Distribution analysis of cellulose nanofibrils in paper handsheets: Dye-labeled Method

Due to the nanoscale and the same chemical structure to cellulosic fibers, it is difficult to directly observe the distribution of CNFs in paper sheets. Herein, dye-labeled CNFs were introduced to analyze the distribution of CNFs in paper handsheets. The dye was successfully loaded on CNFs through hydrogen bonding with an environmentally friendly method. Dye-labeled CNFs were mixed with four types of pulps with different beating degrees to form paper handsheets. The results showed that with the beating degree increasing, the colorimetric values of wire side and felt side were different among the four types of paper, which indicated that distributions of CNFs in the Z-direction of papers were not uniform. The study demonstrated that the dye-labeled CNFs methods is an effective way to analyze the distribution of CNFs in paper-based materials.