Toughening of cyanate ester resin by carboxyl terminated nitrile rubber

The carboxyl terminated butadiene-acrylonitrile (CTBN) rubber was used to improve the toughness of the cyanate ester (CE) resin. The toughness of the modified blends depended on the CTBN content. The addition of 10 phr (g/100gCE) CTBN in CE resin led to a 200% increase in the impact strength with a loss of storage modulus. The transmission electron microscopy result showed the existence of rubber particles, inferring that phase separation had occured after curing. The thermogravimetric analysis curve of CTBN indicated the presence of cavities which also can be observed on the fractured surface in the scanning electron microscopy pictures using high magnification. Thus, phase-separation and cavities toughening mechanisms function together to improve the toughness. Copyright (C) 2004 John Wiley Sons, Ltd.