First normal stress difference in capillary extrusion flow of nanometer calcium carbonate-filled PLLA biocomposites

Authors

  • Ji-Zhao Liang

    Corresponding author
    1. Research Division of Green Function Materials and Equipment, School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640, People's Republic of China
    • Research Division of Green Function Materials and Equipment, School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640, People's Republic of China
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Abstract

The nanometer calcium carbonate (nano-CaCO3)-filled poly-L-lactide (PLLA) biocomposites were prepared using a twin-screw extruder. The first normal stress difference of the composites were measured by means of a capillary rheometer under experimental conditions with temperatures ranging from 170 to 200°C and shear rates varying from 50 to 103 s−1. The first normal stress difference (N1) increased roughly linearly with increasing shear stress (τw). The sensitivity of the N1 to τw increased with an increase of the die length–-diameter ratio, and the N1 value varied slightly with the filler weight fraction (ϕf) as test temperature was constant. When the shear stress was fixed, the N1 reached a minimum value for ϕf = 1%. The values of the N1 of the composite melts decreased roughly linearly with a rise of temperature when the shear rate was constant. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers

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