Abstract
Abstract A series of epoxy resins of varying functionality (in terms of the number of epoxide groups) were used to cure the cyanate ester resin, AroCy L10 (1,1-bis(4-cyanatophenyl) ethane). The effect of thermal spiking on moisture absorption and changes in glass transition temperature ( T g ) were studied. With the tetra functional (MY720) epoxy a more polar crosslinked density matrix forms. However, after thermal spiking to 140 °C a second peak appeared in the DMTA spectrum which was attributed to partial hydrolysis. The other two systems were much more stable. All systems exhibited the enhancement of moisture absorption as a result of thermal spiking. The mechanism of this phenomenon has been discussed in detail and related to the distribution of unoccupied volume in the dry resin and the location of water molecules at hydrogen bonding sites. The redistribution of the water molecules throughout the sites during thermal cycling is considered responsible for the enhancement and the reduction in moisture contents at high thermal spike temperatures.
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