The isothermal crystallization exotherm was determined at three temperatures for two blends of bottle regrind Poly(ethylene terephthalate) (PET) with Cellulose Acetate (CA) as derived by an extrusion process, as well as for the pristine PET. It was observed that the addition of 10 weight-percent CA increased the crystallization rate of PET manifold, which resulted in improved moldability with faster cycle times. The crystallization was observed to be very fast with initiation times of the order of a few seconds, perhaps due to the impurities present in the bottle regrind PET and the synergistic effects of the CA particles. The fast rate of crystallization and high melting point of PET (250 degreesC), and the degradation of CA at temperatures higher than 260 degreesC made extrusion of PET - CA blends difficult. However, increasing the CA content in the blend to 30% decreased the rate of crystallization of PET resulting in an improved extrusion process, but slower cycle times.