Formation and characterization of silica reinforced polyvinyl alcohol.

University of Minnesota M.S. thesis. September 2011. Major: Biosystems/Agricultural engineering. Advisor: Prof. Mrinal Bhattacharya. 1 computer file (PDF) viii, 93 pages.This work discusses the construction and characterization of films of polyvinyl alcohol cross-linked with silica nanoparticles that can be used as a potential bone graft for reinforcing the bones weakened with age. Nanocomposites were prepared by adding silica dispersion (10 wt. %) to the solution of polyvinyl alcohol (10 wt. %) in varying concentrations to obtain solution with 39, 60, 78.4 and 120 (wt. %) silica. These solutions were then drawn into thin films (a few nanometres) using a drawbar coater. The nanocomposites thus formed were characterized using nanoindentation, tensile tests, x-ray diffraction, scanning electron microscopy and infrared spectroscopy . The tensile modulus of the nanocomposite film was calculated to be 8GPa with ultimate tensile strength of 30MPa. The films showed effective cross-linking of the silica with polymer matrix which was studied by scanning electron microscopy, x -ray diffraction and infrared spectroscopy. To mimic the structure of bone, pellet like crystals of calcium hydroxyapatite were grown on the surface of the surface of the nanocomposite films which further increased the modulus to 11GPa and the ultimate tensile strength to 65MPa. Although the increasing concentration of the silica led to an increase in the modulus of the films, the strength of films decreased thus making them brittlethem brittle