열화시간에 따른 폴리에틸렌 파이프의 기계적 물성 거동

원종일; 최길영; Jong-Il Weon; Kil-Yeong Choi

Polymer(Korea), Vol.33, No.5, 446-451, September, 2009

Export Citation

열화시간에 따른 폴리에틸렌 파이프의 기계적 물성 거동

Mechanical Property Behaviors of Polyethylene Pipe due to Thermal-Degradation

원종일 , 최길영 ^†

한국화학연구원 신뢰성평가센터

Jong-Il Weon , and Kil-Yeong Choi^†

Reliability Assessment Center of Chemical Materials, Korea Research Institute of Chemical Technology, Daejeon 305-600, Korea

E-mail:

초록

신뢰성 평가 시험법인 RS M 0042에 따라, 열화시간 경과에 따른 선형저밀도 폴리에틸렌 파이프의 신뢰성 평가를 수행하였다. 열화시간이 증가함에 따라, 인장강도는 250일 열화시점까지 비례적으로 증가하였고, 경도는 비교적 미소한 증가를 보였으며, 연신율은 점진적으로 감소하는 경향을 보였다. 이러한 결과는 열화시간이 증가함에 따른, 결정화도의 증가와 열산화에 의한 가교밀도의 증가, 사슬 전단 및 사슬 운동성의 감소 등에 기인한 것으로 판단된다. 장기정수압시험 결과는 초기의 연성파괴에서 차후 취성파괴로 전환되는 시점이 존재함을 확인하였다. 산화유도시간 측정은 선형저밀도폴리에틸렌 파이프의 열산화 정도를 관찰하기 위해 도입되었다. 측정 결과는 250일 이후 선형저밀도폴리에틸렌 파이프에 첨가된 산화방지제가 거의 고갈되었음을 보여준다. 100 ℃ 열화 조건에서 산화방지제의 잔존량을 계산할 수 있는 실험식을 열화시간의 함수로 표현하여 제안하였다. 적외선분광분석 결과는 열화된 선형저밀도폴리에틸렌 파이프 표면상에 카르보닐 및 하드록실 관능기가 증가하였음을 보여준다. 이는 선형저밀도폴리에틸렌 표면의 탄화수소 그룹의 산화가 국부적으로 발생하였음을 나타낸다.

Reliability evaluations of linear low density polyethylene (LLDPE) pipe with respect of thermal exposure time have been investigated in accordance with RS M 0042, which is a reliability standard for polymer pipe. As the thermal exposure time is prolonged, a progressive increase, until 250 days, in tensile strength and a slight increase in hardness are observed, while a proportional decrease in elongation at break is showed. These results can be explained by the increase of crystallinity, followed by the increase of crosslinking density, chain scission and the decrease in chain mobility, due to thermal oxidation as the exposure time increases. Long term hydrostatic pressure test result implies the existence of transition point from ductile to brittle fracture. Oxidation induction time (OIT) test is employed to monitor the thermo-oxidative degradation of LLDPE pipe. This result shows that after the exposure time is 250 days, the depletion of antioxidants added in LLDPE pipe occurs. An empirical equation as function of exposure time, under 100 ℃ thermal-degradation condition, is proposed to assess the remaining amount of antioxidants owing to thermo-oxidative degradation. Fourier transform infrared spectroscopy results show the increase of carbonyl (-C=O) and hydroxyl (O-H) function groups on the surface of thermally exposed LLDPE pipe. This result suggests that the hydrocarbon groups locally undergo the oxidation on the LLDPE surface due to thermal-degradation.

Keywords:reliability;linear low density polyethylene;thermal-degradation;oxidation induction time

[References]

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Boyd RH, Polymer, 26, 323 (1985)
Krishnaswamy RK, Polym. Eng. Sci., 47(4), 516 (2007)
Hoang EM, Lowe D, Polym. Degrad. Stabil., 93, 1496 (2008)
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Hassinen J, Lundback M, Ifwarson M, Gedde UW, Polym. Degrad. Stabil., 84, 261 (2004)
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Callister WD, Materials science and engineering, 3rd Edition, John Wiley & Sons, Inc. (1994)
Sperling LH, Introduction to Physical Polymer Science, 3rd Edition, John Wiley & Sons, Inc. (2001)
McCrum NG, Buckley CP, Bucknall CB, Principles of Polymer Engineering, 2nd Edition, Oxford University Press Inc., New York (1999)
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Watanabe S, Sano N, Noda I, Ozaki Y, J. Phys. Chem. B, 113, 3385 (2009)

[Referenced By]

[Related Articles]

[1] Raynaud M, “A view of the European plastic pipes market in a global scenario”, Proc. Plast. Pipes XII, Milan, Italy (2004)

[2] Boyd RH, Polymer, 26, 323 (1985)

[3] Krishnaswamy RK, Polym. Eng. Sci., 47(4), 516 (2007)

[4] Hoang EM, Lowe D, Polym. Degrad. Stabil., 93, 1496 (2008)

[5] Andersson U, Proc. Plast. Pipes XI, 311 (2001)

[6] Ifwarson M, Aoyama K, Proc. Plast. Pipes X, 691 (1998)

[7] Gill TS, Knapp RJ, Bradley SW, Bradley WL, Plast. Rubber Compos., 28, 309 (1999)

[8] Dear JP, Mason NS, Polym. Polym. Compos., 9, 1 (2001)

[9] Hassinen J, Lundback M, Ifwarson M, Gedde UW, Polym. Degrad. Stabil., 84, 261 (2004)

[10] Dear JP, Mason NS, Proceedings of IMechE 220 Part L: J. Materials: Design and Applications, 97 (2006)

[11] Colin X, Audouin L, Verfu J, Rozental-Eveque M, Martin F, Bourgine F, Proc. Plast. Pipes XIII, 1 (2006)

[12] Kramer E, Oertli AG, Markus G, Patent WO 03/064511 A2 (2003)

[13] Ho TH, Cham PM, Shramm D, Sehanobish K, Patent WO 2005/056657 A2 (2005)

[14] Weon JI, Chung YK, Shin SM, Choi KY, Polymer(Korea), 28, 309 (1999)

[15] “Tubing for Water Purifier”, RS M 0042 (2008)

[16] Budynas RG, Advanced Strength and Applied Stress Analysis, 2nd edition, McGRAW-HILL (1999)

[17] Qiu W, Sworen J, Pyda M, Nowak-Pyda E, Habenschuss A, Wagener KB, Wunderlich B, Macromolecules, 39, 204 (2005)

[18] Ragnarsson L, Albertsson AC, Biomacromolecules, 4(4), 900 (2003)

[19] Callister WD, Materials science and engineering, 3rd Edition, John Wiley & Sons, Inc. (1994)

[20] Sperling LH, Introduction to Physical Polymer Science, 3rd Edition, John Wiley & Sons, Inc. (2001)

[21] McCrum NG, Buckley CP, Bucknall CB, Principles of Polymer Engineering, 2nd Edition, Oxford University Press Inc., New York (1999)

[22] Allcock HR, Lampe FW, Mark JE, Contemporary Polymer Chemistry, 3rd Edition, Pearson Education Inc. (2004)

[23] Watanabe S, Sano N, Noda I, Ozaki Y, J. Phys. Chem. B, 113, 3385 (2009)