Bone graft substitute is a continuously developing field in orthopedics. When compared to tradition biomaterial in the field such as PLA or PCL, elastomer like polyurethane offers advantages in its high elasticity and flexibility, which establish an intimate contact with surrounding bones. This tight contact can provide a stable bone-material interface for cell proliferation and ingrowth of bone. The aim of this study is to evaluate the osteogenesis capabilities of a porous polyurethane scaffold in a critical size bone defect. In this study, a porous scaffold synthesized from segmented polyurethane is put under in vitro and in vivo tests to evaluate its potential in acting as a bone graft substitute for critical size bone defects. In vitro results indicate osteoblast-like cells are proliferating on the polyurethane scaffold during the 21-days experiment. Cells express their normal morphology when seeded on polyurethane under fluorescent staining. Although cells show a relatively lower cell activity then that seeded on culture plate, they share a similar alkaline phosphatase activity profile with the controls during the experiment period. In the in vivo animal model, reconstructed images from micro CT scanning indicates there are bone ingrowth inside the scaffold. Histology also indicates a tight interface has formed between bone and polyurethane, with osteogenic cells proliferating on the surface. The result has indicates polyurethane is a potential material for orthopedics in acting as a bone graft substitute. / published_or_final_version / Orthopaedics and Traumatology / Master / Master of Philosophy

Dissertation (Ph. D.)--University of Akron, Dept. of Polymer Engineering, 2007. / "December, 2007." Title from electronic dissertation title page (viewed 01/30/2008) Advisor, Kyonsuku Min; Committee members, Mark Soucek, Kevin A. Cavicchi, Gary R. Hamed, Michael H. Cheung; Department Chair, Sadhan C. Jana; Dean of the College, Stephen Z. D. Cheng; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.

Thesis PlanB (M.S.)--University of Wisconsin--Stout, 2007. / Includes bibliographical references.

Thesis (Master)--İzmir Institute of Technology, İzmir, 2006. / Keywords: Solar energy, solar collectors, solar energy systems, air heating, polyurethane foam. Includes bibliographical references (leaves.60-62).

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references. Also available via the Internet.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 111-115). Also available on the Internet.

Thesis (M. Phil.)--University of Hong Kong, 2005. / Title proper from title frame. Also available in printed format.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 111-115). Also available on the Internet.

Thesis () - University of Queensland, 2005/ / Includes bibliography.

Thermosetting polyurethane films were prepared from solution by crosslinking hydroxypropyl lignin derivatives with diisocyanates. The network structure, characterized by the crosslink density, was controlled by two variables: the hydroxy content of the lignin polyol and the molar ratio of NCO:OH. In addition, the effect of network structure on thermal and viscoelastic properties was determined. Both the thermal and viscoelastic properties of the polyurethane films followed the trends found for crosslink density. For those films prepared from the various polyols with reduced hydroxy functionality, T_g was found to vary linearly with the extent of crosslinking as well as with the T_g of the polyol from which it was prepared. As the NCO:OH ratio was increased, the major difference in T_g occurred within the range from 1:1 to 3:1. Similar trends were noted for the viscoelastic properties in both instances. However, it was apparent that the sol fraction contributed significantly to the overall properties of the network, particularly at the high weight fractions. Fracture surface analysis of model substrates (cellulose acetate and cellulose tri-acetate) bonded with a lignin-polyisocyanate resin by Electron Spectroscopy for Chemical Analysis (ESCA) revealed the formation of interfacial bonds on the surface of the cellulose acetate adherend. Furthermore, it was indicated that failure occurred well within the bulk of the cellulose acetate while interfacial failure was apparent for the cellulose tri-acetate model. While mechanical attachment is unquestionably a contributing mechanism, the formation of interfacial bonds should significantly contribute to the performance of bonded joints for this particular adhesive system. / M.S.