Support Factor
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http://www.pfa.org/intouch/new_pdf/hr_IntouchV3.1.pdf The ILD (aka IFD) numbers we toss around are at 25% compression. The Polyurethane Foam Association refers to this as "surface feel" or "firmness". Foams are also measured at 65%, but this number is almost never mentioned. The importance of this number is that two foams can have the same ILD at 25%, but quite different ILD's at 65%. The one with the higher 65% number will be more supportive. This is sometimes referred to as "deep down support." The ratio of the 65% ILD to 25% ILD is "support factor," or "compression modulus." Support is a key function of flexible polyurethane foam. In many ways, it is the most important function foam can provide. In many ways, foam support and firmness are interrelated. In fact, compression modulus is measured by taking the ratio of two foams firmness measurements. And foams with high levels of support can actually feel firmer than foams with the same density and surface firmness measurement but which have lower support levels. Generally speaking, the higher the density, the more "supportive" a foam will be. Typical poly foams will have support factors under 2.0, "High performance" foams will have support factors above 2.0. The higher the density, typically the better the ability of the foam to provide support. This thread in the old forum contains some good discussion on the difference between "firmness" and "support".Support is also important in that foam with higher support can be specified with softer surface IFD, without sacrificing the ability of the foam to bear a load. This message was modified Sep 9, 2007 by haysdb
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Re: Support Factor
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Post deleted by author. I incorporated this post into the previous one. This message was modified Sep 15, 2007 by haysdb
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