Investigation of the friction of flexographic and inkjet prints

Abstract

Friction between different papers, flexographic and inkjet prints made on coated and uncoated papers were investigated experimentally. Static (SCOF) and kinetic (KCOF) friction coefficients paper-to-paper, paper-to-print, and print-to-print were determined using the horizontal plane method. Prints were made with different ink coating (different anilox roller volume, one and four ink-jet coatings). Friction coefficients were determined at different loads (pressures) and the friction force evolution during sliding was investigated. Friction investigation was combined with surface roughness measurements. Friction of all investigated flexographic as well as ink-jet prints is higher than paper to paper friction. Both SCOF and KCOF decrease as load is increased and it is assumed that this effect shows that the friction adhesion component prevails. Analysis of the possible models of friction force evolution during sliding enables to suppose, that sliding of print on print is stick-slip type, in which elastic deformation of asperities participates, but the main role is played by adhesion forces. The comparison of the friction properties of prints made on coated, uncoated papers and special ink-jet paper (photo paper) once again supports the assumption that the friction of prints as well as papers is caused by the adhesive interaction of contacting surfaces.