Paste adhesives knives

Independent of final adhesive viscosity, hand application, by spatula, palette knife or trowel, is often the favoured method. However, once mixed, low viscosity adhesives are frequently pumped to an applicator gun, which is often robotically controlled. Higher viscosity paste adhesives can make use of hand-held cartridge dispensers which not only mix the adhesive, as indicated above, but also can apply a bead or stripe of adhesive to the substrate, dependant on the design of the applicator head. 

Pastes, mastics Highly viscous single- or two-component materials that cure to a very hard or flexible joint depending on adhesive type. Does not run when applied. Shelf and pot life are often limited. Often applied via a trowel, knife, or gun-type dispenser one-component systems can be applied directly from a tube. Various types of roller coaters are also used. Metering-type dispensing equipment in the 2,500 range has been used to some extent. 

To understand the processing and dispensing behavior of adhesives we often need to construct flow models of the process. While all models are approximations, they still have to satisfy continuity of mass and the balance of momentum and thermal energy. The constitutive equation, plus the appropriate initial and/or boundary conditions of the problem at hand, provide closure to these balance laws. While any realistic solution to a particular processing problem will generally involve numerical computations, several generic problems of interest may be amenable to analytical development. For instance, when a pressure-sensitive adhesive is pressed down unto a surface, we have an example of squeeze flow. Similarly, if a paste is spread onto a surface via a knife, we have an example of wedge flow. These two flows will be discussed for the PLF. 

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