Nanofiller effect on the glass transition of a polyurethane

The effect of silica nanofiller on the glass transition of a polyurethane was studied by DSC. The pristine polymer exhibits a single glass transition at about -10 degrees C. Uniform SiO2 spheres with different average sizes and narrow size distributions were synthesized in solution by the Stober method [1]. Both the effects of silica content within the polymer and particle size were investigated, as well as two different surface treatments. Scanning electron microscopy (SEM) clearly confirms the presence of the particles within the polymer matrix, showing uniform distribution and no agglomeration. While shifting of the glass transition has been reported by many authors, we have not seen any noticeable shift in this polymer. Surprisingly, we found no relevant effects when either increasing the filler content or changing the particle size. Different amounts of particles with average diameters of 175, 395 and 730 nm did not affect the glass transition temperature of the pristine polymer.