경우 산화방지제의 감소가 더 큼을 알 수 있었다. 대표적인 현장온도 <TEX>$20^{\circ}C$</TEX>에서의 산화방지제의 수명을 예측하기 위하여 외삽에 의한 Arrhenius 모델을 적용하였다. 자외선 노출 전후의 HDPE 지오멤브레인 시료는 용융지수의 큰 차이는 없었지만 flexible PP 지오멤브레인은 가교발생으로 인한 용융지수 감소가 발생하였다. FTIR 스펙트럼으로부터 자외선에 노출된 시료의 경우 카르보닐기와 관련된 <TEX>$1750\;cm^{-1}$</TEX> 부근에서 작은 피크가 발견되었으며, 이는 산화가 진행되었음을 예시하고 flexible PP 지오멤브레인의 경우 <TEX>$3100{\sim}3500\;cm^{-1}$</TEX>에서 하이드록시기 또는 하이드로퍼옥사이드기에 의한 새로운 피크를 확인할 수 있었다. In this paper the effect of UV (ultraviolet) exposure on HDPE (high density polyethylene)-smooth and f-PP (flexible polypropylene) geomembranes is evaluated under UVB-313 (ultraviolet wavelength 290-315 nm) exposure. Tensile property, melt flow index (MFI), oxidation induction time (OIT), both standard-OIT and high pressure-OIT and Fourier transform infrared spectroscopy/attenuated total reflectance (FTIR/ATR) results are discussed. Although tensile properties of the exposed geomembrane samples remained unchanged, the depletion of antioxidants was found higher for f-PP than for HDPE geomembrane. Arrhenius model by extrapolation was used on the data to predict the antioxidant lifetime to a typical site temperature of <TEX>$20^{\circ}C$</TEX>. There was no significant difference between the MFI value of the virgin and UV exposed HDPE geomembrane samples but a decrease in MFI was found in f-PP geomembrane that signifies that crosslinking has occurred. From FTIR spectra, the small peak (near <TEX>$1750\;cm^{-1}$</TEX>) observed in the spectrum of UV exposed sample corresponds to a carbonyl (C=O) linkage, which suggests that oxidation has occurred in the polymer structure, and another new band for f-PP between 3100 and <TEX>$3500\;cm^{-1}$</TEX> is attributed to a hydroxyl bond and/or hydroperoxide bond.
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