Surface Interaction
A surface interaction involving the reduction of liquid surface tension through chemical agents allows fluids to spread across a solid substrate. Surfactant wetting is necessary for the application of aqueous inks and coatings to non-polar surfaces like plastic films or highly sized paper. Without these agents, the liquid would bead up rather than forming the continuous film required for high-quality printing.
Chemical Mechanism
Amphiphilic molecules migrate to the interface between the liquid and the air, orienting themselves to lower the energy required to expand the surface area. During surfactant wetting, the contact angle between the droplet and the substrate decreases, indicating better coverage. This process happens in milliseconds on a high-speed press, requiring the use of dynamic surfactants that move quickly to the newly created surfaces.
Over-application can lead to unwanted side effects such as foaming or reduced adhesion of subsequent layers.
Application Requirement
Achieving the correct balance of surface energy is a prerequisite for any coating or printing operation on modern packaging materials. Proper surfactant wetting ensures that fine text and halftones are reproduced with sharp edges and no pinholes. The choice of agent depends on the speed of the line and the specific chemistry of the base sheet.
