Non-isothermal cold crystallization kinetics of poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate) (PETG) copolyesters with different compositions

In this work, the non-isothermal crystallization kinetics of poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate) (PETG) random copolyesters with different compositions was first investigated from the glassy state. Regardless of the composition, the value of the Avrami exponent determined from Jeziorny theory was 2.1-2.4, depending on the heating rate, whereas the value of α (the ratio of the Avrami exponent to the Ozawa exponent) obtained from Mo's method was 1.3-1.6, depending on the relative crystallinity. These results indicated that the nucleation and growth mechanism of the PETG copolyesters were apparently identical to those of the poly(ethylene terephthalate) (PET) homopolymer. However, the cold crystallization rate was accelerated by increasing the heating rate, but retarded by incorporating the 1,4-cyclohexanedimethanol (CHDM) unit into the polymer backbone. Based on the crystallization rate coefficient (CRC) and the crystallization rate parameter (CRP) approaches, the cold crystallization rate was in the following order: PET > PETG(30/70) > PETG(85/15) > PETG(50/50) > PETG(70/30).