Anti-icing Applications Research Articles

Nature-inspired slippery polymer thin film for ice-repellent applications

In this study, the authors investigated the anti-icing performance of a hierarchical slippery polymer thin film that is inspired by structures of the lotus leaf and Nepenthes pitcher plant. The polymer solution was mixed with the lubricant at the appropriate concentration to achieve slippery properties. The dry etching method followed by the spin-coating process was used to generate a uniform polymer microstructure on the thin film. The polymer nanostructure was then yielded by an additional plasma-etching method using carbon tetrafluoride (CF4) gas. The anti-icing efficiency was then compared with that of the non-functional samples to demonstrate the advantages of combination in all criteria. Moreover, a theoretical prediction based on the free-energy approach was used to measure the nucleation time at the interface and illustrated good agreement with real-time measurement. The results propose a new and facile approach for outdoor anti-icing applications.

Supersonically sprayed transparent flexible multifunctional composites for self-cleaning, anti-icing, anti-fogging, and anti-bacterial applications

We used supersonic aerosol deposition to fabricate transparent flexible thin “glass” films, comprising SiO2 and ZnO, with antibacterial, superhydrophilic, and anti-fog properties. A polystyrene solution, which was supersonically sprayed onto the glass film to augment the superhydrophobicity, endowed the film with self-cleaning and anti-frost characteristics. The glass films have a thickness of 2–2.5 μm with a maximum roughness of approximately 0.25 μm. The sprayed polystyrene (PS) layer (approximately 200 nm thick) decreased the transparency of the film to 80% relative to that of the pure glass film (90%) at 580 nm. The large water contact angle of 165° renders the PS-coated glass film superhydrophobic, which slows the nucleation of condensing droplets and delays the subsequent formation of ice, known as the anti-frost or anti-icing effect. The superhydrophobicity is also responsible for the self-cleaning effect of the rolling droplets over a tilted substrate. The hydrophilicity of the glass-coated film (or simply, glass film) without PS facilitated the formation of a thin liquid layer, which minimized light scattering and augmented the anti-fog effect. Finally, the bacterial inhibition rates of the glass and PS-coated glass films were 97.5% and 96.3%, respectively. These multifunctional films are expected to minimize the transmission of bacteria resulting from physical contact.

Robust Superhydrophobic Surface on Polypropylene with Thick Hydrophobic Silica Nanoparticle-Coated Films Prepared by Facile Compression Molding

Superhydrophobic surfaces have been extensively studied for their unique interfacial interaction between water and the surface, and they can be used for self-cleaning, drag reduction, anti-icing, and other applications. To make the superhydrophobic surfaces, nano/microscale structures and a low surface energy should be realized. The development of a durable superhydrophobic surface was hindered by the vulnerability of the surface to mechanical contact. To improve the robustness of the superhydrophobic surface toward mechanical damage, the hydrophobic polypropylene (PP) surface was coated with a thick layer of hydrophobic silica nanoparticles (SNPs) using a simple compression molding process. The thick layer consists of SNPs and PP, and the roles of SNPs and PP are nano/microscale structures with a low surface energy and binder for nanoparticles, respectively. This revealed improvement in the superhydrophobic tendency, with an apparent contact angle of about 170° and a sliding angle of less than 5°. The morphology and the corresponding elemental analysis of the PP/SNPs coated films were investigated using field emission scanning electron microscopy and energy-dispersive spectrometry. The mechanical durability of the superhydrophobic surface was evaluated by the scotch tape test and scratch test with sandpaper. The coated films with SNPs showed the superhydrophobic behavior after 25 tape tests. In addition, the coated films with SNPs showed a contact angle greater than 150° and a sliding angle less than 10° after a 100-cm scratch test with 1000 grit sandpaper, under a weight of 500 g, on an area of 40 × 40 mm2. The chemical stability of PP/SNPs coated films was also investigated in acidic, neutral, and alkaline medium solutions. The films showed good stability under the acidic and neutral medium solutions even after 24 h, but an alkaline medium could damage the surface. The obtained results demonstrated the robustness of the superhydrophobic coating with SNPs.

A durable and photothermal superhydrophobic coating with entwinned CNTs-SiO2 hybrids for anti-icing applications

In this work, carbon nanotubes (CNTs) were grafted by silica nanoparticles to prepare CNTs-SiO2 hybrids, which were then incorporated into epoxy matrix to construct a superhydrophobic coating by a facile one-step spaying method. The surface morphology, roughness and wettability of CNTs-SiO2/epoxy coatings were tailored by changing the ratios of CNTs to SiO2. The best hydrophobicity was achieved when the ratio of CNTs to SiO2 was 1:3, showing a WCA of 159.3°. The introduction of entwined CNTs-SiO2 hybrids could not only create a micro-nano hierarchical structure to increase the water repellency, but also offer good mechanical durability of the coating surface against repeated peeling and friction damages, as well as excellent chemical stability under various harsh conditions. Benefiting from the superhydrophobicity of the coating surface and the prominent photothermal conversion capability of CNTs, the CNTs-SiO2/epoxy coating could significantly delay the water freezing time, and efficiently melt the ice layer within seconds under laser irradiation.

Thermal Spray Coating on Polymeric Composite for De-Icing and Anti-Icing Applications

Abstract This paper reports a novel method for fabrication of an electro-thermal heating element, as de-icer or anti-icer, for the polymer-based composites. The plasma spray technique was utilized for the deposition of a Nickel-Chrome-Aluminum-Yttrium (NiCrAlY) coating layer as a heating element on top of the glass/epoxy composite. To improve the adhesion strength and deposition efficiency of the coatings and to protect the composite fibers during grit blasting and spraying, a woven wire stainless steel mesh was added to the composite substrates during the composite fabrication process. Metal mesh will act as an anchor to keep the coating on the surface. Two types of woven wire and two types of NiCrAlY powder with the fine and coarse particle size distributions were used. Good processing parameters for grit blasting and plasma spraying are identified. It is found that the surface modification method applied to the composite substrates prior to the coating process makes a significant improvement in the coating thickness uniformity and deposition efficiency. Several tests were conducted on the coated samples for determination of their mechanical and electrical properties. Using flatwise tensile tests, it is shown that application of proper surface modification method and set of spray parameters could result in improving the coating bonding strength significantly. The electrical and thermal analyses of the coated samples are also performed. It is shown that the coated samples have a high capability in the generation of heat and can be used as a heating element.

Transparent hierarchical micro-nano structure PTFE-SiO2 nanocomposite thin film with superhydrophobic, self-cleaning and anti-icing properties

Superhydrophobic surfaces are often recommended for anti-icing applications due to their high ability to repel water and reduce ice accumulation and adhesion. In this study, PTFE-SiO2 thin films with different concentrations of silica (0, 1, 2 and 5 g/l) were deposited on the glass substrate by a sol-gel dip coating method. Water contact angle on the samples were measured by a water contact analyzer. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and field emission scanning electron microscopy (FE-SEM) techniques were used to investigate the chemical bonds formed on the film surface and film surface morphology. The thermal stability of the films was evaluated at different temperatures (from 200 to 500 °C). Also, the stability of the film under ultraviolet radiation was investigated under UV light irradiation. Also, the anti-icing properties of the films were investigated using both simulated static and dynamic methods. Self-cleaning properties of the film were evaluated using iron oxide powder. The water contact angle on the sample with PTFE film without silica nanoparticles is equal to 146°. The water contact angle on the film surface remains constant with increasing amount of the silica nanoparticles from 0 to 1 g/l. By increasing the amount of the silica nanoparticles to 2 g/l d, the contact angle increases to 155°. With increasing the silica nanoparticles amount to 5 g/l, water contact angle decreases. So, PTFE-SiO2 thin film with 2 g/l SiO2 was selected as an optimal thin film. The results of the thermal stability and UV irradiation tests showed that the films were stable up to 400 °C and 16 days of UV radiation, respectively. Indeed, the optimal thin film showed anti-icing and self-cleaning properties.

A stretchable superhydrophobic coating with electrothermal ability for anti-icing application

Surface icing in the transmission lines may cause serious accidents. Although the superhydrophobic/electrothermal synergistically anti-icing strategy has been introduced, most coatings tended to lose superhydrophobicity under large deformation. In this research, we prepared a kind of stretchable superhydrophobic coating by partially embedding the modified graphene into the Ecoflex elastomer. The excellent resilience of the Ecoflex elastomer together with the outstanding interficial area of graphene results in the maintainment of superhydrophobicity even under 300% strain. Furthermore, this coating has outstanding superhydrophobic and electrothermal property simutaneously due to the introduction of graphene. After applying 20 V voltage, this coating could melt 2 mm thick ice layer within 115 s. Moreover, this superhydrophobic coating demonstrated excellent mechanical and chemical durability, and outstanding thermostability.

Facile fabrication of slippery lubricant-infused porous surface with pressure responsive property for anti-icing application

In this research, a facile template method was developed to prepare the slippery lubricant-infused porous surface (SLIPS). The porous framework consisted of polydimethylsiloxane (PDMS) and softener, and inert dimethyl silicone oil was filled into the pores as the lubricant. Under small external pressure, the sample could be easily compressed, resulting in silicone oil being extruded to the sample surface to improve the surface lubricity. In the absence of pressure, the silicone oil was stored inside the SLIPS. This pressure responsive property avoided long-term exposure and rapid loss of lubricant. By adjusting the content of softener, the pressure responsive property was tuned. When the mass ratio of PDMS to softener increased to 1:1, the extrusion amount of lubricant enhanced significantly and the water sliding angle decreased to approximately 20°, showing good lubricity. This sample exhibited low ice adhesion strength and excellent anti-icing durability. After 25 cycles of icing/deicing tests, the ice adhesion strength was still less than 20 kPa, and the loss ratio of lubricant was only approximately 15%.

Innovative coatings for anti-icing applications

Innovative coatings for anti-icing applications

Efficient Fabrication of Wear-Resistant PEEK Matrix Composite Coating with Superhydrophobicity for Self-Cleaning and Anti-Icing Applications

ABSTRACT For the potential application of superhydrophobic surface to anti-icing of Unmanned Aerial Vehicle(UAV) metal wing,a gradient composite coating was successfully prepared on the common aviation metal 7075Al alloy substrate by electrostatic spraying, with Polytetrafluoroethylene(PEEK) and Polytetrafluoroethylene(PTFE) as raw materials for physical blending. The composite structure was constructed by doping the modified hydrophobic silica(k-SiO2) particles. The wettability, microtopography and chemical components of coating were characterized by contact angle tester, SEM and FT-IR respectively. Results showed that the Water Contact Angle(WCA) of PEEK-PEEK/PTFE composite coating increased with PTFE content increase, and the maximum WCA could reach 149.6°, PTFE and PEEK were cross-linked to form nanofibers closely arranged on the surface. However, when k-SiO2 particles was were added into it, the PEEK-PEEK/PTFE/k-SiO2 superhydrophobic coating that exhibits WCA of 156.4±1° and Water Contact Sliding(WSA) of 2±0.5° was obtained. Micro-nano multi-scale protrusion surrounded by low surface energy fibrous filamentous structure distributed on the surface, which can entrap air pockets, leading to extremely strong dynamic water repellency. Interestingly, it is found that droplets can bounce back quickly after hitting the surface with shorter solid-liquid contact time of 18.25ms. Moreover, the coating exhibits excellent mechanical wear resistance to withstand 51 abrasion cycles with good adhesion to substrate of grade 0, anti-fouling and anti-scaling abilities. Furthermore, compared with the bare 7075Al alloy surface, the prepared superhydrophobic coating has obvious icing characteristic for the reason of a solid-liquid-gas composite contact surface with droplets, making it an ideal anti-icing surface.

Refillable anti-icing SBS composite films

The lifetime of release-based anti-icing systems can be improved by refilling after the complete release of active agents. A novel swelling mediated consecutive filling of Diatomaceous Earth (DE) loaded Styrene-Butadiene-Styrene (SBS) composite films with PEG for anti-icing applications is reported. The degree of swelling and the diffusion of active agents into the composite was controlled by adjusting the composition of a binary mixture consisting of a non-solvent (acetone) and a good solvent (diethyl ether (DiEt)). Rhodamine 6G was used as a probe to show the extent of diffusion of dissolved molecules into SBS. The reversible loading of PEG-600 as anti-icing agent up to 19% by weight into DE/SBS composites and the complete release in the binary mixture having 30 vol. % DiEt was successfully achieved in consecutive cycles. After the 5th loading cycle, these composite films exhibited similar water contact angles (∼ 64°) and freezing delay times within error bars as those of the 1st loading cycle. At −15 °C, the average freezing delay time of the water droplets on DE/SBS composites filled with PEG in 30 vol. % DiEt was increased by a factor of three to 120 s. The successful refilling of the composites with reversible loading/release cycles and without any deterioration in the anti-icing properties at least up to 5 cycles is a significant contribution to the lifetime of release based functional coatings.

Side-by-side field comparison of snow and ice control chemicals for anti-icing applications

This paper presents findings from a side-by-side field comparison of the effectiveness of sodium chloride-based road salt brine (RSB) and magnesium chloride-based Meltdown Apex™ liquid (MDA) as anti-icing chemicals for snow and ice control associated with winter roadway maintenance. The study was sponsored by the Texas Department of Transportation (TxDOT) to support operational decision-making for chemical treatment selections based on the perspective of pavement conditions observed by “the maintenance worker in the truck.” The field test site was a portion of rural service road near Canyon, Texas, located at latitude 35° N. The site was divided into eight 305 m sections that were treated with RSB at 141 l/lane km, MDA at 47 l/lane km, or left untreated for control. Two storm events at the test site during Winter 2014–2015 met pre-established research criteria for snow accumulation and other variables. Test sections were subjected to cycles of plowing, slushing, and additional anti-icing liquid treatment. Digital video data and still image (photo) data were collected throughout the storm events to allow estimation of visible pavement, and vehicle-based decelerometer tests were used to measure pavement friction. Overall results from multiple performance measures indicated comparable effectiveness of RSB and MDA at the applied rates. It was also noted that application of MDA on dry pavement prior to the storm events significantly reduced the pavement friction.

A simple fabrication of superhydrophobic PVDF/SiO2 coatings and their anti-icing properties

Superhydrophobic coatings have been regarded as potential promising solutions to many problems, e.g., ice accumulation in the winter seasons. To be practically useful and economically attractive, it is necessary to fabricate such coatings using facile methods, i.e., with minimal steps and low cost. In this work, a polyvinylidene fluoride (PVDF)/SiO2 coating is successfully prepared with a simple dip coating method. It shows impressive superhydrophobic properties with a large water contact angle (WCA) of 159° and a small sliding angle (SA) of less than 3°. Meanwhile, its superhydrophobic properties are robust in a large temperature range of – 30 to 350 °C and in various environments. Moreover, it shows remarkable anti-icing properties by delaying the freezing time (4 times) and reducing (40%) the adhesion of the ice on the substrate. Therefore, this work has displayed a promising approach for fabricating superhydrophobic coatings towards anti-icing applications.

Industrial applications of superhydrophobic coatings: Challenges and prospects

The use of the superhydrophobic coatings and materials in industry is not satisfactory after the intensive activity in research laboratories in the last two decades. We discussed the reasons for this adverse situation under several topics in this review article. The most important issues are the insufficient mechanical resistance and inevitable contamination of the SH surfaces under outdoor conditions, resulting in short useful life-time. The fabrication of a SH surface requires a rough structure with tiny textures on it and this frail framework has a poor mechanical resistance. The topics of superfluous production of small scale and expensive SH surfaces, the difficulty to obtain transparent and also self-healing SH surfaces, the inefficient anti-icing applications of the SH coatings are also discussed.

An experimental study on different plasma actuator layouts for aircraft icing mitigation

An experimental study was conducted to examine the effects of dielectric-barrier-discharge plasma (DBD) actuator layout on the plasma-induced thermal characteristics and evaluate their effectiveness for aircraft icing mitigation. The experimental investigation was performed in the Icing Research Tunnel of Iowa State University (i.e., ISU-IRT) with an airfoil/wing model embedded with an array of DBD plasma actuators around the airfoil leading edge. The plasma actuators were arranged in different layouts (e.g., orientation, number, and width of exposed electrodes) to evaluate their effects on the anti-icing performance under a typical glaze icing condition pertinent to aircraft inflight icing phenomena. While the dynamics ice accretion or anti-icing process over the airfoil surface before and after turning on the plasma actuators was recorded by using a high-resolution imaging system, a high-speed infrared thermal imaging system was used to quantitatively map the temperature distributions over the airfoil surface. The experimental results clearly reveal that, with the same power consumption level, the plasma actuators in streamwise layout would result in higher plasma-induced surface heating and faster runback of the unfrozen water over the airfoil surface, thereby, having a noticeably better anti-icing performance, in comparison to those in spanwise layout. The plasma actuators in streamwise layout were found to not only be able to prevent ice accretion near the airfoil leading edge, but also allow the plasma-induced surface heating to convect further downstream to delay/prevent the runback ice formation near the airfoil trailing edge. A proper combination of the plasma actuation strength and the plasma discharge coverage over the airfoil surface was found to result in the optimum performance for aircraft anti-icing applications.

Thermal characterisation of electroconductive layers for anti-icing and de-snowing applications on roads

ABSTRACT Heavy snowfall is the most influential factor in the interruption of road vehicular transit during the winter months, sometimes even causing inaccessibility to certain areas. Traditional maintenance strategies address this issue with mechanical solutions combined with the implementation of “de-icing salts”. However, these “de-icing” salts can cause severe damage to the local ecosystem and represent an unsustainable solution to the removal of snow. In order to offer an alternative to the use of “de-icing salts” in roadway maintenance, new environmentally friendly strategies need to be explored. The objective of this paper is to evaluate the thermal performance of electroconductive asphalt mortars under the effect of time-varying magnetic fields, with the aim of using these materials for anti-icing and de-snowing applications on roads. The electroconductive mortars studied were manufactured using the metallic fibres obtained from recycled pneumatic end-of-life vehicle tires. These innovative roadway mortars were tested by measuring the temperature changes produced during and after the activation of the time-varying magnetic field, in a 2-layer system composed of an electroconductive asphalt layer under a conventional bituminous surface course. The results revealed that road temperatures can be controlled depending on the intensity of the magnetic field, the content of metallic fibres and the thickness of the road surface course. Electroconductive mortars might therefore provide a functional alternative for maintaining serviceable roads during snowy winters.

Mechanically robust, self-healing superhydrophobic anti-icing coatings based on a novel fluorinated polyurethane synthesized by a two-step thiol click reaction

Superhydrophobic coatings have big potential to be used in anti-fouling, drug reduction, anti-icing applications. The fabrication of a robust superhydrophobic coating on hard and smooth substrates still remains challenging. It was reported that fluorinated polyurethane (FPU) was a good candidate for superhydrophobic coatings. However, since the preparation methods of FPU at present are rigid and limited, and the substrate adhesion of FPU is unsatisfied, robust FPU-based superhydrophobic coatings on hard and smooth substrates were rarely reported. In this work, a mechanically robust SiO2-FPU superhydrophobic coating on various substrates was synthesized by a two-step thiol click reaction. The branched fluoroalkyl chains were grafted to the polyurethane backbone and then the flexible fluoroalkyl chains tended to migrate to the surface during solvent casting while the strong urethane linkages located at the substrate. The most promising SiO2-FPU coating on glass substrates could maintain superhydrophobic after 30 m sandpaper abrasion, 450 tape peeling cycles and 1.5 h water dripping (~14400 water drops), which are better than the coatings in most of published works. Significantly, the SiO2-FPU coating could recover the superhydrophobicity rapidly after damages because of the accelerated migration of flexible and branched fluoroalkyl chains to the coating surface and the rebuilding of nanoscale structure under heating. The static and the dynamic anti-icing characterizations indicated that the SiO2-FPU coating showed great icing-delaying performance. Both the novel preparation strategy and the FPU-based coating would provide a new perspective in surface protection.

Efficient fabrication of lightweight polyethylene foam with robust and durable superhydrophobicity for self-cleaning and anti-icing applications

The poor robustness and durability of superhydrophobic surfaces under various externally imposed stresses have become a challenging issue for practical applications. Here, an efficient dissolution and modification strategy is proposed for facilely fabricating superhydrophobic polyethylene (F-PE/SiO2) foam with 98.6% porosity using sodium chloride (NaCl) as a sacrificial template and superhydrophobic nano-silica particles as a surface chemical modifier. A microscale porous and interconnected 3D framework is formed when NaCl is dissolved and the nano-silica particles adsorb on the surface of interconnected pores to form nanoscale structures. The F-PE/SiO2 foam exhibits a water contact angle (CA) of 158 ± 2° and a sliding angle (SA) of 4 ± 2°. Interestingly, the F-PE/SiO2 foam could maintain its superhydrophobicity under 980 Pa pressure of water droplet impacting and 8.1 kPa pressure of water flow impacting. Besides robust dynamic superhydrophobicity, the F-PE/SiO2 foam exhibits exceptional mechanical durability against knife scratching, tape-peeling, bending-twisting, and ultrasonication in ethanol because of unique hierarchical micro-nanostructure and the stably adsorbed nano-silica particles. Impressively, the F-PE/SiO2 foam maintains superhydrophobicity upon abrasion damage until all the thickness is worn away, which are potentially advantageous in practical applications. Moreover, this F-PE/SiO2 foam also demonstrated excellence in anti-wetting, self-cleaning and anti-icing, which makes the product can effectively reduce the damage caused by surface pollution, ice formation, and other natural factors when applied to oil-water separation and insulation material of refrigerator.

Amphiphilically modified self-stratified siloxane-glycidyl carbamate coatings for anti-icing applications

Icephobic coatings have applications in many industries to protect surfaces from deterioration and avoid catastrophic incidents. In this work, we report a new strategy to prepare amphiphilic siloxane-glycidyl carbamate coatings (AmpSiGC) coatings with anti-icing property. Polydimethyl siloxane (PDMS) and poly(ethylene glycol) (PEG) provided amphiphilicity for the AmpSiGC coatings. The designed experiment considered several factors: molecular weight of the surface-modifying polymers and their amount in the coating system. Although amphiphilic coatings have demonstrated promising results as marine coatings, investigations on their icephobic applications have been limited. This work discusses three aspects of the developed AmpSiGC systems: (1) preparation of the incorporated ingredients and their characterization by Fourier transform infrared spectroscopy (FTIR); (2) surface characterization of coatings via ATR (attenuated total reflectance)-FTIR, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM); and (3) ice-adhesion, electrochemical impedance spectroscopy (EIS), and mechanical property evaluations. Overall, the surface analysis indicated the presence of both hydrophobic and hydrophilic domains and most of the coatings demonstrated promising performance for anti-icing applications with desirable barrier and mechanical properties in comparison to controls.

Excellent static and dynamic anti-icing properties of hierarchical structured ZnO superhydrophobic surface on Cu substrates

The anti-icing behavior of static and dynamic low-temperature droplets on the surface of microelectronic material was investigated. The ZnO-coated superhydrophobic surface (SPS), hydrophobic surface (HPS), hydrophilic surface (HS) and pure Cu surface were prepared by hydrothermal method and ultraviolet light irradiation. Under the static and dynamic anti-icing condition, the SPS had excellent anti-icing ability before −20 °C. Even if the temperature was −20 °C, the SPS still have longest delayed icing time when compared with other three surfaces. This work offers a theoretical guidance for anti-icing application of microelectronic materials.