The effects of fiber concentration, shear rate and temperature on shear viscosity and die swell have been investigated for carbon fiber-filled polyvinylidene fluoride melt. The rheological properties were measured by using Instron capillary rheometer Flow curves were obtained from 210℃ to 290℃ over the cross head speed 0.2 to 20cm/min. The apparent viscosities of PVDF/carbon fiber melts decreased with an increase in temperature and increased with increasing the amount of carbon fiber. The relative viscosities at constant shear rate was increased with increasing carbon fiber content of composites and increasing temperature, and decreased with an increase in shear rate. It can be, therefore, concluded that relative viscosity was a function of temperature and shear rate as well as fiber volume fraction, as one might expect. The activation energy was found to decrease with increasing shear rate and increasing carbon fiber content of the composites. However the die swell ratio was not affected by the various medium. and the die swell ratio was decreased with increasing the amount of carbon fiber, temperature. and sheat rate.

본 연구에서는 PVDF에 탄소섬유를 충진시킨 고분자 복합재에 있어서 섬유의 농도, 전단 속도 및 온도가 전단 점성과 die 팽창에 미치는 영향을 고찰하였다. 유성학적 성질은 Instron Capillary Rheometer를 사용하여 측정하였고 flow curve는 cross head speed를 0.2에서 20cm/min으로 변화시키면서 210℃∼290℃ 온도범위에서 얻었다. PVDF/carbon fiber 복합재의 겉보기 점성도는 온도가 증가함에 따라 감소하였고 탄소섬유의 함량이 증가함에 따라 증가하였다. 일정한 전단속도하에서 상대점성도는 복합재의 탄소섬유 첨가량과 온도가 증가함에 따라 증가하고, 전단속도가 증가함에 따라 감소하였다. 상대점성도는 부피분율 뿐만 아니라 온도와 전단속도의 함수이었다. 활성화에너지는 전단속도가 증가함에 따라 감소하였고 복합재의 탄소섬유양이 증가함에 따라 감소함을 보였다. 그러나 die의 팽창비는 냉각매체에 영향을 받지 않았으며 탄소섬유의 양, 온도 및 전단속도가 증가함에 따라 감소하였다.

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