Title Aqueous-Based Emulsion Reactive Finishes for Improving Carbon/Vinyl Ester Interfacial Bonding
Source Proc. 50th Intl. SAMPE Symp. and Exhib.
Year 2005
Author(s) Allred, R. E.; Hoyt Haight, A. E.; Gosau, J. M.; Wesson, S. Pl
Abstract This study was undertaken to develop an aqueous-based finish (sizing) to improve the carbon/vinyl ester interfacial bond. A previously developed solvent-based finish for carbon/vinyl ester was modified to be applied as an aqueous emulsion. The finish is composed of a reactive coupling agent, a low viscosity vinyl ester resin, a free radical inhibitor, and a surfactant. Aqueous-based emulsions of the reactive finish components were successfully prepared and applied to unsized T700 fibers. Bromine analysis of the finished fibers showed the presence of the desired residual vinyl groups in the fiber surface coating that can chemically bond to the vinyl ester matrix during composite processing. Unidirectional laminates containing several types of fiber surfaces (unsized, Toray FOE sized, and reactive finishes of varying formulations) were prepared, characterized for microstructure, mechanically tested using interface sensitive test methods (transverse flexure, short beam shear) and a fiber dominated test (longitudinal flexure), and characterized for failure mode. Results show that the reactive finishes substantially improve the carbon/vinyl ester interface dominated mechanical properties compared to the unsized or FOE sized materials. In addition, the toughness of the interface in shear as seen in the area under the load-deflection curves is substantially increased as well. Failure mode analysis shows that interfacial failure dominates the unsized and FOE sized materials, whereas resin cohesive failure dominates the ATI finished materials. This is a strong indication that the desired chemical bonding is occurring at the T700/vinyl ester interface through the reactive finish. These data would also imply that, when the reactive finish is optimized, environmental durability in moisture and fatigue resistance would be greatly improved by the reactive finishes.
Keywords vinyl ester, sizing, coupling agent, fiber reinforcements, aqueous finish, interface, interfacial, emulsion, reactive, free radical inhibitor, surfactant, composite, toughness, durability, fatigue resistance