At Shimco, we have over 25 years of experience producing many different kinds of shims for a range of industries and applications. We are truly experts in shims.
One of the many types of shims we produce—used mainly for the aerospace industry, but certainly not limited to this—are polyimide shims, made out of a polyimide polymer such as Dupont’s Kapton®. The concept of these types of shims is the same as others, but there are certain qualities of the material that make it advantageous for particular needs and applications.
Polyimide shims begin in foil form, just like our metal laminates, but get glued with a unique and proprietary glue compound developed by Shimco. The end product can be peeled just like any other shims but can also be pressed back together by hand if the incorrect number of lawyers are removed.
These polyimide shims are often used between metallic and non-metallic parts. Since polyimide is an electrical insulator, it aids in the electrical isolation of the adjacent parts. This electrical insulation property is important as it helps to stop the transmission of electricity, such as is the case during in-flight lightning strikes.
What’s another benefit? Polyimide is thermally stable over a wide temperature range, as are carbon fiber parts. However, metallic parts expand and contract more readily under temperature fluctuations. Placing Polyimide between metallic and carbon fiber parts provides a buffer for this thermal expansion and contraction, helping to alleviate some of the stress and pressure on the assembled parts when temperatures fluctuate.
Polyimide is also resistant to reaction with many chemicals. Placing it between chemically dissimilar parts helps to prevent undesirable reactions between those parts, reducing the need for frequent inspection, maintenance and possible repairs.