Structural composites consist of a thermoplastic or thermosetting polymer matrix with a stiff filler. The difference between elastomeric composites and structural composites is that in structural composites, the polymer is stiff. This means that either the temperature where the polymer is used is below its glass transition temperature, or the material is crystalline. These types of materials are used in such things as under-the-hood automotive parts (air intakes, protective covers), and in high performance applications such as tennis rackets and military jet planes (i.e. the Stealth Bomber!).
Our research is concerned with changing the mechanical properties of these materials by changing the adhesion between the filler and the polymer. Essentially, there are three categories of adhesion with respect to polymer/filler combinations: 1) The two stick together naturally 2) There is some sort of chemical that must be added to the surface of the filler to get good adhesion or 3) There is no economical way to get good polymer:filler adhesion. Our research is focussed on probing alternate ways of getting adhesion in cases (2) and (3). We use a process called admicellar polymerization, and we can chemically tune the surface composition to maximize adhesion. Research on this project is done by graduate students in the United States, as well as in Thailand.
B.P. Grady, E.A. O'Rear, L. Penn and A. Pedicini, "Admicellar Polymerization of Styrene-Isoprene on Glass Cloth for Use in Composite Manufacture" Polymer Composites, 19, 579 (1998).
H.J. Barraza, M.J. Hwa, K. Blakely, E.A. O'Rear, and B.P. Grady, "Wetting Behavior of Elastomer-Modified Glass Fibers", Langmuir, 17, 5288 (2001).
U. Somnuk, N. Yanumet, J. Ellis, B.P. Grady and E.A. O’Rear, “Adhesion Improvement in Glass Fiber Reinforced Polyethylene Composites via Admicellar Polymerization”, Polymer Composites, 24, 171 (2003).
K. Blakely, B.P. Grady, H.J. Barrazza and E.A. O'Rear, “Effects of Styrene-Isoprene Copolymer Glass Fiber Coatings on Woven Glass Cloth Epoxy Composite Performance”, Polymer Composites, 25, 82 (2004).
M. Hargis, B.P. Grady, L. Aktas, K.R. Bomireddy, S. Howsman, M.C. Altan, T. Rose and H. Rose, “Calorimetric and Rheological Measurements of Three Commercial Thermosetting Prepreg Epoxies”, Journal of Composite Materials, 40, 873 (2006).