LOAD-COMPRESSION BEHAVIOR OF FLEXIBLE FOAMS

The load–compression behavior of a foam reflects its geometric structure and the physical properties of the matrix polymer. Quantitative relations between these parameters have been established in the present study. Based on both theoretical analyses and experimental data obtained on a flexible polyurethane foam, it is shown that the compressive stress can be factored into the product of two terms: (1) a dimensionless function of the compressive strain, ψ(ε), calculated from experimental load–compression data and reflecting the buckling of the foam matrix; and (2) a factor, εEf, where Ef is the apparent Young's modulus of the foam (which is a function primarily of the modulus of the base polymer E0 and of the volume fraction of polymer, φ). Thus the compressive stress behavior of a foamed polymer is determined by E0, φ, and the matrix geometry, the latter described by the function ψ(ε). Using these established relations, it now is possible to delineate precisely the structural features a foam must possess—density, cell shape and size distribution, and modulus of the base polymer—to meet a given load–compression specification. Copyright © 1969 John Wiley & Sons, Inc.