Dielectric spectroscopy during extrusion processing of polymer nanocomposites: a high throughput processing/characterization method to measure layered silicate content and exfoliation

Dielectric spectroscopy was conducted during extrusion processing of polyamide-6 (PA6) and layered silicate/polyamide-6 nanocomposites. Dielectric dispersion parameters were identified that appear sensitive to layered silicate concentration and degree of exfoliation. Specific to measuring layered silicate concentration is that the Maxwell-Wagner strength of dispersion, Deltaepsilon(mw) increases linearly with the % mass fraction layered silicate content. This relationship is independent of exfoliation resulting in nanomorphology-averaged Aepsilon(mw) values that reflect layered silicate concentration; i.e. 12,800 +/- 519 indicates 1.29% mass fraction of a layered silicate in PA6. The nanomorphology is primarily reflected in the Maxwell-Wagner characteristic relaxation frequency value, f(mw), where, for example, 80.4 +/- 5 Hz indicates a mixed intercalated/exfoliated nanomorphology. However, following the nanomorphology with thefts value can in some cases be complicated because different nanomorphologies can yield the same f(mw) value. In these cases we have found that there is a significant difference in the conductive resistance and segmental mobility of these polymers, as indicated by the sigma(DC) and f(alpha) values. For example, the intercalated and exfoliated nanocomposites have a f(mw) value of about 5.1 Hz, but the exfoliated nanocomposites have sigma(Dc) and f(alpha) values that are much larger than determined for the intercalated nanocomposites. (C) 2004 Elsevier Ltd. All rights reserved.