Adhesion strength and superhydrophobicity of polyurethane/organoclay nanocomposite coatings

Steele, Adam; Bayer, Ilker S.; Loth, Eric

doi:10.1002/app.36312

Cited by 78 publications

(56 citation statements)

References 26 publications

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“…Zhang et al 33 checked the easy-to-clean property and the durability of a superhydrophobic γ-alumina-coated stainless steel in a paper machine. Steele et al 34 investigated substrate adhesion for superhydrophobic coatings fabricated from polyurethane modified with waterborne perfluoroalkyl methacrylic copolymer and a montmorillonite clay nanofiller. The authors characterised the adhesion strength with a 90° tape testing method.…”

Section: Durability Of Shsmentioning

confidence: 99%

Assessing durability of superhydrophobic surfaces

Malavasi

Bernagozzi

Antonini

et al. 2015

Surface Innovations

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Superhydrophobic surfaces (SHS) show remarkable water repellency properties, and their use may have a tremendousimpact for a plethora of applications, where liquid water accumulation needs to be controlled or minimised. However, the durability of SHS in operational conditions is a severe issue that currently represents a bottleneck for the technology transfer from laboratory to industrial applications. In the present work, we try to fill in the gap caused by the absence of a standard for evaluation for SHS durability, by developing a protocol for testing surface durability.The proposed protocol includes nine tests as follows: water immersion, acidic environment, alkaline environment, ionic solution, mechanical erosion, ultraviolet exposure, resistance to heating, alcohol immersion and hydrocarbon immersion. The protocol can serve to give an indication of surface robustness in a variety of potentially harmful environments, by providing a global figure of merit and ranking for different SHS and thereby allowing for identifying those surfaces fulfilling requirements for a specific application. To illustrate the protocol, we tested a SHS developed in-house by grafting of lauric acid molecules on an aluminum substrate. This article contains supporting information that is available online.

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Section: Durability Of Shsmentioning

confidence: 99%

Assessing durability of superhydrophobic surfaces

Malavasi

Bernagozzi

Antonini

et al. 2015

Surface Innovations

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“…and typical nanocomposite surfaces have had arithmetic roughness on the order of 10 microns. 7 Developing smoother superhydrophobic surfaces (less than 10 µm) is critical for tuning surfaces for specific anti-wetting properties, such as high contact angle or high water pressure resistance.…”

Section: Resultsmentioning

confidence: 99%

Superhydrophobic Surfaces to Resist Droplet Sprays, Simulated Rain, and Water Jets

Davis¹

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With anti-wetting properties such as contact angles greater than 150• and sliding angles less than 10• , low-cost superhydrophobic coatings hold great promise in reducing fouling and icing. However, these coatings must also resist saturation and erosion caused by water droplet impact. The first experimental study investigates the performance of a polyurethane/organoclay superhydrophobic nanocomposite modified with perfluoroalkyl methacrylic copolymer (PMC) in the presence of a high pressure air-water spray which simulates an icing cloud impact. Superhydrophobic samples were exposed at 25, 45, and 65 cm from the spray nozzle. The velocites of droplets impacting the superhydrophobic samples were estimated computationaly for each of these distances to be 14.5, 4.5, and 3.4 m /s, respectively. It was found that liquid saturation did not occur immediately, but over time, the high mass flow rate of water led to anti-wetting performance degradation. Upon evaporation through heating, contact angle returned to pre-test values, indicating little mechanical erosion. This was consistent with scanning electron microscopy (SEM) which showed that the nano-and micro-structure was preserved, as well as with energy-dispersive X-ray spectroscopy (EDXS), which showed no surface chemistry change after testing. However, sliding angle showed stronger degradation, especially at higher impact velocities.The objective of the second study was to test the mechanical durability of a polyurethane/organoclay/PMC nanocomposite coating in conditions that replicate extended rain impact. Samples were impacted with 1.4 mm droplets at a velocity of 25 m /s and a flow rate of 0.78 gpm for a period of 5 hours by an axial full cone nozzle. The cases of normal and angled 40• droplet impact were examined. After the spray period, samples were heated at 100• C to allow saturated liquid to evaporate from the surface.Contact angle and sliding angle of the superhydrophobic surfaces were measured before and after the spray period. A decrease in performance for both samples was observed, with the vertically sprayed sample showing greater degradation. After iv refunctionalizing the vertically sprayed surface with PMC, an increase in performance was observed. Microscopy of the superhydrophobic samples before and after spray impact revealed a change in surface morphology which, along with leaching of the fluoroacrylic copolymer, was the likely cause of the decrease in performance.In the third study, a novel superhydrophobic surface composed of a PTFE binder and flame-generated carbonaceous soot was created. Importantly, unlike previous surfaces created from flame-generated material, the produced surface showed good adhesive properties. Owing to the natural hydrophobicity of carbon and nanostructure of the deposited soot, surfaces displayed extreme resistance to saturation by an impinging high pressure water jet. Surfaces were found to saturate more easily as they were tilted to the impinging water jet. However, the anti-wetting properties of samples that ...

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“…The reason for the addition of fluoropolymer within the nanocomposite formulation matrix was to reduce the surface energy and promote superhydrophobicity of the coating. 35,36 The existence of this chemical component on the nanocomposite coating has been measured by Steele et al 32 in a previous investigation using the technique of backscattered electron analysis.…”

Section: Nanocomposite Fabricationmentioning

confidence: 99%

“…Since the spray-casting height and pressure can have a significant impact on the performance properties of the resulting coatings, this study sought to systematically investigate these effects. In particular, this was completed for polyurethane clay-fluorine nanocomposite coatings, which have been previously investigated in terms of adhesion strength as a function of mixture components by Steele et al 32 We expand that work by fabricating these superhydrophobic coatings from a range of spray-casting heights and spray air pressures so that its effect on the superhydrophobicity (by measurement of CA and ROA and wear durability (by linear surface abrasion) of the surface can be quantified.…”

Section: Introductionmentioning

confidence: 99%

“…[20][21][22][23][24][25][26][27][28][29][30][31] By introducing heat to the surface thereafter, the polymer chains on the coating can crosslink and self-assemble into a durable, superhydrophobic nanocomposite coating. [32][33][34] This fabrication method is a simple and cost-effective process that can be applied to not only a large surface area but also to a variety of substrate materials.…”

Section: Introductionmentioning

confidence: 99%

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Impinging Drops on Superhydrophobic Surfaces at Icing Conditions

Yeong

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Due to their excellent water repellent characteristics, superhydrophobic surfaces have been hypothesized to be icephobic. This is based on the premise that water droplets will be repelled from the surface before ice nucleation can occur. The icephobic nature of these surfaces provides an attractive solution to current icing problems that can occur in aerospace applications. However, significant challenges remain before anti-wetting coatings could be implemented as an effective ice mitigation tool. For example, the majority of current synthetic superhydrophobic surfaces are fragile and unable to withstand the harsh environmental conditions that are encountered by aerospace applications. In addition, their static and dynamic wettability at varying temperatures and humidity, as well as their ice-shedding performance under the impact of a super-cooled icing cloud, are not well understood.Therefore, in this dissertation, fabrication techniques for a previously developed nanocomposite surface were improved so that coatings of consistent antiwetting performance and durability could be produced. The icephobicity of this nanocomposite coating was then systematically investigated. First, an experiment was conducted to study the wettability of a water drop on the coating for a full temperature cycle (20 -3The investigation was then extended to study the impact and rebound dynamics of a iv drop on an inclined coating, at different fluid viscosities and at various temperatures (50°C to -8°C). This was followed by a study of ice adhesion strength of the coatings -cooled water droplets. The receding contact angle was discovered from these experiments to be a key parameter in controlling superhydrophobic wettability and ice adhesion. Therefore, the receding angle depinning dynamics from a superhydrophobic surface were also studied in detail at micron length scales and at microsecond temporal scales. In summary, results from this dissertation revealed the crucial parameters that govern the icing performance of a nanocomposite superhydrophobic surface.

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Adhesion strength and superhydrophobicity of polyurethane/organoclay nanocomposite coatings

Cited by 78 publications

References 26 publications

Assessing durability of superhydrophobic surfaces

Assessing durability of superhydrophobic surfaces

Superhydrophobic Surfaces to Resist Droplet Sprays, Simulated Rain, and Water Jets

Impinging Drops on Superhydrophobic Surfaces at Icing Conditions

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