• A Study on the PTC Thermistor Characteristics of Polyethylene and Polyethylene Copolymer Composite Systems in Melt and Solution Manufacturing Method
  • Kim JC, Park GH, Nam JD
  • 용액 및 용융 가공방법에 따른 PE 및 PE 공중합물의 PTC 서미스터 특성 연구
  • 김재철, 박기헌, 남재도
Abstract
The positive temperature coefficient (PTC) characteristics of polymer composites were investigated with the nano-sized carbon black particles using solution casting and melt compounding methods. The polymeric PTC composites showed the electrical threshold at 35 wt% for the melt compounding method and 40 wt% for the solution casting method. The ethylene vinylacetate copolymer (EVA) composite showed a gradual increase of resistance as a function of temperature and showed a maximum at the polymer melting point. The resistance of the high-density polyethylene (HDPE) composite remains unchanged with temperature but started to increase sharply near the melting point of HDPE and showed a maximum resistance at the melting point of HDPE. The dispersion of nano-sized carbon black particles was investigated by scanning electron microscopy (SEM) and low rsistance after electrical threshold, and both methods exhibited a well dispersed morphology. When the electric current was applied to the PTC composites, the resistance started increasing at the curie temperature and further increased until the trip temperature was reached. Then the resistance remained stable over the trip temperature. The secondary increase started at Tm of matrix polymer and kept increasing up to the trip temperature.

본 연구에서는 나노입자인 카본블랙을 고분자에 분산시킨 복합체를 각각 용액혼합과 용융혼합을 이용하여 positive temperature coefficient (PTC) 특성을 연구하였다. 전도성 나노입자인 카본블랙과 고분자 복합체의 저항 통전 (threshold)은 용융혼합하였을 때 카본블랙의 함량이 35 wt% 이상에서 나타났으며, 용액혼합에서는 카본블랙 함량이 40 wt% 이상에서 나타났다. Ethylene vinylacetate copolymer (EVA)의 경우, 온도의 변화에 따라서 저항이 서서히 증가하다가 용융점 근처에서 극대값을 나타내었지만, high density polyethylene (HDPE)의 경우는 저항이 온도의 변화에 따라 일정하다가 용융점 근처에서 증가하기 시작하여 용융점에서 극대값을 나타내었다. 통전 후의 낮은 저항과, scanning electron microscopy (SEM)으로 관찰한 결과로부터 전도성 나노입자의 카본블랙 분산방법에서 용액혼합의 분산 정도가 용융혼합 못지않게 나타났다. PTC 소재에 전류인가시 큐리온도에서 1차적으로 저항이 증가하였으며, 고분자의 용융점에서 2차적으로 트립온도가 될 때까지 저항이 증가하다가 트립온도 이후에는 저항이 일정하게 유지됨을 알 수 있었다.

Keywords: positive temperature coefficient (PTC); nano-sized carbon black; electrical resistance; dispersity; curie temperature

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  • Polymer(Korea) 폴리머
  • Frequency : Bimonthly(odd)
    ISSN 0379-153X(Print)
    ISSN 2234-8077(Online)
    Abbr. Polym. Korea
  • 2024 Impact Factor : 0.6
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This Article

  • 2002; 26(6): 812-820

    Published online Nov 25, 2002

  • Received on May 4, 2002
  • Accepted on Nov 12, 2002