Polymer and composite materials used in a wide range of fields, such as in aerospace, automotive and industrial applications, are derived from petroleum-based materials. Due to the increased cost of petroleum and its lack of long-term sustainability, there has been increased interest on replacing non-renewable materials with those made from natural resources, such as vegetable oils.

The ACRES group and others have done considerable work in replacing the cross-linking agent in unsaturated polyesters with plant oil-based cross-linkers.¹ However, resins derived from petroleum and modified vegetable oils typically contain high concentrations of reactive diluents (e.g., styrene) to allow resin transfer molding. Styrene, a hazardous pollutant and a volatile organic compound (VOC), poses significant environmental and health risks; therefore, its replacement with alternative monomers is advantageous on many levels. Recently there have been studies employing a non-volatile reactive diluent, chemically modified fatty acid (MFA), as an alternative to styrene in the production of polymers employing vinyl ester (VE) and unsaturated polyesters resins.^{2, 3} It has been shown that MFA is an excellent alternative to styrene due to its lower VOC emissions.

The main objective of this work was to formulate a resin containing both plant oil-based crosslinkers and plant oil-based reactive diluents. Different bio-based cross-linkers were produced for this purpose: acrylated epoxidized soybean oil (AESO), maleinated AESO (MAESO), maleinated soybean oil monoglyceride (SOMG/MA) and maleinated castor oil monoglyceride (COMG/MA). Two different reactive diluents with the plant oil cross-linkers: methacrylated lauric acid (MLau) and acrylated epoxidized fatty acid methyl ester (MOct).

The viscosity and mechanical properties of the resulting bio-based polymers were measured and analyzed. Bio-based resins prepared employing MFA had a fairly high viscosity, so blends of MFA and styrene were needed to meet the viscosity requirements established by the composite industry (<1000 cP at RT). The results of these studies showed that the glass transition temperature (Tg) of bio-based thermosets copolymerized with MOct had slightly higher values than those with MLau. The Tg values estimated using the Fox equation were similar to the experimental data obtained in this study. In addition, the Tg of bio-based resin/MFA polymers were significantly lower than the bio based-resin/styrene polymers. Decreasing the content of MFA improved the Tg and stiffness. Ternary blends of SOMG/MA or COMG/MA with MFA and styrene improved the mechanical properties to acceptable values comparable to commercial resins. Also, in this work chemically modified lignin (butyrated kraft lignin)⁴ was added to the bio-based resins, leading to significant improvement of the mechanical properties of the matrix.

1. Khot, S.N.; La Scala, J.J.; Can, E.; Morye, S.S.; Williams, G.I.; Palmese, G.R.; Kusefoglu, S.H.; Wool, R.P J. Applied Polym. Sci. 2001, 82, 703.

2. La Scala, J.J.; Sands, J.M.; Orlicki, J.A.; Robinette, E.J.; Palmese, G.R. Polymer 2004, 45, 7729.

3. Can, E.; La Scala, J.J.; Sands, J.M.; Palmese, G.R. J Appl Polym Sci 2007, 106, 3833-3842.

4. Thielemans W.; Wool R. Biomacromolecules 2005, 6, 1895.