Interpretation of water repellency behavior of paper and paperboard by a shape-recognition method

Abstract

The test methods for measuring the water repellency of paper and paperboard by recognizing water traces flowing down onto a specimen might sometimes be influenced by an operator's bias. In order to avoid such bias, a new automatic analysis method that was able to analyze the shapes of different water traces on a specimen was developed based on the different shape features of the liquid traces formed on paper specimens. Through the shape recognition of a liquid track flowing down a specimen with an inclined angle of 45 degrees, the unique features of each liquid track, such as the widths between the heads and tails of the traces, the uniformity of liquid flow, the length of long traces, the eccentricity of liquid traces, etc. could be analyzed to determine the specific degree of water repellency of paper and board specimens. Finally, the automatic analysis of water repellent characteristics based upon the intrinsic shapes of the liquid traces according to different hydrophobic treatments of paper made it possible to readily measure the water resistance of paper and paperboards classified into R0 to R10.