Effect of molecular weight of sodium polyacrylates on the particle size distribution and stability of a TiO2 suspension in aqueous stirred media milling

TiO2 pigment particles of around 0.2 μm are used in a wide range of applications due to their excellent optical properties. The size distribution of these particles should be narrow and in the range 0.2–0.4 μm in order to obtain optimum scattering. TiO2 particles are usually ground in a wet stirred media mill, and their size distribution depends on the operational parameters of the mill. Grinding success is also highly dependent on control of the particle interactions, which is done by adding stabilization chemicals to the suspension, e.g. polyelectrolytes that have an electrosteric stabilization effect. The influence of the molecular weight and dose of sodium polyacrylates on the size distribution of TiO2 pigment particles and the stability of suspensions are studied here. The aim was to obtain a particle size of 0.3 μm and as narrow a particle size distribution as possible. It was found that the molecular weight and dose of sodium polyacrylates affected the particle size distribution and stability of TiO2 pigment particles in aqueous stirred media milling. The lowest viscosity values were obtained with the highest sodium polyacrylate molecular weight (Mw = 12,500) at every dose, and the same sodium polyacrylate is also the preferred one in terms of the resulting the particle size distribution at the lowest dose.