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Characterization and Process Development of Cyanate Ester Resin Composites

Description: Cyanate ester resins offer advantages as composite matrices because of their high thermal stability, low outgassing, low water absorption, and radiation resistance. This paper describes the results of a processing study to develop a high-strength hoop-wound composite by the wet-filament winding method using Toray TI 000G carbon fiber and YLA RS- 14A cyanate ester resin as the constituent materials. The study shows that the cyanate ester resin has a broad process envelope but that an inert-atmosphere cure is essential for obtaining optimum resin and composite properties. Minimizing moisture exposure prior to and during cure is also crucial as it affects the glass transition temperature of the resin and composite. Composite cylinders wound and cured with these methods yielded excellent ring tensile strengths both at room and elevated temperature. A summary of the measured mechanical and thermal property data for these composites is presented. Potential applications for these materials include flywheeI energy storage systems for space and satellite structures.
Date: May 23, 1999
Creator: Frame, B.J.
Partner: UNT Libraries Government Documents Department

Characterization and Process Development of Cyanate Ester Resin and Composite

Description: Cyanate ester (or polycyanate) resins offer advantages as composite matrices because of their high thermal stability, low outgassing, low water absorption and radiation resistance. This report describes the results of a processing study to develop high-strength hoop-wound composite by the wet-filament winding method using Toray T1000G carbon fiber and YLA RS-14A polycyanate resin as the constituent materials. Process trials, tests and analyses were conducted in order to gain insight into factors that can affect final properties of the cured cyanate ester resin and its composites. The study shows that the cyanate ester resin has a broad process envelope but that an inert-atmosphere cure is essential for obtaining optimum resin and composite properties. Minimizing moisture exposure prior to cure is also crucial as it affects the T{sub g} of the resin and composite. Recommendations for reducing moisture contact with the resin during wet-winding are presented. High fiber volume fraction ({approximately}80%) composites wound and cured with these methods yielded excellent hoop tensile strengths (660 to 670 ksi average with individual rings failing above 700 ksi), which are believed to be the highest recorded strengths for this class of materials. The measured transverse properties were also exceptional for these high fiber fraction composites. Based on the available data, this cyanate ester resin system and its composites are recommended for space and vacuum applications only. Further testing is required before these materials can be recommended for long term use at elevated temperatures in an ambient air environment. The results of all analyses and tests performed as part of this study are presented as well as baseline process for fabricating thick, stage-cured composites. The manufacture of a 1 in. thick composite cylinder made with this process is also described.
Date: March 1998
Creator: Frame, B. J.
Partner: UNT Libraries Government Documents Department

Compressive Creep Response of T1000G/RS-14 Graphite/Polycyanate Composite Materials

Description: The response of a T1000G/RS-14 graphite/polycyanate composite material system to transverse compressive loads is quantified via experimentation. The primary objective of the work was to quantify the effects of process environment and test environment on the T1000G/RS-14 compressive creep response. Tests were conducted on both the neat resin and the composite material system. In addition to the creep tests, static compressive strength tests were conducted to define the stress-strain response. The creep behavior for the RS-14 resin was quantified by conducting a series of tests to study the effects of different process environments (air and nitrogen), different cure temperatures, and different test environments (air and vacuum). The combined effect on the RS-14 resin compressive creep of processing in nitrogen and testing under vacuum versus processing in air and testing in air was a 47% decrease in the creep strain after 2177 hr. The test environment appeared to have a greater effect on the resin creep than the process environment. Following the conclusion of the resin creep tests, composite transverse compressive creep tests were conducted. The composite creep test cylinder was post-cured in a nitrogen environment prior to machining test specimens and all tests were conducted in a vacuum environment. The series of tests investigated the effects of initial stress level and test temperature on the creep behavior. At the end of the 2000-hr tests at 275{degrees}F on specimens stressed at 10,000 psi, the nitrogen-processed and vacuum-tested conditions reduced the composite transverse compressive creep strain by 19% compared to processing in air and testing in air. The effects of process and test environment on the creep behavior are not as great for the composite system as they were for the neat resin, primarily because of the low resin content in the composite material system. At the 275{degrees}F test temperature there was ...
Date: January 1, 1998
Creator: Starbuck, J.M.
Partner: UNT Libraries Government Documents Department

Evaluation of bisphenol E cyanate ester for the resin-injection repair of advanced composites

Description: This thesis is a compilation of a general introduction and literature review that ties together the subsequent chapters which consist of two journal articles that have yet to be submitted for publication. The overall topic relates to the evaluation and application of a new class of cyanate ester resin with unique properties that lend it applicable to use as a resin for injection repair of high glass transition temperature polymer matrix composites. The first article (Chapter 2) details the evaluation and optimization of adhesive properties of this cyanate ester and alumina nanocomposites under different conditions. The second article (Chapter 3) describes the development and evaluation of an injection repair system for repairing delaminations in polymer matrix composites.
Date: December 19, 2009
Creator: Lio, Wilber Yaote
Partner: UNT Libraries Government Documents Department

Wet-filament winding fabrication of thick carbon fiber/polycyanate resin composite

Description: Polycyanate resins offer advantages as composite matrices because of their high thermal stability, low outgassing, low water absorption and radiation resistance. This report describes the fabrication of a thick (nominal 1 in.) hoop-wound composite cylinder that is manufactured by the wet-filament winding method using Toray T1000G carbon fiber and YLA RS-14 polycyanate resin as the constituent materials. An analytical model used to evaluate the fabrication process, estimate composite residual stresses and provide input toward mandrel design is presented and the construction of the mandrel used to wet-wind the cylinder is described. The composite cylinder quality is evaluated by dimensional inspection and measurements of density and composition.
Date: June 1, 1997
Creator: Frame, B.J. & Dodge, W.G.
Partner: UNT Libraries Government Documents Department

Process study of polycyanate resin for wet-filament wound high-strength composites

Description: Polycyanate (or cyanate ester) resins offer advantages as composite matrices because of their high thermal stability, low outgassing, low water absorption and radiation resistance. This report describes the results of a processing study to develop high-strength hoop-wound composite by the wet-filament winding method using Toray T1000G carbon fiber and YLA RS-14 polycyanate resin as the constituent materials. T1000G/RS-14 composite cylinders were wet-wound and cured using different process schedules and then evaluated for hoop tensile strength and modulus, transverse flexural strength and short beam shear strength. The results of material characterization tests performed on the T1000G carbon fiber and RS-14 resin constituents used in this study are also presented.
Date: December 31, 1997
Creator: Frame, B.J.
Partner: UNT Libraries Government Documents Department

Testing and performance evaluation of T1000G/RS-14 graphite/polycyanate composite materials

Description: The performance of a graphite fiber/polycyanate matrix composite material system, T1000G/RS-14, was evaluated by performing an extensive mechanical property test program. The test program included both static strength and long-term tests for creep, fatigue, and stress rupture. The system was evaluated at both ambient temperature and elevated temperatures. The specimens were machined from composite cylinders that had a unidirectional layup with all the fibers oriented in the hoop direction. The cylinders were fabricated using the wet-filament winding process. In general, the T1000G/RS-14 system demonstrated adequate static strengths for possible aerospace structural applications. The results from the static tests indicated that very high composite hoop tensile strengths can be achieved with this system at both ambient and elevated temperatures as high as 350{degree}F. However, in the long-term testing for compressive creep and tension-tension fatigue the results indicated a lower elevated temperature was required to minimize the risk of using this material system. Additional testing and analysis activities led to the selection of 275{degree}F as the desired temperature for future performance evaluation. Subsequent testing efforts for determining the resin and composite transverse compressive creep responses at 275{degrees}F indicated that excessive creep strain rates may still be a weakness of this system. In the long-term tests, sufficient data was generated from impregnated strand and composite ring stress-life testing, and composite ring tension-tension fatigue to determine failure probabilities for a given set of design requirements. The statistical analyses of the test data, in terms of determining failure probability curves, will be reported on in a separate report. However, it is expected that this material system will have a very low failure probability for stress rupture based on the collected stress-life data. Material responses that will require further investigation and/or possible performance improvements are fiber- direction tension-tension fatigue, and both resin and transverse composite compressive ...
Date: January 1, 1997
Creator: Starbuck, J.M.
Partner: UNT Libraries Government Documents Department

Viscosity of aqueous and cyanate ester suspensions containing alumina nanoparticles

Description: The viscosities of both aqueous and cyanate ester monomer (BECy) based suspensions of alumina nanoparticle were studied. The applications for these suspensions are different: aqueous suspensions of alumina nanoparticles are used in the production of technical ceramics made by slip casting or tape casting, and the BECy based suspensions are being developed for use in an injection-type composite repair resin. In the case of aqueous suspensions, it is advantageous to achieve a high solids content with low viscosity in order to produce a high quality product. The addition of a dispersant is useful so that higher solids content suspensions can be used with lower viscosities. For BECy suspensions, the addition of nanoparticles to the BECy resin is expected to enhance the mechanical properties of the cured composite. The addition of saccharides to aqueous suspensions leads to viscosity reduction. Through DSC measurements it was found that the saccharide molecules formed a solution with water and this resulted in lowering the melting temperature of the free water according to classic freezing point depression. Saccharides also lowered the melting temperature of the bound water, but this followed a different rule. The shear thinning and melting behaviors of the suspensions were used to develop a model based on fractal-type agglomeration. It is believed that the structure of the particle flocs in these suspensions changes with the addition of saccharides which leads to the resultant viscosity decrease. The viscosity of the BECy suspensions increased with solids content, and the viscosity increase was greater than predicted by the classical Einstein equation for dilute suspensions. Instead, the Mooney equation fits the viscosity behavior well from 0-20 vol% solids. The viscosity reduction achieved at high particle loadings by the addition of benzoic acid was also investigated by NMR. It appears that the benzoic acid interacts with the surface ...
Date: August 5, 2009
Creator: Lawler, Katherine
Partner: UNT Libraries Government Documents Department

Polymer nanocomposites for high-temperature composite repair

Description: A novel repair agent for resin-injection repair of advanced high temperature composites was developed and characterized. The repair agent was based on bisphenol E cyanate ester (BECy) and reinforced with alumina nanoparticles. To ensure good dispersion and compatibility with the BECy matrix in nanocomposites, the alumina nanoparticles were functionalized with silanes. The BECy nanocomposites, containing bare and functionalized alumina nanoparticles, were prepared and evaluated for their thermal, mechanical, rheological, and viscoelastic properties. The monomer of BECy has an extremely low viscosity at ambient temperature, which is good for processability. The cured BECy polymer is a highly cross-linked network with excellent thermal mechanical properties, with a high glass transition temperature (T{sub g}) of 270 C and decomposition temperature above 350 C. The incorporation of alumina nanoparticles enhances the mechanical and rheological properties of the BECy nanocomposites. Additionally, the alumina nanoparticles are shown to catalyze the cure of BECy. Characterization of the nanocomposites included dynamic mechanical analysis, differential scanning calorimetry, thermogravimetric analysis, rheological and rheokinetic evaluation, and transmission electron microscopy. The experimental results show that the BECy nanocomposite is a good candidate as repair agent for resin-injection repair applications.
Date: December 1, 2008
Creator: Sheng, Xia
Partner: UNT Libraries Government Documents Department

PURIFICATION OF Pm$sup 147$ FROM FISSION-PRODUCED RARE EARTHS

Description: Promethium is purified from inactive and radioactive long-lived fission- produced rare earths by the use of Dowex 50 or Nalcite HCR cation exchangers and organic eluants. Americium and promethium, having hydrated ionic radii of the same size, are contained in the same fraction of the eluate. Promethium is purified from americium by adsorbing both elements on Dowex 1 (thiocyanate form) and eluting promethium from the resin with ammonium thiocyanate solution. Equllibrium studies were made in order to determine distribution coefficients of the long-lived radioactive rare earths. Elution curves based on analyses of solutions removed from anion and cation exchangers verify the relative values of the distribution coefficients. From Dowex 1 resin, rare earths 58 through 63 elute with ammonium thiocyanate in the order of increasing atomic number. Conditions are established for the expansion of the present 50- to 100-curie- level processing to levels of 1000 to 5000 curies. (auth)
Date: March 15, 1960
Creator: Pressly, R.S.
Partner: UNT Libraries Government Documents Department

Possible explosive compounds in the Savannah River Site Tank Farm facilities. Revision 1

Description: Since 1970, many studies have been conducted concerning the potential for explosive compounds in tank farm operations including ammonium nitrate, metal oxalates, and silver and mercury compounds. The study currently in progress is the most comprehensive to date, encompassing all previous studies and extending the scope to include all compounds that could be formed from the known species in SRS wastes. In addition to waste storage, the study also considers waste removal and waste processing operations. The total number of possible explosive compounds is so large that it would not be useful to list them all here. Instead, only those compounds are listed that are known to be present or could conceivably be formed from material that is known to be present in the waste. The general approach to the problem is: identify all of the constituents that are known to be present in the waste together with those that might be present from possible chemical and radiolytic reactions, determine the compounds that could be formed from these constituents, compare these compounds with those listed in the literature, and assess the formation and stability of these compounds against the conditions existing in the tank farm facilities.
Date: April 27, 1995
Creator: Hobbs, D.T.
Partner: UNT Libraries Government Documents Department

Cure shrinkage effects in epoxy and polycyanate matrix composites

Description: A relatively new advanced composite matrix, polycyanate ester, was evaluated for cure shrinkage. The chemical cure shrinkage of composites is difficult to model but a number of clever experimental techniques are available to the investigator. In this work the method of curing a prepreg layup on top of a previously cured laminate of identical ply composition is utilized. The polymeric matrices used in advanced composites have been primarily epoxies and therefore a common system of this type, Fiberite 3501-6, was used as a base case material. Three polycyanate matrix systems were selected for the study. These are: Fiberite 954-2A, YLA RS-3, and Bryte Technology BTCy-1. The first three of these systems were unidirectional prepreg with carbon fiber reinforcement. The Bryte Technology material was reinforced with E-glass fabric. The technique used to evaluate cure shrinkage results in distortion of the flatness of an otherwise symmetric laminate. The first laminate is cured in a conventional fashion. An identical layup is cured on this first laminate. During the second cure all constituents are exposed to the same thermal cycles. However, only the new portion of the laminate will experience volumetric changes associate with matrix cure. The additional strain of cure shrinkage results in an unsymmetric distribution of residual stresses and an associated warpage of the laminate. The baseline material, Fiberite 3501-6, exhibited cure shrinkage that was in accordance with expectations. Cure strains were {minus}4.5E-04. The YLA RS-3 material had cure strains somewhat lower at {minus}3.2E-04. The Fiberite 954-2A cure strain was {minus}1.5E-04 that is 70% lower than the baseline material. The glass fabric material with the Bryte BTCy-1 matrix did not result in meaningful results because the processing methods were not fully compatible with the material.
Date: December 22, 1995
Creator: Spellman, G.P.
Partner: UNT Libraries Government Documents Department

Advances in the chemical conversion of energetic materials to higher value products

Description: The objective of this program is to develop novel, innovative solutions for the disposal of surplus explosives resulting from the demilitarization of nuclear and conventional munitions by DOE and DoD. Studies related to the conversion of TNT and Explosive D to potentially useful materials are described. The paper describes the feasibility of conversion of TNT to TATB; conversion of TNT to 3,5-diamino-2,4,6-trinitrotoluene (DATNT); conversion of TNT to tolylene 2,4-diisocyanate (TDI) and nitrotolylene and diisocyanate (NTDI); chelating resins derived from trinitroarenes.
Date: January 24, 1995
Creator: Mitchell, A.R.; Pagoria, P.F. & Sanner, R.D.
Partner: UNT Libraries Government Documents Department

Report for General Research September 18 to December 11, 1950 (Radium Volume)

Description: The purpose of the research work reported in this volume is the development of a process for the separation and subsequent purification of radium from the K-65 (pitchblende) residue. Except for the accumulation of additional experimental data the process is essentially complete. After a preliminary extraction of about 85% of the lead and 40% of the silica with a 40% sodium hydroxide solution, the residue is treated with a solution containing both sodium hydroxide and sodium carbonate to obtain additional lead removal and partial conversion of the radium and barium sulfates to carbonates. After leaching out the soluble carbonates, the residue containing unconverted sulfates is treated with a sodium carbonate solution at 170{sup o} under pressure. A study of the amount and concentration of sodium carbonate required to obtain a satisfactory conversion of the sulfates has shown that the total sodium carbonate may be reduced by 40% and that smaller volumes of solution may be employed without serious decrease in the efficiency of the conversion. In order to make calculations on the number of steps and tank sizes for the radium-barium separation by fractional precipitation, equations have been developed to calculate this information from the theoretical separation factors determined experimentally. Three methods for carrying out the radium-barium separation by fractional precipitation of chromates have been studied and the separation factors determined. The methods differ in the reagent and temperature employed for the neutralization of the nitric acid solution of the chromates. The separation factor improves with decrease in temperature, and a marked improvement has been found by replacing urea which requires boiling temperatures for hydrolysis with potassium cyanate which hydrolyzes at much lower temperatures.
Date: January 15, 1951
Creator: Haring, M.M.
Partner: UNT Libraries Government Documents Department

COMPARISON OF TWO COLORIMETRIC METHODS FOR URANIUM

Description: In order to establish the feasibility of using two colorimetric met;iods for the determination of uranium interchangeably, according to the interferences encountered in a particular sampte. results were obtained by each of the methods and compared. The dibenzoyl methane method and the ethyl acetate-ammonium thiocyanate procedure were compared on the basis of values secured on the same day. on different days, on an analysis of the variance. and on an analysis of the residual error for the methods on different days. On the basis of the findings of these tests. it is concluded that the two methods can be used interchangeably to determine the uranium content of the ethyl acetate extracts of samples. Since the interferences in the two methods are different. the uranium content of a variety of materials can be determined without additional separations being required. (auth)
Date: March 25, 1959
Creator: McCutchen, R.L.
Partner: UNT Libraries Government Documents Department

Thermosetting Polymer-Matrix Composites for Strucutral Repair Applications

Description: Several classes of thermosetting polymer matrix composites were evaluated for use in structural repair applications. Initial work involved the characterization and evaluation of woven carbon fiber/epoxy matrix composites for structural pipeline repair. Cyanate ester resins were evaluated as a replacement for epoxy in composites for high-temperature pipe repair applications, and as the basis for adhesives for resin infusion repair of high-temperature composite materials. Carbon fiber/cyanate ester matrix composites and fumed silica/cyanate ester nanocomposites were evaluated for their thermal, mechanical, viscoelastic, and rheological properties as they relate to their structure, chemistry, and processing characteristics. The bisphenol E cyanate ester under investigation possesses a high glass transition temperature, excellent mechanical properties, and unique ambient temperature processability. The incorporate of fumed silica served to enhance the mechanical and rheological properties of the polymer and reduce thermal expansion without sacrificing glass transition or drastically altering curing kinetics. Characterization of the composites included dynamic mechanical analysis, thermomechanical analysis, differential scanning calorimetry, thermogravimetric analysis, rheological and rheokinetic evaluation, and transmission electron microscopy.
Date: December 1, 2007
Creator: Goertzen, William Kirby
Partner: UNT Libraries Government Documents Department

The Kinetics of the Complexing of Ferric Ion by Thiocyanate and Chloride Ions

Description: An apparatus for rapidly mixing two solutions and recording the light absorption, which was developed by Connick and Below, has been modified. The mixing characteristics were studied and models were developed in an attempt to umder stand the observed mixing phenomena. The apparatus was applied to a study of the kinetics of the reactions Fe/sup +++/ + SCN/sup -/ = FeSCN/sup ++/ and Fe/ sup +++/ Cl/sup -/ = FeCl/sup ++/ in aqueous solution, with both reactions having the forward rate law STAd(FeX/sup ++/)/dt = k/sub 1/ (Fe/sup +++/) (X/sup -/) + k/ sub 2/ (Fe/sup +++/)(X/sup -/)/(H/sup +)!, where X/sup -/ represents either SC N/ sup -/ or Cl/sup -/. The rate constants k/sub 1/ and k/sub 2/ have been measured as a function of temperature, and the heats and entropies of activation have been calculated. Mechanisms for the observed rate law have been discussed and the entropies of activation were compared with those for analogous reaction rates and with some equilibrium entropies of complexing. A rate for chloride complexing of ferric ion was obtained from nuclear magnetic resonance studies and compared with the results of the spectrophotometric kinetic study. (auth)
Date: December 1, 1957
Creator: Coppel, Claude Peter
Partner: UNT Libraries Government Documents Department

Final Report for Radiaiton Resistant Magnets for RIA

Description: Report on techniques for the fabrication of radiation resistant magnets for the RIA Fragment Separator. The development of magnet designs capable of reasonable life times in high-radiation environments and having reasonable performance is of paramount importance for RIA as well as other high-intensity projects under consideration, such as the Neutrino Factory and FAIR project at GSI. Several approaches were evaluated for radiation resistant superconducting magnets. One approach was to simply use a more radiation resistant epoxy for the coil fabrication. Another approach for cryostable magnets, like the S800 Spectrograph dipole, is the use of all-inorganic materials. The final approach was the development of radiation resistant Cable-In-Conduit-Conductor (CICC) like that used in fusion magnets; though these are not radiation resistant because an organic insulator is used. Simulations have shown that the nuclear radiation heating of the first quadrupoles in the RIA Fragment Separator will be so large that cold mass minimization will be necessary with the magnet iron being at room temperature. Three different types of conductor for radiation resistant superconducting magnets have been built and successfully tested. The cyanate ester potted coils will work nicely for magnets where the lifetime dose is a factor of 20 less than the end of life of the superconductor and the rate of energy deposition is below the heat-removal limit of the coil. The all-inorganic cryostable coil and the metal oxide insulated CICC will provide conductor that will work up to the life of the superconductor and have the ability to remove large quantities of nuclear heating. Obviously, more work needs to be done on the CICC to increase the current density and to develop different insulations; and on the cyanate esters to increase the heat transfer.
Date: July 27, 2005
Creator: Zeller, A. F.
Partner: UNT Libraries Government Documents Department