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The Water Wicking Myth: Open Cell Urethane Seals vs Thermoplastic Seals
Others : Theroplastic Closed Cell Foam Forming Process
- Blowing Agent: "Chlorinated flurocarbon blowing agents are preferred, although almost any non-solid blowing agent may be used including pentane, nitrogen and carbon dioxide. Chlorinated fluorcarbon 11 is used in the preferred embodiment."
- Amount of Blowing Agent: "In order to produce a low density foam, a substantial percentage of blowing agent, generally around 10% by weight based on polymer charge,must be mixed with molten resin. In general, blowing agent content may be from 5% to 15% and in the preferred embodiment, is from about 10% to 12% by weight."
- Pressures & Temperatures: "Typically, the blowing agent is injected at pressures form about 1500 to 3000 psi." "The extrusion temperature must be in a window from 295-340°F to produce a good smooth foam product."
The Schlegel Way : Urethane Open-Cell Foam Forming Process
- Blowing Agent: Water Only
- Amount of Blowing Agent: .4 - 1.4%
- Pressures & Temperatures: 20 - 100 psi at 150°F
Foam Seals Process Comparison
| Open-Cell Urethane Foam |
Closed-Cell Foam Thermoplastics |
| Blowing Agent: Water |
Blowing Agent: CFC's |
| .4 to 1.4% water |
5 to 15% CFC's |
| Blowing by product: Carbon Dioxide |
Blowing by product: CFC's |
| Temperature: 150°F |
Temperature: 295 - 340°F |
| Pressure: 20-100 psi |
Pressure: 1500-3000 psi |
| Thermoset |
Thermoplastic product |
Facts and Figures
| Open-Cell Urethane Foam |
Closed-Cell Foam Thermoplastics |
| Compression Set |
Compression Set |
| 25% - 4% |
25% - 10% |
| 50% - 5% |
50% - 17% |
| 75% - 4% |
75% - 16% |
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| Water Wicking (non-compressed) |
Water Wicking (non-compressed) |
| 1 min - .26g |
1 min - .01g |
| 10 min - .36g |
10 min - .02g |
| 1000 min - .90g |
1000 min- .01g |
| 1 gram = 1 cc or approximately 1 drop of water |
The Schlegel Way : Open Cell Foam Properties
Has interconnected cells which allow for the exchange of gases and the equalization of pressure.
- Gives lower CLD (Compression Load Deflection) values.
- Has wider allowable operating temperature range.
- Only when in an uncompressed state, and submerged, can water enter the cells.
- Will absorb water only up to the level of water into which the foam is submerged plus the water pressure of displacement of the liquid.
- Water WILL NOT move throughout the foam.
- Foam must be in non-compressed state to absorb water, ie. The door must be left open.
- Water will run out of the foam as soon as the water source is removed or the seal is compressed.
Others : Closed Cell Foam Properties
- Has seperate, unique sealed cells for gas.
- Contained in the cells is CFC gas produced/used in manufacturing (blowing agent).
- Pressure within its cells cannot be equalized.
- If cells are broken, water can enter the cells and wicking can occur.
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