In this study, we investigated the crystallization behavior and the relationship between the fiber orientation and physical properties as a function of specimen molding method such as compression and injection molding when nickel-coated carbon fiber (Ni-CF) was applied to nylon66/carbon filler composite. Carbon black (CB) and multi-walled carbon nanotubes (MWCNT) were used as the carbon fillers, and the nylon66/CB/CNT/Ni-CF composites were extruded at a die temperature of 280 ℃ and a screw speed of 150 rpm in a twin screw extruder. Compared with pure nylon 66, the crystallization temperature of the composite increased and the crystal size decreased. The results can be interpreted as a result of the carbon filler acting as a heterogeneous nucleating agent, resulting in the formation of many small crystals compared to nylon 66. In the case of injection molded specimens, the fibers were oriented in the direction of injection, which is advantageous to the shielding of the reflection, and the electromagnetic shielding performance and mechanical properties were increased. However, the surface resistance value was rather increased and the electrical characteristic was decreased because the electrical networking in the vertical direction of the flow is decreased.

본 연구에서는 나일론66/탄소필러 복합체에 니켈이 코팅된 탄소섬유(Ni-CF)가 적용될 때 나일론의 결정화 거동을 고찰하고 시편 성형방법(압축, 사출성형)에 따른 섬유 배향과 물성과의 상관관계를 분석하였다. 탄소 필러로는 카본블랙(CB), 다중벽탄소나노튜브(MWCNT)를 사용하였으며, 나일론66/CB/CNT/Ni-CF 복합체를 온도 280 ℃, 스크류속도 150 rpm 조건 이축압출기(twin screw extruder)에서 제조하였다. 순수 나일론66에 비해 복합체의 결정화 온도는 증가하였고 결정크기는 감소하였는데, 이는 탄소필러가 불균일 핵제로 작용하여 나일론66에 비해 다수의 작은 결정이 생성된 결과로 해석할 수 있다. 사출성형 시편의 경우 사출방향으로 섬유가 배향되어 반사차폐에 유리하여 전자파차폐 성능과 기계적 물성은 증가하였지만 흐름의 수직방향으로의 전기적 네트워킹이 감소하여 표면저항 값은 오히려 증가하여 전기적 특성이 감소하는 경향을 나타내었다.

Keywords: nylon66, compression, injection, fiber orientation, crystallization