Chem. J. Chinese Universities ›› 2021, Vol. 42 ›› Issue (6): 2034.doi: 10.7503/cjcu20200717

• Polymer Chemistry • Previous Articles     Next Articles

Nonlinear Rheological Behavior of Long Chain Branching Polypropylene

DU Bin, CHEN Shangtao, ZHANG Fengbo, SHI Xingbo, LI Rongbo()   

  1. PetroChina Petrochemical Research Institute,Beijing 102206,China
  • Received:2020-09-27 Online:2021-06-10 Published:2021-06-08
  • Contact: LI Rongbo E-mail:lirongbo010@petrochina.com.cn

Abstract:

The nonlinear rheological behavior of long chain branching polypropylene was investigated syste-matically with large amplitude oscillatory shear test. The results suggested that the scaling low between the relative amplitude I3/1 and the strain obtained by the Fourier transform can clearly illustrate the difference between the linear and the long chain branching polypropylene, and then the nonlinear coefficient was defined to measure the level of long chain branching. Additionally, the relationship between I3/1 and strain under high strain can further describe the characteristics of long chain branching structure in nonlinear flow field, and thus the relationship between the long chain branching structure and the nonlinear rheological response was obtained. Through the stress wave decomposition method for Lissajous plot, the difference of viscoelasticity between inter- and intra-cycle was found. The nonlinear viscoelastic response of long chain branched structure was weaker than that of linear structure under large amplitude oscillatory shear, and the higher the degree of branching, the weaker the nonlinear response.

Key words: Nonlinear rheology, Large amplitude oscillatory shear, Long chain branched polypropylene, Fourier transform rheology

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