Ice buildup on structures leads to problems that include reduced performance, structural damage and power outages. It is therefore important to limit the energy required for removal of ice from substrates to minimize buildup. Understanding the mechanism of ice adhesion and its dependence on variables like coating thickness, stiffness, surface free energy and morphology is critical for minimizing adhesion. Despite several developments in “icephobic” coatings, which are those that have low ice adhesion, it is important to understand adhesion on the fundamental level to make way for advanced coatings. To do so, a study has been carried out that explores key variables affecting ice adhesion using a commercially available silicone, Sylgard 184®. Sylgard 184 is a two-part, platinum cured silicone elastomer available from Dow Corning with good physical and chemical stability and is used in widely diverse research studies.
The thermodynamic work of ice adhesion is related to the receding contact angle θ_r of water by Equation 1.
wa≈ γ_w (1+cos θ_r) Eq 1.
where γ_w is the surface tension of water. Considering an elastomeric substrate and ice as a rigid cylindrical adherent, the Kendall modelcan be adapted to relate peak removal force (Pc) with work of adhesion (wa), modulus (K), thickness (t), and radius (a) according to Equation 2.
Pc ∝ πa^2 ((2wa K)/t)^(1⁄2) Eq. 2
Considering these relationships, hydrophobic materials with low surface energies and high receding contact angles are generally predicted to show low adhesion. To begin to understand details, the force required to remove an ice cylinder from the silicone elastomer Sylgard 184 was investigated by focusing on three variables: coating thickness, modulus and cure temperature. “Cure” refers to the network formation or crosslinking within the material.
The Wynne research group has previously established a surprising dependence of qR on Sylgard 184 cure temperature.In this thesis, the relationship among variables noted above was examined by measuring Pc for Sylgard coatings. Additionally, effects of test temperature on ice adhesion strength was studied. Surface characterization methods including ATR-IR (attenuated total reflectance infrared spectroscopy), DCA (Wilhelmy plate dynamic contact angles) and AFM (atomic force microscopy) were employed. In summary, defined processing conditions were found optimum for minimizing ice adhesion to Sylgard coatings.
| Identifer | oai:union.ndltd.org:vcu.edu/oai:scholarscompass.vcu.edu:etd-6277 |
| Date | 01 January 2017 |
| Creators | Shylaja Nair, Sithara |
| Publisher | VCU Scholars Compass |
| Source Sets | Virginia Commonwealth University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
| Rights | © The Author |
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