Four different cellulose nanofibers samples were prepared from northern bleached softwood kraft fibers. Fiber diameter distributions were measured from SEM images. Fiber aspect ratios ranging from 84 to 146 were estimated from fiber suspension sedimentation measurements. Three samples had heterogeneous distributions of fiber diameters, while one sample was more homogeneous. Sheet forming experiments using filters with pores ranging from 150 to 5 Î¼m showed that the samples with a heterogeneous distribution of fiber dimensions could be easily formed into sheets at 0. 2% initial solids concentration with all filter openings. On the other hand, sheets could only be formed from the homogenous sample by using 0. 5% or more initial solids content and a lower applied vacuum and smaller filter openings. The forming data and estimated aspect ratios show reasonable agreement with the predictions of the crowding number and percolation theories for the connectivity and rigidity thresholds for fiber suspensions.
Field of Research
091210 Timber, Pulp and Paper 100708 Nanomaterials