Seating pressure distribution using slow-recovery polyurethane foams

A 100 mm thickness of Confor slow-recovery foam caused a 10% lowering of skin pressure under the pelvic ischial tuberosities of a static seated subject compared with open cell polyurethane (PU) seating foams. The reasons for the difference were microstructural (semi-closed cells compared with open cells), and mechanical (a lower shear modulus than the open-cell foams, averaged over a range of compressive strain). There was slightly more load spreading below an indenter for an open-cell PU foam, which correlates with slightly higher seating pressure maxima. The pressure distribution property of the Confor foam cannot be explained by its rate dependent polymer viscoelasticity or cell gas flow; these factors lead to higher pressure peaks at short times.