Understanding the Use of G10 and G11 Glass Epoxy in Cryogenic Applications

Published on November 15, 2023

Since the mid-2000s, composites reinforced with glass fibers have been utilized in numerous industries due to several useful properties. These include featuring a high ratio of strength to weight and resistance to chemicals and corrosion. Glass epoxies can also be easily fabricated into complex forms without requiring an abundance of fasteners. These composites are used in the aerospace industry for various structural components like cryogenic fuel tanks, fuselages, and wings in aircraft. They’re also used in low earth orbit environments for satellites and spacecraft that need to withstand extremely cold temperatures as low as −170°C (-274°F).

In addition to dealing with cryogenic temperature extremes, aerospace components must also deal with several other stressors that degrade composites. Especially when in woven form, glass fibers offer impact resistance at a lower material cost than carbon fibers. This makes them attractive for many structural applications. Glass epoxies are known for resisting microcracking and chemicals while offering traits like chemical inertness and dimensional stability. For this reason, composites like G10 glass epoxy and G11 glass epoxy are often used in both aircraft and automotive applications.

How Glass Epoxy is Used in Cryogenic Applications

Polymer-based composites have become popular for cryogenic environments, particularly aerospace applications. Both G10 and G11 glass epoxy are industrial laminates, as defined by the National Electrical Manufacturing Association (NEMA). Though not initially developed for cryogenic applications, they have proven useful. Properties like their respectable electrical insulation capabilities and superior mechanical strength have proved them excellent materials. At the same time, they continue to be utilized for their original purpose as electromechanical assembly structural supports and printed circuit boards.

What is G10 Glass Epoxy? 

Highly durable and corrosion-resistant, G10 glass epoxy is a composite material made from fiberglass and epoxy. G10 is most commonly used for applications that require a strong material of lighter weight that’s highly resistant to chemicals and absorbs a negligible amount of water, along with providing significant thermal and electrical isolation. This glass epoxy is made from fiberglass cloth woven and impregnated with epoxy resin. Used not just for its strength and chemical resistance, G10 glass epoxy also resists heat and ultraviolet (UV) light. It is often a component in accessories for firearms and other types of weapons.

How G10 Glass Epoxy is Made

Making G10 glass epoxy involves mixing a hardener with epoxy and glass fibers, which are then coated with a glass fabric that’s then infused with epoxy resin. The material created from this fabric offers a number of special properties after cutting and pressing it together. G10 glass epoxy is related to FR4 glass epoxy, though FR4 is flame retardant, whereas G10 is not.

G10 Glass Epoxy Properties 

Because it’s resistant to both oxygen and moisture, G10 glass epoxy doesn’t corrode or rust. This makes it incredibly durable and very wear-resistant. Due to its strength and durability, G10 works well for various applications where strong and lighter-weight materials are necessary. It’s particularly suitable when used under conditions with a high chance of electrical sparks, as G10 glass epoxy’s nonconductive properties prevent electricity and heat from passing through the material.

Benefits of G10 Glass Epoxy

The rigidity of G10 glass epoxy makes it easily machinable using conventional methods. CNC (computer numerical control) machining, like drilling, milling, turning, and routing, can all be done with techniques used for other plastics and those used for metals and alloys.

Some advantageous properties of G10 glass epoxy include: 

  • Corrosion resistance
  • Creep resistance
  • Dielectric properties
  • Dimensional stability
  • Flame retardant
  • Lightweight
  • Strength and durability
  • Thermal isolation capabilities

When used as an internal component, G10 epoxy glass is nearly indestructible. However, exposure to sunlight may truncate its lifespan.  

Applications for G10 Glass Epoxy 

Commonly used in high-humidity applications, G10 is utilized for electronic and electrical testing equipment and insulation in various electronic devices.

G10 glass epoxy works well for a wide array of applications that include: 

  • Aircraft components and equipment, including instruments, panels, and wiring.
  • Electrical fittings and equipment like insulation for busbars and electric motor rotors, along with electrical insulator materials, electronic testing equipment, printed circuit boards, and terminal boards.
  • Fitments for firearms and other weaponry, including gun grips, knife handles and blades, missile casings, rifle stocks, slingshots, and spearguns.
  • Marine and boating equipment like canopies, covers, and hulls.
  • Power generating equipment like insulators, electromechanical components, high voltage insulation, phase barriers, and transformer spacers.

Additionally, G10 glass epoxy is used in medical diagnostic equipment and for parts requiring high chemical resistance and strength.

Downsides of G10 Glass Epoxy

Although it offers multiple advantages, G10 glass epoxy is comparatively expensive against common metals or alloys like aluminum or steel. For this reason, it’s less suitable for smaller projects. Because of the high fiber content and rigidity, G10 glass epoxy is also challenging to work with. However, when comparing G10 glass epoxy to thermoplastics like PEI (polyethylenimine), PEEK (polyether ether ketone), or nylon (polyamides), it’s much more reasonably priced. While G10 has numerous useful properties, the epoxy resin within it cannot handle temperatures above 140°C (284°F). Similar materials, like G11 glass epoxy, are better for higher-temperature applications.

What is G11 Glass Epoxy & How Does It Compare With G10 Glass Epoxy? 

G11 glass epoxy is also a glass cloth epoxy made from a thermosetting fiberglass composite that’s impregnated with an epoxy resin binding it together. However, G11 works at higher temperatures than G10. Though G11 glass epoxy does offer similar properties to G10 glass epoxy, G10 is slightly stronger. However, G11’s mechanical properties are better than G10’s at higher temperatures, so G11 is the better insulator. While G10 ranges naturally from light green to yellow, the natural color range for G11 glass epoxy tends toward yellow, green, amber, or light brown hues.

Benefits of G11 Glass Epoxy 

Featuring high mechanical strength and dimensional stability, G11 glass epoxy also offers commendable electric strength and dielectric loss properties while working well in dry and wet environments. Two classes of G11 glass epoxy – H and F – are available, which are differentiated by how much heat they can handle.

Some beneficial properties G11 glass epoxy offers include: 

  • Chemical resistance
  • Creep resistance
  • Cryogenic serviceability
  • Dimensional stability
  • High dielectric, flexural, and tensile strength
  • Low moisture absorption
  • Radiation resistant

The H-class of G11 glass epoxy can be used in applications with temperatures up to 180°C (356°F), whereas class F can be used at up to 150°C (302°F).

Applications of G11 Glass Epoxy 

NEMA designates G11 glass epoxy as glass cloth. With similar uses to G10 glass epoxy in electromechanical equipment, G11 is better suited to applications exposed to higher heat levels. Like G10, G11 glass epoxy is easily machinable and has a very low moisture absorption rate.

G11 glass epoxy works well for various applications that include: 

  • Equipment used in underwater and other corrosive environments.
  • Insulation for electrical parts in equipment like generators, mechanical barriers, motors, and transformers.
  • Insulation for use in cryogenic fuel tanks, piping systems, railcars, and other cryogenic containers.
  • Medical diagnostic equipment.
  • Military applications like rocket cases.
  • Terminal boards for organizing electrical wiring.
  • Test boards and fixtures.

Additionally, G11 glass epoxy is used for aerospace equipment, antenna insulators, circuit board holders, endplates, and solder frames, among other applications.

Spaulding Composites: Experts for G10 and G11 Glass Epoxy Material & Components

Spaulding Composites Inc. manufactures cryogenic grades of both G10 and G11 glass epoxy, along with components made from these materials like vacuum-insulated piping, tank supports, superconductive magnets, fusion reactor insulation, and Dewar neck tubes for the medical industry. To learn more about how we can help with your specific application, contact Spaulding’s glass epoxy experts or request a quote today.