Material Properties of Bi-Modal Epoxy Networks

Report No. ARL-TR-2413
Authors: Stephen J. MacKenzie, Thomas J. Mulkern, Nora C. Beck Tan
Date/Pages: March 2001; 49 pages
Abstract: The necessity for epoxies in new technologies is overwhelming. For these epoxies to perform at their maximum capabilities, both high strength and toughness must be in the list of mechanical properties. This is where bi-modal networks become important. Their combinations of both long- and short-chain cross linkers vary the cross-link density of the epoxy and thus improve the toughness. Here, a study was done to see if these bi-modal networks increase toughness without loss in modulus. Through the use of the differential scanning calorimeter to find the glass transition temperature, the dynamic mechanical analyzer to find the storage modulus, and the Izod impact machine to find the impact strength, we can make a conclusion whether these networks really work. In the beginning, the results seemed to be what we had hoped for, that is,the decrease in cross-link density did improve the impact strength; however, the storage modulus also decreased with a decrease in cross-link density. Finally, the conclusion can be stated that the bi-modal network does increase the toughness of this system but with a loss in modulus.
Distribution: Approved for public release
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Last Update / Reviewed: March 1, 2001