Molecular Interactions between Model Cellulose Surfaces and Ink – Influence of Surface Energy and Surface Structure on Adhesion

Abstract

The influence of surface roughness and surface hydrophobicity on ink detachment of water-based flexographic ink was studied. It was shown that increased surface roughness and an increased surface hydrophobicity both had a negative effect on ink detachment. The increased surface roughness was suggested to increase the molecular contact area between ink and cellulose and thereby also to decrease ink detachment. Ink cellulose interaction was evaluated from interfacial energies and contact angle measurements. A new technique in which the adhesion properties between ink and the model cellulose surface were directly measured using a Micro Adhesion Measurement Apparatus (MAMA) was also used. Upon increasing the hydrophobicity of the model cellulose surface it was shown that the work of adhesion between ink and model cellulose surfaces decreased. At the same time the interfacial energy between cellulose and ink increased, as did the interfacial energy between cellulose and water resulting in a lower degree of ink detachment.