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The surfactant effect on electrorheological performance and colloidal stability
Hanqi Xu1, Jinbo Wu2, Yaying Hong3
1Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China. phwen@ust.hk.
Soft Matter
|July 14, 2021
Summary
Adding Span surfactants to barium titanyl oxalate (BTRU) suspensions optimizes electrorheological (ER) properties and colloidal stability. An optimal ER fluid with 0.4 wt% Span 85 demonstrates remarkable integrated performance.
Area of Science:
- Materials Science
- Colloid and Surface Chemistry
- Rheology
Background:
- Electrorheological (ER) fluids offer tunable viscosity under electric fields.
- Nonionic surfactants can modify ER fluid performance and colloidal stability.
- Urea-coated barium titanyl oxalate (BTRU) is a potential ER material.
Purpose of the Study:
- Investigate the impact of Span 20 and Span 85 on the electrorheological response of BTRU/silicone oil suspensions.
- Quantify the effect of surfactants on ER performance (yield stress, current density) and colloidal stability (TSI, sedimentation).
- Examine surfactant influence on particle-oil interactions and particle agglomeration.
Main Methods:
- Preparation of BTRU/silicone oil suspensions with varying Span surfactant concentrations.
- Measurement of electrorheological properties: yield stress and current density.
- Assessment of colloidal stability: Turbiscan stability index (TSI) and visual sedimentation observation.
- Characterization of particle-oil interactions via silicone oil permeability.
- Analysis of particle cluster size in the dispersing medium.
Main Results:
- Yield stress showed a local maximum at optimal Span concentrations, attributed to electrostatic interactions and steric hindrance.
- Surfactant addition improved particle agglomeration, enhancing colloidal stability.
- An optimal ER fluid was developed with 0.4 wt% Span 85, exhibiting superior integrated ER properties and stability.
Conclusions:
- Span surfactants significantly influence both the electrorheological response and colloidal stability of BTRU suspensions.
- An optimal balance between ER performance and suspension stability can be achieved through careful surfactant selection and concentration.
- The addition of 0.4 wt% Span 85 provides a promising formulation for advanced ER fluid applications.
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