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In this investigation, it was confirmed that copolymerization of dinorbornene spiroorthocarbonate (DNSOC) with epoxy can reduce sample shrinkage without degrading mechanical properties. To maximize control of shrinkage, it is important to bring epoxy to the gel stage before the DNSOC begins to copolymerize.
DGEBA epoxy was cured with m-phenylenediamine (mPDA) and DNSOC-epoxy samples were cured with mPDA and BF3·diethylenetriamine (BF3 was used to catalyze polymerization of the DNSOC). As compared with carbon fiber-reinforced epoxy, the sample with 5% by weight DNSOC showed 33% reduction in interfacial shear stress as measured by the microindentation test and reduction in residual stress perpendicular to the plies by interferometry. However, the 9% greater fiber volume fraction in the epoxy sample can account for some of these changes. The resin itself showed an increase in tensile strength when 5% by weight DNSOC was incorporated, and the sample showed little shrinkage.
Materials engineer, Naval Surface Warfare Center, Annapolis, MD
Stock #: CTR10094J