Evaluating the surface energy of laboratory-made paper sheets by contact angle measurements

Abstract

Contact angle is one of the most useful tools to easily assess the surface energy of paper sheets. However, the results obtained should be treated with some caution, since these measurements are significantly influenced by the properties of the liquids used and of the paper surface. Our study compares the values of the contact angle and of the surface energy of laboratory handsheets produced with demineralized water and with white water (collected from the paper mill). In addition, and to assess the influence of paper roughness on the contact angle measurements, some 3-D topographical parameters were computed by perfilometry. Complementary measurements were also performed with commercial paper samples. The results clearly demonstrate that the kind of water used in the sheet-making process has a more pronounced influence on the surface energy of the paper sheets than whether the paper sheets were made in a laboratory sheet former or in an industrial paper machine. Application: This study clarifies factors that have influence on the practical determination of the surface energy of paper sheets by contact angle measurements. The results show the influence of the water used in the sheet-making process on the surface energy of paper sheets and are specially useful for experiments carried out in the laboratory.