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Published on May 11th, 2018 | By: April Gocha

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A workout for your glass—Nanoparticle coating makes glass stronger, boosts impact resistance

Published on May 11th, 2018 | By: April Gocha

[Image above] Credit: Lauren Robson Photography; Flickr CC BY-NC-ND 2.0

 

 

My, how far we’ve come.

 

That can probably be said about a lot of things in your life—I know it’s certainly true for me.

 

For instance, today is my last day as an editor with The American Ceramic Society—I’ve been writing about ceramics and glass for more than four years now on Ceramic Tech Today. When I started back in 2014, I barely could pick a ceramic material out of lineup. And now, I’ve written about the material science of ferroelectricsgallium nitride, tattoosgarnetpenguin feathers, MXenes, biomedical implants, spinelgrain boundaries, chocolate, and so much more.

 

And in the midst of learning all that materials science over the past four years, I’ve also moved to two new cities, run a handful of half marathons, rock climbed up the side of a mountain, explored new countries, made countless flights across this country, and driven thousands of miles.

 

My—how far I’ve come (and gone)!

 

The same can be said for glass—for a material that was once produced through very slow, imprecise and trial-and-error processes, glasses today are highly engineered materials that have functionalities and properties we may never have thought were possible for such an otherwise brittle material.

 

But even with all of glass’s impressive properties, we can all use a helping hand now and again. And a new product is perfectly poised to lend a hand to help glass boost its strength.

 

A company called MetaShield (St. George, Utah) has developed a nanoparticle-based coating that significantly enhances the impact resistance of glass. Such strength-boosting coatings could be useful in glass’s many applications, including automobile windows, mobile devices, windows, medical equipment, glass containers, eyeglasses, and more.

 

“Our unique coating, the result of several years of development using the combined work of theoretical physicists, chemists, and engineers, adds only a negligible size and weight,” Jacob Schliesser, materials chemist at MetaShield, says in a MetaShield press release. “Because it is transparent, thin, and simple to apply, MetaShieldGLASS can be easily integrated into existing manufacturing processes.”

 

The transparent MetaShieldGLASS coating—applied via spray, dip, or flood coating and then cured with UV light—can be applied in just five minutes, the company says, and requires no fancy, specialized equipment. It’s designed for use with commercially available systems, making the potential opportunities quite attractive.

 

MetaShield is, not surprisingly, mum on the details of the materials that make up their patent-pending coating. But according to its website, the coating is a silica-based formula containing functional nanoparticles, which can be tailored to give the coating specific properties for a particular application.

 

Versatile, simple, and scalable? That sounds like a win for commercial success—but how does the coating perform?

 

The company recently reported that results from independent testing of its MetaShieldGLASS coating reveal it significantly enhances the impact resistance of both untempered and tempered aluminosilicate glass.

 

The lab, InterTek, measured impact resistance—following standards developed by Asahi Glass to more accurately assess thin cover glass—by dropping a weighted ball from a specified height onto a test sample of glass. By testing many samples (here, n = 30) and measuring at what drop height each sample breaks, these drop-ball tests provide a relative measure of the average kinetic energy required to break each glass sample type.

 

The testing examined two kinds of glass: 0.55-mm thick untempered aluminosilicate glass, and 0.55-mm thick tempered aluminosilicate glass—better known as Corning’s Gorilla Glass 3.

 

These dynamic impact tests showed that a MetaShield coating of just 0.09 mm is enough to significantly increase impact resistance of both untempered aluminosilicate glass and Gorilla Glass 3. Overall, MetaShield reports that its coating improves the break resistance of untempered glass by 83% in blunt impacts and 100% in sharp impact. For Gorilla Glass 3, the coating improves the break resistance by 222% in blunt impact and 150% in sharp impact. You can download the full independent testing report here.

 

MetaShield’s own tests (not independently verified) also show that its coating can increase the impact resistance of simple soda lime glass panels that are thicker than 3 mm, the company reports.

 

“By combining enhanced properties, simple application, and a form factor that is near invisible, MetaShieldGLASS provides a fantastic and potentially transformative cost/benefit to glass industry stakeholders,” Martin Ben-Dayan, CEO and cofounder of MetaShield, says in the release.

 

Credit: MetaShield

 

However, one limitation of the material is its durability. MetaShield reports an average hardness of 550 MPa in nanoindentation testing and 5H in pencil hardness, “which is significantly better than common plastics.” But for glass, that’s not good enough.

 

Abrasion tests show that the coating applied to glass does develop a reasonable haze after repeated abrasion, which could put a damper on applications such as coatings for cover glass. “There’s a terminal hardness with the formulation,” Ben-Dayan says in a phone interview.

 

For some applications, however, the coating could be applied to the inside of the glass, where it would be protected from wear. But that doesn’t work for cover glass, where the coating would interfere with touchscreen capabilities. For applications such as on windows, however, an inside coating would work just fine.

 

As another solution to the durability issues, Ben-Dayan says the company also is working on other alternative strategies, such as a secondary coating. “So far, the results look promising.”

 

Although MetaShield is not being sold for consumer applications, the company has several interesting and diverse applications in the works.

 

For starters, Ben-Dayan says MetaShield has been working with a couple of large OEMs over the past year, one of which “pulled them in” on the Gorilla Glass work.

 

Plus, MetaShield is working with two defense contractors to test cockpit displays, which have regular issues with breaking.

 

“Automotive applications are very interesting as well,” he adds. Akin to Corning’s strategy of placing an inner layer of Gorilla Glass into windshields, Ben-Dayan thinks a layer of MetaShield on the inside of automotive windows could similarly provide added strength.

 

Other potential applications the company is currently pursuing, Ben-Dayan says, are using the coatings for ink dewetting as a way to mitigate ink staining with writing equipment and to reduce smudging on cosmetic packaging—MetaShield can achieve 3–4 times the contact angle of existing coatings, he indicates.

 

But there are many diverse potential applications with a simple, easy-to-apply coating that offers a variety of beneficial properties. “The coatings have a quality that we’ve noticed—they inspire imagination,” Ben-Dayan says. “You’d be surprised by how many requests we get.”

 

MetaShield originally started working on coatings several years ago to increase the efficiency of solar panels, and actually developed a coating that could boost the efficiency of triple junction solar cells by 1%, which is a rather significant boost.

 

Then, two and a half years ago, the company found the coatings’ effects on glass—almost by accident, he says. And because of the widespread applications and potential with glass, MetaShield has grown and diversified its coatings’ potential applications.

 

“Something is happening in advanced materials right now—things are starting to percolate,” Ben-Dayan says. “For many years, physical objects like automobiles remained largely the same. But now they’re changing. We’re creating things that are much better, thanks to all discoveries with advanced materials. And MetaShield is part of that. To be continued.”

 

 


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