Characterization and Qualification of Cyanate Ester/Epoxy Insulation for NSTX-U Fusion Magnets

Fabian, P. E.; Haynes, Mark M.; Babcock, H.; Hooker, Matthew W.

doi:10.1109/tasc.2012.2232344

Cited by 9 publications

(6 citation statements)

References 9 publications

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“…Polycyanurate networks derived from the thermal cyclotrimerization of cyanate ester monomers are becoming increasingly important high-performance materials − in technology areas including printed circuit boards, rocket and missile structures, spacecraft structures, and thermonuclear fusion reactors , due to their advantageous stability characteristics in demanding environments involving elevated temperatures, cryogenic temperatures, exposure to vacuum, and high-energy radiation . In wet environments, these networks demonstrate a mixture of highly desirable traits, such as a very low coefficient of hygrothermal expansion during short-term exposure and low moisture permeability, along with undesirable characteristics such as blistering and loss of mechanical properties during long-term exposure to moisture at elevated temperatures. − Interestingly, many of the desirable traits stem from physical characteristics of the network, such as a high density of cross-links (typically 3 mmol/cm 3 or greater) and the presence of microscale free volume with characteristic hole sizes large enough to accommodate water without swelling, while many of the undesirable traits can be traced to unwanted chemical reactions with either unreacted cyanate ester groups and/or with cured cyanurate groups. − This distinction implies that tailoring of the chemical structure of polycyanurate networks may enable mitigation of the undesirable traits while retaining the desirable ones.…”

Section: Introductionmentioning

confidence: 99%

Mechanisms of Decreased Moisture Uptake in Ortho-Methylated Di(cyanate ester) Networks

Guenthner¹,

Wright

Chafin

et al. 2014

Macromolecules

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Decreases of up to 50% in the moisture uptake of polycyanurate networks based on 2,2-bis(4-cyanatophenyl)propane (BADCy) and 1,1-bis(4-cyanatophenyl)ethane (LECy) were observed when analogous networks containing a single methyl group ortho-to each aryl−cyanurate linkage were prepared by reduction and acid-catalyzed coupling of salicylic acid followed by treatment with cyanogen bromide and subsequent cyclotrimerization. The differences in water uptake were observed despite similar decreases in packing fraction as conversion proceeded in all networks studied. Conversely, the presence or absence of methyl groups at arylene bridges, remote from the cyanurate oxygen, had no influence on water uptake. Vitrification during cure had little effect on either free volume development or moisture uptake. These results confirm that steric hindrance from ortho-methyl groups inhibits absorption of water presumably by decreasing the thermodynamic favorability of sterically permitted interaction with the cyanurate oxygen. A further examination of the effect of two different catalysts, 2 parts per hundred of a 30:1 by weight mixture of nonylphenol and copper(II) acetylacetonate and 500 ppm of dibutyltin dilaurate (DBTDL), compared to analogous uncatalyzed networks, showed that hydrolytic stability was dramatically affected by catalyst choice, while thermochemical stability was also impacted. These results provide important insights into the mechanisms that determine structure−property relationships in polycyanurate networks.

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Section: Introductionmentioning

confidence: 99%

Mechanisms of Decreased Moisture Uptake in Ortho-Methylated Di(cyanate ester) Networks

Guenthner¹,

Wright

Chafin

et al. 2014

Macromolecules

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“…Polycyanurate networks formed from the cyclotrimerization of cyanate ester monomers have proven to be an especially useful class of thermosetting material, with numerous high‐performance applications in the microelectronics and aerospace industries . Some of the more interesting example applications include magnet casing for nuclear fusion reactors and the Large Hadron Collider, brush seals for turbine engines, and spacecraft structures such as frameworks for telescope mirrors, and solar panel supports . In many applications, protection against oxidation during short‐term exposure to temperatures at or above 500 °C is highly desirable.…”

Section: Introductionmentioning

confidence: 99%

Silicon-containing trifunctional and tetrafunctional cyanate esters: Synthesis, cure kinetics, and network properties

Guenthner

Vij

Haddad

et al. 2013

J. Polym. Sci. Part A: Polym. Chem.

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The synthesis and physical properties of new silicon-containing polyfunctional cyanate ester monomers methyl[tris(4-cyanatophenyl)]silane and tetrakis(4-cyanatophenyl)silane, as well as polycyanurate networks formed from these monomers are reported. The higher crosslinking functionality compared to di(cyanate ester) monomers enables much higher ultimate glass transition temperatures to be obtained as a result of thermal cyclotrimerization. The ability to reach complete conversion is greatly enhanced by cocure of the new monomers with di(cyanate ester) monomers such as 1,1-bis(4-cyanatophenyl)ethane. The presence of silicon in these polycyanurate networks imparts improved resistance to rapid oxidation at elevated temperatures, resulting in char yields as high as 70% under nitrogen and 56% in air in the best-performing networks. The water uptake in the siliconcontaining networks examined is 4-6 wt % after 96 h of immersion at 85 C, considerably higher than both carbon-containing and/or di(cyanate ester) analogs. V C 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 767-779

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“…Among thermosetting polymers, polycyanurates (also known as “cyanate ester resins”) − offer an outstanding combination of physical properties that have made them highly desirable for applications ranging from printed circuit boards and radomes to magnet casings for thermonuclear fusion reactors , and support structures for interplanetary space probes . These properties include excellent flame, smoke, and toxicity characteristics, glass transition temperatures of up to 400 °C in fully cured networks, low moisture uptake, and a very low coefficient of hygroscopic expansion, as well as an unusually low dielectric constant and dielectric loss factor compared to other thermosetting resins of similar expected polarity .…”

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Di(cyanate Ester) Networks Based on Alternative Fluorinated Bisphenols with Extremely Low Water Uptake

et al. 2014

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A new polycyanurate network exhibiting extremely low moisture uptake has been produced via the treatment of perfluorocyclobutane-containing Bisphenol T with cyanogen bromide and subsequent thermal cyclotrimerization. The water uptake, at 0.56 ± 0.10% after immersion in water at 85 °C for 96 h, represents some of the most promising moisture resistance observed to date in polycyanurate networks. This excellent performance derives from a near optimal value of the glass transition at 190 °C at full cure. Superior dielectric loss characteristics compared to commercial polycyanurate networks based on Bisphenol E were also observed. Polycyanurate networks derived from this new monomer appear particularly well-suited for applications such as radomes and spacecrafts where polycyanurates are already widely recognized as providing outstanding properties.

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Characterization and Qualification of Cyanate Ester/Epoxy Insulation for NSTX-U Fusion Magnets

Cited by 9 publications

References 9 publications

Mechanisms of Decreased Moisture Uptake in Ortho-Methylated Di(cyanate ester) Networks

Mechanisms of Decreased Moisture Uptake in Ortho-Methylated Di(cyanate ester) Networks

Silicon-containing trifunctional and tetrafunctional cyanate esters: Synthesis, cure kinetics, and network properties

Di(cyanate Ester) Networks Based on Alternative Fluorinated Bisphenols with Extremely Low Water Uptake

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