scholarly journals The Use of Solid State NMR to Characterize High Density Polyethylene/Organoclay Nanocomposites

2009 ◽  
Vol 3 (3) ◽  
pp. 187-190
Author(s):  
Tathiane Rodrigues ◽  
◽  
Maria Tavares ◽  
Igor Soares ◽  
Ana Moreira ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Relaxation Time ◽  
Solid State ◽  
Magnetic Resonance ◽  
High Density Polyethylene ◽  
Melt Processing ◽  
Proton Spin ◽  
High Density ◽  
Spin Lattice Relaxation ◽  
Nuclear Magnetic

Recently the development of new materials, in special polymeric nanocomposites, formed by polymer and layered silicates, have gained attention. In this work nanocomposites based on high-density polyethylene matrix (HDPE) and organically modified clay were prepared by melt processing and characterized by the determination of proton spin-lattice relaxation time through solid state nuclear magnetic resonance (NMR) spectroscopy. This work has a proposal to add one quantitative technique to help the researchers to better evaluate polymeric nanocomposite, because NMR is an important tool employed to study both molecular structure and dynamic molecular behavior. The nanocomposites were mixed in a twin-screw extruder, varying the shear rate parameter: 60 and 90 rpm at 463 K. Nanocomposites obtained were characterized through X-ray diffraction; thermal analysis; impact resistance and nuclear magnetic resonance. The T1H results showed that the samples present different molecular domains according to the clay dispersion, forming an intercalated and/or exfoliated nanocomposites. The measurement of relaxation time, using low field NMR, is a useful method to evaluate changes in the molecular mobility of nanocomposite and can infer whether the sample is exfoliated and/or intercalated, since lamellar filler is used.

scholarly journals Imaging of nuclear magnetic resonance spin–lattice relaxation activation energy in cartilage

2018 ◽  
Vol 5 (7) ◽  
pp. 180221 ◽  
Author(s):  
R. J. Foster ◽  
R. A. Damion ◽  
M. E. Ries ◽  
S. W. Smye ◽  
D. G. McGonagle ◽  
...  
Keyword(s):  
Activation Energy ◽  
Nuclear Magnetic Resonance ◽  
Relaxation Time ◽  
Magnetic Resonance ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Cartilage Tissue ◽  
Spin Lattice ◽  
Resonance Spin ◽  
Nuclear Magnetic

Samples of human and bovine cartilage have been examined using magnetic resonance imaging to determine the proton nuclear magnetic resonance spin–lattice relaxation time, T 1 , as a function of depth within through the cartilage tissue. T 1 was measured at five to seven temperatures between 8 and 38°C. From this, it is shown that the T 1 relaxation time is well described by Arrhenius-type behaviour and the activation energy of the relaxation process is quantified. The activation energy within the cartilage is approximately 11 ± 2 kJ mol −1 with this notably being less than that for both pure water (16.6 ± 0.4 kJ mol −1 ) and the phosphate-buffered solution in which the cartilage was immersed (14.7 ± 1.0 kJ mol −1 ). It is shown that this activation energy increases as a function of depth in the cartilage. It is known that cartilage composition varies with depth, and hence, these results have been interpreted in terms of the structure within the cartilage tissue and the association of the water with the macromolecular constituents of the cartilage.

Nuclear-magnetic-resonance determinations of fluorine content and relaxation times in bone powder

1986 ◽  
Vol 64 (3) ◽  
pp. 282-288 ◽  
Author(s):  
M. E. Ebifegha ◽  
R. F. Code ◽  
K. G. McNeill ◽  
M. Szyjkowski
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Relaxation Time ◽  
Magnetic Resonance ◽  
Fluorine Content ◽  
Spin Lattice Relaxation ◽  
Relaxation Processes ◽  
Fluorine Concentration ◽  
Bone Powder ◽  
Rat Bone ◽  
Nuclear Magnetic

The detection of trace amounts of fluoride ions from ground rat-bone samples using a 27-MHz solid-state single-coil pulsed nuclear-magnetic-resonance (NMR) spectrometer is described. The fluorine content in the bone samples as determined from the amplitudes of the free-induction-decay (FID) signals is in good agreement with analyses based on standard chemical and neutron-activation techniques. The value of the spin-lattice relaxation time T1 is 1.46 ± 0.07 s in dry rat-bone powder and is slightly longer in wet bone powder depending on the water content. The contribution of cross-relaxation processes to these results is discussed. The value of the spin–spin relaxation time T2 (as determined from the point where the 19F FID signal has decayed to 1/e of its maximum amplitude) is approximately 75 μs. The Hahn echo sequence [(π/2)0-τ-(π)0] applied to 7 g of bone powder with a fluorine concentration of 3 mg F/g bone in a relatively homogeneous region of the external magnetic field yields echoes that persist for times 2τ up to ~0.5 ms.

A new nuclear magnetic resonance property of lung

1985 ◽  
Vol 58 (3) ◽  
pp. 759-762 ◽  
Author(s):  
A. H. Morris ◽  
D. D. Blatter ◽  
T. A. Case ◽  
A. G. Cutillo ◽  
D. C. Ailion ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Relaxation Time ◽  
Magnetic Resonance ◽  
Spin Lattice Relaxation ◽  
Surrounding Tissue ◽  
Proton Density ◽  
Lung Inflation ◽  
Body Tissues ◽  
Regional Lung ◽  
Nuclear Magnetic

Inflated lung has a nuclear magnetic resonance (NMR) free-induction decay (FID) which is short compared with that of collapsed lung and those of other body tissues. An almost identically short FID is obtained from a slurry of 5-micron alumina particles in water. Interfaces between air and water in lung and between alumina and water in the slurry appear to be the source of spatial internal magnetic inhomogeneities which produce NMR line broadening and the short FID. Paired images that included lung, taken with paired symmetric and asymmetric NMR spin-echo sequences, permit the generation of an image, by subtraction, of the lung isolated from surrounding tissue. These new lung images are neither proton density, T1 (spin-lattice relaxation time), nor T2 (spin-spin relaxation time) images. They complement current NMR images and provide information about regional lung inflation. This previously unrecognized NMR property of lung tissue has potential application in NMR imaging, in quantitative determination of lung water and its distribution, and in the quantitation of regional lung inflation.

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