Thermosetting polymers from cationic copolymerization of tung oil: Synthesis and characterization

The cationic copolymerization of tung oil with the divinylbenzene comonomer initiated by boron trifluoride diethyl etherate produces promising plastic s. The gel times are largely dependent on the relative composition and the reaction conditions and vary from a few seconds to 1 h. Controlled reaction s producing homogeneous materials can be obtained by (1) lowering the react ion temperature or (2) decreasing the initiator concentration to less than 1 wt % or (3) adding a certain amount of a less reactive oil, such as soybe an oil, low saturation soybean oil (LoSatSoy), or conjugated LoSatSoy to th e reaction. The resulting polymers are rigid and dark brown in color. The w eight % of the starting materials converted to the crosslinked polymer is s imilar to 85-98% as determined by Soxhlet extraction with methylene chlorid e. The structure of the bulk product is that of a crosslinked polymer netwo rk plasticized by a small amount of low molecular weight oil. The chemical composition of the bulk, polymers varies with the original composition of t he tung oil system. Dynamic mechanical analysis shows that the resulting pr oducts are typical thermosetting polymers with densely crosslinked structur es. The modulus of the plastics is approximately 2.0 x 10(9) Pa at room tem perature. One broad glass transition is observed at approximately 100 degre es C. Thermogravimetric analysis shows that the tung oil polymers are therm ally stable below 200 degrees C with a 10% weight loss in air around 430 de grees C. (C) 2000 John Wiley & Sons, Inc.