458992 Preparation and Properties of Soybean Oil-Based Composites Containing Natural Fillers
Crosslinked polymers of acrylated epoxidized soybean oil (AESO) and styrene were first successfully produced across the entire composition range via bulk free radical polymerization. Mechanically, these copolymers varied from hard and rigid at high styrene contents, to soft and rubbery at high AESO contents.
The intermediate 50:50 copolymer was chosen as the matrix for composites containing varying amounts of pecan nutshell flour or powdered eggshells. Composites were produced by pre-blending the fillers into the comonomer mixture before reaction and solidification. Through the AESO and filler contributions, these composites contain substantial fractions of biobased starting materials.
Copolymers and their composites exhibited good structural integrity, and were characterized by flexural testing to fracture, dynamic mechanical analysis, SEM imaging, as well as hardness and impact testing.
Addition of the natural fillers to the matrix resulted in substantial increases in hardness and stiffness, with a nearly six-fold increase in modulus observed at 35 volume% eggshell filler. These increases were accompanied by modest decreases in breaking strength and impact energy, and no observed effect on the glass transition temperature of the matrix. Use of coupling agents  to increase adhesion and potentially further modify mechanical properties will be discussed.
General comparison of the filled polymer properties to a baseline of neat polystyrene shows improved or similar individual mechanical characteristics, indicating viability of such biobased composites as a replacement material.
 Nachtigall, S.M.B., Cerveira G.S., Rosa S.M.L., Polymer Testing, 26(5), 2007.