Open Access
Icephobic coating based on novel SLIPS made of infused PTFE fibers for aerospace application
(MDPI, 2024) Vicente Gómara, Adrián; Rivero Fuente, Pedro J.; Rehfeld, Nadine; Stake, Andreas; García, Paloma; Carreño, Francisco; Mora, Julio; Rodríguez Trías, Rafael; Ingeniería; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa, PJUPNA1929
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.
Open Access
Comparative study of electrospun polydimethylsiloxane fibers as a substitute for fluorine-based polymeric coatings for hydrophobic and icephobic applications
(MDPI, 2024-11-30) Vicente Gómara, Adrián; Rivero Fuente, Pedro J.; Santos, Cleis; Rehfeld, Nadine; Rodríguez Trías, Rafael; Ingeniería; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Univertsitate Publikoa, PJUPNA1929
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.
Open Access
Icephobic and anticorrosion coatings deposited by electrospinning on aluminum alloys for aerospace applications
(MDPI, 2021) Vicente Gómara, Adrián; Rivero Fuente, Pedro J.; García, Paloma; Mora, Julio; Carreño, Francisco; Rodríguez Trías, Rafael; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; Ingeniería
Anti-icing or passive strategies have undergone a remarkable growth in importance as a complement for the de-icing approaches or active methods. As a result, many efforts for developing icephobic surfaces have been mostly dedicated to apply superhydrophobic coatings. Recently, a different type of ice-repellent structure based on slippery liquid-infused porous surfaces (SLIPS) has attracted increasing attention for being a simple and effective passive ice protection in a wide range of application areas, especially for the prevention of ice formation on aircrafts. In this work, the electrospinning technique has been used for the deposition of PVDF-HFP coatings on samples of the aeronautical alloy AA7075 by using a thickness control system based on the identification of the proper combination of process parameters such as the flow rate and applied voltage. In addition, the influence of the experimental conditions on the nanofiber properties is evaluated in terms of surface morphology, wettability, corrosion resistance, and optical transmittance. The experimental results showed an improvement in the micro/nanoscale structure, which optimizes the superhydro-phobic and anticorrosive behavior due to the air trapped inside the nanotextured surface. In addi-tion, once the best coating was selected, centrifugal ice adhesion tests (CAT) were carried out for two types of icing conditions (glaze and rime) simulated in an ice wind tunnel (IWT) on both as-deposited and liquid-infused coatings (SLIPs). The liquid-infused coatings showed a low water adhesion (low contact angle hysteresis) and low ice adhesion strength, reducing the ice adhesion four times with respect to PTFE (a well-known low-ice-adhesion material used as a reference).

Vicente Gómara, Adrián

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