Document Type


Date of Award

Spring 5-31-1998

Degree Name

Master of Science in Chemical Engineering - (M.S.)


Chemical Engineering, Chemistry and Environmental Science

First Advisor

Marino Xanthos

Second Advisor

Ulku Yilmazer

Third Advisor

Piero M. Armenante


Intrinsic viscosity (IV) has often been misused for estimating both melt viscosity and elasticity of poly(ethylene terephthalate) (PET). A rheological study was conducted to determine the variations between a virgin unmodified PET and a recycled and chemically modified PET, both having a reported nominal IV of 0.95.

The modified material had a larger melt viscosity (capillary and dynamic) than the virgin material (by an average of 61%). The extrudate swell, a better indicator of melt elasticity, of the modified was more than 110% greater than that of the unmodified material. Activation energies for melt viscosity and extrudate swell were found to be approximately 20 KJ/mol and 3 kJ/mol respectively, for the unmodified material at high shear rates. The melt viscosity for both materials was found to be best fitted by the Cross Model using a least-squares fit.