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Length-temperature measurements for several polymers and mixtures for detection of transitions and determination of location and magnitude of expansion coefficient changes
Low temperature measurements of length- temperature curves of polyethylene, polypropylene, mixtures of polyethylene and polypropylene, and copolymers
Liners for nitric and hydrofluoric acid tanks show no sign of deterioration after 18 months of continuous use. Each side of each edge of the polypropylene sheets is chamfered, and sheets are welded from both sides with polypropylene filler rod and a special hot-air welding torch.
Mylar and polypropylene laminates with aluminum as materials for communication satellites
Polypropylene repeated cold drawing and annealing, noting extension recovery and morphological changes
Polypropylene thermal conductivity temperature dependence variations caused by Co 60 gamma radiation
Polypropylene preparation and evaluation as soft X ray detector window material
Molecular orientation and mechanical isotropy in polyethylene, polypropylene, and polyethylene terephthalate films
A sample of polypropylene was evaluated for toxicity of pyrolysis gases, using the toxicity screening test method developed at the University of San Francisco. The gases from this sample appeared to be equivalent or less toxic than the gases from a sample of polyethylene under these particular test conditions. Carbon monoxide appeared to be the principal toxicant.
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A generalized procedure for fabricating the separator is described. Some of the desired properties considered in fabricating the separator material for nickel-cadmium cells were good mechanical strength, good chemical stability, good wettability to the electrolyte, high electrolyte retention, and gas passage.
The RadWorks Wearable Technology team is dedicated to developing protective garments to ameliorate the effects of radiation caused by Solar Particle Events (SPEs). This work requires that we remain open to new avenues for processing hydrogen-rich materials that may be useful in the development of these protective garments. The purpose of this research was to identify new ways of processing polyolefin polymers (polypropylene, more specifically) with additive manufacturing techniques. First, we conducted a literature review to identify known problems with processing polypropylene using additive manufacturing. Then, we looked toward finding ways to manage these difficulties within the additive manufacturing process. The primary goal was to develop techniques for processing polypropylene in a way that would generate a product amenable to inclusion in a worn garment (e.g., flexible, strong, and with ample radiation protection). In the end, we were able to generate designs which addressed polypropylene’s high coefficient of thermal expansion and lack of material adhesion, while meeting the requirements set forth by the use-case for wearable technology. This research offers novel avenues for processing one of the most common plastics in the world, which could contribute to the development of protective garments, as well as new avenues to explore for additive manufacturing in low-gravity environments.
Heterogeneous chemical systems have been studied for the synthesis of isotactic polypropylene in order to establish baseline parameters for the reaction process and to develop sensitive and accurate methods of analysis. These parameters and analytical methods may be used to make a comparison between the polypropylene obtained at one g with that of zero g (gravity). Baseline reaction parameters have been established for the slurry (liquid monomer in heptane/solid catalyst) polymerization of propylene to yield high purity, 98% isotactic polypropylene. Kinetic data for the slurry reaction showed that a sufficient quantity of polymer for complete characterization can be produced in a reaction time of 5 min; this time is compatible with that available on a sounding rocket for a zero-g simulation experiment. The preformed (activated) catalyst was found to be more reproducible in its activity than the in situ formed catalyst.
Improved inorganic-organic separators developed by NASA were commercially prepared. A single-ply asbestos substrate was developed, as well as alternative substrates based on cellulose and on polypropylene fibers. The single-ply asbestos was bound with butyl rubber and was functionally superior to the formerly used polyphenylene oxide saturated sheet. Commercially prepared separators exhibited better measured separator properties than the NASA standard. Cycle life in Ni/Zn and Ag/Zn cells was related to substrate, decreasing in the order; asbestos cellulose paper nonwoven polypropylene. The cycle life of solvent-coated separators was better than aqueous in Ni/Zn cells, while aqueous coatings were better in Ag/Zn cells.
The technology of an inorganic-organic (I/O) separator, which demonstrated improved flexibility, reduced cost, production feasibility and improved cycle life was developed. Substrates to replace asbestos and waterbased separator coatings to replace the solvent based coatings were investigated. An improved fuel cell grade asbestos sheet was developed and a large scale production capability for the solvent based I/O separator was demonstrated. A cellulose based substrate and a nonwoven polypropylene fiber substrate were evaluated as replacements for the asbestos. Both the cellulose and polypropylene substrates were coated with solvent based and water based coatings to produce a modified I/O separator. The solvent based coatings were modified to produce aqueous separator coatings with acceptable separator properties. A single ply fuel cell grade asbestos with a binder (BTA) was produced. It has shown to be an acceptable substrate for the solvent and water based separator coatings, an acceptable absorber for alkaline cells, and an acceptable matrix for alkaline fuel cells. The original solvent based separator (K19W1), using asbestos as a substrate, was prepared.
Experimental studies to investigate the mechanical properties of ultra-lightweight polyimide foams for space applications, compression after impact (CAI) properties for low velocity impact of sandwich composites, and aspen fiber/polypropylene composites containing an interface adhesive additive, Maleic Anhydride Grafted Polypropylene (MAPP), were performed at Clark Atlanta University. Tensile, compression, flexural, and shear modulus tests were performed on TEEK foams categorized by their densities and relative cost according to ASTM specifications. Results showed that the mechanical properties of the foams increased as a function of higher price and increasing density. The CAI properties of Nomex/phenolic honeycomb core, fiberglass/epoxy facesheet sandwich composites for two damage arrangements were compared using different levels of impact energy ranging from 0 - 452 Joules. Impact on the thin side showed slightly more retention of CAI strength at low impact levels, whereas higher residual compressive strength was observed from impact on the thick side at higher impact levels. The aspen fiber/polypropylene composites studied are composed of various percentages (by weight) of aspen fiber and polypropylene ranging from 30%-60% and 40%-100%, respectively. Results showed that the MAPP increases tensile and flexural strength, while having no significant influence on tensile and flexural modulus.
Three commercial-off-the-shelf (COTS) hollow fiber (HoFi) membrane evaporators, modified for low pressure, were tested in a vacuum chamber at pressures below 33 pascals as potential space suit water membrane evaporator (SWME) heat rejection technologies. Water quality was controlled in a series of 25 tests, first simulating potable water reclaimed from waste water and then changing periodically to simulate the ever concentrating make-up of the circulating coolant over that is predicted over the course of 100 EVAs. Two of the systems, comprised of non-porous tubes with hydrophilic molecular channels as the water vapor transport mechanism, were severely impacted by the increasing concentrations of cations in the water. One of the systems, based on hydrophobic porous polypropylene tubes was not affected by the degrading water quality, or the presence of microbes. The polypropylene system, called SWME 1, was selected for further testing. An inverse flow configuration was also tested with SWME 1, with vacuum exposure on the inside of the tubes, provided only 20% of the performance of the standard configuration. SWME 1 was also modified to block 50% and 90% of the central tube layers, and tested to investigate performance efficiency. Performance curves were also developed in back-pressure regulation tests, and revealed important design considerations arising from the fully closed valve. SWME 1 was shown to be insensitive to air bubbles injected into the coolant loop. Development and testing of a full-scale prototype based on this technology and these test results is in progress.