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Radiation ResistanceBecause of its excellent radiation resistance, Kapton® is frequently used in high radiation environments where a thin, flexible insulating material is required. In outer space, Kapton® is used both alone and in combination with other materials where radiation resistance at minimum weight is necessary. U.S. Government laboratory test data on gamma and neutron radiation exposure of Kapton® is summarized in Talbes I and II. Kapton® remains functional after exposure to radiation dosages up to 107 Gy. Additional testing by CERN, the European Organization for Nuclear Research, confirms this data. Kapton® is also used in nuclear reactors and linear accelerators. Many of these applications require testing that involves exposure to an adverse chemical environment in addition to radiation. For example, Loss of Coolant Accident (LOCA) tests for qualification in containment areas in nuclear power plants expose the system to steam and sodium hydroxide; both of which tend to degrade Kapton®. Accordingly, when Kapton® is used in nuclear power systems that require certification to IEEE-323 and -383, engineered designs which protect Kapton® from direct exposure to LOCA sprays are required. The excellent ultraviolet resistance of Kapton® in the high vacuum of outer space has been confirmed by NASA's Lewis Research Center. The data is shown in Table III. In the earth's environment, however, there is a synergistic degrading effect on Kapton® if it is directly exposed to some combinations of ultraviolet radiation, oxygen and water. Figure 1 shows this effect as a loss of elongation when Kapton® is exposed in Florida test panels. Figure 2 shows the loss of elongation as a function of exposure time in an Atlas Weatherometer. Design consideration should be given to recognize this phenomenon. Normal room fluorescent lighting has no noticeable degrading effect on Kapton®. It should also be noted that the dielectric strength of Kapton® which has undergone physical property loss is not significantly affected unless material fracture due to system stresses occurs. TABLE I |
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| Property | Control
1 mil film |
104 Gy
1h |
105Gy
10h |
106 Gy
4d |
107 Gy
42d |
| Tensile Strength
Mpa psi x 103 |
207
30 |
207
30 |
214
31 |
214 | 152
22 |
| Elongation (%) | 80 | 78 | 78 | 79 | 42 |
| Tensile Modulus
Mpa Psi x 103 |
3172
460 |
3275
475 |
3378
490 |
3275
475 |
2903
421 |
| Vol. Resistivity
ohm-cm x 1013 @ 200°C |
4.8 | 6.6 | 5.2 | 1.7 | 1.6 |
| Diel. Constant 1kHz @ 23°C | 3.46 | 3.54 | 3.63 | 3.71 | 3.50 |
| Dis. Factor 1kHz @ 23°C | .0020 | .0023 | .0024 | .0037 | .0029 |
| Diel. Strength kV/mm |
256 | 223 | 218 | 221 | 254 |
TABLE II
EFFECT OF ELECTRON EXPOSURE ON
KAPTON® POLYIMIDE FILM MIXED
NEUTRON AND GAMMA
| 5 X 107 Gy | 108 Gy | |
| 5 x 1012 neutrons/cm/s Flux @175 deg;C | Film Darkened | Film Darkened and Tough |
TABLE III
EFFECT OF ULTRAVIOLET EXPOSURE ON
KAPTON® POLYIMIDE FILM*
| 1000 h Exposure | |
| Tensile Strength, % of initial value retained | 100 |
| Elongation, % of initial value retained | 74 |
*Vacuum environment, 2 x 10-6 mmHg at 50 °C. UV intensity equal to space sunlight to 2500A
Figure 1. Effect of Florida Aging on Kapton® Polyimide Film
Figure 2. Effect of Weathering on Kapton® Polyimide Film
(Atlas Weatherometer)
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The information give herein is based on data believed to be reliable, but DuPont makes no warranties express or implied as to its accuracy and assumes no liability arising out of its use by others. This publication is not to be taken as a license to operate under, or recommendation to infringe, any patent.
Caution: Do not use in medical applications involving permanent implantation in the human body. For other medical applications, see "DuPont Medical Caution Statement", H-50102.
