Study on preparation and mechanical properties of polyurethane foam with negative Poisson's ratio

Auxetic foam was a new kind of material which exhibit negative Poisson's ratio effect. It has a wide application prospect. However, auxetic foam would gradually expand to its original volume with time increasing, and the negative Poisson's ratio effect will disappear. The practical use of the auxetic foam has been limited, and it becomes an urgent problem to be solved before its application. The preparation conditions and the recovery ability of auxetic foam, the 60 ppi open cell polyurethane (PU) foam was used as the parent material. The PU foams were compressed in three dimensions and been heat treated at setting temperatures. After cooling down, the auxetic foams were made. In this study, all samples were set with the same radial compression ratio, but three different axial compression ratios. During the heat treatment process, the setting temperatures were 140 degrees C, 150 degrees C and 160 degrees C respectively. It was found that the setting temperature in the condition of this study should be heated until 150 degrees C to obtain the re-entrant structure.