KOSEN 한인과학기술자네트워크

>폴리에스터 제품 두개를 DSC 분석하였는데 >하나는 HOMO-PET이고, 다른 하나는 CO-PET의 특성을 나타낸다고 합니다. > > >CO-PET는 어떤걸 말하는건가요? >구체적으로 설명해주세요, 예를 들어서 설명해주셔도 되구요. >copolymer라는 말 같은데... > >그리고, CO-PET가 HOMO-PET랑 다른점도 설명 해주세요. > homo-pet는 순수 pet로 보통 terephthalic acid와 ethylene glycol을 축중합하여 만듭니다. 구조를 보시면 아시겠지만 어느 정도의 결정성이 있습니다. co pet는 terephthalic acid와 ethylene glycol 중 terephtalic acid 나 ethylene glycol 대신 다른 물질 isophthalic acid 나 cyclohexane dimethanol 등을 일부 사용하여 중합시킬때 생성된 고분자를 말하는 것 같습니다. 장점으로는 isophthalic acid 나 cyclohexane dimethanol 등 구조를 보시면 아시겠지만 곁가지 있어 폴리머 사이사이 패킹 즉 결정성이 순수 pet 보다 떨어집니다. 즉 melting point 나 Tg(glass transition temperature)가 낮아져서 낮은 온도에서 가공 및 성형이 유리하게 됩니다. 경우에 따라 결정성 있는 모노머를 사용할 경우 결정성이 증가해 tg 및 melting point가 증가 될수 도 있겠죠 Wikipedia 자료 In addition to pure (homopolymer) PET, PET modified by copolymerization is also available. In some cases, the modified properties of copolymer are more desirable for a particular application. For example, cyclohexane dimethanol (CHDM) can be added to the polymer backbone in place of ethylene glycol. Since this building block is much larger (6 additional carbon atoms) than the ethylene glycol unit it replaces, it does not fit in with the neighbouring chains the way an ethylene glycol unit would. This interferes with crystallization and lowers the polymer's melting temperature. Such PET is generally known as PETG (Eastman Chemical and SK Chemicals are the only two manufacturers). PETG is a clear amorphous thermoplastic that can be injection molded or sheet extruded. It can be colored during processing. Replacing terephthalic acid (right) with isophthalic acid (center) creates a kink in the PET chain, interfering with crystallization and lowering the polymer's melting point.Another common modifier is isophthalic acid, replacing some of the 1,4-(para-) linked terephthalate units. The 1,2-(ortho-) or 1,3-(meta-) linkage produces an angle in the chain, which also disturbs crystallinity. Such copolymers are advantageous for certain molding applications, such as thermoforming, which is used for example to make tray or blister packagings from PETG film, or PETG sheet. On the other hand, crystallization is important in other applications where mechanical and dimensional stability are important, such as seat belts. For PET bottles, the use of small amounts of CHDM or other comonomers can be useful: if only small amounts of comonomers are used, crystallization is slowed but not prevented entirely. As a result, bottles are obtainable via stretch blow molding ("SBM"), which are both clear and crystalline enough to be an adequate barrier to aromas and even gases, such as carbon dioxide in carbonated beverages.