MODEL SIMULATIONS GIVE NEW INSIGHTS INTO PAPER STRENGTH

The use of fiber network computer simulations in paper research allows one to avoid many difficulties encountered in experimental studies. T he simulation networks are simpler in structure than real paper but th eir properties are still governed by the same laws of nature. Ever sin ce 1988, the microscopic strength mechanisms of paper have been studie d in Finland using computer simulations. Recently a large project was completed in the program New Generation Paper Technology sponsored by the Tecnology Development Centre (TEKES). The simulations focus on the tensile load-elongation curve of paper. The first part of the curve - prior to the rupture point yields parameters that relate fiber proper ties to important paper performance characteristics, such as the bendi ng stiffness. The simulations reveal how the effects of paper structur e can be separated from the curve so that one can infer the tensile be havior of fibers. The effects of formation can be studied using a latt ice model. The model illustrates for example how long transverse flocs decimate paper strength more than do longitudinal Aocs. The relative bonded area, density surface roughness and light scattering power of t he three-dimensional fiber network can be computed with PAKKA model. T he model can be directly applied to practical product development New tools for the interpretation of measured paper properties have been de veloped in the simulation studies. Next the knowhow must be applied to practice. Among other things one should find out if it is possible to modify chemical pulping methods in order to improve those fiber prope rties that correspond to the relevant parameters of the theoretical mo dels.