TY - JOUR
T1 - Wall slip of polyolefin plastomers under oscillatory shear
AU - Li, Jingqing
AU - Wang, Lei
AU - Yu, Donghong
AU - Christiansen, Jesper de Claville
AU - Jiang, Shichun
PY - 2018/1/1
Y1 - 2018/1/1
N2 - The oscillatory shear rheological behaviors of a polyolefin plastomer (POP) at various temperatures were examined within its linear viscoelastic (LVE) regime. The apparent storage modulus, loss modulus, complex modulus, complex viscosity, and phase angle of POP at various temperatures are all found gap dependent, revealing that wall slip occurred under the applied oscillatory shear with the shear stress amplitude controlled constant. All Han plots and van Gurp-Palmen (vGP) plots of POP samples overlapped each other at various gaps at a certain temperature, suggesting that a time-gap-superposition (TGS) is valid with all the apparent angular frequency dependent storage modulus and loss modulus of POP at various gaps shifted to their master curves at a selected reference gap. This indicates that the wall slip can be understood as adding a dashpot in series to POP sample only with the apparent relaxation time multiplied by a shift factor. By TGS, a method to determine the wall slip length b and the actual oscillatory shear rheology of the fluids was consequently established. The results showed that the obtained b is dependent on temperature and wall slip made it possible to extend the experimental angular frequency range to lower frequencies. Further analysis revealed that wall slip did not influence the Arrhenius viscosity dependence of POP on temperature, while the viscous flow activation energy decreased.
AB - The oscillatory shear rheological behaviors of a polyolefin plastomer (POP) at various temperatures were examined within its linear viscoelastic (LVE) regime. The apparent storage modulus, loss modulus, complex modulus, complex viscosity, and phase angle of POP at various temperatures are all found gap dependent, revealing that wall slip occurred under the applied oscillatory shear with the shear stress amplitude controlled constant. All Han plots and van Gurp-Palmen (vGP) plots of POP samples overlapped each other at various gaps at a certain temperature, suggesting that a time-gap-superposition (TGS) is valid with all the apparent angular frequency dependent storage modulus and loss modulus of POP at various gaps shifted to their master curves at a selected reference gap. This indicates that the wall slip can be understood as adding a dashpot in series to POP sample only with the apparent relaxation time multiplied by a shift factor. By TGS, a method to determine the wall slip length b and the actual oscillatory shear rheology of the fluids was consequently established. The results showed that the obtained b is dependent on temperature and wall slip made it possible to extend the experimental angular frequency range to lower frequencies. Further analysis revealed that wall slip did not influence the Arrhenius viscosity dependence of POP on temperature, while the viscous flow activation energy decreased.
KW - Linear viscoelastic regime
KW - Oscillatory shear rheology
KW - Shift factor
KW - Time-gap-superposition
KW - Wall slip
KW - Wall slip length
UR - http://www.scopus.com/inward/record.url?scp=85049529799&partnerID=8YFLogxK
U2 - 10.3933/APPLRHEOL-28-33226
DO - 10.3933/APPLRHEOL-28-33226
M3 - Journal article
AN - SCOPUS:85049529799
SN - 1430-6395
VL - 28
JO - Applied Rheology
JF - Applied Rheology
IS - 3
M1 - 33226
ER -