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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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A polymer has been developed that has excellent potential for use as windows in spacecraft as well as conventional aircraft. This polymer, phenolphthalein polycarbonate, has outstanding thermal properties, e.g., in place of melting or burning, it produces an insulating charred foam that closes off transmission of radiant heat through the window. This fact, coupled with an oxygen index of 0.43 and a 177 C tensile strength of 58 mega Newtons/sq m, makes this polymer a prime candidate for further development. Pilot plant preparation in a 20 gallon Pfaudler kettle was accomplished and large test specimens were prepared for evaluations.
Polymers for aircraft and spacecraft structures are considered, giving attention to novel foams and porous structures, aircraft nacelle composite structure technology, properties and processing of polyimidazoquinazoline composites, and the processing of organic matrices into structural composites. Other subjects discussed are related to high temperature resins and composites, elastomers for high temperature applications, fire retardant materials, polymers for critical pollution control, and polymers for critical medical use. Individual items are announced in this issue.
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A typical Advanced Technology Laboratory mission flight plan was developed and used as a guideline for the identification of a number of experiment considerations. The experiment logistics beginning with sample preparation and ending with sample analysis are then overlaid on the mission in order to have a complete picture of the design requirements. The results of this preliminary design study fall into two categories. First specific preliminary designs of experiment hardware which is adaptable to a variety of mission requirements. Second, identification of those mission considerations which affect hardware design and will require further definition prior to final design. Finally, a program plan is presented which will provide the necessary experiment hardware in a realistic time period to match the planned shuttle flights. A bibliography of all material reviewed and consulted but not specifically referenced is provided.
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Some analytical methods developed in flammability research are reviewed. Computerized analytical systems are used to separate, identify, and quantify components of complex mixtures of low-boiling volatiles, high-boiling volatiles, and solid residues resulting from pyrolysis, oxidative degradation, and flaming combustion processes. To demonstrate the procedure for determining a material's response to a thermal flux administered under dynamic conditions, the treatment of data is reported for samples of an aromatic polyamide fabric which were degraded under isothermal conditions of 550 C following a dynamic heating rate of 100 C/min from ambient to final temperature.
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A literature search in the field of ultraviolet and charged particle irradiation of polymers was utilized in an experimental program aimed at the development of radiation stable materials for space applications. The rationale utilized for material selection and the synthesis, characterization and testing performed on several selected materials is described. Among the materials tested for ultraviolet stability in vacuum were: polyethyleneoxide, polyvinylnaphthalene, and the amino resin synthesized by the condensation of o-hydroxybenzoguanamine with formaldehyde. Particularly interesting was the radiation behavior of poly(ethyleneoxide), irradiation did not cause degradation of optical properties but rather an improvement in transparency as indicated by a decrease in solar absorptance with increasing exposure time.
Polymers were tested and allowed to outgas isothermally at 125 C and .000001 torr or less. The performance was investigated by thermogravimetric analysis from room temperature to 450 C or until the substance decomposed.
Materials intended for use in spacecraft are routinely tested at low pressures, and outgassed substances are condensed on cold surfaces at liquid nitrogen temperature, -196 C. These condensates are then analyzed by infrared spectroscopy, and gas chromotography-mass spectroscopy. The polymers were tested and allowed to outgas isothermally at 125 C and 0.000001 torr or less. Valuable information was obtained by extending the temperature range below and above 125 C. The performance of substances of interest to NASA were investigated by thermogravimetric analysis (TGA) from room temperature to 450 C or until the substance decomposed. Thermogravimetric analysis of a substance is a useful technique for studying its thermal nature in both static and dynamic thermal environments. It gives considerable insight into the stability and characterization of substances and the changes they undergo in varying thermal environments. The system is able to get pressures down to 1 micron or 0.001 torr.
All available newly developed nonmetallic thermally stable polymers were examined for the development of processes and techniques by compression molding, injection molding, or thermoforming cabin interior parts. Efforts were directed toward developing molding techniques of new polymers to economically produce usable nonmetallic molded parts. Data on the flame resistant characteristics of the materials were generated from pilot plant batches. Preliminary information on the molding characteristics of the various thermoplastic materials was obtained by producing actual parts.
A description is presented of a strategy for analyzing the combustion process and the degradation products which are formed. One of three primary objectives in the study of polymer degradation is related to the characterization of the material to be studied and the investigation of the thermal behavior of the material. Another objective is concerned with the definition of the nature of the decomposition process by identification and quantitation of the degradation products. The third objective involves the determination of the mechanism and kinetics of the decomposition process. The methods of sample degradation include pyrolysis, oxidative degradation, flaming combustion, and the use of large-scale combustion chambers. Methods of chemical separation and identification are considered, taking into account low-boiling volatiles, high-boiling volatiles, and ancillary techniques.
Electrodes and electrolytes of nickel cadmium sealed batteries were analyzed. Different thermal analysis of negative and positive battery electrodes was conducted and the temperature ranges of occurrence of endotherms indicating decomposition of cadmium hydroxide and nickel hydroxide are identified. Atomic absorption spectroscopy was used to analyze electrodes and electrolytes for traces of nickel, cadmium, cobalt, and potassium. Calibration curves and data are given for each sample analyzed. Instrumentation and analytical procedures used for each method are described.
Factors contributing to the final failure of Ni-Cd batteries are listed. A differential thermal analyzer was used to study several positive and negative battery electrodes. The negative plates show a very large peak (endotherm) between 245 C and 250C. The second endotherm occurs at 300C indicating the decomposition of Cd(OH)2. In positive plates, a first weak endotherm occurs at 100C, which indicates loss of H2O from Ni(OH)2(H2O)n molecules. A second large endotherm occurs in the range of 290C to 300C, indicating the decomposition of Ni(OH2) to NiO and H2O. Atomic absorption spectroscopy was used to determine nickel, cobalt, cadmium, and potassium content in battery electrolytes and electrodes. Results are presented in tables.
The effects of resin composition, curing conditions fillers, and flame retardant additives on the flammability of diglycidyl ether of bisphenol-A (DGEBA) as measured by the oxygen index is examined. The oxygen index of DGEBA cured with various curing agents was between 0.198 to 0.238. Fillers and flame retardant additives can increase the oxygen index dependent on the material and the amount used. Changes in the basic cured resin properties can be anticipated with the addition of noncompatible additives. High flame resistant epoxy resins with good stability and mechanical properties are investigated.
A computerized system was established and the electrochemical fluorination of trichloroethylene, polyacrylic acid and polyvinyl alcohol in anhydrous hydrogen fluoride was attempted. Both solid substrates as well as membranes were used. Some difficulties were found in handling and analyzing the solid substrates and membranes. Further studies are needed in this area. A microprocessor aided electrochemical fluorination system capable of obtaining highly reproducible experimental results was established.
The constitutive equation for the relaxation behavior of time-dependent, chemically unstable materials developed by Valanis and Peng (1983), which used the irreversible thermodynamics of internal variables in Eyring's absolute reaction theory and yielded a theoretical expression for the effect of chemical crosslink density on the relaxation rate, is presently applied to the creep behavior of a network polymer which is undergoing a scission process. In particular, two equations are derived which may for the first time show the relations between mechanical models and internal variables in the creep expressions, using a three-element model with a Maxwell element.