The Effects of Filler Contents and Beating on Porous Structure and Mechanical Strength of High Filler-Containing Papers

High filler-containing papers were prepared by incorporating silica fillers into pulp beaten in different degrees. Filler particles used in this experiment were PW-5 and PW-20, average diameter of which were 4.5μm and 15μm, respectively. The fibers were conifer pulp beaten at CSF600, CSF400 and CSF200, The pore size distribution of the sample sheets were measured by a mercury intrusion porosimeter. When no filler was incorporated, paper sheet made from CSF200, CSF400 and CSF600 fiber were rich in 1-5μm, 1-10μm and 1-20μm pores, respectively. In paper sheets made from CSF200 fiber and PW-5 filler, and, CSF600 fiber and PW-20 filler, total pore volume increased with the increase in the filler contents. On the other hand, in paper sheets made from CSF200 fiber and PW-20 filler, and, CSF600 fiber and PW-5 filler, the increase in the total pore volume reached a plateau with the increase in filler content. This difference between the curves was accounted for by the flexibility or the inflexibility of fibers. For the mechanical strength, the sheets with CSF200 fiber were stronger than those with CSF400 or CSF600 fiber. The strength decreased with an increase in the filler contents, especially for those with PW-5 filler.