Doctor of Philosophy
Ragogna, Paul J.
Ice accumulation is a major engineering challenge in many fields including aerospace, power generation, transportation, and infrastructure. A variety of solutions are being researched to address this challenge. Perhaps the most promising method of combating ice accumulation is by applying coatings with low values of interfacial ice adhesion strength, τice. Icephobic materials are those with ice adhesion below 100 kPa, and it has been shown that passive delamination can occur on surfaces with τice below 20 kPa. While various low adhesion surfaces have been prepared, durability concerns pervade applications where surfaces experience repeated icing or freeze-thaw cycles, mechanical abrasion, and particulate erosion. The present thesis explores methods of improving the durability of state-of-the-art icephobic materials in order to make them more suitable solutions to ‘the icing problem.’ Ice adhesion was measured using in-house load cell and centrifugation methods, allowing for the direct comparison of τice values between the materials developed. Various ways of improving the durability of icephobic surfaces were identified, including the stabilization of slippery lubricant-infused porous surfaces (SLIPS) via polymer cross-linking at the interface, copolymerization of commercial poly(dimethylsiloxane) resins with acrylate / styrene monomers yielding highly cross-linked network copolymer coatings, and lowering ice adhesion on commercially available adhesive films by introducing areas of substrate-film detachment. A collaborative study of femtosecond laser micromachining done with McGill University is also included which showed the cross-link density dependence of threshold fluence, and the varied surface morphologies that could be accessed by these means. These studies show effective methods of influencing icephobic material durability using straightforward methodologies and will inspire new investigations toward creating more durable icephobic materials that can alleviate concerns with ice accumulation for people that live in cold climates. Our investigations and proposed work show that cutting-edge research in this field can be done at Western, making Canada a viable leader of global anti-icing research.
Summary for Lay Audience
Ice accumulation occurs in many places in nature and in industry, threatening to destroy vital infrastructure such as roads and power transmission lines. The North American Ice Storm of 1998 is an example of the expense of extreme weather, causing $5 Billion in damage in Canada over the course of six days and cost 35 Canadians their lives. Preventing large-scale damage to our infrastructure is of critical importance to protect lives, and to reduce the cost of maintenance paid by taxes.
Icephobic (ice-fearing) coatings are those that resist or prevent ice growth on their surfaces. To date, the best-performing materials are rubber-based and oil-containing coatings operating on a simple principle: rigid materials like ice do not adhere to flexible materials like rubber and oil. While there has been considerable success in applying well-known rubbers like silicones, challenges remain before these materials can be used on a large scale. Firstly, the materials must be made more durable. Icephobic materials, in particular those including oils, are prone to damage through abrasion, such as that experienced if sand or ice particles are blown across surfaces by high winds. Secondly, coatings must be applied to surfaces on a huge scale, such as on all powerlines within a city. To address these challenges, we hope to toughen these materials through different chemical modifications. These methods are presented in the present thesis: 1) Using cross-linking in silicone rubber coatings to retain oil in icephobic materials; 2) Inscribing special surface morphologies in rubber surfaces to reduce ice growth; 3) Making silicones more durable by incorporating plastic-like materials; 4) Decreasing ice adhesion strength on commercial adhesive tapes by changing how they adhere to their substrates.
The expected impact of this work is to inspire new investigations toward creating more durable icephobic materials that can alleviate concerns with ice accumulation for people that live in cold climates. Our investigations and proposed work show how cutting-edge research in this field can be done at Western, making Canada a viable leader of global anti-icing research.
Coady, Matthew J., "Progress Toward Durable Icephobic Materials" (2019). Electronic Thesis and Dissertation Repository. 6590.