Abstract
The compressive modulus and the handle “hardness” of multi-layer foams, which are made up of flexible polyurethane foams having different compression characteristics, were discussed.
The results obtained are as follows:
1) The compressive modulus YB of multi-layer foams can be calculated with the following equation. Where, li and Yi are the thickness and the compressive modulus of foams which compose multi-layer foams.
Good agreement between the calculated values of YB and the measured ones is obtained.
2) The handle “hardness” of multi-layer foams depends on two physical properties. The one is the compressive modulus YB of multi-layer foams and the other is the compressive modulus Yt of the top-layer foam in multi-layer foams.
By a discriminant function analysis, following equation is obtained. Z is discriminant function for the handle “hardness” of multi-layer foams.
The correlation coefficients between the values Z of discriminant function and subjective rating (hardness) Sh are 0.991 in two-layer foams, 0.975 in three-layer foams and 0.988 in four-layer foams.
3) From the equation of Z, it is seen that YB is more affecting to the handle “hardness” of multi-layer foams than Yt.
