Abstract
The free-volume properties in a system of zinc oxide (ZnO) nanoparticles (20 nm) dispersed in waterborne polyurethane (WBPU) were measured using positron annihilation lifetime spectroscopy. Two glass-transition temperatures (Tg), lower Tg ∼ 220 K and higher Tg ∼ 380 K of the ZnO/WBPU nanocomposites, were found and both increase with increasing zinc oxide content from 0% to 5%. These two glass transitions are interpreted from two segmental domains of WBPU; the lower Tg is due to soft aliphatic chains and high Tg is due to polar hard microdomains, respectively. The increase in Tg with the addition of ZnO fillers is mainly attributed to interfacial interactions through hydrogen bonding, van der Walls forces, and electrostatic forces between the polymer matrix and zinc oxide nanoparticles. These results are supported by the data from the dynamic mechanical thermal analysis (DMTA). The relationship between the free volume obtained from nanoscopic positron method and the physical cross-link density from macrosc...
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
