초록
Various poly(ethylene terephthalate) (PET) samples were prepared from two conventional polycondensation processes using dimethyl terephthalate(DMT) and terephthalic acid(TPA) together with ethylene glycol (EG) in the absence of catalyst. Cyclic oligomeric components in the PET samples as made were extracted by using dissolution/precipitation method. The effect of polymerization conditions and the presence of cyclic oligomer on the crystallization behavior of PET was investigated under dynamic cooling conditions. Non-iso-thermal crystallization processes were carried out by differential scanning calorimetry(DSC) . All the data from DSC were calculated by Ozawa's equation In conclusion, the absence of cyclic oligomer in PET gives lower values of Avrami exponent n. n value does not give any noticeable change with the increase of diethylene glycol(DEG) content. However, PET sample prepared from DMT process showed considerably low n value of 1.0∼0.9.