The influence of the size and surface modification of TiO2 nanoparticles on the rheological properties of alkyd resin

Spherical TiO2 particles of different size were dispersed in alkyd resin based on soybean oil. Four samples of TiO2 particles were used, three commercial and one obtained by acid catalyzed hydrolysis of titanium tetraisopropoxide. The size of the synthesized nanoparticles was determined by transmission electron microscopy. Surface modification of TiO2 nanoparticles was performed with propyl gallate and lauryl gallate. The influence of the size of TiO2 nanoparticles, their concentration and type of the surface modification on the rheological properties of alkyd resin was investigated. The obtained results have shown that the viscosity of the prepared dispersions was higher than viscosity of the pure resin, it increases with decreasing particle diameter and decreases with frequency increase. Surface modified particles showed higher influence on the viscosity of alkyd resin than unmodified, because their hydrodynamic volume is higher due to the presence of the adsorbed gallates, leading to the increase of effective volume fraction of particles in dispersion. For the lowest TiO2 concentration, the viscosity was higher for sample modified with lauryl gallate, due to the higher thickness of the adsorbed layer. The increase of concentration, because of less dispersion stability of the particles modified with propyl gallate, leads to particles agglomeration. The presence of agglomerates, which was confirmed by a change in the slope of the functional dependence of storage modulus on loss modulus, leads to a rapid increase in viscosity. [Projekat Ministarstva nauke Republike Srbije, br. 172062 i br. 45020]