Quantitative analysis of three phases of high-density polyethylene with 2D time-domain proton NMR

Changho Choi, Linda Bailey, Alfred Rudin, M. Mik Pintar

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

With two-dimensional time-domain NMR analysis in the proton spin rotating frame three phases are identifiable in the solid polyethylene. The major proton magnetization fraction is due to the polymer's crystalline region, where the motion is least isotropic and slowest. A magnetization fraction with intermediate relaxation rate is also intermediate in magnitude. This component is proposed to comprise chain loops on the surfaces of crystallites and effectively entangled chain segments. The most mobile fraction, which is most liquid-like with a T2 of near 1 ms at 12O°C, is also the smallest It is proposed that it is due to polymer chains in the amorphous phase. In the crystalline phase the chain motion is an unexpectedly effective relaxation mechanism at ∼50 KHz. This process, which involves propagation of a twisted region along the crystallite, as has been suggested before, is either not present in the other two phases of the HDPE or is less efficient because of the lower polymer density. The activation energies for the crystalline, intermediate and amorphous phases are estimated to be 34 ± 3, 13 ± 3, and 8 ± 2 Kcal/mol, respectively. The frequencies of the relaxation process at 12O°C are 43 KHz, 350 KHz, and 1.5 MHz, respectively.

Original languageEnglish (US)
Pages (from-to)2551-2558
Number of pages8
JournalJournal of Polymer Science, Part B: Polymer Physics
Volume35
Issue number15
StatePublished - Nov 15 1997

Fingerprint

Polyethylene
High density polyethylenes
quantitative analysis
Protons
polyethylenes
Polymers
Nuclear magnetic resonance
Crystalline materials
nuclear magnetic resonance
protons
Magnetization
polymers
Chemical analysis
magnetization
Relaxation processes
Crystallites
crystallites
Polyethylenes
Activation energy
activation energy

Keywords

  • 2D time-domain analysis
  • Amorphous
  • Crystalline
  • Intermediate
  • Polyethylene
  • Proton NMR
  • Rotating frame

ASJC Scopus subject areas

  • Materials Chemistry
  • Polymers and Plastics

Cite this

Quantitative analysis of three phases of high-density polyethylene with 2D time-domain proton NMR. / Choi, Changho; Bailey, Linda; Rudin, Alfred; Pintar, M. Mik.

In: Journal of Polymer Science, Part B: Polymer Physics, Vol. 35, No. 15, 15.11.1997, p. 2551-2558.

Research output: Contribution to journalArticle

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AB - With two-dimensional time-domain NMR analysis in the proton spin rotating frame three phases are identifiable in the solid polyethylene. The major proton magnetization fraction is due to the polymer's crystalline region, where the motion is least isotropic and slowest. A magnetization fraction with intermediate relaxation rate is also intermediate in magnitude. This component is proposed to comprise chain loops on the surfaces of crystallites and effectively entangled chain segments. The most mobile fraction, which is most liquid-like with a T2 of near 1 ms at 12O°C, is also the smallest It is proposed that it is due to polymer chains in the amorphous phase. In the crystalline phase the chain motion is an unexpectedly effective relaxation mechanism at ∼50 KHz. This process, which involves propagation of a twisted region along the crystallite, as has been suggested before, is either not present in the other two phases of the HDPE or is less efficient because of the lower polymer density. The activation energies for the crystalline, intermediate and amorphous phases are estimated to be 34 ± 3, 13 ± 3, and 8 ± 2 Kcal/mol, respectively. The frequencies of the relaxation process at 12O°C are 43 KHz, 350 KHz, and 1.5 MHz, respectively.

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