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Growing more ductile epoxies: an essential work of fracture study

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Abstract

Ambient, amine-cured epoxy compositions exist within the dual constraints of VOC regulation and the vitrification effect, which limits the ultimate T g of these materials. These combined constraints result in epoxy products that are densely crosslinked and which contain appreciable quantities of nonfugitive diluents or plasticizers. Such materials tend to be more brittle than traditional solvent-based epoxy coatings based on solid epoxy resin and polyamide hardeners. There is thus a need for a practical method to measure their fracture toughness. This work introduces the method of essential work as a useful way to determine the fracture toughness of thermoset systems. This method is then used to relate fracture toughness to the crosslink network structures of amine-cured epoxy compositions. The test compositions are varied systematically with a view to structure/properties interpretation, and employ an in situ chain extension approach to “grow” more ductile networks. Solvent uptake of selected compositions is also determined, and the relative trade-off between ductility vs. solvent uptake is examined.

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Acknowledgments

The author wishes to thank Prof. Alan Lesser of the University of Massachusetts, Amherst, for introducing the method of essential work of fracture to us and for providing invaluable guidance; also, Fred Gelfant of Stonhard for many helpful suggestions; and Matthew Rossi for his excellent laboratory work.

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Authors and Affiliations

  1. Stonhard, Division of The StonCor Group, Inc., 1 Park Ave, Maple Shade, NJ, 08052, USA

    Frederick A. Pfaff

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  1. Frederick A. Pfaff
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Correspondence to Frederick A. Pfaff.

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This article was awarded the Outstanding Paper Award in New Coatings Technology at the 33rd Annual International Waterborne, High-Solids, and Powder Coatings Symposium in New Orleans, LA, February 2006, and was presented at the Thermoset Resins Formulators Association Conference in Montreal, Quebec, Canada, September 2006.

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Pfaff, F.A. Growing more ductile epoxies: an essential work of fracture study. J Coat Technol Res 4, 151–159 (2007). https://doi.org/10.1007/s11998-007-9013-4

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