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Solid state nuclear magnetic resonance (NMR) is a powerful technique to analyze polymer composites. The use of proton relaxation data to evaluate the dispersity of the dispersion phase in the composite and its homogeneity are very wide. In this work PVC=silica composites were prepared using different ratios to obtain a new material to be used in chromatograph column for separation of plant extracts. Thus, this study used proton spin-lattice and spin-spin nuclear magnetic resonance relaxation data, determined in a low field NMR spectrometer as a method to characterize those composites in relation to silica dispersion as well as PVC= silica compatibility. From the relaxation data analyses, the best ratio of PVC= silica, according to the components dispersion and consequently composite compatibility, was 80=20, according to the determined T 1 values.

Research Summary Polymer-Matrix CompositesHow would you… …describe the overall signifi cance of this paper? This paper discusses the methodology for preparation of the nanocomposite and also the use of low-fi eld solid-state nuclear magnetic resonance as a technique to separate exfoliated and intercalated organoclay in the polymeric matrix.…describe this work to a materials science and engineering professional with no experience in your technical specialty?The authors describe an interesting work that involves a new characterization method to study polymeric nanocomposites. …describe this work to a layperson?This work presents a useful method to evaluate nanocomposites through nuclear magnetic resonance.Polymeric nanocomposites, which are hybrids of polymers and modifi ed inorganic clay with organic surfactants, are extremely attractive in both science and industry. These materials present improvements in such polymer properties as modulus, heat capacity, thermal stability, fl ame resistance, and so on. Research has been conducted in recent decades to obtain high-quality materials that can be used in applications like food packing, car components, and combustible cells. Polymeric nanocomposites present many advantages in relation to composites due to the quantity of fi ller added to the polymer and also to the improved properties. In a composite, the quantity of fi ller must be as high as possible (i.e., over 30%). In the polymeric nanocomposite the quantity of fi ller varies from 1% to 5% because of the nanosize of the particles. These nanoparticles often have a large surface area that results in improved polymer-matrix properties. Ana M. Moreira is with RioPol, Balneário Jardim Santa Clara, Duque de Ca. Dr. Tavares can be reached at mibt@ima.ufrj.br.

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.

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