Analysis of viscoelastic behavior and dynamic mechanical relaxation of copolyester based layered silicate nanocomposites using Havriliak-Negami model

The solid-state viscoelastic properties are examined for intercalated nanocomposites based on a copolyester and (2-ethyl-hexyl)dimethyl hydrogenated-tallow ammonium montmorillonite. The nanocomposites are prepared via the direct melt intercalation technique using a conventional twin-screw extruder. Dynamic mechanical thermal analysis of the nanocomposites is conducted using two different test setups. The dynamic mechanical relaxation spectra show an increase in the storage modulus of the nanocomposite over the entire temperature range under study as compared to the pristine polymer (except in the transition region from 70 to 80 degreesC). These results are analyzed using the empirical Havriliak-Negami (HN) equation. The four temperature independent HN parameters (alpha, beta, E-0, and E-infinity) and one temperature dependent parameter (taud, the relaxation time) are determined by solving the HN equation for each temperature over the range of temperatures. The calculated moduli results fit well with the experimental values of the relaxation spectra for the nanocomposites. This study shows that the HN model can be applied to polymer layered silicate nanocomposites, and it can be used to predict their dynamic mechanical properties over a wide range of temperatures and frequencies a priori. (C) 2004 Wiley Periodicals, Inc.