Icephobic Coatings Research Articles

Icephobic Durability of Branched PDMS Slippage Coatings Co-Cross-Linked by Functionalized POSS.

Ice accretion poses a severe impact on diverse aspects of human life. Although great efforts have been dedicated to prevent or alleviate ice adhesion to the surface of substrates by developing various icephobic coatings, it is still needed to improve the integrated performance. Herein, we present a novel strategy to prepare poly(dimethylsiloxane) (PDMS) slippage coatings by combining a soft architecture-driven branched PDMS with partial short PDMS-functionalized polyhedral oligomeric silsesquioxane (POSS) as a co-cross-linker, in which silicone oil with certain viscosity was added as a lubricant. The chemical structure, surface morphology, and icephobic durability of the prepared coatings were investigated with concerns for the potential anti-icing uses. The PDMS slippage coating shed light on extraordinary icephobic durability with the ice shear strength at approximately 11.2 kPa and maintained low values below 14 kPa even after 50 icing/deicing cycles. Due to the elaborate control of the cross-link density, the side chains of the branched PDMS provided a rich storage space for entrapped silicone oil for the formation of the interfacial slippage. Moreover, the introduction of the functionalized POSS brought about significantly improved mechanical resistance in abrasion and elastic modulus. It is suggested that the branched PDMS slippage coating is a promising candidate in practical anti-icing applications.

When superhydrophobic coatings are icephobic: Role of surface topology

Among different types of anti-icing coatings, superhydrophobic coatings have attracted considerable attention due to their water repellency and low heat-transfer rate. However, condensation on superhydrophobic surfaces at low temperatures usually causes an increase in ice adhesion because of the induced wetting of micro- and nanostructures. By tuning the weight ratio of surface-modified nanoparticles to unmodified ones, five superhydrophobic coatings with different structural features at the microscale were developed. Ice-adhesion strength and ice-nucleation temperature were studied, together with the effect of moisture condensation on ice adhesion. It was found that the ice-adhesion strength and icing temperature of these coatings do not necessarily follow the same order among these surfaces because of different mechanisms involved. Surface roughness is inadequate to describe the necessary surface features that critically affect the anti-icing behavior of the coatings. Detailed topology/geometry has to be considered when designing icephobic coatings. Superhydrophobic coatings can be adopted for icephobic applications once the surface topology is carefully designed.

AFM Peakforce QNM mode for measurement of nanosurface mechanical properties of Pt-cured silicones

Sylgard 184 is used for diverse applications including nanoimprinting, micro-electronic and mechanical systems (MEMS), soft robots, ice-phobic coatings and tactile and epidermal sensors. For such applications, understanding effects of processing conditions on nanoscale mechanical properties is essential for performance. It is surprising, then, that little attention has been paid to effects of cure temperature on surface and mechanical properties. The present work adds depth to understanding the complex relationships among hydrosilylation and little recognized autoxidation of SiH to SiOH and secondary network formation by condensation. Peakforce Quantitative Nanomechanical Mapping (PF-QNM), an atomic force microscopy (AFM) mode was used to provide a nanoscale map of deformation, adhesion, dissipation, modulus and morphology as a function of varying cure temperature and base-to-crosslinker ratio. The interaction of the SiOH rich oxide layer of the silicon AFM tip with the outermost Sylgard 184 silicone surface provided modulus and adhesion measurements that revealed important effects of cure conditions and composition. Results were interpreted in terms of a model for the concentration of near surface SiOH from autoxidation and changes due to SiOH condensation at high temperature cure. Moduli were found to be comparable with dynamic mechanical analysis (DMA), supporting PF-QNM as a tool for mechanical property measurements. The dependence of nanosurface mechanical properties on composition and network formation conditions provides guidance for future work using Pt-cured silicones.

Hydrophobic/icephobic coatings based on thermal sprayed metallic layers with subsequent surface functionalization

Hydrophobic/icephobic coatings have been fabricated using a combination of thermal sprayed metallic MCrAlY (M = Ni, Co) coatings with a subsequent deposition process using 1H,1H,2H,2H-perfluorooctyltriethoxysilane (POTS). The MCrAlY coatings provide the desirable surface roughness feature for hydrophobicity, and water contact angle of 135° was directly obtained after aged in the atmosphere for 1 week. However, it was found that the hydrophobicity of MCrAlY was not stable under water impinging due to unstable hydrocarbon absorption. Better hydrophobicity with water contact angle of 154° and improved durability have been achieved by further modification using POTS vapour on the rough MCrAlY coatings. X-ray photoelectron spectroscopy results revealed that replacement of absorption of hydrocarbon by functional C-F groups played important role in the improvement of hydrophobicity and durability. The ice adhesion test confirmed that lower ice adhesion strength of MCrAlY based coatings have been obtained compared with the threshold for icephobicity which is desirable to be applied as icephobic coatings for aircraft. The electro-thermal heating de-icing test showed an energy saving of 28.6% for de-icing with the two-step MCrAlY based coatings. The combination of strong metallic MCrAlY rough layers and the subsequent functionalization enables a new approach for the fabrication of durable hydrophobic/icephobic coatings.

Design and durability study of environmental-friendly room-temperature processable icephobic coatings

Ice accumulation leads to improper functioning or even damages to ships, offshore platforms, sports facilities and land buildings in cold climate regions. Although fluorochemicals have demonstrated attractive performance for icephobic applications, their use has been restricted due to health and environmental concerns. Here, we present a facile method to fabricate fluorine-free icephobic coatings with potential applications for outdoor facilities and structures. The coating consists of a silicone-epoxy hybrid resin, polydimethylsiloxane (PDMS) and SiO2 nanoparticles with different sizes. Particularly, the use of different sized (10–20 nm and 200 nm) SiO2 nanoparticles results in excellent icephobicity and mechanical properties. The mechanical properties and durability of the coating were analysed according to respective test standards and compared with other reported icephobic coatings. The durable icephobic potency of the coatings is very promising as a sustainable green solution for various practical anti-icing applications.

Mechanically Robust Transparent Anti‐Icing Coatings: Roles of Dispersion Status of Titanate Nanotubes

AbstractIce accretion on automobiles, aerospace components, precision instruments, and photovoltaic devices detrimentally affect their performance and increase the maintenance cost. Despite significant efforts devoted to the investigation of anti‐icing coatings in the past decades, mechanically robust and transparent anti‐icing coatings are rarely reported. In this study, titanate nanotubes are used as filler to prepare mechanically robust anti‐icing coatings with a sol‐gel method. Specially, the effect of dispersion status of nanotubes on the transmittance, surface roughness, and water repellency is investigated. The optimized smooth, transparent coating exhibits higher water repellency and better anti‐icing performance in terms of ice‐adhesion strength, icing delay time, and ice‐nucleation temperature than the rough one. Much higher hardness and scratch resistance than that of commercially available icephobic or anti‐icing coatings is obtained on the smooth, transparent sample; the coating also presents good adhesion to the substrate.

Development and evaluation of poly(dimethylsiloxane) based composite coatings for icephobic applications

Formation and accretion of ice on the leading edge surface of aircrafts wings may lead to disasters. The current de-icing system for aircraft will build up weight, increase energy consumption and add complexity to the aircraft systems. Development of icephobic coatings is a potential solution to prevent ice formation and/or reduce accretion on the critical surface of aircraft. Icephobic coatings based on poly(dimethylsiloxane) (PDMS) with modification by fluorosilane and incorporation of silica nanoparticles have been fabricated. The hydrophobicity of the coatings has been measured in normal conditions with atmospheric pressure and room temperature, showing improvement of hydrophobicity by the fluorination of PDMS and incorporation of silica nanoparticles. The water droplet icing behaviour shows better anti-icing performance for fluorinated PDMS (F-PDMS)/silica coatings with a rough surface. The ice adhesion strength test results show that F-PDMS coatings without silica nanoparticles have lower ice adhesion strength implying better de-icing performance. The wettability of the coatings was also measured at reduced pressure and temperature, to study the mechanism of higher ice adhesion strength of F-PDMS/silica coatings comparing with F-PDMS based coatings. For the design and fabrication of icephobic coatings, compromise on the roughness induced hydrophobicity may become a critical requirement to avoid mechanical interlock between the ice and the rough surface.

On a simplified method to produce hydrophobic coatings for aeronautical applications

The deposition of ice on wings and tails surfaces of aircrafts often alters the airflow reducing the lift force and causing aerodynamic stall. In order to prevent these kind of serious problems, de-icing and anti-icing systems, which act by removing the ice once it has formed, and by preventing its formation, respectively, are usually employed. In particular, the anti-icing superhydrophobic and icephobic coatings can be achieved by designing and realizing nanostructured surfaces by taking inspiration from effective surface present in nature, e.g., the lotus leaf. However, this process is often expensive and requires specialized equipment. The effort of the present work is to find out a simplified and not-expensive method to prepare superhydrophobic coatings to be applied on large aircraft surfaces. Among the investigated methods, the deposition of several layers of a homogeneous hydrophobic silica nanoparticles by using a simple aerograph allowed to build-up a coating which exhibits a contact angle of 154°. The coating withstands to aging tests simulating flight conditions. Also during typical flight conditions, i.e., −12 °C and 0.5 bar, it retains its hierarchical superficial morphology with roughness features from nano- to micro-scale and shows contact angle higher than the commercial reference.

Scalable and durable polymeric icephobic and hydrate-phobic coatings.

Ice formation and accumulation on surfaces can result in severe problems for solar photovoltaic installations, offshore oil platforms, wind turbines and aircrafts. In addition, blockage of pipelines by formation and accumulation of clathrate hydrates of natural gases has safety and economical concerns in oil and gas operations, particularly at high pressures and low temperatures such as those found in subsea or arctic environments. Practical adoption of icephobic/hydrate-phobic surfaces requires mechanical robustness and stability under harsh environments. Here, we develop durable and mechanically robust bilayer poly-divinylbenzene (pDVB)/poly-perfluorodecylacrylate (pPFDA) coatings using initiated chemical vapor deposition (iCVD) to reduce the adhesion strength of ice/hydrates to underlying substrates (silicon and steel). Utilizing a highly-cross-linked polymer (pDVB) underneath a very thin veneer of fluorine-rich polymer (pPFDA) we have designed inherently rough bilayer polymer films that can be deposited on rough steel substrates resulting in surfaces which exhibit a receding water contact angle (WCA) higher than 150° and WCA hysteresis as low as 4°. Optical profilometer measurements were performed on the films and root mean square (RMS) roughness values of Rq = 178.0 ± 17.5 nm and Rq = 312.7 ± 23.5 nm were obtained on silicon and steel substrates, respectively. When steel surfaces are coated with these smooth hard iCVD bilayer polymer films, the strength of ice adhesion is reduced from 1010 ± 95 kPa to 180 ± 85 kPa. The adhesion strength of the cyclopentane (CyC5) hydrate is also reduced from 220 ± 45 kPa on rough steel substrates to 34 ± 12 kPa on the polymer-coated steel substrates. The durability of these bilayer polymer coated icephobic and hydrate-phobic substrates is confirmed by sand erosion tests and examination of multiple ice/hydrate adhesion/de-adhesion cycles.

Transparent icephobic coatings using bio-based epoxy resin

Ice accretion and accumulation pose serious challenges for maintaining the operation and performance of outdoor facilities in cold climate. Epoxy resin, with a wide range of formulation possibilities, is widely used as protective coatings for outdoor facilities. However, bisphenol A (BPA), a key ingredient of conventional epoxy, is known to interfere with human's natural hormones and cause various disorders in the body system. Reduction or complete elimination of the usage of BPA is therefore high in the agenda of the coatings industries. In this study, a transparent, anti-icing, bio-based epoxy coating was developed for room-temperature processing. As a result of hydrophobic treatment with addition of silanes, the glass-transition temperature and anti-icing performance of bio-based epoxy resin increased significantly. The optimum coating exhibited good water repellency and ice-adhesion strength as low as 50kPa at −20°, which was half of the widely accepted threshold value of 100kPa for icephobic coatings. The icing delay time was much delayed compared with that of an uncoated glass substrate. To further demonstrate the anti-icing performance of the optimized coating, supercooled-water dripping on coated wooden outdoor floors and wooded boards was conducted at −15°C, superior anti-icing performance was observed on the coated substrates.

Self-crosslinking coatings of fluorinated polysiloxanes with enhanced icephobicity

Fluorinated polysiloxanes with different grafting densities of fluorinated groups were synthesized via hydrosilylation reaction between polymethylhydrosiloxane and tridecafluorooctyl methacrylate (13FMA). By further introduction of vinyltriethoxysilane (VTES), the produced polymers underwent self-crosslinking to generate icephobic coatings. Characterizations of surface chemical composition and morphology of the fluorinated polysiloxanes coatings suggested that the fluorine content and the surface roughness of the coating surface increased with the amount of 13FMA. When the fluorinated polysiloxanes grafted a suitable amount of 13FMA and VTES, supercooled water droplets could easily slip away from the tilted coating surface at −15°C, ascribing to its high receding contact angle, and the ice shear strength could reduce to 83±2kPa. Results of this study further demonstrated the importance of the synergistic effect of silicon and fluorine for contribution to the enhanced icephobicity, and the self-crosslinking fluorinated polysiloxane coatings could find more feasible applications for anti-icing.

Amphiphilic icephobic coatings

Abstract A series of amphiphilic siloxane polyurethane (AmSiPU) coatings were investigated for their icephobic properties. The use of coatings having amphiphilic surfaces for anti-icing applications has not been studied to a large extent although these types of coatings have more recently been studied for anti-fouling (AF)/foul release (FR) applications. Several polyurethane based amphiphilic coatings were prepared having variations in the composition as well as molecular weight of hydrophobic polydimethyl siloxane (PDMS), and hydrophilic polyethylene glycol (PEG). Surface characterizations of the coatings revealed the presence of both PDMS and PEG moieties, implying amphiphilic surface characteristics. The icephobic properties of these coatings were evaluated to investigate if amphiphilic formulations can deter ice adhesion. Water absorption and barrier behaviors of these coatings and their correlation to anti-icing properties were also studied.

Self-Healing Icephobic Coatings: The Promise of a New Pairing

Self-Healing Icephobic Coatings: The Promise of a New Pairing

Performance and durability tests of smart icephobic coatings to reduce ice adhesion

The accretion of ice can cause damage in applications ranging from power lines and shipping decks, to wind turbines and rail infrastructure. In particular on aircraft, it can change aerodynamic characteristics, greatly affecting the flight safety. Commercial aircraft are therefore required to be equipped with de-icing devices, such as heating mats over the wings. The application of icephobic coatings near the leading edge of a wing can in theory reduce the high power requirements of heating mats, which melt ice that forms there. Such coatings are effective in preventing the accretion of runback ice, formed from airborne supercooled droplets, or the water that the heating mats generate as it is sheared back over the wing's upper surface. However, the durability and the practicality of applying them over a large wing surface have been prohibitive factors in deploying this technology so far.Here, we evaluated the ice adhesion strength of four non-conductive coatings and seven thermally conductive coatings by shearing ice samples from coated plates by spinning them in a centrifuge device. The durability of the coating performance was also assessed by repeating the tests, each time regrowing ice samples on the previously-used coatings. Contact angle parameters of each coating were tested for each test to determine influence on ice adhesion strength. The results indicate that contact angle hysteresis is a crucial parameter in determining icephobicity of a coating and hydrophobicity is not necessarily linked to icephobicity.

Icephobic Surfaces Induced by Interfacial Nonfrozen Water.

It is known that smooth, hydrophobic solid surfaces exhibit low ice adhesion values, which have been shown to approach a lower ice adhesion strength limit (∼150 kPa) defined by the water receding contact angle. To overcome this limit, we have designed self-lubricating icephobic coatings by blending polydimethylsiloxane (PDMS)-poly(ethylene glycol) (PEG) amphiphilic copolymers into a polymer matrix. Such coatings provide low ice adhesion strength values (∼50 kPa) that can substantially reduce the lower bound of the ice adhesion strength achieved previously on smooth, hydrophobic solid surfaces. Different molecular mechanisms are responsible for the low ice adhesion strength attained by these two approaches. For the smooth hydrophobic surfaces, an increased water depletion layer thickness at the interface weakens the van der Waals' interactions between the ice and the polymeric substrate. For the self-lubricating icephobic coatings, the PEG component of the amphiphilic copolymer is capable of strongly hydrogen bonding with water molecules. The surface hydrogen-bonded water molecules do not freeze, even at substantial levels of subcooling, and therefore serve as a self-lubricating interfacial liquid-like layer that helps to reduce the adhesion strength of ice to the surface. The existence of nonfrozen water molecules at the ice-solid interface is confirmed by solid-state nuclear magnetic resonance (NMR) spectroscopy.

Anti-icing Behavior of Thermally Sprayed Polymer Coatings

Surface engineering shows an increasing potential to provide a sustainable approach to icing problems. Currently, several passive anti-ice properties adoptable to coatings are known, but further research is required to proceed for practical applications. This is due to the fact that icing reduces safety, operational tempo, productivity and reliability of logistics, industry and infrastructure. An icing wind tunnel and a centrifugal ice adhesion test equipment can be used to evaluate and develop anti-icing and icephobic coatings for a potential use in various arctic environments, e.g., in wind power generation, oil drilling, mining and logistic industries. The present study deals with evaluation of icing properties of flame-sprayed polyethylene (PE)-based polymer coatings. In the laboratory-scale icing tests, thermally sprayed polymer coatings showed low ice adhesion compared with metals such as aluminum and stainless steel. The ice adhesion strength of the flame-sprayed PE coating was found to have approximately seven times lower ice adhesion values compared with metallic aluminum, indicating a very promising anti-icing behavior.

Highly icephobic properties on slippery surfaces formed from polysiloxane and fluorinated POSS

Recent emerging strategies to prepare icephobic coatings have focused on slippery surfaces containing a liquid lubricant with low surface energy, which significantly reduces ice adhesion. In this work, a facile technique was developed for preparation of polysiloxane coatings with efficient and durable icephobicity. Fluorinated polyhedral oligomeric silsesquioxanes (F-POSS-SiH) with different fluorinated groups and Si-H active sites were synthesized via hydrosilylation between fluorinated methacrylates and octakis(dimethylsiloxy) octasilsequioxane. The F-POSS-SiH hybrid compound was subsequently applied as a co-crosslinker in the system of polymethylhydrosiloxane (PMHS) and polymethylvinylsiloxane to create silicone coatings. The low surface energy of fluorinated groups could drive F-POSS-SiH towards the coating surface, leading to a gradient distribution in which F-POSS-SiH was self-assembled on the top surface, while silicone was rich in the bottom layer. Meanwhile, wavy surfaces were generated spontaneously by compressive stress during the coating formation. The wavy microstructure of coatings provided space for the unreacted silicone oil, i.e., low molecular weight PMHS, that could be considered as a liquid lubricant and controlled by the dosage. Therefore, the slippery wavy coatings showed highly icephobic properties with extraordinarily low ice shear strengths at a lowest value of 3.8 ± 1.8 kPa, only 5 percentage of Sylgard 184. Moreover, the coatings remained icephobicity after 15 icing/deicing cycles, demonstrating excellent durability.

Durable coatings that repel ice

Surface Science Preventing ice buildup on surfaces is crucial for ensuring the proper operation and safety of airplanes, ships, communication towers, and wind turbines. Golovin et al. studied the mechanisms that control how ice detaches from surfaces. They developed durable coatings with extremely low ice adhesion, from which ice simply falls off under its own weight. These high-performing icephobic coatings could be spun, dipped, sprayed, or painted onto any underlying substrate. The coatings functioned well outdoors over winter or after extreme abrasion or exposure to harsh chemicals. Sci. Adv. 2 , 10.1126.sciadv.01496 (2016).

Designing durable icephobic surfaces.

Ice accretion has a negative impact on critical infrastructure, as well as a range of commercial and residential activities. Icephobic surfaces are defined by an ice adhesion strength τice < 100 kPa. However, the passive removal of ice requires much lower values of τice, such as on airplane wings or power lines (τice < 20 kPa). Such low τice values are scarcely reported, and robust coatings that maintain these low values have not been reported previously. We show that, irrespective of material chemistry, by tailoring the cross-link density of different elastomeric coatings and by enabling interfacial slippage, it is possible to systematically design coatings with extremely low ice adhesion (τice < 0.2 kPa). These newfound mechanisms allow for the rational design of icephobic coatings with virtually any desired ice adhesion strength. By using these mechanisms, we fabricate extremely durable coatings that maintain τice < 10 kPa after severe mechanical abrasion, acid/base exposure, 100 icing/deicing cycles, thermal cycling, accelerated corrosion, and exposure to Michigan wintery conditions over several months.

UV-curable POSS-fluorinated methacrylate diblock copolymers for icephobic coatings

Abstract Low surface energy materials have been extensively investigated for building icephobic surfaces in recent years. Polydimethylsiloxane (PDMS) and fluoropolymers have been introduced to this field, while control of their structures is of importance to produce deicing surfaces. In this work, fluorinated methacrylate block copolymers containing polyhedral oligomeric silsesquioxane (POSS) moieties were synthesized by reversible addition-fragmentation chain transfer polymerization and transformed into thiolated-copolymers by aminolysis to adjust the self-assembly and modify surface morphology. The icephobic coatings were developed via UV-curable thiol-ene reaction with tunable amounts of thiol-modified POSS-fluorinated methacrylate diblock copolymers with vinyl-functionalized PDMS and thiol-functionalized PDMS. Characterizations of atomic force microscopy, X-ray photoelectron spectroscopy, and contact angle showed the evidence of the POSS-fluorinated diblock copolymers on the outmost surface of the coatings. Owing to the crystallization of perfluoroalkyl side groups, the coatings containing thiol-modified poly(methacrylisobutyl POSS)- b -poly(2-perfluorooctylethyl methacrylate) ( S17F ) exhibited excellent icephobicity, and water droplets could rebound completely on all S17F -containing surfaces at both normal and tilt modes before freeze even at −15 °C. The ice shear strengths of the prepared UV-cured coatings were about one-eighth of that on bare aluminum surface, while the coating containing 5% S17F achieved the lowest ice shear strength of 105 ± 12 kPa. It was found that the icephobicity of these coatings were attributed primarily to the synergistic effect of the POSS-fluorinated methacrylate diblock copolymer and the PDMS component.