Introduction

Ice accretion and its strong adhesion to a variety of surfaces impact a wide range of applications, from essential infrastructure like power grids and buildings to transportation vehicles such as aircraft and ships. Hundreds of articles on innovative ice-shedding surfaces and coatings have been published in the last few years. However, the absence of standardized methods for forming and detaching ice from different substrates has made it difficult to accurately test new coatings and compare their performance against the prior state of the art.^1-3ÌýPush-off tests on static ice frozen from bulk water are the most commonly used methodology to quantify ice adhesion. However, differences in applied freezing conditions can significantly alter the measured adhesion to surfaces.³ÌýIn particular, the effects of freezing under isotropic and anisotropic temperature environments have not been adequately studied.

In an anisotropic temperature environment, produced by Peltier plates or other cooling surfaces, the latent heat is dispelled unidirectionally into the cooling surface. In an isotropic temperature environment, such as inside a freezer, the water is surrounded by cold air, and the latent heat can be dispelled outwards in all directions.³ÌýIn both cases, when water freezes, it undergoes a volume expansion of approximately 9% as it solidifies into ice. If this volume expansion is constrained by ice, the substrate, or the walls of a mold used to form ice, residual stresses can develop in the ice and at the ice-substrate interface. Residual stresses induced from this phase change and from thermal contraction have been shown to reduce the adhesion of ice to different surfaces.^4-6ÌýThe magnitude and distribution of these stresses, and thereby the measured ice adhesion, likely depend heavily on the freezing process.

In this article, the effects of anisotropic and isotropic ice freezing methods on ice adhesion are examined. Ice push-off tests are conducted across a range of coated and uncoated surfaces. Videos and finite element analysis (FEA) of the freezing process provide further insight into differences between the two modes of freezing. By accounting for the effects of freezing mode on adhesion, the relative ice shedding ability of coatings can be more accurately evaluated.

Methods and Materials

Bulk ice adhesion to surfaces was tested using a push-off setup, similar to those described in prior literature.⁷ÌýA digital force gauge mounted to a motorized stage pushed the adhered ice at a constant displacement rate of 73.5 μms^-1Ìýuntil detachment. Ice was formed by pipetting room temperature DI water into 3D printed acrylonitrile butadiene styrene (ABS) cuvette molds with open bases to allow for adhesion to a surface. Ice height and width were constant at h = 0.6 cm and w = 1 cm, while lengths from 1 cm to at least 14 cm were tested on all surfaces. To freeze water under anisotropic temperature conditions, the surface is mounted on top of a Peltier cooling plate set to -10 °C, with the surrounding air at room temperature. To freeze water under isotropic temperature conditions, the surface is mounted to a push-off setup inside a walk-in freezer so that both the surface and the air surrounding the water are initially cooled to -10 °C.

Ice adhesion properties for freezing by both isotropic and anisotropic temperature conditions were evaluated on three common plastic surfaces from McMaster Carr and two ice-shedding coatings previously investigated in prior work. The plastics, polytetrafluoroethylene (PTFE; Catalog No. 8545K22), polymethylmethacrylate (PMMA; 8560K171), and polycarbonate (PC; 8574K24) each had a thickness of t = 1.6 mm. Two thin coatings with low-interfacial toughness (LIT) designed to facilitate largescale ice shedding through the propagation of an interfacial crack, LIT PDMS and LIT PVC, were brushed onto aluminum substrates following the methods described in a previous work.⁷ÌýThese coatings consist of elastomers of polydimethylsiloxane (PDMS) and polyvinylchloride (PVC) further plasticized by uncrosslinked oils.

Time-dependent 3D simulations of the two freezing processes were performed in COMSOL Multiphysics^®. To replicate the experimental setup, a 0.6 cm (h) × 1 cm (w) × 8 cm (l) ice/water slab in a 1 mm-thick ABS cuvette rested on a 1.59 mm (h) × 3 cm (w) × 10 cm (l) plastic substrate. The computational domain was reduced by simulating one-fourth of the model size, leveraging the symmetrical planes along the ice’s length and width.

The heat equation

was used in the Heat Transfer in Solids and Fluids module to simulate temperatureÌýTÌýover timeÌýt. The densitiesÌýÒÏ, heat capacitiesÌýC_p, and thermal conductivitiesÌýkÌýof the materials in the simulation are listed inÌýTable 1.ÌýInitial temperatures were set at 20 °C for the water and cuvette, and at -10 °C for the substrate. To simulate isotropic freezing, external surfaces exchanged heat with ambient air at -10 °C via Neumann (heat-flux) boundaries. For anisotropic-freezing, the bottom of the substrate was fixed at -12 °C so that the top of the substrate maintained an approximate temperature of -10 °C, while all the other surfaces exchanged heat with ambient air at -10 °C (Neumann). The convective heat transfer coefficient was 8 W/m²K.

Phase-change behaviors were delineated using the Apparent Heat Capacity Method by setting a phase transition fractionÌýθÌýso that pure ice givesÌýθÌý= 1 and pure water givesÌýθÌý= 0. Apparent heat capacity and thermal conductivity during phase transition could then be calculated as

,

and

,

where latent heat isÌýLÌý= 333 kJ/kg. To illustrate the freezing process, regions withÌýθÌý< 0.5 were set as blue to represent water, and regions withÌýθÌý> 0.5 were set as red to represent ice.

Continue reading in the March-AprilÌýissue of CoatingsTech

The construction industry is experiencing a paradigm shift from focusing solely on sustainability to embracing comprehensive resilient design, driven by increasingly severe weather events and rising financial risk. While sustainable design emphasizes minimizing environmental impact and resource conservation, resilience—the capacity to adapt and maintain functionality after a disturbance—demands a systems-based approach that addresses future-looking hazards like high winds, hail, fire, and flooding. This article argues that true durability requires building materials, including advanced coatings, to work collaboratively as integrated systems to resist extreme loads that exceed minimum building code requirements. It explores current design resources like LEED v5 and FM Global standards, and provides specific examples of how materials are engineered to resist hazards. These examples include multilayer roofing systems designed for very severe hail, and innovative coatings and membranes used in water-retention assemblies to manage urban storm runoff. Ultimately, resiliency is redefining what it means to create durable, lasting buildings, positioning systems-level thinking—rather than isolated product properties—as the foundation for a future-proof built environment.

Introduction

Resilient design has become a catchphrase within the construction and architecture communities. Over the last two decades, forward-thinking designers and building owners have focused not just on the now, but on the future, when determining their designs. This challenge started with a focus on sustainability. The U.S. Green Building Council (USGBC) defines sustainable design as “creating places that are environmentally responsible, healthful, just, equitable, and profitable.”¹ÌýSustainable solutions often refer to minimizing the burden on the natural environment, recycling, and conserving energy and other natural resources. These goals have created a multitude of industry buzzwords, including durability, recycled content, energy efficiency, and carbon neutral. However, sustainability is not the same as resiliency.

Resilience is defined by the Resilient Design Institute as “the capacity to adapt to changing conditions and to maintain or regain functionality in the face of stress or disturbance. Resilient design solutions often consider durability as well as the ability to keep a building functional after a weather event.”²ÌýSolutions such as having a generator to maintain power are very resilient, though not necessarily sustainable (Figure 1). To be truly resilient, designers and building product manufacturers must look at more than product properties such as Volatile Organic Compounds (VOC) and embodied carbon, often the go-to for sustainable design, and more at materials working together as systems. There is no one property that ensures resilience. Designers and manufacturers need to collaborate to create complete systems of materials that work together to achieve a successful outcome. The ultimate goal is for designed solutions to meet both sustainability and resiliency targets, such as slowing the release of storm water to prevent overloaded sewers while also using some of the captured rainwater for irrigation.

One example of resilient design is the Sand Palace, which was one of the only structures left standing in its area after Hurricane Michael in 2018. Built specifically to withstand severe storms, the house utilized advanced materials like insulated concrete forms (ICFs) and was designed to resist winds of up to 250 mph, significantly exceeding state building codes at the time. The homeowner explained that they deliberately went “above and beyond code” when making material and design decisions by consistently asking, “What would survive the big one?” It is estimated that the house cost 15-20% more as a result of these decisions. Although they did have to replace utilities and experienced the loss of the first floor along with one of the air handlers, the overall damage was minimal compared to the surrounding properties.

Resiliency has become an important design strategy for many reasons, but the primary driver is money. It is expensive to rebuild after severe weather events, and insurance companies are noticing. In some parts of the United States, it is becoming more expensive and more difficult to get insurance, particularly in coastal regions and areas prone to wildfire. For example, a 2024 report from the Senate Budget Committee shows that the nonrenewal rate in Florida increased 280% between 2018 and 2023.³ÌýAdditionally, FM Global, one of the largest insurers of commercial properties, continues to expand the areas where their buildings must meet very severe hail requirements.

On the residential side, prospective homebuyers are paying attention to the potential weather impacts on properties. In 2024, Zillow started posting hazard ratings for climate-related impacts such as flood, wildfire, wind, heat, and air quality on property listings.⁴ÌýAs with other trends within the construction industry, significant attention is paid when there are clear drivers to profits and losses. This article introduces published resources and references being used by designers to design for resilience. It then looks closely at specific examples in which coatings and other building materials work together as systems to withstand increased building loads.