1998 Fiscal Year Final Research Report Summary
Rheology Control of Colloidal Suspensions
| Project/Area Number |
09650821
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
化学工学一般
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| Research Institution | Chiba University |
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Principal Investigator |
OTSUBO Yasufumi Chiba University.Faculty of Engineering, Associate Professor, 工学部, 助教授 (10125510)
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| Project Period (FY) |
1997 – 1998
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| Keywords | Colloidal suspensions / Rheology / Shear-thinning flow / Shear-thickening flow / Bridging flocculation / Polymer adsorption |
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| Research Abstract |
The study is designed to provide a new technique of rheology control, in which the viscosity level and flow pattern of suspensions can be independently modified. Ordinary flocculated suspensions are generally shear-thinning over a wide range of shear rates, because the flocculated structure is progressively broken down with increasing shear rate. The shear- thinning profile is due to the nature of colloidal interactions, which lead to hard and fragile particle-particle bonds. For rheology control, a new type of interparticle interactions must be developed and hence the polymer bridging mechanism is introduced. Since a polymer chain may attach to the surface at several points and not be able to desorb simultaneously from all site, the polymer bridging is essentially irreversible, When the polymer chains do not have very strong affinity for the particle surface, a flexible bridge between particles is made by reversible adsorption. Since the polymer bridges are forming and breaking in a quiescent state, the suspensions flocculated by reversible bridging are Newtonian at low shear rates. The suspensions which are flocculated by polymer coils with comparable size to particles show shear-thickening flow in high shear fields. The force generated by rapid extension of bridges within the lifetime is responsible for the shear thickening. The nonlinear viscoelastic model with a single relaxation time is proposed to quantitatively describe the shear-thickening flow. The model prediction reasonably agrees with the experimental data. The shear-thickening flow is attributed to entropy elasticity of flexible bridges. The flow profiles of suspensions flocculated by polymer bridging are controlled by changing the adsorption affinity of polymers. The reversible bridging has great potential in controlling the rheology of colloidal suspensions.
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Research Products
(8 results)
