DESIGN NEWS REPORT OPEN-PORE POLYURETHANE FOAM AND FELT

E&MP 90.005e

Noise Control

November 25, 1964

[DESIGN NEWS REPORT pamphlet page 4]

to which thickness is reduced. Standard reductions in thicknesses of 3, 5,10 and 15 firmnesses are presently available.

(Intermediate firmnesses and firmnesses as high as 25 also can be obtained.) "Firmness" indicates the relationship between original and final thickness.

For example, a 1/4-inch-thick piece of 15 firmness material would have been reduced by 3-4/4 inches (15 one-quarter-inch increments) from its original 4-inch thickness.

Texture of the felts depends on pore size and firmness of the original foam material as well as heat and pressure required to set the felt. It ranges from soft and velvety to smooth and leathery.

Flow and Filtering Characteristics
In tests of foam made at an air velocity of 350 fpm, 1/2-inch-thick pads of the previously mentioned 20-100 ppi porosity grades cause pressure drops ranging from 0.045 to 1.0 inch of water. For thicknesses other than 1/2 inch, pressure drop can be computed by multiplying the drop at 1/2

Original Caption by Science Service
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