With the addition of 5% (w1 vol%) 33 nm ZnO nanoparticles
into polyurethane (polymer/particle interfacial area is
about 200 m2/100 g of composite), the Young’s modulus, storage
modulus and strain at fracture of the composite decreased
approximately 38, 52, and 80%, respectively, while the soft
segment glass transition temperature (Tg) increased w11 C
compared to the neat polyurethane. These changes were attributed
to the disruption of the phase separation by the addition
of the ZnO nanoparticles. The origin of the disruption is the
reaction between the polyurethane and the surface hydroxyl
groups on the particles [8]. The high modulus and large strain
at fracture of the polyurethane are related to the phase separation
of the hard and soft segments [18]. Therefore, it is reasonable
to propose that a disruption of the phase separation in the
polyurethane nanocomposites results in the observed decrease
both in the modulus and strain at fracture. The increased Tg
results from constraints induced by the interfacial reactions