Epoxidized soybean oil was effectively converted to carbonated soybean oil (CSBO) containing five-membered cyclic carbonates by reaction with carbon dioxide in the presence of tetrabutylammonium bromide as catalyst at 110degreesC in high yield. CSBO could easily react with di- or tri- primary amines to give the corresponding nonisocyanate polyurethane networks (NIPUs). A model reaction between CSBO and n-butylamine showed the effective ring opening of five-membered cyclic carbonate moieties in the triglyceride molecules by the amme to form beta-hydroxyurethane systems. NIPUs were further characterized by the three techniques of solvent extraction, dynamical mechanical analysis, and limited tensile testing. The data from these methods confirmed the network character of all materials and also showed how the levels of extractables, Tg, and mechanical properties varied with type of amine and, in the case of ethylenediamine, the effect of stoichiometry. (C) 2004 Wiley Periodicals, Inc.