NMR Measurements Related to Clay-Dispersion Quality and Organic-Modifier Stability in Nylon-6/Clay Nanocomposites
David L. VanderHart, A Asano, Jeffrey W. Gilman
Solid state NMR measurements have been made on pure nylon-6 as well as 4 nylon-6/clay nanocomposites containing paramagnetic clays. The paramagnetic character of the clay shortens proton longitudinal relaxation times, T1H, owing to the non-stoichiometric Fe content of the clays. It is shown that for a given clay with a given Fe content and nanocomposites with the same overall polymer/clay stoichiometry, the same thermal history and the same level of dryness, one can use T1H to rank the quality of clay dispersion. Also, in order to compatibilize the clay for blending with the nylon-6, one uses an organic modifier (OM), often in the form of a tetrasubstituted ammonium ion. It is shown that proton NMR can be used to identify non-volatile products of chemical degradation of certain OM's. Interestingly, the extent of degradation is strongly correlated with the quality of dispersion. In other words, once the OM is exposed to the polymer during blending, serious chemical degradation ensues. Hence, the implication is that more stable OM's must be found. This stability must be stability under shearing forces as well as thermal stability.
, Asano, A.
and Gilman, J.
NMR Measurements Related to Clay-Dispersion Quality and Organic-Modifier Stability in Nylon-6/Clay Nanocomposites, Macromolecules, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=851822
(Accessed June 1, 2023)