Importance of Hydrophobic and Oleophobic Nano-Coatings in Filtration

Topics Covered

P2i Nano-Coating for Filtration
Paper Extract: Liquid Repellent Nano-Coatings for Gas Turbine Filtration Improvements
     The P2i Process
About P2i


Non-woven and membrane filters play a vital role in the longevity and reliability of products. In harsh environments such as automotive, electronics and gas turbines, in particular, these products can be of high value and require the highest levels of oil and water repellency.

P2i’s technology enables a step change in material selection through advancements in surface modification. Although traditional filtration materials can provide hydrophobic properties, P2i is unique in its ability to repel the highest levels of oil repellency through its oleophobic properties.

Thenano-scale thickness of the coating ensures pore size is maintained and there is no change to the air-flow of the media. As such, easily formed economical filter media such as nylon or cellulose, can become a cost effective alternative with the addition of liquid and oil repellent benefits.

P2i Nano-Coating for Filtration

P2i’s patented technology increases the hydrophobicity (water repellency) and oleophobicity (oil repellency) of filtration media to the highest levels. Surface energies as low as 7mN/m can be achieved, giving repellency up to oil-9 on the AATCC 118-2012 scale.

The nano-coating has no effect on pore size, delivering superior repellency whilst maintaining air-flow. This maximises the lifetime of the filter and minimises pressure drop due to absorbed liquids.

As the technology is applicable to any filter media it offers new opportunities by widening the selection of materials available. For example, a lower cost or higher permeability material treated with P2i’s technology can be used instead of ePTFE for applications that require high levels of water repellency.

Furthermore, the performance and applicability of naturally water repellent materials such as polypropylene or PTFE can be enhanced further by P2i’s technology. Increasing the levels of oil and alcohol repellency allows their use in the most demanding environments such as automotive, industrial, gas turbine, and pharmaceutical product protection.

The P2i nano-coating is deposited via a vacuum plasma deposition process, ensuring the highest levels of process repeatability and control. The sealed, low pressure, processing chamber ensures an environmentally clean process with minimal energy usage and emissions. A variety of machine options are available allowing processing of media in roll or sheet format or, alternatively, processing of the complete filter assembly.

Paper Extract: Liquid Repellent Nano-coatings for Gas Turbine Filtration Improvements

Paper by Mike McCarthy from P2i for World Filtration Congress


Gas Turbines have been used for many years as a convenient source of electricity for stable self-contained industrial sites, peak shaving to an established power grid, or an inexpensive source of electricity at natural gas production sites. Gas Turbine engines continue to evolve and improve power generation to electricity generating efficiency by use of lightweight materials and increased engine tolerances. These improvements have also had a follow on effect of a holistic approach to the role of the air cleaning/filtration system.

Due to the changes in engine design and the requirements for greater generating efficiency, the filtration systems have been required to respond with steadily improved particulate removal efficiency. The goal of these higher particulate removal efficiency filters is to keep the turbine blades clean, free of particulate, and thus extending the on line days or conversely reducing the PM downtime intervals allocated to turbine cleaning and filter replacement.

Marine and ocean side installations create unique filtration issues due to fog and sea water spray. Mist and salt water droplets can penetrate through conventional filtration media and reach the gas turbine engine. When this happens the gas turbine will need to be taken off line and cleaned. If salt water droplets are captured at the final filter, the resulting evaporation of the water and deposition of the salt crystals can block filter pores resulting in a premature rise in filter pressure drop or differential pressure. Once the filters become blocked, the gas turbine must be taken off line and the filters replaced. The result from both scenarios is a loss in operational efficiency and profitability for the gas turbine.

The use of P2i’s liquid repellent nano coating will prevent water mist and salt water clogging the filter pores and from reaching the gas turbine engine thereby allowing for greater and longer performance of the gas turbine.

The P2i Process

The normal coating process involves a dip-saturate-squeeze-dry sequence. The challenges with this process are the coating is not “bound” to the substrate, the sustainability of the coating is a function of the strength of the coating crosslinking to itself, preferential coating concentration resides on the substrate surface, and a wicking over or blocking of small pores in the substrate. For some applications these conditions features may be acceptable. But for a high performance gas turbine filter, these features can reduce filter performance.

The P2i nanocoating creates permanently bound functional groups on the surface of a substrate through plasma surface activation and covalent bonding. These functional groups are nano in thinness – 10 – 50 nm thin. The nanocoating is also affixed evenly throughout a substrate by coating each individual fiber or component in a filter. Thus the resulting treated substrate has a permanent nano coating affixed to each and every fiber in the media structure and does not inhibit air flow. At the same time the nano coating offers superior water and oil repellency.

About P2i

P2i is uniquely positioned to provide tailored, invisible functionality across a range of manufacturing requirements, through proven nano-coating solutions. With commercial expertise driving application across five market sectors and a commitment to global service and support, P2i delivers outstanding performance improvement and new market opportunities to a wide range of products.

P2i was established in 2004 to commercialize technologies developed by the UK Government’s Defence Science & Technology Laboratory (DSTL). Research and development have identified innovative applications equipment and processing methods, culminating in a growing patent portfolio extending to over 65 families. Ongoing acquisitions have provided valuable new technologies such as antimicrobial, super hydrophilic and protein resistance coatings - making P2i the global leader in invisible surface functionality.

In addition to headquarters in the United Kingdom, P2i has a technology centre in the United States and an applications centre in China. P2i's technology is indicated in the Electronics sector by either its splash-proof or Dunkable™ nano-coatings.

This information has been sourced, reviewed and adapted from materials provided by P2i.

For more information on this source, please visit P2i.

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