+ Site Statistics
+ Search Articles
+ PDF Full Text Service
How our service works
Request PDF Full Text
+ Follow Us
Follow on Facebook
Follow on Twitter
Follow on LinkedIn
+ Subscribe to Site Feeds
Most Shared
PDF Full Text
+ Translate
+ Recently Requested

Solid-state (13)C NMR and synchrotron SAXS/WAXS studies of uniaxially-oriented polyethylene



Solid-state (13)C NMR and synchrotron SAXS/WAXS studies of uniaxially-oriented polyethylene



Solid State Nuclear Magnetic Resonance 72: 27-40



We report solid-state (13)C NMR and synchrotron wide-and small-angle X-ray scattering experiments (WAXS, SAXS) on metallocene linear low density polyethylene films (e.g., Exceed™ 1018 mLLDPE; nominally 1MI, 0.918 density ethylene-hexene metallocene copolymer) as a function of uniaxial draw ratio, λ. Combined, these experiments provide an unambiguous, quantitative molecular view of the orientation of both the crystalline and amorphous phases in the samples as a function of draw. Together with previously reported differential scanning calorimetry (DSC), gas transport measurements, transmission electron microscopy (TEM), optical birefringence, small angle X-ray scattering (SAXS) as well as other characterization techniques, this study of the state of orientation in both phases provides insight concerning the development of unusually high barrier properties of the most oriented samples (λ=10). In this work, static (non-spinning) solid-state NMR measurements indicate that in the drawn Exceed(TM) films both the crystalline and amorphous regions are highly oriented. In particular, chemical shift data show the amorphous phase is comprised increasingly of so-called "taut tie chains" (or tie chains under any state of tautness) in the mLLDPE with increasing draw ratio - the resonance lines associated with the amorphous phase shift to where the crystalline peaks are observed. In the sample with highest total draw (λ=10), virtually all of the chains in the non-crystalline region have responded and aligned in the machine (draw) direction. Both monoclinic and orthorhombic crystalline peaks are observed in high-resolution, solid-state magic-angle spinning (MAS) NMR measurements of the oriented PE films. The orientation is comparable to that obtained for ultra-high molecular weight HDPE fibers described as "ultra-oriented" in the literature. Furthermore, the presence of a monoclinic peak in cold-drawn samples suggests that there is an appreciable internal stress associated with the LLDPE. The results are confirmed and independently quantified by Herman's Orientation Function values derived from the WAXS measurements. The degree of orientation approaches theoretically perfect alignment of chains along the draw direction. We deduce from this observation that a high fraction of the non-crystalline chains are either tie chains that directly connect adjacent lamellae or are interlocking loops from adjacent lamellae. In either case, the chains are load-bearing and are consistent with the idea of "taut tie chains". We note that transmission electron micrographs recorded for the ultra-oriented Exceed showed the lamellae are often appreciably thinner and shorter than they are for cast or blown Exceed 1018. Combined with higher crystallinity, the thinner lamellae statistically favor more tie chains. Finally, the remarkably large decrease in permeability of the λ=10 film is primarily attributed to the high degree of orientation (and loss of entropy) of the amorphous phase.

Please choose payment method:






(PDF emailed within 0-6 h: $19.90)

Accession: 058876187

Download citation: RISBibTeXText

PMID: 26476811

DOI: 10.1016/j.ssnmr.2015.10.003


Related references

Early oriented isothermal crystallization of polyethylene studied by high-time-resolution SAXS/WAXS. Analytical and Bioanalytical Chemistry 387(2): 649-661, 2007

Synchrotron SAXS and WAXS study of the interactions of NSAIDs with lipid membranes. Journal of Physical Chemistry. B 115(24): 8024-8032, 2011

Silk fiber assembly studied by synchrotron radiation SAXS/WAXS and Raman spectroscopy. Journal of the American Chemical Society 130(50): 17070, 2008

Orientational distribution of parentdaughter structure of isotactic polypropylene: a study using simultaneous synchrotron WAXS and SAXS. Journal of Materials Science 43(19): 6459-6467, 2008

Preliminary study of human breast tissue using synchrotron radiation combining WAXS and SAXS techniques. Applied Radiation and Isotopes 68(4-5): 799-803, 2010

Time-Resolved Simultaneous SAXS/WAXS of the Drawing of Polyethylene at the Daresbury SRS. Journal of Synchrotron Radiation 3(Pt 2): 84-90, 1996

The structural principles of multidomain organization of the giant polypeptide chain of the muscle titin protein: SAXS/WAXS studies during the stretching of oriented titin fibres. Journal of Structural Biology 155(2): 251-262, 2006

Structural elucidation of rapid solution-mediated phase transitions in pharmaceutical solids using in situ synchrotron SAXS/WAXS. Molecular Pharmaceutics 9(9): 2787-2791, 2012

High-pressure potato starch granule gelatinization: synchrotron radiation micro-SAXS/WAXS using a diamond anvil cell. Biomacromolecules 8(7): 2092-2097, 2007

Study of temperature dependence of crystallisation transitions of a symmetric PEO-PCL diblock copolymer using simultaneous SAXS and WAXS measurements with synchrotron radiation. European Physical Journal. E Soft Matter 27(4): 357-364, 2008

In situ observations of particle size evolution during the hydrothermal crystallization of TiO2 A time-resolved synchrotron SAXS and WAXS study. Journal of Crystal Growth 344(1): 0-58, 2012

Dehydration/ recrystallization mechanisms, energetics, and kinetics of hydrated calcium silicate minerals; an in situ TGA/ DSC and synchrotron radiation SAXS/ WAXS study. Chemical Geology 167(1-2): 141-159, 2000

Interface structure in solid oxide fuel cells by anomalous/high-energy SAXS/WAXS. Acta Crystallographica Section A Foundations of Crystallography 61(A1): C412-C412, 2005

Time-resolved SAXS/WAXS study of the phase behavior and microstructural evolution of drug/PEG solid dispersions. Molecular Pharmaceutics 8(3): 932-939, 2011

Two types of graphoepitaxy of tellurium onto uniaxially-oriented polyethylene. Journal of Materials Science 33(19): 4787-4790, 1998