Fracture toughness of inorganic-organic hybrid coatings

The concepts of fracture toughness and the energy release rate at fracture for thin polymeric films are introduced. Fracture toughness and energy release rate data for ceramer films based on a linseed oil alkyd, a sunflower oil alkyd, and a commercial alkyd with titanium diisopropoxide bis(acetylacetonate), titanium(IV) isopropoxide, and zirconium(IV) propoxide are presented and compared to previously reported tensile data. Differences between the fracture data and the tensile data demonstrate the usefulness of fracture toughness testing. The energy release rate at fracture may be the one property to maximize in order to optimize all of the other coating properties. It may therefore be a great aid in the optimization of coating formulations. Data from dynamic mechanical thermal analysis indicate that there may be a correlation between fracture properties and secondary relaxation processes in the films. Department of Polymers & Coatings, Fargo, ND 58105.