Effective large-scale deicing based on the interfacial toughness tuning of a UV-curable PDMS coating

Abstract

In this study, the effective large-scale deicing based on the interfacial toughness-tuning strategy of an ultraviolet-curable PDMS coating was developed. Methacrylate groups were grafted on the hydroxyl-terminated PDMS molecular chains to endow PDMS the response to UV irradiation. Then the precursor was doped with different proportions of silicon dioxide nanoparticle (SiO₂ NP) to tune the interfacial toughness between the coating and the ice layer. The PDMS coating was fabricated through manual spraying and the polymerization under UV irradiation. The effects of the amounts of the methacrylate groups and SiO₂ NP on the deicing properties of UV-curable PDMS coatings were investigated systematically. In addition, it was found that the large-scale deicing performance of the PDMS coating with 10% SiO₂ NP improved when lowering the ambient temperature, which was mainly related to the increase of the shear modulus and thermal residual stress on the interface and might indicate attractive advantage on the extremely cold environment. Meanwhile, the durability and the adaptability to different substrates of the PDMS coating were also examined for the verification of the possible practical application. In summary, the effective large-scale deicing based on the interfacial toughness tuning of a UV-curable PDMS coating was achieved and the coating showed great potential for practice.

Introduction

Avoiding ice accretion on the surface is necessary and important for the safe operation of many facilities in the cold environment, such as aircraft, railway transportation, wind turbine blade and power transmission [[1], [2], [3], [4]]. To solve this problem, anti-icing and icephobic materials based on the surface engineering technology have been developed in recent years. Compared to the traditional methods, anti-icing and icephobic surfaces are potential to become the new substitutes due to the higher efficiency, the lower energy consumption and the less environmental hazard [[5], [6], [7]].

For example, superhydrophobic surface can prevent water from spreading and contacting. The micro/nano morphologies of the surface reduces the real contact area of water droplet and suppresses the heat transfer for the nucleation [[8], [9], [10]]. However, SHS may not work once ice penetrates into the surface morphology in an extremely cold and humid environment [[11], [12], [13], [14]]. Another kind of the surface is the slippery liquid impregnated surface. A thin liquid layer can be formed to avoid the direct contact between the water/ice and the surface. Impacting water droplets slide off the surface more easily and icing on the surface can also be delayed [15,16]. In addition, the low adhesion between the ice and the liquid layer facilitates the removal of ice after icing. However, one of the key limitations of this surface is the gradual depletion of lubricating liquid [[17], [18], [19], [20]]. In most cases, icing on the surface is inevitable when suffering from a cold and humid environment for a long time, so surfaces based on the interfacial fracture mechanics are developed specially for the easy removal of the accreted ice [[21], [22], [23]]. Low interfacial toughness (LIT) material is one of these surfaces based on the toughness-controlled regime of interfacial delamination. In short, when the interfacial length is over a critical value, the cracking of ice-solid interface is controlled by the toughness regime. The shear force for deicing remains constant and has no change with the increasing interfacial length. The lower interfacial toughness, the lower constant shear force [[24], [25], [26]]. Therefore, it is expected that the LIT material shows great potential in the large-scale deicing of the outdoor equipment with large area and it is possible for the self-dislodging of ice under gravity. Many factors can influence the interfacial toughness, including the thickness of the coating, lubricating status, interfacial slippage, surface morphology and so on [24,25,27]. From the perspective of cohesive zone model, lowering the interfacial toughness can be regarded as reducing the area of the region under the traction-separation law curve [24]. Yu et al. provide a method for lowering the ice-solid interfacial toughness effectively through doping different amounts of silicon dioxide nanoparticle and phenylmethyl silicone oil into the PDMS matrix simultaneously, which shows the possibility of improving the large-scale deicing performance for the existing materials [27].

Although excellent performances of the effective anti-icing and deicing surfaces have been achieved, there still lacks the foundation for the practical application of these surfaces. According to a statistical result about the recent researches on the anti-icing and deicing surfaces in Table S1, almost all preparation processes go through relatively long and complex periods. Some methods do not support the in-situ fabrication, such as spin-coating [14,28], dip-coating [29,30], and casting [31,32]; some methods are not suitable for the large-scale fabrication, such as drip-coating [26] and chemical vapor deposition (CVD) [13]; some other methods need delicate equipment, including laser ablation [33], photolithography [21], dry ion etching [34], high-velocity oxyfuel (HVOF) thermal spray [25] and so on. Therefore, a rapid, scalable and in-situ fabrication method is necessary and important for the development of the effective anti-icing and deicing surfaces. Recently, UV-curable material has been paid much attention due to the rapid and continuous fabrication process [[35], [36], [37]]. Some attempts have also been made on the development of anti-icing and deicing surfaces combining UV-induced polymerization [[38], [39], [40], [41]]. For example, Coady et al. introduced a method of lowering the cross-linking density by incorporating different comonomers into a commercially available UV-curable siloxane resin. The surfaces showed an ice adhesive strength of approx. 50 kPa for at least 50 icing-deicing cycles [41]. Li et al. developed transparent antifogging/anti-icing coatings from amphiphilic block copolymers through UV-curing. Their coatings exhibited apparent freezing delay for more than 2 min at −15 °C [39]. However, the above researches still cannot meet the requirement for the rapid, in-situ and scalable fabrication of deicing surface.

Because of the low surface adhesive work and high flexibility, PDMS is widely used in the researches including anti-fouling [42,43], nanoparticle self-assembly [44] and anti-icing surfaces [13,45]. In this work, the effective large-scale deicing based on the interfacial toughness-tuning strategy of a UV-curable PDMS coating was achieved. UV-curable PDMS material was obtained by grafting methacrylate groups on the PDMS chains. The interfacial toughness was tuned by doping SiO₂ nanoparticle and it is found that the large-scale deicing performance of the PDMS coating showed improvement with 10% SiO₂ nanoparticle. In addition, the effect of the ambient temperature on the deicing property was also investigated. To verify the advantage of the coating for the practical application, the durability and the adaptability to different substrates of the coating were also evaluated.