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Using the flotation of a single sphere to measure and model capillary forces
1Entegris, Inc., 3500 Lyman Boulevard, Chaska, Minnesota 55318, USA. chuck_extrand@entegris.com
Langmuir : the ACS Journal of Surfaces and Colloids
|April 3, 2009
Summary
Capillary forces help small polymer spheres float in liquids. Water suspended larger spheres than formamide or ethylene glycol due to surface tension and lyophobicity, with polycarbonate spheres floating larger than poly(tetrafluoroethylene) ones.
Area of Science:
- Physical chemistry
- Materials science
- Fluid dynamics
Background:
- Capillary forces play a critical role in the behavior of small particles at liquid interfaces.
- Understanding these forces is essential for applications involving particle suspension and manipulation.
Purpose of the Study:
- To investigate the influence of capillary forces on the flotation of small polymer spheres in different liquids.
- To determine the maximum flotation diameters for poly(tetrafluoroethylene) (PTFE) and polycarbonate (PC) spheres in water, formamide, and ethylene glycol.
Main Methods:
- Experimental observation of polymer sphere flotation in various liquid media.
- Systematic variation of sphere material (PTFE, PC) and liquid properties (surface tension, lyophobicity).
- Estimation of maximum flotation diameters using iterative and closed-form analytical methods.
Main Results:
- Capillary forces significantly contribute to the buoyancy of polymer spheres.
- Water suspended larger spheres than formamide or ethylene glycol due to higher surface tension and lyophobicity.
- Polycarbonate spheres (up to 10 mm) floated at larger diameters than PTFE spheres (up to 5 mm) in water, attributed to a smaller density difference.
Conclusions:
- The study quantifies the effect of capillary forces on polymer sphere flotation.
- Lyophobicity and surface tension are key factors determining flotation limits.
- Analytical models provide reasonable estimations for maximum flotation diameters.
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