Sealants: A Brief Introduction

In the aerospace industry, sealants play a critical role. So is it any wonder why SkyGeek sells it?

In many ways, aviation served as the driving force behind modern bonding technology. Building planes and propelling them in the air requires weight-saving measures. What would be lighter, metal fasteners or chemical substances? The development of adhesives and sealants not only cuts down on an aircraft’s weight but it also cuts down on costs.

blog-ppg-sealant-visual aid

Sealants – different purposes, different applications. (Courtesy PPG)

We gathered a brief set of useful notes to provide just enough insight on sealants to reinforce their importance.

What is a sealant?

A sealant performs prevention. Preventing what? It prevents things like air, gas, fire, liquid, smoke and even noise from penetrating one surface and traveling to another. Sealants seal, plain and simple.

What are its functions?

To know a sealant is to know its purpose. When two substrates (or more) form a gap, a sealant will fill it. By doing so a barrier is formed as the sealant’s physical properties adhere to the substrates. Once cured, a sealant is designed to maintain its properties for the lifetime of its use and under conditions and environments specified by the manufacturer.

Three forms

According to, sealants are categorized by classes – one component, two-component, and tapes.

One component sealants are packaged in cartridge form and thus require no further equipment during application.

Meanwhile, two-component sealants “require bulk guns and mixing equipment to prepare and apply the sealant, and are typically packaged in separate buckets.” This class of sealant consists of a base component and an activator component. The two are usually mixed for a pre-determined amount of time prior to application.

Finally, sealant tape is characterized by sealant found on flexible backing.

When Compared to Adhesives

Sealants may be grouped with adhesives but they are not identical structurally or chemically. It’s not advisable to swap one for the other since they are not always interchangeable. We have already mentioned the purpose of a sealant but an adhesive’s main duty is to bond surfaces together. That’s it.

Some strong sealants may be considered adhesives. Additionally, sealants are considered really low-strength putties and caulks. So if you want to know comparatively the range of sealant, it falls somewhere between a strong adhesive and a weak caulk.

And while adhesives (bonding), caulks and putties (fill space) tend to perform one purpose, sealants can be applied for multiple reasons. Specially formulated sealants can serve as fire barriers, insulation (acoustic and thermal), or electrical, corrosion, and moisture inhibitors.

Additional Resources

There are many resources available out there to get you started on using sealants on your plane safely and effectively. While this post is by no means meant to be comprehensive that doesn’t mean SkyGeek doesn’t want to supply you with a way to learn more:

PPG Aerospace Sealant Glossary

Tips for Applying Sealants

Benefits of Sealants (and Adhesives)

LORD: (Not So) Shockingly Grand


LORD Corporation’s logo and slogan

What’s an e-commerce site but a place that sells products? That’s essentially what it all boils down to, right? Or so it would seem.

With a large inventory a site is bound to offer several brands. And we do. Over 500 brands and manufacturers form the basis of what we provide our customers.

One such manufacturer is LORD.

LORD Corporation started in the 1920s in Erie, Pennsylvania. Hugh Lord, the founder, sought a way to reduce automobile noise pollution outside his workplace. And the rest is history.

With over 90 years of experience, LORD continues to be a solver of problems. The company has grown and developed its operations, both geographically and industrially.

“Ask Us How.” That is the company slogan. We asked (in the form of an online search about their company). Their answer – a corporate video explaining LORD’s scope:

As you see in the video, their innovative ideas cater to the aviation industry. “Flight critical components keep air passengers comfortable by reducing noise and vibration throughout the flight.”

In particular, their engine mounts are excellent at ensuring vibration does not shock and eventually compromise onboard systems. The end result is enhanced durability and control, two factors you want to possess while piloting an aircraft (or really any vehicle).

There were several phrases one can hear in that video: “Transform innovative ideas into long-term value”; “…materials for demanding applications in a wide variety of industries”; “…[allows] passengers to ride safely and in comfort.” With such an emphasis on innovation, collaboration, service and reliable performance, you can see why LORD is a part of the SkyGeek virtual catalog.

Perhaps the best way to sum up the culture, core value, and overall character of LORD is in this statement: “LORD was not founded to sell a product but rather to solve a problem.” With that said, is it really surprising why they have been so successful for almost  a century?

Yeah, we sell products but by proxy and by selling LORD we too seek to serve and solve the problems of our ever growing customer base.

Understanding Durometer


You’ve heard of odometers, speedometers, altometers (lots of –ometers). But what, pray tell, is durometer? Hint:  It’s not an instrument you slap on the inside of your cockpit.


Figure 1 – Where to find durometer or “Hardness Rating” on an O-ring product page on (CLICK TO ENLARGE)

Basically, durometer refers to both the measuring device and the measurement of a material’s hardness. In fact, “duro” is Latin for “hard/tough.”  The “-ometer” refers to the fact that it is based on a scale; it is a measurement of some kind. Durometers indicate a material’s resistance to permanent indentation. In the aviation industry it often corresponds to products with an elastomer, polymer, or rubber composition. This is especially true when dealing with O-rings.

You will find specifications on the product pages of many O-rings we sell. Durometer is synonymous with “Hardness Rating.” (See Figure 1)

So why is this important? When applying an O-ring to a part of your aircraft that requires one, its material composition will give you an indication of its function and durability. Some assemblies call for harder elastomers, others softer. It’s the durometer that will indicate if the O-ring is the right fit.

For a brief overview of durometer, you can watch this informative Youtube clip. The content is great at giving a casual viewer a basic understanding of the topic. However, be warned: the speaker in the video is weird and his mannerisms may or may not be amusing.


Shore Durometer Chart courtesy of the incredibly useful blog site from Alan Garratt. (CLICK TO ENLARGE)

Another aspect of durometer you may be wondering about is the use of the word Shore. Not only does Shore refer to the creator of the durometer, Albert Shore (1876-1936), it also is used in classifying the types of durometer scales.

There are many types but the two most common are Type A and Type D. According to Alan Garratt, “There is a simple logic laid behind the sequence of the early Shore scale letters and how they evolved to measure harder and harder materials. Later the need to measure materials softer than the range of Shore ‘A’ accuracy proved more difficult to fit into this progressive sequence of lettering.”

Garratt’s blog, Shore Durometer History,  is an excellent resource on the topic and is shore sure to provide those technically-inclined geeks out there with information on the development of this system. In particular I recommend reading the section “Evolution of the Shore Scales.” The bulleted points briefly explain why the classification is the way it is. Even better – there is a convenient chart of the various scales to compare and contrast (as seen above).

As mentioned, Type A is considered perhaps the most common of the Shore durometer scales. But within that type is a range. Numbers on this range go from softer to harder as they increase. Still, that may be too vague to understand so we retrieved this comparative list from Mykin Inc. The list provides real-world examples associated next to the numbers to give you a better idea.




Rubber Band


Pencil Eraser


Car Tire Tread


Running Shoe Sole


Leather Belt


Shopping Cart Wheel


Remembering the Stars and Stripes

SkyGeek may not be some things, like a Fortune 500 company. We are not big business. But there is one thing you can be sure of: We are proud to be American.

As we celebrate Fourth of July, among the BBQs and the fireworks we realize that sometimes the more important aspects of the holiday are pushed aside.

Freedom and independence – ideals that were hoped for by a bunch of colonial rebels and now are dreams realized and remembered among the stars and stripes of Old Glory.

Imagine being a minuteman up against a formidable opponent, a lobsterback, a soldier better equipped and suited for combat? To be outnumbered and out-trained is enough to retreat for good. Isn’t it amazing that colonials in the 1770s didn’t back down when it made sense to?

History tells who prevailed and that is why year after year we celebrate those who sacrificed to ensure a country was established based primarily on inalienable rights for citizens seeking life, liberty, and the pursuit of happiness.

Fast forward to today and you will see America has grown to a superpower. Pretty impressive given such humble beginnings.

This may seem like a a long rant. It is (hey, it’s my inalienable right). But there is a point.


The little engine that could. The logo for

SkyGeek is a small business and while other aviation supply companies are bigger, that doesn’t mean we won’t continue to fight to serve you, the customer. Perhaps our journey will be like America’s, an underdog ready to rise and eventually reaching the top. We shall see if history favors us…

Speaking of history and speaking of underdogs I want to mention a nice site I stumbled on recently:

At first glance, this site looks like a piece of history itself – something out of the 1990s. The layout is in need of an upgrade and the links are not very refined. But the amount of research and effort put into the content is commendable.

I applaud the owner of the site for compiling a list of aviation museums, which a visitor can search by state. I think this is a great site not only for Fourth of July but one way to discover ideas for summer vacations or really vacations of any kind, especially for aviation enthusiasts.

“These airplane museums not only tell about aviation history, but they tell us about the history of all mankind. They tell us about the tremendous wars that we have fought to keep our freedom.”

Who wouldn’t love to explore a site with that kind of mission statement? may no longer have an up-to-date list as information is always changing. What I would say is explore the site and give the owner feedback so he can improve an already comprehensive directory. It would be wonderful to contribute and help out someone so determined to preserve and promote aviation. A true patriot!