15 Oct Hydrophobicity and Oleophobicity: WHY IS THIS IMPORTANT FOR CERAMIC COATINGS?
In the last few years there has been a lot of new terminology introduced to car care enthusiasts and ceramic coating installation experts. This is particularly true when it comes to car coatings. In the old school days, it was all about wax. Maybe the only term one had to understand was “Carnauba” or “Paste Wax” or “Liquid Wax.” The measure of performance was typically, “How well does the surface bead water?”
Beading water is still important, but today, with the advent of ceramic coatings, things have become more technical. For the enthusiast that’s a good thing because the performance of protective coatings has advanced a great deal. Cars and the paint applied to them are so much more advanced…. and expensive, so there is a lot to protect. So welcome to 2020. Yes, there is a lot more to understand but knowing some of the basic terms related to ceramic coatings can help in comparison of coatings.
Two words that should be understood are Hydrophobicity and Oleophobicity. When these terms are used to describe a surface, they refer to the repellency of the surface. The adjective “hydrophobic” describes a surface that repels water and “oleophobic” repels oils. A car’s surface can be hydrophobic, oleophobic, both or neither. There is a more detailed write-up of these terms on the NanoSlic website. An instrument called a Goniometer is used to measure the Hydrophobicity or Oleophobicity. Basically, the instrument deposits a very small drop of water or oil respectively and measures how spherical the drop is. The more repellent the surface, the more the drop will pull back on itself and appear as a sphere. The measurement is called the Contact Angle. The higher the number, the more repellent the ceramic coated surface.
Hydrophobicity is measured with water. Deionized water is typically used to minimize any inconsistencies from contaminants in the water. To measure oleophobicity a standard fluid such as n-hexadecane is typically used. It is very important to note, that when a ceramic coating manufacturer states a certain contact angle for hydrophobicity or oleophobicity, the fluid used should be listed. Otherwise you cannot accurately compare with another manufacturer’s product.
So why is Hydrophobicity and Oleophobicity important? Well one of the most sought-after properties of ceramic coatings is their ability to bead water. And although beading water may look cool there are several functional reasons why it’s a good thing. Here are three: 1) If water beads up instead of spreading out, the water will be carried off the car faster and more completely, thus protecting the car from the damaging effects of atmospheric water. i.e. minerals, acid, etc. 2) As the water beads up it has a tendency to pick up dirt and carry it off the surface and 3) If applied to glass, it can reduce the need for windshield wipers.
If you are reading this, you probably know that many companies state a contact angle (with water i.e. Hydrophobicity) for their coatings. These measurements are typically taken when the coating has been just applied. In other words, new. At DuraSlic, we believe the real test is how long the coating holds up to washing. Because over the life of the coating that is what breaks it down. By nature, ceramic polymers are UV resistant so that is not the real issue. Its repeated washing. So, we conduct abrasion tests, using ASTM standards and auto detergent that simulate the real-life experience of the coating. We measure the hydrophobicity during the scrubbing to see how long the coating lasts and we provide that data to our customers, so they know what to expect.
But don’t forget about oleophobicity, the ability to repel oils. There is a lot of stuff out there that is oil-based that ends up on a car’s surface; tar and oils for example. Don’t forget about bugs. Bugs that splat on the car typically will not stick to an oleophobic surface. A truly repellent surface will be both hydrophobic and oleophobic. In this regard DuraSlic NS 1500 Extreme is in a class by itself with a water contact angle of 105o and n-hexadecane of 63o.
So yes, when it comes to ceramic coatings Hydrophobicity and Oleophobicity are very important. But there are other parameters that we believe are important. We will cover those in a future article.