Elastomers and Composites

The Rubber Society of Korea (한국고무학회)
권호 표지

Effect of Low-temperature Thermal Treatment on Degree of Crystallinity of a Low Density Polyethylene: $^{1}H$ Nuclear Magnetic Resonance Study

저밀도 폴리에틸렌의 결정화도에 대한 저온 열처리 효과: 수소 핵자기공명 연구

  • Lee, Chang-Hoon (Dept. of Polymer Science & Engineering, Chosun University) ;
  • Choi, Jae-Kon (Dept. of Polymer Science & Engineering, Chosun University)
  • 이창훈 (조선대학교 응용화학소재공학과) ;
  • 최재곤 (조선대학교 응용화학소재공학과)
  • Published : 2008.12.31
Download PDF
⟨ Previous Next ⟩

Abstract

An effect of low-temperature long-term thermal degradation on a degree of crystallinity of a low density polyethylene (LDPE) was investigated by using $^1H$ solid state nuclear magnetic resonance (SSNMR). Firstly, the long-term thermal treatment makes a color of LDPE from white to pale yellow which is indicative of thermal oxidation. Secondly, it makes the $^{1}H$ NMR spin-spin and spin-lattice relaxation times ($T_1$) to be long. Lastly, the degree of crystallinity of the semicrystalline aged-LDPE also decreases with thermal treatment. Above all, the $T_1$ increase is envisaged to be due to either a decrease of the amorphous regions governing overall spin-lattice relaxation mechanism in LDPEs or a dynamically restricted motion of specific molecular motions by intermolecular hydrogen bonding or crosslinking. However, since the decrease of crystallinity implies an increase of amorphous regions by the thermal treatment, the former case is contrast to our results. Accordingly, we concluded that the latter effect is responsible for the $T_1$ increase.

저밀도 폴리에틸렌에 대한 장시간 저온 열처리가 저밀도 폴리에틸렌 고분자의 결정화도에 미치는 효과를 고체 수소 핵자기공명을 이용하여 연구하였다. 장시간 열처리는 첫째, 저밀도 폴리에틸렌의 색깔을 엷은 노란색으로 변하게 하였고 둘째, 저밀도폴리에틸렌에서 수소 핵의 스핀-스핀 및 스핀-격자 완화시간을 증가시켰으며, 셋째, 결정화도를 줄어들게 하였다. 먼저, $T_1$의 증가를 저밀도폴리에틸렌의 전체 스핀-격자 완화시간을 결정하는 비정질 영역의 부피 감소에 의한 것이거나 분자간 가교나 수소결합에 의한 특정 분자 운동 성분의 느려짐에 의해 발생하는 것으로 고려하였다. 하지만 결정화도의 감소는 열처리에 의한 비정질 영역의 감소를 의미하므로 전자와는 배치되었다. 따라서 $T_1$의 증가는 후자에 의한 결과임을 알 수 있었다.

Keywords

References

  1. Y. Tanaka, N. Ohnuma, K. Katsunami, and Y. Ohki, "Effects of Crystallinity and Electron Meanfree- path on Dielectric Strength of Low-Density Polyethylene", IEEE Trans. Electr. Insul., EI-26, 258 (1991)
  2. V. J. Mcbrierty and D. C. Douglass, "Recent Advances in the NMR of Solid Polymers", J. Polym. Sci.: Macromol. Rev., 16, 295 (1981) https://doi.org/10.1002/pol.1981.230160105
  3. Q. Chen and H. Kurosu, "Solid-state NMR studies on semicrystalline Polymers" in Annual Reports of NMR spectroscopy 61, p. 247, Academic Press, New York, 2006
  4. Jiri Spevacek, Josef Baldrian, "Solid-state $^{13}C$ NMR and SAXS characterization of the amorphous phase in low-molecular weight poly(ethylene oxide)s", European Polymer Journal, 44, 4146 (2008) https://doi.org/10.1016/j.eurpolymj.2008.10.005
  5. E. Fukushima and S. B. W. Roeder, Experimental Pulse NMR; A Nuts and Bolts Approach, Addison-Wesley, London, 1981
  6. N. Bloembergen, E. Purcell, and R. V. Pound, "Relaxation Effects in Nuclear Magnetic Resonance Absorption", Phys. Rev., 73, 679 (1948) https://doi.org/10.1103/PhysRev.73.679
  7. A. R. Blythe, Electrical properties of polymers, Cambridge Univ. Press, London, 1979
  8. A. Barlow, "The Chemistry of Polyethylene Insulation", IEEE Trans. Elec. Ins., 7, 8 (1991)
  9. J. V. Benham and T. J. Pullukat, "Analysis of the Types and Amounts of Carbonyl Species Present in Oxidized Polyethylene", J. Appl. Polym. Sci., 20, 3295 (1976) https://doi.org/10.1002/app.1976.070201210
  10. R. D. Deanin, Polymer Structure, Properties and Applications, Cahners publication, Boston, 1972
  11. L. C. Dickinson, P. Morganelli, C. W. Chu, Z. Petrovie, W. J. MacKnight and J. C. W. Chien, "Molecular Motion in Model Network Polymers", Macromolecules, 21, 338 (1988) https://doi.org/10.1021/ma00180a010