Development of a method for assessment the distribution of starch-containing compositions in the z-direction of paper and its suitability assessment

The phenomena occurring during surface treatment of paper are very complex and not fully understood. Despite the work carried out in this direction, many factors remain that affect the uncertainty of the final result and are primarily due to the use of natural materials whose properties cannot be reproduced with due accuracy. The properties of paper formed during surface sizing directly depend on these components and are determined by the depth of penetration of the compositions and their distribution in the z-direction of the paper sheet. The methods proposed for determining these indicators do not allow us to estimate the distribution of starch in the z-direction of already manufactured paper, which complicates the study of the effect of surface sizing factors on the distribution of starch in real industrial production conditions. This determined the purpose of the work, which was to develop a method for determining the depth of penetration of starch applied during surface sizing and to study its distribution in the z-direction of paper. The proposed method for determining starch penetration during surface sizing of paper allows one to judge both the depth of starch penetration and its distribution over the entire thickness of the paper with sufficient accuracy (the absolute error in estimating the average values of the substance content of the composition is no more than 5 %). The essence of the method was to treat paper samples with an iodine-based composition in order to bind it into complex compounds with starch, obtain images of cross sections of paper and process them using software. To assess the suitability of the method, comparative measurements were carried out on two paper samples manufactured under industrial conditions, sized from the surface with compositions based on oxyethylated starch, having different viscosity characteristics due to differences in the concentration of the composition. The use of meta-mathematical processing methods for the obtained data made it possible to objectively demonstrate the sensitivity of the method to the characteristics of starch-based sizing compositions due to different dry matter content.