Characterization of Kapton polymer containing an inorganic additive

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Title: Characterization of Kapton polymer containing an inorganic additive
Author: Betancourt, Juan
Abstract: With a full space program in progress, new types of materials are needed for spacecraft construction. These materials need to be strong, have good thermal stability and be good insulators. One of the materials with these properties is Kapton, manufactured by Dupont. Being a polyimide, it provides these characteristics, and being quite stable to ultraviolet light makes it the best of its kind for space use. The only concern is that, at the altitudes where earth observing spacecrafts orbit the earth, high concentrations of monoatomic oxygen (AO) react with the organic material and produce CO and H20. In an attempt to solve the problem, layers of protective paint or silicon oxide are used to coat the surface of the polymer. They seem to protect the material very well but, after long exposure to the AO, the coatings crack causing corrosion of the polymer underneath. Silicon blends with Kapton were also subjected to AO at length, but harmful fumes are produced contaminating adjacent components, e.g. solar arrays. Using the silicone Kapton blend as a reference point, other chemical elements were evaluated to find a similar protective mechanism without the contamination problem. Zirconium (Zr) was the element of choice. Besides producing stable oxides, it is heavier than silicon and doesn't produce fumes. As for the silicon blend, the Zr additive {Zr(acac)4}2 will be introduced throughout the polymeric material. Upon the attack of the monoatomic oxygen, a layer of Zr oxide will eventually be formed and polymeric material will remain underneath it. In case of any crack formation, there will be enough material left to form more oxide and stop the polymeric oxidation. Several techniques were used to characterize the films made from the polymer containing the additive, and to answer questions such as: (1) How is the strength of the material affected by the addition of the additive?, (2) How long does it take to form the oxide surface and how much polymer material is left underneath?, (3) Is the addition of Zr(acac)4 a good choice or does it cause phase separation? It has been found that the addition of the additive reduces the strength of the material about 50%, i.e., not to an extent that it becames useless. Plasma studies show that as the concentration of Zr in the Kapton is increased, the rate of erosion is reduced about 75%. With state of the art electron microscopy and atomic force microscopy, no evidence of phase separation was observed. Instead, some particles were found in the films, their concentration independent of the concentration of the additive. In summary, the addition of the Zr(acac)4 inorganic additive causes a trade off between tensile strength and AO resistance.
Record URI: http://hdl.handle.net/1850/13953
Date: 1998-11-16

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