Abstract
Polymeric nanocomposites based on polyethylene (PE) and Brazilian natural montmorillonite clay (MN) were obtained by melt processing, using a twin-screw extruder. The main objective of this work is focusing on the characterization of composites materials by solid-state nuclear magnetic resonance (NMR). The solid-state NMR measurements were used to observe both polymer matrix (through carbon-13 and hydrogen nuclei) and the clay (silicon-29 and aluminum-27). The polymer matrix analyses were carried out applying solid state techniques, such as: cross-polarization magic angle spinning (CPMAS), variable contact time (VCT) and by the proton spin-lattice relaxation time in the rotating frame parameter (T1ρH), detected from the resolved carbon-13 decay of the VCT experiment and through the determination of spin-lattice relaxation time, T1H (using low field NMR). The clay was analyzed by 29Si and 27Al, employing MAS NMR technique. From those techniques we can have principally response on clay dispersion in the polyethylene matrix, as well as the interactions between both components in the nanostructured material. The T1H response was an important result which showed, that the materials formed, presented different molecular domains (according to the domain size that varied from 25 to 50 nm, measured by relaxation), considering the clay dispersion mode in terms of intercalation and/or exfoliation in the polymer matrix.
Highlights
Polymeric composites are class of materials that employ a mixing of polymer and fibers or inorganic compounds
The polymer matrix analyses were carried out applying solid state techniques, such as: cross-polarization magic angle spinning (CPMAS), variable contact time (VCT) and by the proton spin-lattice relaxation time in the rotating frame parameter (T1ρH), detected from the resolved carbon-13 decay of the VCT experiment and through the determination of spin-lattice relaxation time, T1H
For its composites the profile decay changed to similar behavior of amorphous material, which is attributed to montmorillonite clay (MN) incorporation in the polymer matrix due to the changes promoted in the molecular organization, which gives us the first indication of some interaction between both composite components
Summary
Polymeric composites are class of materials that employ a mixing of polymer and fibers or inorganic compounds. Size and form of inorganic filler incorporated in the polymeric matrix, polymer composites possess particular properties, i.e., polymeric nanocomposite. The polymeric nanocomposite morphologies are a consequence of the formed nanostructure, which influences directly the final properties of these materials that are depended on the dispersion mode of the inorganic nanoparticle in the matrix [1,2,3,4,5,6]. More recently solid-state nuclear magnetic resonance has been employed, with success, to better understand the nanostructure formed in the polymeric nanocomposite [7,8,9,10,11,12]. The success comes to the fact that solid-state NMR spectroscopy allows obtaining information on chemical molecular structure; components interaction and filler homogeneity dispersion at molecular level [7,8,9,10,11,12,13,14,15,16]
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