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First normal stress difference in capillary extrusion flow of nanometer calcium carbonate‐filled PLLA biocomposites
Author(s) -
Liang JiZhao
Publication year - 2013
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.23435
Subject(s) - materials science , composite material , extrusion , rheometer , shear rate , calcium carbonate , shear stress , capillary action , composite number , nanometre , mass fraction , plastics extrusion , shear (geology) , viscosity , rheology
The nanometer calcium carbonate (nano‐CaCO 3 )‐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 10 3 s −1 . The first normal stress difference ( N 1 ) increased roughly linearly with increasing shear stress (τ w ). The sensitivity of the N 1 to τ w increased with an increase of the die length–‐diameter ratio, and the N 1 value varied slightly with the filler weight fraction (ϕ f ) as test temperature was constant. When the shear stress was fixed, the N 1 reached a minimum value for ϕ f = 1%. The values of the N 1 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