New thermosetting resins for applications of sheet-molding compounds (SMCs) were successfully synthesized from linseed oil, which is the most molecularly unsaturated of all plant oils. The carbon-carbon double bonds were opened by epoxidation, followed by acrylation, and then maleinization, which provided more crosslink sites and added acid functionality on the triglyceride molecules to develop thickening. Dynamic mechanical analysis showed that the storage modulus of these new polymers was approximately 2.5 GPa at 30 degrees C, and the glass-transition temperature was above 100 degrees C. During maturation the resins reached a molding viscosity quickly and stayed stable. Mechanical tests showed a flexural strength of 100 MPa and a flexural modulus of 2.8 GPa. Thermogravimetric analysis showed a single degradation ranging from 300 degrees C-480 degrees C, which was a result of the carbonization of the crosslinked network. These bio-based resins are promising as replacements of some petroleum-based resins in the SMC industry. (c) 2005 Wiley Periodicals, Inc.