Risk Mitigation for Cyanate Ester Insulation of Large Magnets Through Cure Optimization

Abstract

The toroidal field (TF) coils for the internationally supported ITER nuclear fusion reactor currently being assembled in France will be part of the largest superconducting magnet system ever to be assembled. Due to the relatively high radiation dose expected, the TF coils will utilize a cyanate ester/epoxy blended insulation. It is estimated that this application will represent the single largest use of cyanate ester resins to date. Although magnet coils for the National Spherical Torus Experiment (NSTX) and Wendelstein 7-X have been successfully manufactured using a cyanate ester/epoxy blended insulation, the sheer size of the ITER TF coils create new challenges and concerns with the processing of such large quantities of liquid cyanate ester materials. Handling cyanate ester/epoxy resins can require different equipment and procedures than are required for handling pure epoxies. In particular, cyanate ester/epoxy systems are known for their energetic polymerization, requiring extra care to minimize the risk of an uncontrolled reaction when handled on a large scale. In support of the ITER TF coil manufacturers, LORD Corporation and Composite Technology Development, Inc. (CTD) have qualified two cyanate ester/epoxy resin systems, CTD-425 and CTD-435, and have demonstrated processing robustness and specifically designed cure profiles that will enable coil manufacturers to employ their preferred resin impregnation processes with confidence, even at the very large scale of the ITER project. A description of the cure experiments performed as well as the recommended cure profiles and handling practices for LORD CTD-435 will be presented.Index Terms-Cyanate ester resin, insulation, ITER, TF coil.

Synthesis and characterization of siloxane‐based cyanate ester elastomers from readily available materials: a top‐down approach

“…These benefits have led to CEs being employed in a number of different areas including the electronics, aerospace and automotive fields . More recently CEs have also been used for drug delivery systems, biosensors, antibacterial and corrosive coatings, shape memory polymers, magnetic insulation and other specialized applications …”

Cyanate Ester—Epoxy Blends for Structural and Functional Composites

“…Recently, CE–EP blends have been researched extensively for several fusion programs such as the International Thermonuclear Experimental Reactor (ITER) and Mega Ampere Spherical Tokamak (MAST) and are being considered as suitable insulation material for fusion magnets in nuclear fusion reactors. , For instance, superconducting magnets of ITER essentially consist of insulation structures which are made of fiber-reinforced polymers. Since these systems are subjected to harsh radiations and extreme structural and thermal loads, the insulation material must be able to withstand these adverse environments for longer durations of time.…”

Effect of Segmental Configuration on Properties of n-Propyl-Bridged Polycyanurate Networks

“…Monomer Synthesis. 4,4′-(Propane-1,1-diyl)bis(3-methylphenol) (5) and 2-(1-(4-Hydroxy-2-methylphenyl)propyl)-5-methylpheol (7). A mechanically stirred mixture of 144 mL of propionaldehyde (2 mol) and 840 mL of m-cresol (8 mol) was cooled to −10 °C while 4 mL of concentrated HCl was added over 30 min.…”

“…As a class of thermosetting polymer networks, polycyanurates − have proven to be exceptionally useful in extreme environments due to the highly stable nature of the cyanurate cross-links formed from cyanate ester monomers. Some notable environments where polycyanurate networks have proven useful include the charged particle and radiation environment around Jupiter encountered by the Juno space probe, the heat of atmospheric entry for the Mars Curiosity heat shield, and the intense neutron bombardment expected within the ITER thermonuclear fusion reactor − and other superconducting magnets exposed to high radiation doses . From a more fundamental perspective, the high stability of the cyanurate cross-link allows for the formation of networks with a very well-defined and, fortuitously, easy to monitor chemical structure even in the fully cross-linked state.…”