Adhesive and Sealant Applications & Tools

Experts in the tools used for specific applications. The tool may cost you very little, but it accounts for over 50% of the success in the application.

Sunday, January 9, 2011


The Equation F=PA

Why do we have so many different types of tools, and how do we select the right tool for the right application? This is one of the hardest questions and one we don't give much thought to. Heck, a caulking gun is a caulking gun, right? Wrong, and here is why.

Force = Pressure x Area

This is a basic engineering formula that you can apply to dispensing tools. Simply put, it takes pressure in the cartridge, sausage, or bulk barrel (a material containment unit or MCU) to get material to flow out of the nozzle. Different amounts of pressure are required depending on:
a. How thick the material is.
b. The nozzle opening. Think of the pressure required to push material through a static mixer. A static mixer is a mixing nozzle which mixes two component materials before the material reaches the substrate.

PRESSURE makes things happen.

To determine the FORCE required of your dispensing tool you must calculate the area of the piston pushing on the material in the MCU. Lets compare the simple 1/10 gallon cartridge and the common quart cartridge. You don't generally see thick material in a quart cartridge. Why?

1/10 Gallon Cartridge Area = (Diameter Squared * Pi/4) = (1.8*1.8*3.1416)/4 = 2.55 square inches

Quart Cartridge Area = 5.19 square inches

5.19/2.56= 2.002

The Quart Cartridge Area is double that of a 1/10th Gallon Cartridge Area. This basic engineering formula reveals that it will require double the force to develop the same pressure in a Quart Cartridge versus a 1/10 Gallon Cartridge.

What can we draw from this?
1. Thin material requires less pressure and thus less force... and a lower-end dispensing tool.
2. Thicker material or very small or long nozzles require more pressure and thus more force... and thus a stronger or more forceful dispensing tool.
3. If you increase the diameter of the MCU you will need to develop more force from your dispensing tool. Most materials packaged in a Quart Cartridge are low pressure materials which require large nozzle openings and little accuracy in applying. A good example is subfloor adhesive. Your objective there is to get material down quickly.

In the next blog segment we will talk about how to measure force on a dispensing tool. Also, we will discuss what rod displacement means and how it needs to be factored in when selecting the right tool.

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