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FBM claimed in an older post that According to PFA the statement appears true for PU foam
Is this statement applicible to Latex ? PU foam has High resiliance, latex has no resiliance. Looking more for the facts than opinions.
Anyone ?
This message was modified Mar 25, 2010 by zzzombie
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| There is a formula for figuring ILD (AKA IFD) so that there is a consistency across differing thickness of latex. I feel confident that Latex Internatioal uses this formula when measuring there latex. |
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From my limited understanding ILD/IFD measures the stiffness/firmness of the foam by indicating the amount of pressure requiredto compress a specimen of specific dimensions by a particular fractional depth (typically 25% or 65%). Implicitly the actual depth of compression is dependent on both the thickness of the specimen and the target fraction (e.g. 2%5 of 4" is 1" and 25% of 8" is 2"). Everything else being constant, reducing the thickness of the specimen would effectively reduce the actual target depth but also reduce the volume of material available to resist the applied force. Thus the relationshipis not really linear (there are conversion charts), but effectively the required force is reduced giving a lower measured ILD. It is better to have the dimensions of the specimen used during the test to enable a fair comparison. I dont think the ASTM D 3574 standards of test measurements are mandatory. Resilience of a foam is measured using the dropped ball test and is a measure of the elasticity/springiness of the foam. Standard PU foam has low resilience, HD is about 30-40%, Lux/Evlon is about 40-50%, HR is about 50-60% and latex is usually greater than 60%. A related measure is the compression set which measures the amount of 'permanent' deformity after the foam has been under compression for a sustained period. Low values are good and is slightly correlated with resilience and density Density is probably the most reflective of durability. Denser products (of same material) tend to maintain their specifications longer. |