Effect of length of branched-chain of PAA-g-MPEO on dispersion of CaCO3 aqueous suspensions

The viscosity of CaCO3/poly(acrylic acid) grafted methoxyl poly(ethylene oxide) (PAA-g-MPEO) aqueous suspensions was influenced by length of the branched-chain and content of PAA-g-MPEO. The viscosity of CaCO3/PAA-g-MPEO suspensions first decreased and then increased with increasing length of branched-chain of PAA-g-MPEO at the same PAA-g-MPEO content. The viscosity of CaCO3 suspensions containing PAA-g-MPEO with short branched-chain (M-n = 200 g/mol and 600 g/mol) decreased with increasing the PAA-g-MPEO content. However, the viscosity of CaCO3 suspensions containing PAA-g-MPEO with long branched-chain (M-n = 1500 g/mol) increased with increasing the PAA-g-MPEO content. The size distribution of CaCO3 particles in CaCO3 suspensions containing PAA-g-MPEO with the short branched-chain became narrower and the average size decreased with increasing length of the branched-chain. This is due to the steric hindrance of branched-chain of the PAA-g-MPEO adsorbing on surface of the CaCO3 particles increased with increasing length of the branched-chain. The size distribution of CaCO3 particles in CaCO3 suspensions containing PAA-g-MPEO with the long branched-chain had two regions, and the average size increased compared with that of CaCO3 particles in the CaCO3 suspensions containing PAA-g-MPEO with the short branched-chain. This is due to the flocculation of fractional CaCO3 particles induced by "tangle" between the long branched-chain of PAA-g-MPEO adsorbing on surface of CaCO3 particles.