Abstract
Highly controlled polymers and nanostructures are increasingly translated from the lab to the industry. Together with the industrialization of complex systems from renewable sources, a paradigm change in the processing of plastics and rubbers is underway, requiring a new generation of analytical tools. Here, we present the recent developments in time domain NMR (TD-NMR), starting with an introduction of the methods. Several examples illustrate the new take on traditional issues like the measurement of crosslink density in vulcanized rubber or the monitoring of crystallization kinetics, as well as the unique information that can be extracted from multiphase, nanophase and composite materials. Generally, TD-NMR is capable of determining structural parameters that are in agreement with other techniques and with the final macroscopic properties of industrial interest, as well as reveal details on the local homogeneity that are difficult to obtain otherwise. Considering its moderate technical and space requirements of performing, TD-NMR is a good candidate for assisting product and process development in several applications throughout the rubber, plastics, composites and adhesives industry.
Highlights
Nowadays, polymers are of major practical importance, since they have low cost and show unique physical properties, such as viscoelasticity, toughness, and ability to form either glasses, semi-crystalline or elastic materials, that scale with minimal variation of either chemistry, and molecular weight [1]
We focus just on 1 H, and we would like to highlight the main applications of pulse sequences that can be conducted on low-field nuclear magnetic resonance (NMR)
The stronger is the interaction, the more restricted is the degree of swelling, because of the topological restrictions imposed at the filler interface, while there is no significant change in the crosslink density measured through low-field NMR and the deviation from the masterline is higher
Summary
Polymers are of major practical importance, since they have low cost and show unique physical properties, such as viscoelasticity, toughness, and ability to form either glasses, semi-crystalline or elastic materials, that scale with minimal variation of either chemistry, and molecular weight [1]. Though 1H LF‐TD‐NMR doesfrom not provide chemicalofinformation, sincerestoration after Fourier This information can be drawn the relaxation of transform a spin thermal chemical shift dispersion is extremely limited and basically all the protons contribute to a single equilibrium state with the lattice in an external static magnetic field, following a perturbation through resonance, it has been proved to be useful to study the dynamical properties of polymer chains. Referring to Equation (1), the analysis of the dispersion curve of T1 vs ω0 (Larmor frequency, that is the frequency associated with the precession of the spin caused by the magnetic field) allows to distinguish different correlation times, which define different dynamics inside the polymeric material [9] This can be useful to perform “molecular rheology” experiments. Preliminary studies have been made to assess the physical properties of these new materials
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