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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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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Investigation of Test Methods, Material Properties, and Processes for Solar Cell Encapsulents

The technical activities were directed toward the assessment of encapsulation processes for use with ethylene/vinyl acetate copolymer as the pottant. Potentially successful formulations were prepared by compounding the raw polymer with ultraviolet absorbers and crosslinking agents to give stabilized and curable compositions. The compounded resin was then converted to a more useful form with an extruder to give pottant in sheets that could be more easily used in lamination. After experimenting with various techniques, the vacuum-bag process was found to be an excellent encapsulation method. Miniature single-celled and multi-celled solar modules of both substrate and superstrate designs were prepared by this technique. The resulting modules were of good appearance, were bubble-free, and successfully passed the thermal cycle test.

Source record↗
NASA NTRS1979

Investigation of Test Methods, Material Properties, and Processes for Solar Cell Encapsulants

During this quarter the technical activities were directed toward the reformulation of ethylene/vinyl acetate copolymer for use as a compound in solar cell module fabrication. Successful formulations were devised that lowered the temperature required for cure and raised the gel content. A major volatile component was also eliminated (acrylate crosslinking agent) which should aid in the production of bubble free laminates. Adhesive strengths and primers for the bonding of ethylene/vinyl acetate to supersyrate and substrate materials was assessed with encouraging results. The incorporation of silane compounds gave high bond strengths. A survey of scrim materials was also conducted.

Source record↗
NASA NTRS1979

Investigation of Test Methods, Material Properties, and Processes for Solar Cell Encapsulants

The reformulation of a commercial grade of ethylene/vinyl acetate copolymer for use as a pottant in solar cell module manufacture was investigated. Potentially successful formulations were prepared by compounding the raw polymer with antioxidants, ultraviolet absorbers and crosslinking agents to yield stabilized and curable compositions. The resulting elastomer was found to offer low cost (approximately $0.80/lb.), low temperature processability, high transparency (91% transmission), and low modulus. Cured specimens of the final formulation endured 4000 hours of fluorescent sunlamp radiation without change which indicates excellent stability.

Willis, P. B.↗
NASA NTRS1981

Investigation of test methods, material properties, and processes for solar cell encapsulants

The development of pottant compounds is emphasized. Formulation of the butyl acrylate syrup/casting pottant was completed. The formulation contains an ultraviolet stabilizer system and may be cured with an initiator that, unlike former selections, presents no shipping of handling hazards to the user. The catalyzed syrup is stable at room temperature and has a pot life of at least eight hours. The formulation of the ethylene/methyl acrylate lamination pottant was also completed. This compound is the alternative pottant to EVA and is similarly produced as an extruded sheet that is wound into rolls. This resin is inherently nonblocking.

Willis, P. B.↗
NASA NTRS1981

Investigation of Test Methods, Material Properties, and Processes for Solar Cell Encapsulants

Encapsulant materials and processes for the production of cost effective, long life solar cell modules are identified, and evaluated. Ethylene vinyl acetate lamination pottant studies are conducted with respect to the time/temperature cure requirements for successful use of this compound. The time needed to produce successful gel contents are redetermined at a variety of temperatures and are related to the peroxide half life temperature curve. Formulation of the butyl acrylate syrup casting pottant is complete. The formulation contains an ultraviolet stabilizer system and is cured with an initiator that presents no shipping or handling hazards. The catalyzed syrup is stable at room temperature and has a pot life of at least an eight hour period of time. The syrup cures to a transparent rubber in 18 minutes at a temperature of 60 C.

Willis, P. B.↗
NASA NTRS1981

Investigation of test methods, material properties, and processes for solar cell encapsulants

Encapsulant materials and processes for the production of cost-effective, long-life solar cell modules were investigated. The following areas were explored: (1) soil resistant surface treatment; (2) corrosion protecting coatings from mild steel substrates; (3) primers for bonding module interfaces; and (4) RS/4 accelerated aging of candidate encapsulation compounds

Willis, P. B.↗
NASA NTRS1982

Investigation of test methods, material properties, and processes for solar cell encapsulants

Technical investigations concerned the development of advanced cure chemistries for lamination type pottants; the continued evaluation of soil resistant surface treatments, and the results of an accelerated aging test program for the comparison of material stabilities. New compounds were evaluated for efficiency in curing both ethylene/vinyl acetate and ethylene/methyl acrylate pottants intended for vacuum bag lamination of solar cells. One compound in particular, designated Lupersol - TBEC (Lucidol Division of Pennwalt Corp.) was found to be unusually effective in promoting the rapid cure of both these materials. Formulation of these resins with TBEC resulted in compositions of very high gel content, lower temperatures of activation, and much lower cure times, even in the ethylene/methyl acrylate polymer that is more difficult to cure. It is expected that TBEC modified pottant formulations may permit the lamination/encapsulation step to be operated at lower temperatures, higher speed, higher throughput and a much wider tolerance for intentional or accidental variations in the cure schedule. An experimental program continued to determine the effectiveness of soil resistant coatings.

Willis, P. B.↗
NASA NTRS1982

Investigation of Test Methods, Material Properties and Processes for Solar Cell Encapsulants

The evaluation of potentially useful low cost encapsulation materials is discussed. The goal is to identify, evaluate, test and recommend encapsulant materials and processes for the production of cost effective, long life solar cell modules. Technical investigations concerned the development of advanced cure chemistries for lamination type pottants; the continued evaluation of soil resistant surface treatment, and the results of an accelerated aging test program for the comparison of material stabilities. New compounds were evaluated for efficiency in curing both ethylene/vinyl acetate and ethylene/methyl acrylate pottants intended for vacuum bag lamination of solar cells. Two component aliphatic urethane casting syrups were evaluated for suitability as solar module pottants on the basis of optical, physical and fabrication characteristics.

Willis, P.↗
NASA NTRS1983

Investigation of test methods, material properties, and processes for solar cell encapsulants

A study of potentially useful low cost encapsulation materials for the Flat-Plate Solar Array project is discussed. The goal is to identify, evaluate, test and recommend encapsulant materials and processes for the production of cost-effective, long life solar cell modules. Technical investigations included studies of aging and degradation of candidate encapsulation materials, continued identification of primers for durable bonding of module interfaces, continued evaluation of soil resistant treatments for the sunlit surface of the module and testing of corrosion protective coatings for use low cost mild steel substrates.

Willis, P. B.↗
NASA NTRS1983

Investigation of test methods, material properties and processes for solar cell encapsulants

Low cost encapsulation materials for the Flat Plate Solar Array Program (FSA) are investigated. The goal of the program is to identify, test, evaluate and recommend encapsulation materials and processes for the fabrication of cost effective and long life solar modules. Accelerated aging techniques for module component lifetime studies, investigation of candidate outer cover films and continued evaluation of soil repellant coatings are also included.

Willis, P. B.↗
NASA NTRS1983

Investigation of test methods, material properties and processes for solar cell encapsulants

The goal of the program is to identify, test, evaluate and recommend encapsulation materials and processes for the fabrication of cost-effective and long life solar modules. Of the $18 (1948 $) per square meter allocated for the encapsulation components approximately 50% of the cost ($9/sq m) may be taken by the load bearing component. Due to the proportionally high cost of this element, lower costing materials were investigated. Wood based products were found to be the lowest costing structural materials for module construction, however, they require protection from rainwater and humidity in order to acquire dimensional stability. The cost of a wood product based substrate must, therefore, include raw material costs plus the cost of additional processing to impart hygroscopic inertness. This protection is provided by a two step, or split process in which a flexible laminate containing the cell string is prepared, first in a vacuum process and then adhesively attached with a back cover film to the hardboard in a subsequent step.

Willis, P. B.↗
NASA NTRS1984

Investigation of test methods, material properties, and processes for solar cell encapsulants

Photovoltaic (PV) modules consist of a string of electrically interconnected silicon solar cells capable of producing practical quantities of electrical power when exposed to sunlight. To insure high reliability and long term performance, the functional components of the solar cell module must be adequately protected from the environment by some encapsulation technique. The encapsulation system must provide mechanical support for the cells and corrosion protection for the electrical components. The goal of the program is to identify and develop encapsulation systems consistent with the PV module operating requirements of 30 year life and a target cost of $0.70 per peak watt ($70 per square meter) (1980 dollars). Assuming a module efficiency of ten percent, which is equivalent to a power output of 100 watts per square meter in midday sunlight, the capital cost of the modules may be calculated to be $70.00 per square meter. Out of this cost goal, only 20 percent is available for encapsulation due to the high cost of the cells, interconnects, and other related components. The encapsulation cost allocation may then be stated as $14.00 per square meter, included all coatings, pottant and mechanical supports for the cells.

Source record↗
NASA NTRS1991

Processing and properties of SiC whisker- and particulate-reinforced reaction bonded Si3N4

The microstructure and mechanical properties of reaction bonded Si3N4 (RBSN) reinforced with SiC whiskers of particles were investigated using RBSN composites made from colloidally pressed octanol dispersions of high-purity Si powders mixed with either SiC whiskers or alpha-SiC particles. Results of investigations, revealing high conversions of Si to Si3N4, specific surface areas, and constant relative densities and strengths, showed that the uniform microstructure and small flaw size of the matrix were maintained in the composites and that no degradation of the reinforcements was taking place. Neither the monolithic nor the composite materials exhibited R-curve behavior. A modest increase in fracture toughness was observed only in the RBSN containing 33 vol pct SiC(p).

Lightfoot, A.↗
NASA NTRS1992

Effects of a noncoplanar biphenyldiamine on the processing and properties of addition polyimides

Addition curing polyimides, prepared from noncoplanar 2,2'-bis(trifluoromethyl) 4,4' diaminobiphenyl (BTDB) with various dianhydrides were evaluated as high temperature polymer matrix materials. T sub g of these polymers were measured by mechanical methods as well as by thermal mechanical analysis. Physical and mechanical properties as well as the thermo-oxidative stability of neat resins and the corresponding G40-600 graphite fiber reinforced composites were compared to that of PMR-II-50 and V-CAP-75.

Chuang, Kathy C.↗
NASA NTRS1995

Processing and properties of fiber reinforced polymeric matrix composites: I. IM7/LARC(TM)-PETI-7 polyimide composites

A phenylethynyl terminated imide oligomer formed from the reaction of benzophenone tetracarboxylic acid dianhydride, an 75:25 molar ratio of 4,4'-oxydianiline and meta-phenylenediamine and 4-phenylethynylphthalic anhydride as the endcapper at a theoretical number average molecular weight (Mn) of approximately 3,700 g/mol was evaluated as a composite resin matrix. A glass transition temperature (Tg) of 315 deg C was reached after 250 deg C/1 hr annealing of the matrix resin. Unidirectional prepreg was made by coating an N-methylpyrrolidinone solution of the amide acid oligomer onto unsized IM7 graphite fibers. The thermal and rheological properties and the solvent/volatile depletion rates of the amide acid/NMP system were determined. This information was used to successfully design a molding cycle for composite fabrication. Composites molded under 800 Psi at 371 C consistently yielded good consolidation as measured by C-scan and optical photomicrography. The composite's short beam shear strength (SBS), longitudinal and transverse flexural strengths and moduli were measured at various temperatures. These composites exhibited excellent room temperature (RT) longitudinal flexural strength and modulus and RT SBS strength retention at 177 C.

Hou, Tan-Hung↗
NASA NTRS2000

Processing and Properties of SiC/MoSi2-SiC Composites Fabricated by Melt Infiltration

Hi-Nicalon SiC fiber reinforced MoSi2-SiC matrix composites (SiC/MoSi2-SiC) have been fabricated by the melt infiltration approach. The composite consists of approximately 60 vol%, 2-D woven BN/SiC coated Hi-Nicalon SiC fibers and approximately 40 vol% MoSi2-SiC matrix. The room temperature tensile properties and thermal conductivity of the SiC/MoSi2-SiC composites were measured and compared with those of the melt infiltrated SiC/SiC composites. The influence oi fiber architecture on tensile properties was also evaluated. Results indicate that the primary modulus, stress corresponding to deviation from linearity, and transverse thermal conductivity values for the SiC/MoSi2-SiC composites are significantly lower than those for the SiC/SiC composites. Microcracking of the matrix due to the large difference in thermal expansion between MoSi2 and SiC appears to be the reason for the lower matrix dominated properties of SiC/MoSi2-SiC composites.

Bhatt, Ramakrishna T.↗