Effect of chitosan molecular weight on rheological behaviour of chitosan modified nanoclay in highly hydrated states

L. Liu, S. Liang, L. Chen, P. Yuan, Q. Huang, K. L. Yam

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

Effect of chitosan molecular weight (Mcs) on the rheological properties of chitosan-modified clay (CMCs) at highly hydrated state was investigated. With special emphasis on its effect on the thixotropy of CMCs, the structure recovery at rest after underwent a pre-shearing process was further performed by the oscillatory shear measurements in the linear viscoelastic region. It was observed that both stress-strain behaviour and moduli of CMCs are closely correlated to Mcs. An interesting slope transition from negative to positive in the tan δ versus lg ω plot is observed at ω = 2.5 rad/s. The value of tan δ<0.5 over the entire range of frequency suggests a strong association in CMCs and a dominant elastic response of CMCs. Small peak-like transition of the shear viscosity, which denotes the yield region of the CMCs network, shifts to high shear rate with the increase of Mcs. Remarkably different thixotropic behaviour of these considered CMCs are observed relating to Mcs. G′After of CMCs with high Mcs shows a linearly monotonic increase with the increase of the testing time, which well matches the power law of G′ After ∼ tn. G′After of those CMCs with low Mcs, however, is distinctly deviated from the power law and possesses an exponential increase. The deviation of G′After becomes more marked with the decrease of Mcs. Furthermore, the effect of the pre-shearing history on the thixotropic properties of CMCs is performed by employing a large range of the pre-shear rate. Analysis of the empirical Cox-Merz rule indicates a failure of the rule in CMCs system. CMCs prepared from low Mcs. chitosan are easier to be orientated at low shear rate.

Original languageEnglish (US)
Pages (from-to)247-261
Number of pages15
JournalJournal of the Balkan Tribological Association
Volume17
Issue number2
StatePublished - 2011

All Science Journal Classification (ASJC) codes

  • Mechanics of Materials
  • Surfaces, Coatings and Films

Keywords

  • Chitosan
  • Clay
  • Hydrated state
  • Molecular weight
  • Rheological behaviour

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