Nissan’s self-cleaning Leaf vehicle is on the streets. The exterior of the 2015 Leaf boasts the Japanese automaker’s proprietary Ultra-Ever Dry paint treatment which Nissan says repels every type of liquid from rain to eggs.
Pierre Loing of Nissan North America claims that the Leaf is already one of the cleanest vehicles around even without this innovative paint technology. “That said, we’re not afraid to get our hands dirty to take this to the next level,” he says.
According to maker Ultratech International Inc., Ultra-Ever Dry is a super hydrophobic (water-hating) and oleophobic (hydrocarbon-hating) coating that will repel most water-based and some oil-based liquids. The product uses proprietary omniphobic technology to coat an object and create a surface chemistry and texture with patterns of geometric shapes that have peaks or high points.
These points repel water, some oils, wet concrete, and other liquids. Ultra-Ever Dry has better adhesion and abrasion resistance compared to other super-hydrophobic technologies allowing it to be used in applications where greater durability is required.
Hydrophobic means water-hating surface. The degree of water hating is expressed as surface contact angle. For example, untreated glass has a contact angle of 25 degrees so rainwater drops flatten and spread out, whereas if rain gets on your arm it would bead up slightly because human skin is oily.
The reason is oil has a surface contact angle close to that of the mineral seal oil (80 degrees) in drying agents used in many car washes. Rain repellent has a contact angle of 100 degrees and carnauba wax 120 degrees. In other words, the latter provide superior water beading.
Super-hydrophobic products can impart a surface contact angle of 150 degrees or more. In other words, water drops would literally stand-up and look for the nearest exit.
According to research released by the Institute of Civil Engineers Publishing (ICE), producing geometrically controlled rough surfaces of a material and reducing its surface energy by the addition of low surface energy materials, or tailoring the low surface energy material by creating roughness at micro/nano scales would achieve super-hydrophobic surfaces.
Super-hydrophobic vehicle-paint sealants are single- or two-step processes. Single-step products are sprayed on and rinsed off.
Our example is a concentrate. One oz/ml makes four oz/ml ready-to-use spray. Dilution rate is one part concentrate to three parts water. Active ingredients are Trimethylated Silica, a sodium salt usedin sealants; Polydimethylsiloxane, a silicon-based organic polymer; and Ethanol, a solvent.
According to the ICE paper, super-hydrophobic coatings made with ethanol as a solvent exhibit less adhesion. Arguably, this is why the manufacturer claims durability of between and three and six months.
Conversely, researchers find better adhesion is achieved by layering nano-sized, uniform spherical silica particles separated to various sizes by centrifugation to obtain super-hydrophobicity. Using acidic silica binder instead of ethanol helps increase adhesive strength by forming cross-links with substrate and silica particles.
Ultra-Ever Dry contains acetone, an industrial solvent that is used in paint thinner and nail-polish remover; silica or silicon dioxide, which is commonly found in quartz; and a proprietary additive.
However, Ultra-Ever Dry does not dry clear. It cannot be used on automobile windshields and obscures visibility through glass.
How well do these products work? The information in the table below reflects some of my experience with hydrophobic and super-hydrophobic products.
Although Nissan’s advertising bravado predicts its “self-cleaning car” will make car washing obsolete, I believe professional car wash operators have little to fear.
Considering the trend in premium on-line extra services, perhaps the next innovation will be a spray-and-rinse super-hydrophobic sealant that would last 90 days or more.
Bob Roman is president of RJR Enterprises – Consulting Services (www.carwashplan.com). You can reach Bob via e-mail at email@example.com.