First normal stress difference in capillary extrusion flow of nanometer calcium carbonate‐filled PLLA biocomposites |
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| Authors: | Ji‐Zhao Liang |
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| Affiliation: | 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 (?f) as test temperature was constant. When the shear stress was fixed, the N1 reached a minimum value for ?f = 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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