The influence of the dispersants on printing ink properties of metal oxides nanoparticles

Colloidal stability of inkjet printing inks is one of the key parameters for their good printing
performance. The stability of particles dispersed in water–based inks is usually achieved by
electrostatic, steric, or electrosteric stabilization. Adsorption of polyelectrolytes of increased
molecular weight at the solid interface of dispersed particles is responsible for electrosteric
stabilization. In this work, stable homogeneous suspensions of MOx (TiO2 and ZnO) were
prepared using gum arabic (GA) and solsperse 40000 as dispersants. GA is a natural polyanionic
polysaccharide with carboxylic groups as anchors, while Solsperse 40000 is an anionic
phosphated alkoxylated polymer of Lubrizol. Both dispersants provide electrosteric stabilization
of pigments in water based inks. GA was employed as dispersant to study the effect
on the surface properties of MOx nanoparticles. GA has been used as the stabilizing agent
for ink pigments for a long time. It is well known that GA can make the MOx nanoparticles
have good dispersibility and stability in GA colloidal solution for its low viscosity. The investigations
on the optimum concentration of dispersants and the mechanism determining the
dispersion behavior of MOx in aqueous dispersants solution were performed. Suspensions
of MOx and GA/Solsperse were prepared first by dissolving dispersants in water. MOx were
added in appropriate amounts. The weight ratio between MOx and GA (solsperse) was varied
from 1/1 to 3.5/1. The ball milling was performed in a Retch PM 100 planetary ball mill at
a constant milling speed of 250 rpm using YSZ jar and balls. The effects of different milling
time (15, 30, 60, 90 and 180 min) on average particle sizes were investigated. Results show
improved dispersion with a reduction of average particle sizes with increasing of milling time.
Different ink formulations composed of MOx/dispersants (with the addition of 1, 2 propylene
glycol and n-propanol) were prepared and their printability properties were tested using Inkjet
printer Fuji Dimatix DMP-3000. The main goal of this work is to analyze the influences
of different quantity of dispersants and milling conditions on the printing quality parameters
of the ink using different substrates.