Research and Development

As previously stated, polyurethane foam is made up of dodecahedron cells. The walls of these cells are constructed of struts and membranes that stretch between the struts. The struts vary in diameter depending upon the density of the foam. The membranes or windows are very thin and may or may not be ruptured.

For filtration purposes, it would be ideal if all these membranes were removed to allow for low flow restriction, yet all the struts remained to form the structure and tortuous path for the air and dust particles to flow into. As the air flows into the cell structure, dust is trapped within the dodecahedrons.

To accomplish this ideal media, the windows can be totally removed by one of two processes. The first process is via chemical etching or quenching (Figure 1) and consists of passing the polyurethane foam through a caustic bath at a controlled concentration, temperature and speed. The quenching process etches away the thin membranes between the struts and the surface of the struts. The final product is a completely open or reticulated structure. The surfaces of the remaining struts are rough from etching. The quenching process is ideal for polyester-based polyurethane foam.

The second process is called thermal reticulation (Figure 2). Thermal reticulation takes place in a pressure vessel capable of withstanding the ignition of a mixture of hydrogen and oxygen gases. Polyurethane foam is placed in the vessel, a vacuum is pulled on the vessel, and an explosive mixture of hydrogen and oxygen gases is introduced into the vessel. When the proper charge is obtained an ignition source is activated which causes a flame front to pass through the foam at sub sonic speed causing the polyurethane foam membranes to burn back to the strands. The thermal reticulation process yields windowless foam with a flame-polished surface on its struts. The process can be performed on all three polyol based polyurethane foams (Ether, Ester and Polymer Polyol). Thermally reticulated foam yields slightly lower pressure drop values than chemically quenched foam for a given air flow.

Felting is a thermoforming process that permanently compresses foam.

The degree of compression controls the physical properties of the felt

Increases the effective density
Affects fluid-to-foam interactions

The "Firmness" of a felt is the felting ratio

Equals original thickness/final thickness
Usually ranges from 3 to 10+

A proprietary and patented FXI process

Alters foam surface in up to five different ways:

1. By pattern
2. By the size of the pattern
3. By depth of cut
4. By the spacing between patterns
5. By the location of each distinct pattern

Uses:

1.Redistribute Pressure
2.Maximize comfort without compromising support
3.Provide a "zoned" cushioning layer
4.Enhance air circulation