Maleated ethylene-propylene-diene terpolymer (MEPDM) was prepared from solution polymerization of EPDM and maleic anhydride. MEPDM-grafted-poly(dimethylsiloxane)(PDMS) copolymer (MEPDM-g-PDMS) was prepared from copolymerization of MEPDM with α,ω-hydroxyl group terminated PDMS. The MEPDM-g-PDMS was compounded with HDPE and 4-ethoxybenzoic acid modified MWCNT at 180 ℃ and positive temperature coefficient (PCT) behavior of the MWCNT composite was investigated. Surface modification of MWCNT enabled it to be more uniformly dispersed in polymer matrix and decreased aggregation of particles. Electrical resistivity of the composite was abruptly increased at melting temperature and PTC intensity of 2.3 was obtained at 15% loading of surface modified CNT.

EPDM에 maleic anhydride를 그래프트시켜 말레화 EPDM(MEPDM)을 제조하고 여기에 양 말단에 hydroxyl기를 갖는 α,ω-poly(dimethylsiloxane)(PDMS)을 반응시켜 MEPDM-g-PDMS 공중합체를 제조하였다. MEPDM-g-PDMS와 HDPE 및 4-ethoxybenzoic acid로 표면처리된 MWCNT를 internal mixer에 가하고 180 ℃에서 컴파운딩하여 MEPDM-g-PDMS/HDPE/CNT 복합체를 제조하였다. 복합체에서 CNT의 모폴로지를 전자현미경으로 측정한 결과 표면처리된 CNT를 사용한 경우가 분산이 균일하게 이루어졌으며 입자의 응집현상도 감소되는 것으로 나타났다. 온도변화에 따른 전기저항은 용융온도부근에서 전기저항이 급격히 증가하였으며 EtO-CNT의 함량을 15%로 하여 제조한 복합체의 경우가 PTC intensity가 2.3으로 가장 우수한 PTC 특성을 나타내었다.

Keywords: maleated EPDM; poly(dimethylsiloxane); CNT; positive temperature coefficient; electric resistivity