The influence of phenolic cofactors on the properties of calcium carbonate flocs formed with PEO

The tensile strength of flocs formed from the flocculation of precipitated calcium carbonate (PCC) by the addition of cofactor (poly(vinyl phenol-co-sodium acrylate)) followed by PEO was measured as a function of the cofactor/PEO mass ratio. The maximum floc strength corresponded to a cofactor/PEO ratio of 2–3. Two modes of floc rupture were observed. Weak flocs tended to give ‘stretchy’ behavior in which the flocs extended under tension leaving a long thin polymer tether with single embedded PCC particles. Strong flocs showed a ‘tough’ mode in which elongation at rupture was low. Stretchy flocs gave distances between neighboring embedded PCC particles in the tethers as great as 30 μm indicating that many PEO chains are involved in the bridges or tethers between two particles. We speculate that these PEO assemblies originate from the mechanical entanglement of the very long PEO chains supplemented with PEO-to-PEO binding from the small cofactor molecules.