On the strategies for incorporating nanosilica aqueous dispersion inthe synthesis of waterborne polyurethane/silica nanocomposites:Effects on morphology and properties

In this work the synthesis of waterborne polyurethane/nanosilica nanocomposites by using two differ-ent strategies is presented, starting from a vinyl terminated polyurethane prepolymer (PUP) based onisophorone diisocyanate and polypropylene glycol, and varying the nanosilica content. In one case, thePUP was dispersed in an aqueous solution containing glycerol-functionalized colloidal nanosilica parti-cles and the dispersion was further polymerized; in the other case, the PUP was dispersed in an aqueousmedia, then colloidal nanosilica was added to the dispersion and then polymerized. A physical mixturewas also prepared for comparative purpose. Films were prepared by casting of the aqueous dispersion.The morphology of the dispersions and films depended on the incorporation route of nanoparticles aswas observed by SAXS, SEM and TEM. While the blends had significantly less hydrogen bonding betweenthe hard segments of the PU and nanosilica particles, samples prepared by the two different methodsproposed in this work showed an strong interaction between both materials in agreement with FTIR andDSC results. Synthesis pathway plays an important role in order to obtain high performance waterbornepolyurethane/nanosilica composites, since final properties of the films also depended on the nanoparticleincorporation strategy.