Ice adhesion tests are widely used to assess the performance of potential icephobic surfaces and coatings. A great variety of test designs have been developed and used over the past decades due to the lack of formal standards for these types of tests. In many cases, the aim of the research was not only to determine ice adhesion values, but also to understand the key surface properties correlated to low ice adhesion surfaces. Data from different measurement techniques had low correspondence between the results: Values varied by orders of magnitude and showed different relative relationships to one another. This study sought to provide a broad comparison of ice adhesion testing approaches by conducting different ice adhesion tests with identical test surfaces. A total of 15 test facilities participated in this round-robin study, and the results of 13 partners are summarized in this paper. For the test series, ice types (impact and static) as well as test parameters were harmonized to minimize the deviations between the test setups. Our findings are presented in this paper, and the ice- and test-specific results are discussed. This study can improve our understanding of test results and support the standardization process for ice adhesion strength measurements.

The relationship between the bulk thermomechanical properties and rain erosion resistance of development polyaspartate-based coatings as candidate leading edge protection (LEP) materials for wind turbine blades is investigated by the combined application of dynamic mechanical analysis (DMA) and rain erosion testing (RET) within a novel test method (DMA+RET). This method introduces the use of DMA+RET to both monitor the change in thermomechanical properties with respect to raindrop impact and subsequently rationalise differences in rain erosion resistance between coating formulations of comparable composition. The application of this combined process has demonstrated the importance of relatively high viscoelastic moduli at increased strain rates and creep recovery after RET as key material properties to be considered for LEP material development, whereas previous research presented in the scientific literature has primarily focussed on the use of routine characterisation procedures by tensile testing or stand-alone DMA to evaluate coating formulations prior to rain erosion testing. This journal article therefore presents a novel method to evaluate key material properties relevant to rain erosion resistance before and after subjection to raindrop impact using standard ASTM G73 RET equipment. The test method is demonstrated on a novel polyaspartate-based coating, PA-U, that exhibits notable rain erosion resistance in comparison to commercial LEP products. PA-U exhibited negligible mass loss after 30 h of rain erosion testing and favourable thermomechanical properties (E″ = 35 MPa at critical strain; equilibrium recoverable compliance of 0.05 MPa⁻¹) in comparison to alternative formulations.

In this study, we assessed the effects of ice types, test parameters, and surface properties on measurement data of the ice adhesion centrifuge test. This method is often used for the evaluation of low ice adhesion surfaces, although no test standard has been defined yet. The aim of this paper is to improve the understanding of the relevant test parameter and identify crucial criteria to be considered in harmonization and standardization efforts. Results clearly indicate that the ice type (static vs. impact ice) has the greatest impact on the test results, with static ice delivering higher values in a broader data span. This is beneficial for material developers as it eases the evaluation process, but it contradicts the technical efforts to design tests that are as close as possible to realistic technical environments. Additionally, the selected ice type has a significant impact on the relevance of the surface properties (roughness, wettability). Despite the complexity of interactions, a trend was observed that the roughness is the determining surface parameter for high impact velocity ice (95 m/s). In contrast, for tests with static ice, the wettability of the test surface is of higher relevance, leading to the risk of overestimating the icephobic performance of structured surfaces. The results of this paper contribute to the demanding future tasks of defining well-founded test standards and support the development of icephobic surfaces.

The development of slippery surfaces has been widely investigated due to their excellent icephobic properties. A distinct kind of an ice-repellent structure known as a slippery liquid-infused porous surface (SLIPS) has recently drawn attention due to its simplicity and efficacy as a passive ice-protection method. These surfaces are well known for exhibiting very low ice adhesion values (τice < 20 kPa). In this study, pure Polytetrafluoroethylene (PTFE) fibers were fabricated using the electrospinning process to produce superhydrophobic (SHS) porous coatings on samples of the aeronautical alloy AA6061-T6. Due to the high fluorine–carbon bond strength, PTFE shows high resistance and chemical inertness to almost all corrosive reagents as well as extreme hydrophobicity and high thermal stability. However, these unique properties make PTFE difficult to process. For this reason, to develop PTFE fibers, the electrospinning technique has been used by an PTFE nanoparticles (nP PTFE) dispersion with addition of a very small amount of polyethylene oxide (PEO) followed with a sintering process (380 °C for 10 min) to melt the nP PTFE together and form uniform fibers. Once the porous matrix of PTFE fibers is attached, lubricating oil is added into the micro/nanoscale structure in the SHS in place of air to create a SLIPS. The experimental results show a high-water contact angle (WCA) ≈ 150° and low roll-off angle (αroll-off) ≈ 22° for SHS porous coating and a decrease in the WCA ≈ 100° and a very low αroll-off ≈ 15° for SLIPS coating. On one hand, ice adhesion centrifuge tests were conducted for two types of icing conditions (glaze and rime) accreted in an ice wind tunnel (IWT), as well as static ice at different ice adhesion centrifuge test facilities in order to compare the results for SHS, SLIPs and reference materials. This is considered a preliminary step in standardization efforts where similar performance are obtained. On the other hand, the ice adhesion results show 65 kPa in the case of SHS and 4.2 kPa of SLIPS for static ice and <10 kPa for rime and glace ice. These results imply a significant improvement in this type of coatings due to the combined effect of fibers PTFE and silicon oil lubricant.

Significant progress in the field of icephobic coatings has raised a demand for evaluation criteria to assess and monitor the related icephobic effects and their durability. The initial coating performance in preventing ice formation and reducing ice adhesion needs to be proven over a given period by withstanding technically relevant stressors. In this study, silanized polyurethane (PUR) coatings are assessed in conjunction with a standardized accelerated ultraviolet (UV)-ageing procedure in order to identify potential monitoring tools that are also applicable during in-service inspections. Wettability and roughness parameters are recorded after pre-defined ageing intervals, compared with the ice adhesion strength, and tested using a modified centrifuge. Correlation assessments indicate that the chosen parameters cannot generally be used for the monitoring of icephobic effects for the selected material class. It is more likely that specific coating parameter sets need to be defined for in-service monitoring, as an important step towards the integration of icephobic coatings into technical applications.

The development of superhydrophobic, waterproof, and breathable membranes, as well as icephobic surfaces, has attracted growing interest. Fluorinated polymers like PTFE or PVDF are highly effective, and previous research by the authors has shown that combining these polymers with electrospinning-induced roughness enhances their hydro- and ice-phobicity. The infusion of these electrospun mats with lubricant oil further improves their icephobic properties, achieving a slippery liquid-infused porous surface (SLIPS). However, their environmental impact has motivated the search for fluorine-free alternatives. This study explores polydimethylsiloxane (PDMS) as an ideal candidate because of its intrinsic properties, such as low surface energy and high flexibility, even at very low temperatures. While some published results have considered this polymer for icephobic applications, in this work, the electrospinning technique has been used for the first time for the fabrication of 95% pure PDMS fibers to obtain hydrophobic porous coatings as well as breathable and waterproof membranes. Moreover, the properties of PDMS made it difficult to process, but these limitations were overcome by adding a very small amount of polyethylene oxide (PEO) followed by a heat treatment process that provides a mat of uniform fibers. The experimental results for the PDMS porous coating confirm a hydrophobic behavior with a water contact angle (WCA) ≈ 118° and roll-off angle (αroll-off) ≈ 55°. In addition, the permeability properties of the fibrous PDMS membrane show a high transmission rate (WVD) ≈ 51.58 g∙m⁻²∙d⁻¹, providing breathability and waterproofing. Finally, an ice adhesion centrifuge test showed a low ice adhesion value of 46 kPa. These results highlight the potential of PDMS for effective icephobic and waterproof applications.