Thermal System

Re: Kapton

PRF — Thu, 14 Apr 2005 16:22:50 GMT

I agree with Buck, the Kapton leadwire insulation is the source of any controversy involving Kapton in the aerospace industry. Kapton (in sheet form) is the material specified by NASA for insulation of heating elements (See GSFC Spec S311-P-079) and some sensors that go into mission-critical applications. It has been this way for almost half a century, and they still use Kapton. Currently, leadwires used in most aerospace applications are not Kapton, but PTFE or ETFE insulated. I would say that concerns using Kapton Heaters and sensors in aerospace are unfounded.

Re: Kapton

Buck45 — Wed, 13 Apr 2005 18:31:58 GMT

Aircraft wiring and the insultation used on the wiring has been a debate since a TWA plane caught fire back in the late 1970's. It was not until a couple years ago that the FAA decided to investigate aircraft wiring. On an aircraft, there are bundles of wires in close proximity. Due to age and vibration, some of the insulation can be removed. The amount of energy available in this location if you have metal to metal conductors touching is incredible. This energy could ignite inflammable material and/or cause all kinds of power surges on equipment. Some tests have shown that the polyimide insulation (Dupont's Kapton) coating over the wire will produce hairline fractures under the normal working environment of an aircraft (vibration, humidity, salty conditions). These fractures subsequently allowed electrical arcing. The problems in the insulation over wire is not limited to Kapton. Poly-X insulation coating is also under scrutiny. To date, Dupont says it knows of no aircraft accident which, on analysis, has been linked to Kapton. It is important to note that this debate is based on the coating on wires. It does not affect Kapton sheet laminates which are used to make flexible heaters, flexible circuits and surface mount style temperature sensors. Also part of this debate centers on the fail safe systems that must be in place to counteract a "runaway situation" (e.g. current limitation controls, fuses etc).

Re: Kapton

Star_E — Wed, 13 Apr 2005 18:16:52 GMT

Kapton is used extensively in the aerospace industry. There can be concerns, in specific applications, about out-gassing of the adhesive used to bond the Kapton but several options for bonding adhesive are available. Can your end user explain their concern further? Solutions abound but sometimes the right question is the problem.

Kapton

ski forever — Tue, 12 Apr 2005 20:36:09 GMT

Why does Kapton have a bad reputation in the aerospace industry? I have an end user who is uncertain about using Kapton heaters and sensors. Are his concerns justified?