Flexographic Aqueous Latex Barrier Coating Viscosity Measurement Fundamentals
Flexographic aqueous latex barrier coating viscosity requires multi-shear rotational measurement to ensure accurate anilox transfer and barrier film continuity.
Non-Newtonian Flow
Rheological Behavior
Fluid movement that does not follow a linear relationship between shear stress and shear rate characterizes many complex liquid mixtures used in industrial processes. In paperboard manufacturing, non-newtonian flow is observed in clay coatings, polymer starches, and flexographic inks where the viscosity changes depending on how hard the liquid is being pumped or spread. This property prevents the fluid from being described by a single viscosity value.
Shear Response
Liquid mixtures containing suspended pigments or long-chain polymers undergo structural changes when exposed to high velocity and agitation. At low shear, the particles are randomly oriented, creating high resistance to flow and a thick consistency. As the pump or applicator blade applies force, the particles align parallel to the flow direction, which causes the viscosity to drop significantly.
This rapid thinning allows the coating to be spread smoothly across the paper surface at high speed without tearing the sheet or overloading the machinery.
Converting Optimization
Controlling this force-dependent viscosity is essential for achieving a smooth finish on the finished paperboard. Once the shear force from the coating blade is removed, the fluid must quickly regain its structure to prevent the coating from running or dripping before it enters the drying oven. This balance of thinning and recovery ensures that the paperboard receives a uniform, high-quality surface treatment.