The dynamic rheology behaviors of reactive polyacrylic acid/nano-Fe3O4 ethanol suspension

The interaction between polyacrylic acid (PAA) and nano-Fe3O4 particles was studied using Fourier transform infrared spectrometry (FTIR) and the dynamic rheology behaviors of the reactive polyacrylic acid/nano-Fe3O4 ethanol suspension were investigated by the advanced rheology expanded systems (ARES). The results showed that polyacrylic acid could react with nano-Fe3O4 on the surfaces of the particles, forming cross-linking network structures via coordination linkages. Monitoring of the rheological behaviors can be utilized as a probe to reveal the inner microstructural changes during the network forming process. It was found that the storage modulus (G′), loss modulus (G″) and complex viscosity (η*) of the suspension increased with increasing reaction time. Moreover, the value of G″ was found to be larger than G′ when the reaction time was less than 5 h, and then became smaller than that of the G′ with longer reaction time, indicating a liquid-gel transition behavior during the reaction. On the other hand, the values of G′ and G″ increased whereas the η* reduced with increasing measuring frequency. Within the measuring strain range, the values of G′, G″ and η* changed slightly at low strain and increased abruptly at high strain (>50% strain), which indicated that the values of G′, G″ and η* were strongly dependent on the frequency but independent relatively on the lower strain.