Why is Vespel® so extreme?  Well, it’s one of the most dynamic engineering plastics on the market.  If you need a high performance plastic that can do everything and cost is no issue then Vespel® may be for you.  Also, Vespel® excels in extreme environments.  Looking to blast some plastic fasteners into outer space?  Vespel® could be your answer.  Read on for more information on Vespel’s® many superior qualities including strength, chemical resistance, low-coefficient of friction and more.

Vespel® is the registered trademark for a polyimide engineering plastic by Dupont®.    It is a condensation type polyimide produced from pyromellitic dianhydride (PMDA) and 4,4′ diamino diphenyl ether (ODA). 1  

It is one of the most commonly used engineering plastics in the aerospace industry.  Virtually every jet engine made in the Western World contains Vespel® parts.  It is also the material of choice in the manufacture of semiconductors and in transportation applications.  Vespel® parts can endure extreme environments from reactor chambers to deep space.  This engineering plastic is recommended in applications in which temperature extremes, a vacuum, or radiation are present and where wear resistance, dimensional stability, oxygen compatibility, light weight, low outgassing as well as minimal electrical and thermal conductivity are required.  It is used for seal rings and valve seats, bushings, spacers, screws and bearings, wafer guides, brake pad assemblies and in jet engines as well as small motors, vacuum pumps and antilock brake systems, to name a few.

Vespel® is available in an unfilled grade as well as in filled grades with various percentages of graphite, PTFE/graphite or molybdenum disulfide.   The unfilled grade is often referred to as SP1.  We will discuss the characteristics of that grade here. 

Thermal Properties:  Vespel® SP1 is a semi-crystalline material thus it has a structure that has both crystalline and amorphous regions.  Consequently is has no melting point but unlike other semi-crystalline plastics it also has no observable glass transition temperature below its decomposition temperature of more than 750/400 ⁰F/⁰C.  Vespel® SP1 has a maximum continuous service temperature of 500/260 ⁰F/⁰C but can tolerate temperatures of as high as 900/482 ⁰ F/⁰C for a short period of time without loss of its mechanical properties.  It is no surprise then that SP1 has a flammability rating of UL 94 V-0 and is flame retardant. 

Vespel® SP1 has a low co-efficient of friction. Additionally, it is lubricious, meaning that SP1 is slippery so this material improves fuel efficiency and is wear resistant.  It has the highest unlubricated pressure-velocity (PV) limit performance of any engineered plastic (.29 -3.5 MPa-m/s.). With low abrasion and low particle generation characteristics, SP1 is recommended for use in the semiconductor manufacturing industry and clean room applications.

SP1 allows for significant weight savings over metal parts and thus improves fuel efficiency. It has one half the weight of cast aluminum.  Its specific gravity is 1.4 while cast aluminum is 2.8 and titanium has a specific gravity of 4.5.

Vespel® SP1 is chemically resistant to a variety of organic solvents, acids and industrial fluids.

Also SP1 is low out gassing.  It is flight approved by NASA and the US Air Force.  The NASA outgassing values for SP1 are 1.09% TML (Total Mass Lost), 0.00% CVCM (Collected Volatile Condensable Materials) and 0.04% WVR (Water Vapor Regained.)

Finally, along with the properties discussed above, Vesel® SP1 is dimensionally stable under extreme conditions. It has minimum electrical and thermal conductivity, low creep, low water absorption and is radiation resistant.

More information on Vespel® is available on the Dupont® website.

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1   C10 H2  O6  and   C12 H12  N2 O

What’s your favorite engineering plastic?  What’s your experience with Vespel?  Let us know in the comments section below!

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