For the modification of polyethylene terephthalate(PET) the butanediol(BD) isomers, 1,2-BD, 1,3-BD or 1,4-BD were introduced as third components. Copolyester was prepared from dimethyl terephthalate(DMT), ethylene glycol(EG) and BD by melt polycondensation method with varying the amounts of EG and BD. The chemical structure of the copolyester was confirmed and the composition of the copolyester was determined by nuclear magnetic resonance spectroscopy(NMR). Thermal properties obtained with differential scanning calorimetry(DSC) were discussed in terms of structural differences, particularly the effects of composition and chain flexibility. The melting temperature(T_m) of the copolyester was decreased with increasing mole % of BD units and correlated with Flory''s equation. The glass transition temperature(T_g) and the crtstalliaztion temperature(T_c) of the copolyester were decreased with increasing mole % of BD unit. The effects of BD units on the cold crystallization temperature(T_cc) were dependent on the structure of BD. The degree of crystallinity measured by density was decreased with increasing mole % 1,3-BD unit, while moisture regaining of the copolyester was increased with increasing, mole % of 1,3-BD unit.

PET의 개질을 위하여 DMT와 EG 이외에 제3성분으로서 부탄디움(BD), 1,2-BD, 1,3-BD 및 1,4-BD를 사용하여 용융축중합 방법에 의해 copolyester를 제조하였다. 핵자기 공명 분석에 의해 copolyester의 구조와 조성을 확인하였으며, DSC 분석에 의해 연적성질을 조사하여 구조적 차이, 특히 조성과 사슬의 유연성 에 따른 영향에 대해 고찰하였다. copolyester의 융점은 BD 단위의 함량이 증가함에 따라 감소하였으며, 이 경향은 Flory 식에 잘 부합되었다 BD 단위의 함랑이 증가함에 따라 copolyester의 유리전이온도와 결정화온도는 감소하였으나 BD단위의 함량이 copolyester의 저온결정화온도에 미치는 영향은 BD의 구조에 따라 서로 다른 경향을 보였다. 1,3-BD를 포함한 copolyester에 있어서, 결정화도는 1,3-BD 단위의 함량 증가에 따라 감소하였으며 이 결과 흡습성은 증가하였다.