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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Development of a Cure Model for Unsaturated Polyester Resin Systems Based on Processing Conditions

Unsaturated polyester resin (UPR) systems are extensively used in composite materials for applications in the transportation, marine, and infrastructure sectors. There are continually evolving formulations of UPRs that need to be evaluated and optimized for processing. Differential Scanning Calorimetry (DSC) provides valuable insight into the non-isothermal and isothermal behavior of UPRs within a prescribed temperature range. In the present work, non-isothermal DSC tests were carried out between temperatures of 0.0 °C and 250 °C, through different heating and cooling ramp rates. The isothermal DSC tests were carried out between 0.0 and 170 °C. The instantaneous rate of cure of the tested temperatures were measured. The application of an autocatalytic model in a calculator was used to simulate curing behaviors under different processing conditions. As the temperature increased from 10 °C up to 170 °C, the rate of cure reduced, and the heat of reaction increased. The simulated cure behavior from the DSC data showed that the degree of cure (α) maximum value of 71.25% was achieved at the highest heating temperature of 85 °C. For the low heating temperature, i.e., 5 °C, the maximum degree of cure (α) did not exceed 12% because there was not enough heat to activate the catalyst to crosslink further.

Polymer Science↗
NASA NTRS1979

A comparative study of the toxicity of the combustion products of Tedlar and a fluorenone-polyester film

The relative toxicity in rats resulting from a 30 minute exposure to the combustion products of two materials, Tedlar and fluorenone-polyester film was assessed. The combustion products were generated into a static exposure system using a laboratory-scale furnace. The toxicity was assessed using the primary measurements employed in a more detailed overall toxicity evaluation. The toxicological events observed during the 30 minute exposure are reported.

Farrar, D. G.↗
NASA NTRS1985

Stabilized unsaturated polyesters

An unsaturated polyester, such as propylene glycolmaleic acid phthalic acid prepolymer dissolved in styrene is interpolymerized with an ultraviolet absorber and/or an antioxidant. The unsaturated chain may be filled with H or lower alkyl such as methyl and tertiary alkyl such as tertiary butyl. A polymer stable to exposure to the outdoors without degradation by ultraviolet radiation, thermal and/or photooxidation is formed.

Vogl, O.↗
NASA NTRS1987

Tapered, tubular polyester fabric

A tapered tubular polyester sleeve is described to serve as the flexible foundation for a spacesuit limb covering. The tube has a large end and a small end with a length to be determined. The ratio of taper is also determined by scale factors. All the warp yarns extend to the large end. A requisite number of warp yarns extend the full length of the sleeve. Other warp yarns extend from the large end but are terminated along the length of the sleeve. It is then woven with a filling yarn which extends in a full circle along the full length of the sleeve to thereby define the tapered sleeve. The sleeve after fabrication is then placed on a mandrel, heated in an oven, and then attached to the arm or other limb of the spacesuit.

Lapointe, Donat J. E.↗
NASA NTRS1988

Tapered, tubular polyester fabric

A tapered tubular polyester sleeve as set forth. It has a large end 12 and a small end 14 with a length to be determined. The ratio of taper is also determined by scale factors. All the warp yarns extend to the large end 12. A requisite number of warp yarns 16 extend the full length of the sleeve. Other warp yarns exemplified at 18, 22, 26, 28, 30 and 32 extend from the large end but are terminated along the length of the sleeve. It is then woven with a filling yarn 40 which extends in a full circle along the full length of the sleeve to thereby define the tapered sleeve. The sleeve after fabrication is then placed on a mandrel 42, heated in an oven 44 and is thereafter placed on the arm or other limb of a space suit exemplified at 50.

LaPointe, Donat J. E.↗
DOE OSTI2023

Dual Recycling of Depolymerization Catalyst and Biodegradable Polyester that Markedly Outperforms Polyolefins

Chemically recyclable, circular polymers continue to attract increasing attention, but rendering both catalysts for depolymerization and high-performance polymers recyclable is a more sustainable yet challenging goal. Here we introduce a dual catalyst/polymer recycling system in that recyclable inorganic phosphomolybdic acid catalyzes selective depolymerization of high-ceiling-temperature biodegradable poly(δ-valerolactone) in bulk phase, which, upon reaching suitable molecular weight, exhibits outstanding mechanical performance with a high tensile strength of ≈66.6 MPa, fracture strain of ≈904 %, and toughness of ≈308 MJ m –3 , and thus markedly outperforms commodity polyolefins, recovering its monomer in pure state and quantitative yield at only 100 °C. In sharp contrast, the uncatalyzed depolymerization not only requires a high temperature of >310 °C but is also low yielding and non-selective. Importantly, the recovered monomer can be repolymerized as is to reproduce the same polymer, thereby closing the circular loop, and the recycled catalyst can be reused repeatedly for depolymerization runs without loss of its catalytic activity and efficiency.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Degradation of Polyester Polyurethane by Aspergillus sp. Strain S45 Isolated from Soil

A polyurethane (PU)-degrading fungus designated as strain S45 was isolated from a solid waste-dumping site in Islamabad, Pakistan. Strain S45 was identified as Aspergillus sp. through microscopic, morphologic as well as 18S rRNA sequencing (99% similarity with Aspergillus fumigatus). The degradation ability of strain S45, was analyzed through measurement of weight loss and evolution of CO{sub 2} as a result of breakdown of PU film. The degradation was confirmed through scanning electron microscopy, fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC). Surface changes like pits, cracks and holes were observed in scanning electron micrographs upon degradation of PU film by strain S45. FTIR spectra were carefully examined, changes were observed in various peaks at different wavelength ranges that also correspond to degradation of PU film. Differential scanning calorimetric technique was used to measure the melting temperature of PU film pieces before and after incubation with strain S45. DSC curve indicated an increase in melting temperature of PU from 191 to 196 °C that might be due to increase in crystallinity of the exposed PU after degradation of amorphous soft segment. A gradual increase in specific activity of esterase was observed up to the maximum of 15th day of incubation with PU film in mineral salt medium. Enzyme activity was further confirmed by tween 20 agar plates, demonstrated by formation of calcium complex. It is concluded from the results that Aspergillus sp. strain S45 might be applied for the treatment of plastics-contaminated environments.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗