The process behind cryogenic storage is fascinating and applies to all sorts of medical and scientific applications. Commonly, to preserve biological samples, a laboratory will use a dewar, a specialized container that stores cryogen materials like liquid helium or liquid nitrogen that are imperative to this preservation. Without a specialized container, these cryogenic materials would boil well below room temperature, ruining the sample.

This container in which cryogenic materials are contained is suspended in a vacuum, surrounding another container where the samples are kept. To access the sample from the outside without ruining it, researchers use a cryogenic neck tube that connects the inner container to the outside world. This neck tube is often made from a glass epoxy type known as G10-CR, which can handle the cryogenic temperatures that protect the sample. Understanding the advantages that G10-CR provides for such applications should be a consideration for all those who work with cryogenic materials.

How G10 Composites Improve Cryogenic Materials

G10 is also known as garolite, a composite material that can withstand higher pressures. A fiberglass laminate is made by stacking layers of glass cloth soaked first in an epoxy resin. These layers are then compressed while heated until the material cures. G10 is manufactured in thin glass sheets that are often only a few millimeters thick.

Versatile and widely used, G10 materials are known for their considerable strength, chemical resistance, and electrical characteristics. The type of G10 used for cryogenic materials is known as G10-CR, though it’s only used for applications where the material doesn’t need to be flame retardant. As such, it’s used for environments where there’s little risk of fire, including those that are cryogenic. Materials like G10-CR are thus often used for cryogenic lab applications where normally gases are liquified to preserve scientific and medical samples.

Though regular glass epoxy grades like G10 are often used as insulation as they don’t degrade physically when exposed to cryogenic temperatures, many are only rated to -55°C (-67°F). G10 can withstand temperatures at which helium becomes liquid, which is between -155°C and -270°C (-247°F and -454°F). Yet below -55°C (-67°F), G10 performs measurably worse, especially affecting its mechanical qualities. This is why G10-CR is the primary material used for cryogenic neck tubes.  

G10-CR Properties & Cryogenic Neck Tubes

Because of its reliability when exposed to extremely low temperatures, G10-CR is a preferred composite for working with cryogenic materials. When subjected to cryogenic temperatures, its physical and electrical properties also make it ideal for sealing cryogenic materials, including nitrogen, helium, and argon in liquid form and solid carbon dioxide (dry ice). G10-CR also resists wear and corrosion with low heat leakage traits, which helps ensure its performance when working with cryogenic materials.

Using G10-CR for cryogenic neck tubes provides advantages that include: 

• In liquid nitrogen, G10-CR composites have good mechanical and dielectric strength.
• Its low thermal conductivity makes G10-CR an efficient insulator.
• Low rate of thermal diffusion at cryogenic temperatures.
• Meets the military specification MIL-I-24768/2 for rods, sheets and tubing made from plastic laminated thermosetting materials.
• NEMA standards are met for this grade of G10 glass epoxy laminate.
• Offers similar properties to G10 when it comes to structural support.
• Provides good dielectric and mechanical strength within liquid nitrogen.
• Retains physical characteristics and electrical properties in continuous high operating temperatures up to 140°C (284°F) and for cryogenic temperatures down to -270 °C (-454°F).
• Specifically designed, G-10 CR naturally offers better performance for environments where cryogenic temperatures are a factor.

Although it has a lower strength than G10, G10-CR composites work well for experimental probes or winding transitions unless exposed to high-field magnets that cause extreme stress. Additionally, machining any epoxy composites like G10 can release environmental toxins.

Other Applications for G10-CR Composites

G10-CR’s ability to withstand the extremely cold temperatures at which nitrogen becomes liquid without compromising its properties makes it useful for almost any laboratory that works with cryogenic materials. For example, samples can be bonded within a sample holder made from G10-CR. Fiberglass materials like G10, G10-CR and G11 are all used for supports and suspension for laboratory stationary tanks due to their low thermal conductivity.

G10-CR composites are often used for cryogenic necks to decrease conduction as they retain material properties at these low temperatures. Cryogenic necks made from G10-CR can also be used in hydrogen liquefaction systems that use liquid nitrogen for pre-cooling. Compared to 300 series stainless steels used within lab settings, G10-CR has triple the kinetic energy in environments at 80 Kelvin (about -193°C or -315°F).

Besides its use with cryogenic materials, G10-CR can also be applied to aerospace, nuclear, and other applications as they contain no halogens and extremely reactive compounds that can form strong acids when exposed to water. For example, satellites require materials like G10-CR that work well in the cryogenic temperatures found in space and where there’s an extremely low risk for fires. The National High Magnetic Field Laboratory uses G10-CR at its Pulsed Field Facility for spacers for the magnet conductor wiring, as liquid nitrogen is used to cool the magnet during operation.

Spaulding Composites: Your Source for Cryogenic Neck Tubes

Faulty Cryogenic necks can result in damaged samples, leading to losses in the millions of dollars. Such catastrophes should be avoided, so anyone working with cryogenic materials should work with a trusted supplier like Spaulding Composites. With experience working with G10, G10-CR, and other glass epoxies for working with cryogenic materials, Spaulding can provide a reliable storage solution to meet your needs. To learn more about our experience in making cryogenic neck tubes and other equipment for cryogenic laboratories, contact the experts at Spaulding.