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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Synthesis of improved polyester resins

Eighteen aromatic unsaturated polyester prepolymers prepared by a modified interfacial condensation technique were investigated for their solubility in vinyl monomers and ability to provide high char yield forming unsaturated polyester resins. The best resin system contained a polyester prepolymer of phthalic, fumaric and diphenic acids reacted with 2,7-naphthalene diol and 9,9-bis(4-hydroxyphenyl)fluorene. This prepolymer is very soluble in styrene, divinyl benzene, triallyl cyanurate, diallyl isophthalate and methylvinylpyridine. It provided anaerobic char yields as high as 41 percent at 800 C. The combination of good solubility and char yield represents a significant improvement over state-of-the-art unsaturated polyester resins. The majority of the other prepolymers had only low or no solubility in vinyl monomers. Graphite composites from this prepolymer with styrene were investigated. The cause for the observed low shear strengths of the composites was not determined, however 12-week aging of the composites at 82 C showed that essentially no changes in the composites had occurred.

Mcleod, A. H.↗
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↗
DOE OSTI2019

Fabrication of diatomite‐based microencapsulated flame retardant and its improved fire safety of unsaturated polyester resin

To achive excellent fire resistance, new microcapsule flame retardants (DMCAD and DMPPD) were prepared using 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide combined with melamine cyanurate or melamine polyphosphate as the shell material and diatomite as the core material. The successful assembly of DMCAD and DMPPD was detailed characterized by Fourier transform infrared (FT‐IR) spectra, X‐ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Meanwhile, the flame retardancy and thermal stability of the unsaturated polyester resin (UPR)/DMCAD and UPR/DMPPD composites were also studied. The addition of DMCAD and DMPPD effectively improves the flame retardance properties of UPR, and the effect of DMPPD was better. The limiting oxygen index (LOI) of UPR/DMPPD‐3 increased by 11.6% when compared with that of UPR, and the sample achieved V‐0 rating. Moreover, the peak heat release rate (pHRR) and the total heat release (THR) rate of UPR/DMPPD‐3 were reduced by 67% and 26%, respectively. Under nitrogen condition and air condition, UPR/DMPPD showed better thermal stability and char‐forming ability from the thermogravimetric (TG) results. Residual char of the UPR composites was systematically analyzed with SEM and XPS. Finally, the flame retardant mechanism of DMPPD was proposed.

Chen, Gang↗
NASA NTRS1980

Synthesis of improved phenolic and polyester resins

Thirty-seven cured phenolic resin compositions were prepared and tested for their ability to provide improved char residues and moisture resistance over state of the art epoxy resin composite matrices. Cyanate, epoxy novolac and vinyl ester resins were investigated. Char promoter additives were found to increase the anaerobic char yield at 800 C of epoxy novolacs and vinyl esters. Moisture resistant cyanate and vinyl ester compositions were investigated as composite matrices with Thornel 300 graphite fiber. A cyanate composite matrix provided state of the art composite mechanical properties before and after humidity exposure and an anaerobic char yield of 46 percent at 800 C. The outstanding moisture resistance of the matrix was not completely realized in the composite. Vinyl ester resins showed promise as candidates for improved composite matrix systems.

Delano, C. B.↗
NASA NTRS1983

Forming Mirrors on Composite Materials

Smooth coatings deposited on hard-to-polish substrates. Lightweight mirror, leaning against conventional glass mirror, consists of metallic relective layer on substrate coated with polyester resin. Smooth surface of polyester resin made by covering freshly applied resin with piece of smooth glass coated with release agent.

Gauldin, R. E.↗
DOE OSTI2022

On the Mechanism of the Steady-State Gamma Radiolysis-Induced Scissions of the Phenyl-Vinyl Polyester-Based Resins

The major societal problem of polymeric waste necessitates new approaches to break down especially challenging discarded waste streams. Gamma radiation was utilized in conjunction with varying solvent environments in an attempt to discern the efficacy of radiolysis as a tool for the deliberate degradation of model network polyesters. Our EPR results demonstrated that gamma radiolysis of neat resin and in the presence of four widely used solvents induces glycosidic scissions on the backbone of the polyester chains. EPR results clearly show the formation of alkoxy radicals and C-centered radicals as primary intermediate radiolytic products. Despite the protective role of the phenyl groups on the backbone of the radiation-induced polyester chains, the radiolytic-glycosidic scissions predominate. Among the following three solvents used in this study (water, isopropyl alcohol, and dichloromethane), the highest radiolytic yield of glycosidic scission was achieved using water. The •OH radicals produced in the radiolysis of phenyl unsaturated polyester aqueous suspensions very rapidly abstract H atoms from the methylene group, which is followed by a very rapid glycosidic scission. The lowest glycosidic yield was found in the dichloromethane solutions of these polyester resins due to scavenging by the fast electron capture reactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Water-thinnable polymers for durable coatings for different materials

The methods of obtaining water-thinnable polymers - water-thinnable unsaturated polyester resins (WTUPR) - by polycondensation were elaborate and optimized. As hydrophilic monomers different types of sulfonate monomers were used. The monomers, with sulfonate groups and other reactive groups, were obtained by sulfonation of organic compounds with satisfactory yield. All products were analyzed by {sup 1}H NMR and {sup 13}C NMR spectra. WTUPR were used as polymeric binders for coatings applications. Coatings with relatively high pendulum hardness, good properties and durability, useful for practical applications, were obtained. Typical existing equipment for the production of unsaturated polyester resins can be applied for the industrial preparation of WTUPR.

36 MATERIALS SCIENCE↗
NASA NTRS2021

Pyrolysis Rate and Yield Strength Reduction Incarbon Fiber and Glass Fiber Composites Underreentry Heating Conditions

The behavior of composite materials, specifically carbon fiber reinforced plastic (CFRP) and glass fiber reinforced plastic (GFRP), under reentry conditions poses a problem for space debris reentry risk modeling. Since these materials pyrolyze rather than melt and their different components demise at different rates, modeling their destruction to determine ground impact risk is complex. Modern spacecraft are using these materials in ever-greater quantities owing to their superior strength-to-weight characteristics, and this has required that the orbital debris community improve its understanding of how these materials demise on reentry. The NASA Orbital Debris Program Office undertook an extensive test campaign to better understand the rate at which several types of GFRP and CFRP materials pyrolyze under reentry heating conditions and how that pyrolysis affects the ultimate strength of the material. GFRP with a polyester resin (G10/FR-4) and CFRP with epoxy, cyanate ester, vinyl ester, and phenolic resins were tested. The test campaign was carried out at the Inductively Coupled Plasma (ICP) Torch Facility at the University of Texas at Austin. Because the ICP facility operates in a shirt-sleeve environment, test samples can be changed within seconds or minutes, allowing many samples to be tested in a short period. Two heat flux rates, 20 W/m2 and 30W/m2, and two oxygen concentration conditions, 0% and 2% of atmospheric, were applied to all five types of material. To measure both the char rate and the effect of pyrolysis on the ultimate material strength, two types of test were carried out for each material: a char rate test on a ~10 mm thick sample of material and an in-situ bending stress test of a ~2 mm thick sample of material. Measurements of the char rate showed very similar average pyrolysis front velocity in epoxy resin CFRP as in G10 at 3.6 mm/min and 3.4 mm/min, respectively. However, the total mass loss rate in theG10 was nearly double that of the CFRP at 3.8 g/min and 2.2 g/min, respectively. This result represented a slow ablation rate of carbon fibers in the CFRP at the temperatures encountered in low Earth orbit reentry and a comparatively rapid removal of the glass fibers in G10 due to melting and spallation. Pyrolysis front velocity was more significantly affected by the type of plastic than the type of fiber, with the cyanate ester CFRP samples displaying an average pyrolysis front velocity of only 1.9 mm/min. Similarly, the effect of thermal exposure on the ultimate strength of the material depended heavily on the type of plastic and very little on the type of fiber in the material. Epoxy, vinyl ester, and polyester resins all behaved very similarly, with complete structural failure at between 400 J/g and 600 J/g of specific absorbed heat. Phenolic and cyanate ester resins, on the other hand, displayed a change in structural properties that was only barely measurable with the current apparatus even after the maximum exposure time tested. These data are being incorporated into a numerical model of the ablation and demise of composite materials that will be used to more accurately calculate the ground casualty risk of future spacecraft.

Benton R. Greene↗
DOE OSTI2016

Influence of additional coupling agent on the mechanical properties of polyester–agave cantala roxb based composites

The mechanical and morphological properties of the unsaturated polyester resins (UPRs)-agave cantala roxb based composite are investigated in this paper. The cantala fiber woven in 3D angle interlock was utilized as the composite reinforcement. Surface grafting of the cantala fiber through chemical treatment was performed by introducing silane coupling agent to improving the compatibility with the polymer matrix. The fabrication of the composite specimens was conducted using vacuum bagging technique. The effect of additional coupling agent to the morphological appearance of surface fracture was observed using scanning electron microscopy. Meanwhile, the influence of additional silane to the mechanical properties was examined using tensile, bending and impact test. The photograph of surface fracture on the treated specimens showed the residual matrix left on the fibers in which the phenomenon was not found in the untreated specimens. Based on mechanical tests, the treated specimens were successfully increased their mechanical properties by 55%, 9.67%, and 92.4% for tensile strength, flexural strength, and impact strength, respectively, at 1.5% silane coupling agent.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Renewable unsaturated polyesters from muconic acid

cis,cis -Muconic acid is an unsaturated dicarboxylic acid that can be produced in high yields via biological conversion of sugars and lignin-derived aromatic compounds. Muconic acid is often targeted as an intermediate to direct replacement monomers such as adipic or terephthalic acid. However, the alkene groups in muconic acid provide incentive for its direct use in polymers, for example, in the synthesis of unsaturated polyester resins. Here, biologically derived muconic acid is incorporated into polyesters via condensation polymerization using the homologous series of poly(ethylene succinate), poly(propylene succinate), poly(butylene succinate), and poly(hexylene succinate). Additionally, dimethyl cis,cis -muconate is synthesized and subsequently incorporated into poly(butylene succinate). NMR measurements demonstrate that alkene bonds are present in the polymer backbones. In all cases, the glass transition temperatures are increased whereas the melting and degradation temperatures are decreased. In the case of poly(butylene succinate), utilization of neat muconic acid yields substoichiometric incorporation consistent with a tapered copolymer structure, whereas the muconate diester exhibits stoichiometric incorporation and a random copolymer structure based on thermal and mechanical properties. Prototypical fiberglass panels were produced by infusing a mixture of low molecular weight poly(butylene succinate-co-muconate) and styrene into a woven glass mat and thermally initiating polymerization resulting in thermoset composites with shear moduli in excess of 30 GPa, a value typical of commercial composites. The increased glass transition temperatures with increasing mucconic incorporation leads to improved composites properties. We find that the molecular tunability of poly(butylene succinate-co-muconate) as a tapered or random copolymer enables the tunability of composite properties. Altogether, this study demonstrates the utility of muconic acid as a monomer suitable for direct use in commercial composites.

09 BIOMASS FUELS↗
NASA NTRS1984

Friction and morphology of magnetic tapes in sliding contact with nickel-zinc ferrite

Friction and morphological studies were conducted with magnetic tapes containing a Ni-Zn ferrite hemispherical pin in laboratory air at a relative humidity of 40 percent and at 23 C. The results indicate that the binder plays a significant role in the friction properties, morphology, and microstructure of the tape. Comparisons were made with four binders: nitrocellulose; poly (vinyledene) chloride; cellulose acetate; and hydroxyl-terminated, low molecular weight polyester added to the base polymer, polyester-polyurethane. The coefficient of friction was lowest for the tape with the nitrocellulose binder and increased in the order hydroxylterminated, low molecular weight polyester resin; poly (vinyledene) chloride; and cellulose acetate. The degree of enclosure of the oxide particles by the binder was highest for hydroxyl-terminated, low molecular weight polyester and decreased in the order cellulose acetate, poly (vinyledene) chloride, and nitrocellulose. The nature of deformation of the tape was a factor in controlling friction. The coefficient of friction under elastic contact conditions was considerably lower than under conditions that produced plastic contacts.

Miyoshi, K.↗
DOE OSTI2019

Synthesis and Performance Evaluation of Unsaturated Polyester Blends of Resins and Its Application on Non-woven/Fabric Jute Fibers Reinforced Composites

The present study focuses on the generation of eco-friendly value added product by utilizing bio-based material as reinforced and matrix phase. Processing of soy and alkyd resin as matrix was carried out by utilization of soy flour and Ricinodendron heudelotii oil, followed essential modification in few inferior properties of soy flour resin by blending with alkyd resin. Separate sets of resin were prepared by maintaining 0%, 5% and 10% of alkyd resin in 100 g of soy flour resin respectively in each set to attain a comparative study on performance of prepared sets of resin blend. Subsequently, performance evaluation of polyester blends was evaluated by processing with non-woven/fabric jute fibers reinforced composites. The blend of R. heudelotii oil based alkyd and soy-flour resin in processing of composites was the noval approach of the study. The resins blend were characterized by FT–IR, viscosity and zeta potential measurements while thermo-mechanical analyses, water absorbancy and surface analyses were performed in composites. Significant increases noticed in the viscosity of blend, the blend containing 10% alkyd resin is two times more viscous compared to soy-flour resin. Furthermore, improvement in properties including water absorption, thermo-mechanical properties and better fiber-matrix interfacial adhesion of the composite could be observed. Higher glass transition temperature T{sub g} value i.e. 126.8 °C obtained for composites with 10% blend as matrix might emphasizes on increase of the degree of cross linking provided by the α-eleostearic fatty acid chain moiety. The enhancements in properties indicate extending opportunities for fiber-reinforced composites in several industries including building material, furniture, aerospace, nano etc.

36 MATERIALS SCIENCE↗
NASA NTRS1990

The assessment of metal fiber reinforced polymeric composites

Because of their low cost, excellent electrical conductivity, high specific strength (strength/density), and high specific modulus (modulus/density) short metal fiber reinforced composites have enjoyed a widespread use in many critical applications such as automotive industry, aircraft manufacturing, national defense, and space technology. However, little data has been found in the study of short metal fibrous composites. Optimum fiber concentration in a resin matrix and fiber aspect ratio (length-to-diameter ratio) are often not available to a user. Stress concentration at short fiber ends is the other concern when the composite is applied to a load-bearing application. Fracture in such composites where the damage will be initiated or accumulated is usually difficult to be determined. An experimental investigation is therefore carefully designed and undertaken to systematically evaluate the mechanical properties as well as electrical properties. Inconel 601 (nickel based) metal fiber with a diameter of eight microns is used to reinforce commercially available thermoset polyester resin. Mechanical testing such as tensile, impact, and flexure tests along with electrical conductivity measurements is conducted to study the feasibility of using such composites. The advantages and limitations of applying chopped metal fiber reinforced polymeric composites are also discussed.

Chung, Wenchiang R.↗
DOE OSTI2022

Characterization of the Emissions and Crystalline Silica Content of Airborne Dust Generated from Grinding Natural and Engineered Stones

Abstract In this study, we systematically characterized the airborne dust generated from grinding engineered and natural stone products using a laboratory testing system designed and operated to collect representative respirable dust samples. Four stone samples tested included two engineered stones consisting of crystalline silica in a polyester resin matrix (formulations differed with Stones A having up to 90wt% crystalline silica and Stone B up to 50wt% crystalline silica), an engineered stone consisting of recycled glass in a cement matrix (Stone C), and a granite. Aerosol samples were collected by respirable dust samplers, total dust samplers, and a Micro-Orifice Uniform Deposit Impactor. Aerosol samples were analyzed by gravimetric analysis and x-ray diffraction to determine dust generation rates, crystalline silica generation rates, and crystalline silica content. Additionally, bulk dust settled on the floor of the testing system was analyzed for crystalline silica content. Real-time particle size distributions were measured using an Aerodynamic Particle Sizer. All stone types generated similar trimodal lognormal number-weighted particle size distributions during grinding with the most prominent mode at an aerodynamic diameter of about 2.0-2.3 μm, suggesting dust formation from grinding different stones is similar. Bulk dust from Stone C contained no crystalline silica. Bulk dust from Stone A, Stone B, and granite contained 60, 23, and 30wt% crystalline silica, respectively. In Stones A and B, the cristobalite form of crystalline silica was more plentiful than the quartz form. Only the quartz form was detected in granite. The bulk dust, respirable dust, and total dust for each stone had comparable amounts of crystalline silica, suggesting that crystalline silica content in the bulk dust could be representative of that in respirable dust generated during grinding. Granite generated more dust per unit volume of material removed than the engineered stones, which all had similar normalized dust generation rates. Stone A had the highest normalized generation rates of crystalline silica, followed by granite, Stone B, and Stone C (no crystalline silica), which likely leads to the same trend of respirable crystalline silica (RCS) exposure when working with these different stones. Manufacturing and adoption of engineered stone products with formulations such as Stone B or Stone C could potentially lower or eliminate RCS exposure risks. Combining all the effects of dust generation rate, size-dependent silica content, and respirable fraction, the highest normalized generation rate of RCS consistently occurs at 3.2-5.6 µm for all the stones containing crystalline silica. Therefore, removing particles in this size range near the generation sources should be prioritized when developing engineering control measures.

Public, Environmental & Occupational Health↗
DOE OSTI2014

Dosimetry in Thermal Neutron Irradiation Facility at BMRR

Radiation dosimetry for Neutron Capture Therapy (NCT) has been performed since 1959 at Thermal Neutron Irradiation Facility (TNIF) of the three-megawatt light-water cooled Brookhaven Medical Research Reactor (BMRR). In the early 1990s when more effective drug carriers were developed for NCT, in which the eye melanoma and brain tumors in rats were irradiated in situ, extensive clinical trials of small animals began using a focused thermal neutron beam. To improve the dosimetry at irradiation facility, a series of innovative designs and major modifications made to enhance the beam intensity and to ease the experimental sampling at BMRR were performed; including (1) in-core fuel addition to increase source strength and balance flux of neutrons towards two ports, (2) out of core moderator remodeling, done by replacing thicker D 2 O tanks at graphite-shutter interfacial areas, to expedite neutron thermalization, (3) beam shutter upgrade to reduce strayed neutrons and gamma dose, (4) beam collimator redesign to optimize the beam flux versus dose for animal treatment, (5) beam port shielding installation around the shutter opening area (lithium-6 enriched polyester-resin in boxes, attached with polyethylene plates) to reduce prompt gamma and fast neutron doses, (6) sample holder repositioning to optimize angle versus distance for a single organ or whole body irradiation, and (7) holder wall buildup with neutron reflector materials to increase dose and dose rate from scattered thermal neutrons. During the facility upgrade, reactor dosimetry was conducted using thermoluminescent dosimeters TLD for gamma dose estimate, using ion chambers to confirm fast neutron and gamma dose rate, and by the activation of gold-foils with and without cadmium-covers, for fast and thermal neutron flux determination. Based on the combined effect from the size and depth of tumor cells and the location and geometry of dosimeters, the measured flux from cadmium-difference method was 4 - 7 % lower than the statistical mean derived from the Monte-Carlo modeling (5% uncertainty). The dose rate measured by ion chambers was 6 - 10 % lower than the output tallies (7% uncertainty). The detailed dosimetry that was performed at the TNIF for the NCT will be described.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1967

Dispersion of borax in plastic is excellent fire-retardant heat insulator

A mix of borax powder and a chlorinated anhydrous polyester resin yields a plastic composition that is fire-retardant, yields a minimum of toxic gases when heated, and exhibits high thermal insulating properties. This composition can be used as a coating or can be converted into laminated or cast shapes.

Evans, H.↗