Something seemingly contradictory – microscopic glass bubbles that make things light and strong. These tiny glass microspheres are hollow but incredibly tough. They show up in unexpected places and in things you use every single day. The reason they’re so ubiquitous? They have some unique characteristics and can be mixed into a wide range of polymer materials while maintaining important physical attributes.
Microscopic spheres may look simple, but there’s complex science behind these impeccably engineered bubbles. And they are miniscule. On average, they are smaller across than a human hair. So teeny that about 239 million of them would fit into a thimble.
Warren Beck, the inventor of 3M™ Glass Bubbles, first discovered them in the 1940s when he was working with reflective glass beads. A batch of beads intended for road signs came across his lab bench. They were scattering the light instead of bouncing it back. Warren saw bubbles in the glass beads that weren’t supposed to be there. He grabbed the opportunity to do further research and found a solution to make the particles small enough to create single bubbles.
Warren was able to devote 15 percent of his time to studying the microspheres because of 3M’s culture that encourages employees to spend time on projects outside of their regular job responsibilities. He knew they would be useful for making lightweight materials that held their strength – a great fit for automotive, aerospace and underwater applications.
Today, 3M glass microspheres, made from soda-lime-borosilicate glass, are used for weight reduction, thermal insulation, solar reflectivity and more. As Warren predicted, they are used in transportation to enable fuel efficiency. Scientists have continued to build on the original technology to create a variety of stronger and more versatile bubbles. You probably have glass bubbles both inside and outside your car or in the train or bus you take to work. Automobile and commercial vehicle manufacturers use them in trim, consoles, fenders and hoods. They’re also used in sheet-molded and injection-molded components in watercraft, ATVs and snowmobiles.
Your vehicle isn’t the only place you might be benefitting from glass microspheres. There’s a good chance they are in your home or place of work – on the walls and on the roof. Glass bubbles can help your paint roll on more smoothly and keep it burnish resistant – turning shiny with wear – so hopefully you have to paint less often. Because they are tiny spheres, they act like little ball bearings, easily rolling over each other to help improve the flow.
They also help lower weight and cause less shrinkage, so they are probably also in the caulk around your tub, in spackling in your walls and in adhesives in your floors and countertops. And, bonus, they’re solar reflective, so they can help reflect the sun’s heat from your exterior walls and rooftop.
You could even be sitting on some glass bubbles right now. They are used in polymer wood composites that are ideal for outdoor furniture and deck material.
Another place you might find these cool spheres? Deep under the earth or suspended below the surface of the ocean. They may impact everything from your fuel to your drinking water.
They are used in several ways for mining and drilling. Since they are water resistant and they have high strength, these microspheres work in deep sea applications. They help reduce the density of cement allowing it to flow deep down in oil wells.
And they help keep things on top of the water. Teams of student engineers design, build and test their own floating concrete canoes, often made with glass microspheres to make them buoyant. They’re also used to make foams that help with keeping cables and pipes insulated and afloat.
3M glass bubbles are providing a life-saving answer for the island nation of Cyprus. As an island, Cyprus is surrounded by water, but has a scarcity of fresh water for drinking and agriculture. Turkey is supplying 50 years’ worth of water via a pipeline through the Mediterranean Sea. The pipeline couldn’t run along the seabed, because the water pressure is too great. It couldn’t float on the surface because it would interfere with ships. Instead, the pipes are suspended at a depth of 820 feet using flotation devices containing 3M glass bubbles.
Glass microspheres have even been used in the very deepest part of the ocean – the Mariana trench. 3M experts worked alongside a team of engineers and scientists to help create a new type of submersible made with a new super-durable syntactic foam.
Glass bubbles even show up in some of your favorite hobbies – running, bowling, fishing and snowboarding. Rubber makes an excellent sole for athletic shoes, but it’s pretty heavy, adding unwanted weight for your tennis match or run. Shoe makers have figured out that by mixing in hollow, thin-sided microspheres, they can cut weight of the outsole – from 130 grams to 82 grams, in the case of one Korean shoe manufacturer. They also make fly fishing lines buoyant, so they can float on water and help you snag that prize trout, and in the core of bowling balls to help you score that perfect 300-point game.
So, why are these glass bubbles everywhere? Why do they work in so many materials? They have some properties that naturally make them easier to work with, and 3M engineers have made advancements in recent years that make them stronger, so they work in more applications.
Since Warren Beck first developed them in the 1940s, 3M scientists have continued to evolve the technology. According to Steve Amos, a product developer in 3M’s Advanced Materials Division, glass bubbles have been used for years as a filler. Steve and other scientists have continued to work closely with customers to improve them and find new uses. By changing properties and developing coatings, they’ve created more versatile and useful bubbles with greater strength and continue to find new ways they can be useful.
Here are a few of the reasons why they are so ubiquitous:
The sphere has less surface area per volume than other shapes. The lower surface area, along with low density compared to fillers like clay and talc, can lower material costs.
The glass bubbles also allow materials to maintain a workable viscosity – making it potentially more practical to stir.
The round shape also means they are isotropic, so they fill and provide the same properties all directions. That’s an important property, because it prevents shrinkage, warpage and sink marks. Glass bubbles also make compounds easier to cut, sand and shape with less gauging and less tool clogging.
These glass bubbles are so tiny that they almost don’t register to the naked eye as bubbles. They look like a white powder, and if you shake or swirl them in a test tube, it looks like a milky liquid. On average, they are 18 to 65 microns. Micron is short for micrometer – one millionth of meter. For comparison, an average human hair is about 75 microns across. This small size allows them to be used in high-gloss, class-A painted automotive parts.
In recent years, scientists have developed bubbles that have high strength-to-density ratios. This allows them to be used in high pressure processes, like injection molding, without breaking. Most of the plastic parts in your car are made through injection molding – a common manufacturing process that heats and melts material and forces it into a mold where it cools and hardens.
Scientists have also developed methods to treat and coat the bubble surfaces. These surface treatments enhance bonding with a resin or minimize water pickup in a foam. These treatments also provide other improvements in strength and stiffness.
But, there are times when you want the bubbles to break. When you’re pounding a nail or inserting a screw into wood and polymer composites, you want the porous give of real wood. In those cases, the bubbles actually break up to allow for more give.
Depending on the need, scientists have created dozens of variations of glass bubbles with different treatments, sizes and crush strengths.
3M glass bubbles are made from soda-lime-borosilicate glass, making them more water resistant than sodium silicate hollow glass microspheres. They can be boiled in water for more than 40 minutes without dissolving.
3M glass bubbles for plastics and rubber applications have a range of density from .1 to .6 grams per cubic centimeter. Compared to other dense fillers like talc, calcium carbonate, glass fiber and clay, they can occupy 20 times more space at the same weight. This means manufacturers can make more parts per pound of resin containing glass bubbles. It also means they help make materials lighter in weight which impacts fuel economy for transportation – as the original inventor predicted five decades ago. It is a potential way to help keep cars, trucks, trains and ships lighter and more fuel-efficient.