Synthesis and characterization of SMC resins and nanocomposites from plant oils.

摘要

Sheet molding compounds (SMCs) are widely used in automotive parts, appliances, furniture, and construction. These materials heavily depend on the petroleum supply, which is depleting fast. The use of plant oils as alternative sources for SMC resins presents economic and environmental advantages over petroleum.; Two synthetic methods have been used to develop new resins from triglycerides. The double bonds presented on the fatty acid chains are first converted to epoxy or hydroxyl functionality, the hydroxyl groups are maleinized, while the epoxies are acrylated and then further maleinized. These monomers, when combined with 33.3 wt % styrene, exhibit adequate thickening with MgO paste. The resulting polymers show storage moduli in the range of 1.9 to 2.5 GPa, and the glass transition temperatures range from 99 to 118°C. The cross-link densities show a linear increase with increasing number of functionality on the triglycerides. The prediction of cross-link density by the Miller and Macosko model matches the trend of experimental data, although it over predicts the cross-link density. The flexural strengths of these polymers vary in the range of 61--100 MPa, and flexural moduli are in the range of 1.90--2.79 GPa. The tensile strengths and moduli vary from 27 to 44 MPa and 1.6 to 2.5 GPa, respectively. The strengths of these polymers are following the prediction by vector percolation. The mechanical properties of these new polymers are comparable to those of commercial unsaturated polyesters.; To further improve the physical and mechanical properties of these polymers, clay nanocomposites have been successfully synthesized by in situ polymerization. The morphology of nanocomposites can be described as a mix of intercalated and partially exfoliated sheets. The flexural modulus increases 30% at only 4 vol % clay content, but there is no significant effect on flexural strength, glass transition temperature and thermal stability. Property enhancement is related to the degree of exfoliation, which depends on both the polarity and flexibility of the monomers. In addition, three methods have been used to increase toughness of triglyceride-based SMC resins, which include liquid rubber toughening, plasticizer and inorganic nano-filler, and their toughening effects are compared.