Crosslinked copolymers and IPNs were synthesized from vegetable oils (e.g., cottonseed oil, castor oil, and tung oil). The dynamic mechanical behavior of the polymer blends was studied by Dynamic Mechanical Spectroscopy (DMS). The tan delta-temperature curves of these kinds of copolymers and IPNs show a single peak, which indicate good compatibility. They represent a kind of damping materials with high tan delta values over wide temperature ranges. Thus a new way has been found to use natural products of agriculture to produce damping materials. Effects of various factors on the dynamic mechanical behavior were studied. (C) 2003 Wiley Periodicals, Inc.