Studies on the effect of equi-biaxial stretching on the exfoliation of nanoclays in polyethylene terephthalate

TEM image analyses of PET nanocomposites were done to study the effect of equi-biaxial stretching and stretch ratio on the exfoliation and other tactoid properties. Though XRD spectra did not show any evidence of exfoliation, TEM image analysis revealed 10% exfoliation of clay platelets in the unstretched sheets. Stretching further improved the exfoliation as the concentration of thinner tactoids in the matrix increased due to stretching. Stretching also caused an increase in the concentration of longer tactoids and tactoids having higher aspect ratio, the reason for which was assumed to be due to the slippage of the platelets while stretching. It was found that stretch ratio affected the nanocomposite properties as increase in stretch ratio improved the exfoliation of clay platelets. Equi-biaxial stretching imparted preferential orientation of the tactoids in the matrix. Dynamic mechanical and barrier property measurements confirmed the observations made by the TEM image analysis.