Wednesday, 13 October 2004 - 2:40 PM

This presentation is part of : Mechanics and Thermodynamics of Polymers

Fragility of PETg-montmorillonite layered silicate nanocomposites

Ajit Ranade1, Allison Saiter2, Jean-Marc Saiter2, and Nandika Dsouza1. (1) University of North Texas, Department of Materials Science and Engineering, Denton, TX 76203, (2) Université de Rouen, LECAP, UMR6522 BPM, Institut des matériaux, 12 avenue de l'Université, Saint etienne du rouvray, 76420, France

Amorphous PETG and PETG nanocomposites were analyzed to study the sub Tg relaxation and dynamic fragilities. PETG nanocomposites were prepared on a twin screw extruder with varying concentration (1%, 2%, 3% and 5% by weight) of montmorillonite layered silicates (MLS). The effect of MLS on the chain dynamics was analyzed. A small depression in Tg was observed with increase in MLS content. The drop in glass transition was related to pressure effect exerted by stiff inorganic platelets on soft PETG chains. Calorimetric technique (DSC) was used to evaluate the values of DCp(Tg)i.e. the heat capacity variations at Tg, fragility index (m), and activation energy Dh. The fragility index dropped with increase in MLS concentration up to 2% then decreases and finally is found identical to pure PETG for greater compositions. A constant value of heat capacity variations at Tg was observed for all the samples. Viscosity measurements were done to determine the entropic non-linearity parameter. The high pressure effect of MLS platelets was also observed in x-ray diffraction (XRD). Diffraction analysis showed high orientation of MLS in PETG-MLS nanocomposites.

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