Improved Electrical Characteristics of Airborne Radomes

Technical Abstract The physical properties of a polymer cause the response of their mechanical and electrical properties to lag an applied, reversed, or removed stimulus with a similar delay. This lagging or relaxation delay is measured by a time constant t that is inherently related to energy absorption for both models. The relaxation is thermally dependent. Mechanical strength of a polymer occurs because its long, string-like molecules intertwine and chemically attach (cross link) at points. Higher temperature weakens the cross linking and increases the slippage under strain and changes the relaxation. Extended high temperature exposure of a cross linked polymer, such as a cyantate ester, has been shown to weaken the molecular attachments of the cross linking and perhaps mechanical integrity of the polymer itself in a manner that is similar to natural aging at a lower temperature. The similarity of the relaxation models for mechanical and electrical properties for a polymer suggests that the electrical properties are also changed by aging, natural or simulated by high temperature exposure. This investigation proposes to evaluate changes of the electrical properties of cyanate ester and epoxy resins which have had accelerated aging by high temperature exposure. BENEFIT: Anticipated Benefits Potential Commercial Applications The chemistry of the polymer resins will be evaluated before and after the simulated aging. This would point the way to modification of the resin for improved resistance to aging of the materials regarding their electrical and perhaps mechanical performance