Toughening of epoxies with block copolymer micelles of wormlike morphology

Jia Liu, Zachary J. Thompson, Hung Jue Sue, Frank S. Bates, Marc A. Hillmyer, Marv Dettloff, George Jacob, Nikhil Verghese, Ha Pham

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155 Scopus citations

Abstract

An amphiphilic poly(ethylene-alt-propylene)-b-poly(ethylene oxide) (PEP-PEO) block copolymer (BCP) was blended with a bisphenol A-based epoxy resin formulation and self-assembled into a wormlike micelle structure. With an incorporation of 5 wt % of the BCP material, the fracture toughness was improved by >100% over the neat epoxy. The morphology and mechanical properties of this BCP-modified epoxy were investigated using transmission electron microscopy, dynamic mechanical analysis, tensile tests, and fracture toughness measurements. Toughening mechanisms from the wormlike micelle-modified material were investigated using the double-notch four-point-bending technique, and the results are compared with data obtained from the same epoxy thermoset formulation containing a BCP that self-assembled into spherical micelles. Elongated cylindrical micelles produce improved toughness, which is interpreted on the basis of a combination of mechanisms including crack tip blunting, cavitation, particle debonding, limited shear yielding, and crack bridging. The implications of the present study for polymer toughening in general are also discussed.

Original languageEnglish (US)
Pages (from-to)7238-7243
Number of pages6
JournalMacromolecules
Volume43
Issue number17
DOIs
StatePublished - Sep 14 2010

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