The effects of two-step reactive processing on the properties of recycled poly(ethylene terephthalate)

A simple approach for preparing recycled poly(ethylene terephthalate) (r-PET) with excellent processability and melt strength has been developed in this research. To increase the intrinsic viscosity of r-PET, a two-step chain extension process using a combination of SAG-008 and tetraglycidyl-4,4'-diaminodiphenylmethane (TGDDM) was investigated. To evaluate the chain extension degree of the modified r-PET, its intrinsic viscosity (IV) and rheological properties were characterized, and found to be correlated to the long-chain branches and molecular weight. The results indicated that the combination of SAG-008 and TGDDM at the optimized conditions provided the highest IV of 1.18 dl/g while controlling the gel formation to a low value. The increases in storage modulus, loss modulus and complex viscosity revealed the enhancement of melt strength and viscoelasticity of r-PET. The differential scanning calorimetry results showed that the crystallinity was reduced with the addition of chain extenders. On the other hand, stepwise annealing method from room temperature to crystal melting temperature promoted the crystallization, which was confirmed by wide-angle X-ray diffraction measurement.