A deposition efficiency model for fiber–filler flocculation by microparticle retention system

A deposition efficiency model was developed in order to predict the effect of the dosage of retention aids (polymer and bentonite) on filler retention and validated with a pilot machine trial. The deposition efficiency is a function of the surface coverage of adsorbed and transferred polymer on solids (fiber and filler) and the surface coverage of microparticles on the polymer-adsorbed layer. The model includes the effect of bimodal particles (i.e., fiber and filler) and the polymer transfer from fiber to filler. In addition, the interaction between bare surfaces was included in the model and different bond strength of each interaction was considered. It was shown that an increase in the deposition efficiency leads to an increase in the filler retention. The dosage of CPAM is more predominant variable affecting deposition efficiency and thus filler retention than that of bentonite.