Article
  • Engineering Analysis of PET in Injection Molding Process
  • Cho HM, Lee KH, Jin BS
  • PET 사출성형공정의 공학적 해석
  • 조형민, 이광희, 진병석
Abstract
Nonisothermal crystallization rate of PET was derived by using the data obtained from the DSC. The profile changes of temperature and crystallinity in the mold with the injection temperature, mold temperature and specimen thickness were calculated through the computer simulation. To verify the propriety of this computer simulation, the calculated values were compared with the data of crystallinity measured experimentally with the injection molded specimen. For neat PET, the profiles of temperature and crystallinity within the specimen were relatively uniform, but cooling time more than 5 min was required due to slow crystallization rate. On the other hand, for the nucleated PET, the crystallization was completed in 3 min, but considerable change in the temperature and crystallinity with the position of specimen was observed. As the mold temperature or specimen thickness was increased, the crystallization at the center position of mold was delayed due to the decreased cooling effect. Especially, the effect of specimen thickness on crystallization was found to be more significant. The variation in morphology with injection molding condition had an effect on the mechanical property of specimen. The injection molded specimen at higher temperature showed lower impact strength because of the relatively larger spherulites.

본 연구에서는 DSC를 이용하여 PET의 비등온결정화 속도를 구하고, 컴퓨터 모사를 통하여 사출온도, 금형온도, 시편두께 등의 사출성형조건에 따른 금형 내에서의 온도구배와 결정화도의 변화를 계산하였다. 계산된 결과는 실제 사출시편의 부위별 결정화도 측정 결과와 비교함으로써 컴퓨터 모사의 타당성을 입증하였다. 핵제를 첨가하지 않은 PET의 경우에는 시간에 따른 시편 내의 온도 및 결정화도 구배가 비교적 균일하였으나 느린 결정화속도로 인하여 5분 이상의 냉각시간이 필요하였다. 반면에 핵제가 첨가된 PET의 경우에는 3분 이내에 결정화가 종결되었으나 시편의 위치에 따른 온도 및 결정화도의 변화에는 큰 차이를 보여 주었다. 금형온도나 시편두께의 증가는 냉각효과의 저하를 가져오기 때문에 중심부에서의 결정화를 느리게 하였으며, 특히 시편두께의 영향이 현저하게 나타났다. 사출성형조건에 따른 몰폴로지 차이는 시편의 기계적 물성에 영향을 주는데, 높은 금형온도에서 제조된 시편의 경우 구정이 상대적으로 크게 성장하여 낮은 충격강도를 보여 주었다.

Keywords: nonisothermal crystallization; PET; nucleating agent; computer; simulation; injection molding

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  • Polymer(Korea) 폴리머
  • Frequency : Bimonthly(odd)
    ISSN 0379-153X(Print)
    ISSN 2234-8077(Online)
    Abbr. Polym. Korea
  • 2022 Impact Factor : 0.4
  • Indexed in SCIE

This Article

  • 1996; 20(5): 893-901

    Published online Sep 25, 1996