PGS & GRAPHENE THERMAL STRAPS

The X-Series®

In recent years, the need for exponentially greater heat dissipation and strap flexibility has spiked in the aerospace industry. In some cases, this has rendered traditional metallic and graphite fiber straps ineffective. To meet these thermal and mechanical challenges, TAI offers our X-Series® thermal straps. These straps are ideal for applications with: 1) extremely-low stiffness and vibration-transmission requirements, 2) restricted volumes with minimal deflection, and/or 3) an extremely high thermal conductance to low mass ratio.

X-Series® straps are made with high conductance Pyrolytic Graphite Sheets (PGS), and are also available with Graphene Foils (when suitable). While they offer superior thermal performance to GFTS® products, all forms of pyrolytic graphite and graphene foil (sheet) straps are more fragile than metallic or graphite fiber straps, and are not suitable for certain applications (nor are they ideal for cryogenic applications). As a result—just as is the case in any other thermal strap program—it is critical that customers work with our experts to ensure an X-Series® strap is an appropriate solution.

Custom and Standard Model (X-Series®) Straps

PGL™ and GTL™ products are made entirely of NASA approved, low/zero outgassing materials, and are provided in standard and custom configurations. X-Series® Links/Straps are our standard model line, and can be manufactured with either PGS or Graphene Foil (depending on customer preference and performance requirements). The X-Series® is comprised of 6 standard models, with multiple end fitting options (at no additional cost). To learn more about our standard and custom strap offerings, request the X-Series® Catalog.

X-SERIES® STRAPS

Available in 3 Fixed Widths
Available in 2 Thicknesses
Available with PGS or Graphene Foil
6 Models to Choose From
2 Semi-Customizable End Fitting Types Available
Length Customizable
Bolt Pattern Customizable
No NRE or Design Fees
Thermal Test(s) - OPTIONAL
End Fitting Chromate / Passivation - OPTIONAL
Typical 7-8 Week Lead Times

Pictured: X6-501 X-Series® with dual aluminum L-fittings.

CUSTOM PGL™ & GTL™

Available in Nearly any Width
Available in Nearly any Thickness
Available with PGS or Graphene Foil
End Fitting Material Customizable
Fully-Customizable End Fittings
Length Customizable
Bolt Pattern Customizable
Prototype/Protoflight Program Required
Thermal Test(s) - INCLUDED
End Fitting Chromate / Passivation - OPTIONAL
Typical 8-9 Week Lead Times

Pictured: Custom PGL™ with dual flat aluminum fittings.

Superior Thermal Performance

Thermal Strap Conductivity - Carbon Based Straps

TAI's X-Series® products offer the highest thermal performance available in the industry; providing a material thermal conductivity of 1,600- 2,500 W/(m-K), depending on material, operating temperature, and sheet thickness (though graphene sheets may one day offer even higher thermal performance than the current 1,840 W/(m-K) available in the industry, as the technology improves). However, the materials used are just one aspect that makes our products unique. These materials, when combined with our proprietary design and assembly methods (which minimize resistance losses), result in unrivaled thermal performance.

Though these straps do not have years of spaceflight heritage (like our copper and graphite fiber thermal straps), they are a unique product, offering a particular set of benefits which make them ideal in volume-restricted applications like Xilinx™ electronics boxes, FPGA/chip & PCB cooling applications, and cubesats.

*It should be noted that we do not provide "monolayer graphene straps," as there are no (actual) monolayer graphene sheet thermal straps available in the industry. While a single layer of graphene can achieve a thermal conductivity in excess of 3,500 W/(m-K), it is only 0.35 nm thick.

Graphene Thermal Straps

Pictured: GTL™, 1.0" x 3.0", Conductance = 0.86 W/K (March 2018).

PGL S-Link - Graphite Thermal Link

Pictured: PGL™, 1.0" x 3.0", Conductance = 0.70 W/K (March 2018).

X-Series® Spaceflight Qualification

X-Series PGS Thermal Strap - NASA Thermal Test__October 2018

TAI's X-Series® (PGL™) products have been space qualified by NASA, and are slated for use in multiple spaceflight programs starting in 2019 in both Europe and the United States. Testing performed by TAI, NASA, and test facilities include: Thermal Conductance, Thermal Cycling, Post-Thermal Cycling Conductance, Stiffness, Vibration, and Contamination Testing.

This extensive qualification proved that TAI's X-Series® straps are the cleanest and most flexible carbon sheet strap on the market, and are durable enough to withstand extremely high vibration environments (while at the same time offering the highest thermal performance of any space-qualified strap in the industry). For test data, please contact our Director of Business Development (more data now available in January 2019, as further testing concluded at the end of 2018).

X-Series PGL Thermal Strap - NASA Stiffness Test

Pictured: X6-501 NASA Stiffness Test (October 2018).

X-Series Thermal Strap Vibration Test - NASA

Pictured: Dual X6-501 NASA Vibration Test (November 2018).

PGL™ - The "Zero-Stiffness" Thermal Strap

Perhaps one of the most unique and exciting benefits of our X-Series® PGL™ products, is their inherent "low/zero stiffness" attribute (when assembled and encapsulated using TAI's proprietary process). Not only does the PGS material used in our products offer superior flexibility to graphene foils and all other strap materials, but stiffness tests performed on our X6-501 PGL™ products resulted in a measured stiffness on all axes in the mN/mm range; exceeding all expectations and coming in well under the most restrictive stiffness requirements ever levied on a thermal strap product. For more information and stiffness qualification data, contact us today.

Pictured (Right): X6-501 PGL in shipping fixture (October 2018).

Pyrolytic Graphite Sheet (PGS) vs. Graphene

Though our team has used multiple PGS materials & sheet thicknesses, the most common is our laboratory-verified, 1,600 W/(m-K) sheet. At 1,840 W/(m-K), our Graphene Foil offers the industry's highest strap material thermal conductivity—but there are trade-offs to consider...

Determining which material is best-suited to your application is dependent upon your thermal and mechanical requirements. While Graphene Foil offers slightly higher performance (on the assembly level), a strap made with PGS is more flexible, and less prone to stress fractures & kinks when sheets are flexed. PGS is also preferred by aerospace organizations (due to supplier availability & quality issues), and the thermal performance of our PGL™ products peaks near 150K, making them better-suited for lower temperature applications (60 - 200K), than Graphene Foils (which peak at 220K).

Pictured (Top): PGL™ manufactured by TAI (November 2014).

Which Carbon-Based Thermal Strap is Right for Me?

TAI offers multiple carbon-based strap products because no single configuration or material is ideal under all operational and environmental conditions.

Though they have a lower thermal performance, our Graphite Fiber-based straps are typically more durable and lighter than carbon sheet straps, and they do not need to be designed into longer, heavier, and less efficient S-shapes to be flexed on the lateral axis/provide lateral deflection (which is helpful for applications such as battery pack cooling, antenna arrays, optical instruments, and some deployable/moving/rotating instruments and equipment). Though spaceflight customers most commonly choose GraFlex I and II, GraFlex III is also ideal for applications with extremely limited volumes, but requiring flexibility on each axis.

Graphite/Graphene sheet straps are better-suited to applications with compact envelopes, requiring little to no flexibility/range of motion or repeated flex cycles (such as electronics boxes, chip cooling, etc.), or those with extremely low stiffness requirements. Because of their higher performance at lower temperatures, PGL™ products are now a superior replacement for aluminum foil thermal links at temperatures as low as 50K, and can be used in place of OFHC copper straps at temperatures as low as 70 - 80K (to reduce mass but offer similar thermal performance).

Pictured (Right): Custom PGL™ pre-thermal conductance test (May 2018).

Important Limitations To Consider

First and foremost: don't confuse "single/monolayer graphene," with "graphene films/sheets/foils," or be deceived by claims regarding the durability of pyrolytic graphite and graphene sheets. Straps can be torn if mishandled during installation, flexed on the lateral axis, or if they are subjected to repeated flexing or movement on ANY axis (as this can cause localized creasing, damage, and eventual tearing of sheets).

It is also important to understand that despite any claim to the contrary, all carbon materials; graphite, pyrolytic graphite, and graphene sheets/films/foils, will particulate, pose contamination risks, and generate FOD. As a result, all carbon-based straps must be encapsulated (typically with an aluminized mylar sleeve, or "blanket").

This does not mean that PGL™ and GTL™ products are not suitable for any application; only Torn PGS Thermal Strap

that they are ideal under certain circumstances, and environmental & operational conditions. Our experts will help you to determine which product best suits your operational environment and performance requirements, to ensure the success of your program.

Pictured (Top): All forms of graphite, pyrolytic graphite, and graphene foil/sheet present FOD & contamination risks (and must be encapsulated). (Bottom): First generation PGL/PGS thermal strap with tearing/mechanical failure due to improper handling during installation and removal from test fixture.

PGS Thermal Conductivity vs Other Strap Materials

Important Note on Material Thermal Conductivity: the values in the graph represent the conductivity of the various ("flexible portion") materials used in thermal straps, at different temperatures. They are not necessarily indicative of the measured performance of a thermal strap assembly (i.e., a GFTS®, GTL™, or PGL™ strap assembly will not guarantee 2X - 4X the performance of an equivalent-sized copper cable or foil configuration). This is due to densities and cross sectional area of various materials, and resistance losses associated with assembly processes (epoxying, clamping, and swaging), and via adding additional sheets, ropes, or rows. For performance projections for any of our strap products, please contact us at any time. Our front end design and assessment services are complimentary, and we are happy to help!