Cyanate ester monomers are currently utilized in high-temperature thermoset resin-fiber composites. The resin is cured, typically with a transition metal catalyst, and forms a 3D polycyanurate thermoset network. Once cured, the catalyst is entrained in the network and cannot be removed economically. An issue with the catalyst is that it remains active and maintains the ability to degrade the composite leading to a reduction in physical, mechanical, and chemical properties. A potential solution to this issue is the use of a catalyst that can be selectively deactivated. After polymerization, the catalyst can be rendered inactive via an external stimulus. This work focuses on three different methodologies to determine the viability of selective deactivation. One such methodology is the use of steric crowding to deactivate the metal center. The second method incorporates the use of a disulfide-containing ligand. The disulfide is cleaved and the sulfur then coordinates to the metal center deactivating the catalyst. The third method utilizes a protected sulfide group. A traditional ligand, such as an aromatically-substituted ethylenediamine system, has a protected sulfur group attached to the ligand. Once the catalyst has performed the cure, the sulfur group is deprotected and coordinates to the metal center thus deactivating the catalyst. This presentation will focus on the disulfide and protected sulfide methodologies. Ligand synthesis, the formation of metal catalysts, and their activity will be discussed.

Selective catalyst deactivation for high-temperature resin systems

2019 Fall National Meeting

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