Hybrid silicas/waterborne polyurethane composite properties: In situ formation vs. grafting methods
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A series of composites of commercial waterborne polyurethane and hybrid silica were prepared by the sol–gel process through in situ synthesis. Mechanical properties, small angle X-ray scattering and differential scanning calorimetry measurements were performed to evaluate the effects that hybrid silica has on the properties of the resulting polyurethane composites. A series of 13 different organosilanes differing in polarity and alkyl chain length was studied. Under the present evaluated conditions, composites bearing hybrid silica were more likely to exhibit a reduction in mechanical resistance when compared to bare polyurethane. Samples also exhibited a negligible variation in glass transition temperature and a reduction in ΔCp. The enthalpy of the crystallization process exhibited an increase. Based on the small angle X-ray scattering measurements, the composites exhibited a small reduction in the interdomain spacing and an increase in the degree of phase separation.
KeywordsAdhesives Polyurethane Hybrid silica Nanoparticles SAXS
Heck thanks CNPq for the grant. The authors thank the LNLS (Project SAXS1-11797) for the measurements on the SAXS beamline (Project SAXS1-11797).
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Conflict of interest
The authors declare that they have no competing interests.