Performance evaluation of cyanate ester resin

Abstract

Traditional epoxy resin systems have long been used for vacuum impregnation of large electro-magnets. However, the mechanical strength of these systems is disappointingly low when operated at temperatures above about 7O0C where the failure mechanism is more often by adhesion at the copper interface than by cohesion within the resin. A range of resin systems based on cyanate ester are currently being developed by CTD Inc. which are suitable for vncuum impregnation and may offer advantages over the epoxy resin systems. In order to BSSESS the thermo-mechanical performance of these newly developed materials a programme of testing and evaluation of the basic cyanate ester resin (CTD 403) has been carried out and the results are presented here. I INTRODUCTIONThe first stage of the testing programme involved manufacturing and testing lap shear test specimens at various temperatures to compare the strength of glass-reinforced cyanate ester with that of glass-reinforced epoxy resin. These results proved very encouraging so a series of mechanical strength tests was carried out on pure cyanate ester (CE) and epoxy resin to determine and compare their mechanical properties including their fiacture toughness and glass transition temperatures. A series of large torsion and tension test samples formed fiom glass reinforced cyanate ester resin discs, were then tested at room temperature and 10D°C. These provided shear strength with and without compression and tensile strength data on test specimens which do not contain the high stress concentrations produced in the lap shear specimens. Finally a reduced series of tests was carried out on pure cyanate ester resin samples formed using different curing temperatures to investigate the effect of cure temperature on the mechanical properties. I1 DESIGN, MANUFACTURE AND TESTING OF LAPSHEAR TEST SPECIMENS The simple lap shear test specimen geometry was chosen as it has been previously used by many Laboratories and companies [1,2] for testing epoxy resin systems providing an extensive data base for comparisons, and is also relatively easy to manufacture and test. A cross section showing the specimen geometry is shown in fig. 1.The copper plates were machined from half hard silver bearing copper (DIN 17666), which is commonly used for the manufacture of large copper coils.The main stages in the preparation of the specimens was:i) Grit blast and clean surfaces to give a mechanical key ii) Coat with a CE primer and cure primer. iii) Lay 52 glass cIoth layers between the copper plates and assemble into an impregnation fixture. iv) Dry the assembly in a vacuum oven. v) Vacuum impregnate with CE resin at room temperature. vi) Gel and then cure the resin at 1 3 5 T for 4 hours, .o Fig. I . Lap Shear Test SpecimenA total of 15 lap shear test specimens were manufactured and were tested using the lnstron 1195 testing machine at the Culham Science Centre. The lap-shear test specimens were supported in a stainiess steel "U' shaped holder before being compressed between chromium plated steel platens....

Synthesis, Characterization and Applications of Polyurethane Aryl Cyanate Ester Resin

“…When compared with the PU adhesive neat system, the LSS for the blends of PU-CER with PU system was almost doubled at ambient and high temperatures for both MS-MS and Al-Al, possibly due to the secondary forces of hydrogen bonding and dipole-dipole interaction of cyanate ester adding more cohesion within the PU adhesive and PU-CER than the adhesion at the MS or Al interface, as stated by Voss et al [11] and also reported by Shimp [16] on the unique properties of thermosetting cyanate ester resins. The toughness-T g combination is attributed to the adhesion strength by ether-like oxygen linkages and relatively low crosslink density.…”

Spherical tokamaks: Present status and role in the development of fusion power

“…These could be removed and replaced with the centre column, but are still a critical item since they are so closely coupled to the divertor design. It is suggested that the coil be insulated with cyanate-ester (CE) impregnated glass fibre [28] which has improved radiation resistance compared to conventional epoxy-resins [29]. The gamma flux in the CTF design above is, however, higher than the ITER reference level for coil insulation.…”

“…70-100 • C). CE has a (noncompressed) shear stress limit of 40-60 MPa at 100 • C compared to conventional epoxy resins which have dropped to ∼20 MPa at this temperature [28].…”

Manufacture and Test of a Prototype Cyanate Ester Coil

“…The highly stressed solenoid can be allowed to reach 100 , rather than the operational limit of 70 typically applied to epoxy due to its decreasing strength with increasing temperature. The Culham Centre for Fusion Energy (CCFE) has worked for some years with Composite Technology Development (CTD) characterizing the CTD-403 resin [5]. Manufacture of a test coil using conventional industrial techniques and equipment was considered a vital next step in qualifying the material for use on MAST-Upgrade.…”