Flocculation and floc strength : from the laboratory to the FEX paper machine

The state of flocculation in a papermaking suspension is altered by retention aid systems, and this can affect the paper properties. Paper formation can in many cases be improved by hydromechanical action on the paper web during forming at which stage there is a certain fibre network strength in the suspension from which the paper is formed. This implies that, for a full understanding of the influence of the retention aid systems, investigations both of the flocculation in flowing suspensions and of the fibre network strength are needed. The aim of the present work was two-fold. Firstly, to carry out laboratory investigations of the mechanisms of flocculation and of fibre network strength in suspensions flocculated by single and two-component retention aid systems. Secondly, on the basis of results from the laboratory experiments, to test models for flocculation under realistic papermaking conditions on a pilot scale in the FEX experimental paper machine.