Positron lifetime, magnetometry, tensile strength, and thermo mechanical measurements are used to study 1-5% nanoclay incorporated aromatic and aliphatic polyurea films. The third lifetime component related to positronium lifetime in these samples, which is related to free volume in polymer, shows a clear difference between aromatic and aliphatic polyurea films with more porosity for aromatic. Adding nanoclay did not bring significant change for aromatic polyurea, but nanoclay addition in aliphatic polyurea showed a difference in positron parameters indicating a structural change.Magnetic curves showed mostly diamagnetic with a small ferromagnetic component for all polyurea samples.  The ferromagnetic component is higher for aliphatic and nanoclay showed a drastic change in aliphatic compared to aromatic polyurea. The ferromagnetic component saturation magnetization (Ms) showed 61% decrease in aliphatic polyurea due to nanoclay while aromatic polyurea showed only 49% decrease; and the magnetic coercivity (Hc) showed 300% increase in aliphatic compared to 40% increase in aromatic films.  This suggests a strong interaction of nanoclay with aliphatic chains compared to aromatic chains. This may explain the corresponding changes in    the tensile strength observed for these aliphatic and aromatic polyurea films with and without nanoclay. The strength at break point is increased by 57% in aliphatic polyurea by introducing nanoclay, while aromatic polyurea showed only 14% increase.Thermo-mechanical analysis was performed on aliphatic polyurea with 1-5% nanoclay using a penetration probe at a constant pressure of 0.2 N and the surface displacement was obtained over a temperature range of 20oC to 250oC. Thermo-mechanical analysis showed systematic decrease in the glass transition temperature at around 63 �C with increasing wt% nanoclay in the aliphatic polyurea-nanoclay composites.

Physical properties of aliphatic and aromatic polyurea-nanoclay composites

241st National Meeting (2011)

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