A novel blend material to improve the crystallization and mechanical properties of poly (ethylene terephthalate)

To resolve the problems of phase separation in the process of toughness improvement for poly (ethylene terephthalate) (PET) by blending rubber phase, referencing the technology of interpenetrating polymer network (IPN) hindering phase separation, here a solution of phase separation restraining was developed in the process of adding thermoplastic polyester-ether elastomer (TPEE) to improve the toughness of PET by using nucleation agent bicyclo[2.2.1]heptane-2,3-dicarboxylic acid disodium salt (HPN-68 L) to enhance greatly gelation temperature to hinder the melt movement under the high temperature. It was found that TPEE and HPN-68 L could improve the crystallization rate and toughness of PET at the same time. The long period of PET increased after adding HPN-68 L and TPEE, while the crystal form of PET had a negligible effect. In addition, the spherulites arranged more closely and the size was more uniform after adding the nucleator HPN-68 L into PET/TPEE blends. In mechanical properties testing, with increasing the TPEE content, the flexural strength and flexural modulus of PET/TPEE/HPN-68 L blends were decreased, but the toughness of the blends was greatly improved. Especially, no distinct phase separation was observed and the tissue morphology of the blends was very uniform.