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 –10C.
Uniform SiO2 spheres with different average sizes and narrow size distributions
were synthesized in solution by the Stber method . 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.