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Spaceport Structures and Materials

New Materials for the Repair of Polyimide Electrical Wire Insulation

wo viable polyimide backbone materials have been identied that will allow the repair opolyimide electrical wire insulation ound on the Space Shuttle and other aging aircrat.Tis identication is the outcome o ongoing eorts to assess the viability o using suchpolyimides and polyimide precursors (polyamic acids [PAAs]) as repair materials or aging

polyimide electrical wire insulation. Tese repair materials were selected because they match thechemical makeup o the underlying wire insulation as closely as possible. Tis similarity allows

or maximum compatibility, coupled with the outstanding physical properties o polyimides.Te two polyimide backbone materials allow the polymer to be extremely fexible and to melt atlow temperatures. A polymer chain end capping group that allows the polymer to crosslink intoa nonfowable repair upon curing at around 200 C was also identied. Te table highlights tworepair materials prepared rom each o the two backbone materials identied. wo lms, one romeach backbone, are sot, fexible lms suitable or manually wrapping damaged wire. Te other twoare stier, more rigid lms to be ormed into sleeves that can easily be slipped onto a wire. Botho the wire repair materials achieved excellent results. Figure 1 shows that the repairs (on 12-gaugepolyimide insulated wire) are small and compact, exhibiting excellent fexibility. Methods have alsobeen established to repair electrical wire insulation based on fuoropolymers (polytetrafuoroethylenematerials [Figure 2]). In addition, a heater was developed to melt and fow the materials, which

enables the curing process required or repairs. A portable soldering iron was modied with a customhead designed to accommodate a wire wrapped with repair lm. Figure 3 shows the wire holders thatwere modied or repairing wires.

Polymer Type Film Forming

Ability

Wire Repair

Results

Comments

A-1 Imide Excellent Good Soft for wrapping; very good on voltage breakdown

A-2 Imide Excellent Good Stiff for sleeve type repair

B-1 Imide Excellent Good Soft for wrapping; v. good adhesion

B-2 Imide Excellent Good Stiff for sleeves

Figure 1. Small, compact repairs on 12-gauge insulated wires exhibit excellent exibility.

Wire/Cable

Inspection

and Repair

Characteristics of repair materials prepared from two viable polyimide backbone materials.

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KSC Technology Development and Application 2006-2007

Contacts: Dr. Tracy L. Gibson , (321) 867-7572, and Dr. Scott T. Jolley (321) 867-7568, ASRC Aerospace; and Dr. Martha K. Williams, NASA-KSC, (321) 867-4554

Participating Organizations: NASA-KSC (Dr. LaNetra C. Tate, Trent M. Smith, and Dr. Luke B.Roberson) and ASRC Aerospace (Lilliana Fitzpatrick, Rubiela D. Vinje, and Steven L. Parks)

Figure 2. Repairs to various types of wire insulation materials.

Figure 3. Wire holders modied for repairing wires.