Cellular polymers or foams can be classified according to their cellular morphology into closed and open cell materials . On the one hand, in closed cell foams, the gas is enclosed in the cells. On the other hand, 100% open-cell foams are characterized by a total interconnection among the cells and as a consequence, the gas can freely move throughout the whole cellular structure. However, the interconnection among the cells can be very different depending on the material.
In the case of a flexible polyurethane (PU) foam, the cells are formed only by struts without the presence of cell walls, whereas the interconnection between cells is due to the presence of holes on the cell walls. Open cell polyolefin foams present this type of cellular structure.
Tortuosity can be defined as the ratio between the real and the shortest distance that the gas molecules have to cover from one side to the other side of a foamed sample. Tortuosity strongly depends on the way the cells are connected each other . For example, the gas can diffuse easily throughout a cellular structure comprised only of struts. However, the cellular structure of open cell polyolefin foams can be tuned generating many and larger holes on the cell walls, giving, as a result, a low tortuous material or these foams can have few and small holes in the walls, giving a high tortuosity foam .
This work is focused on the analysis of the effect of the cellular structure tortuosity on the physical properties of open cell polyolefin foams. For this purpose, polyolefin open cell foams with low and high tortuosities and an open cell PU foam, used for comfort applications, have been tested and compared. The mechanical properties at high and low strain rates of deformation, the acoustic behavior and the oil absorptive response have been exhaustively characterized, demonstrating the critical influence of the cellular structure tortuosity on the final properties.
Furthermore, promising results have been obtained for open cell polyolefins with low tortuosity in several properties, becoming these materials potential alternatives to flexible open-cell PU foams in many applications such as comfort, acoustic insulation or as oil absorptive materials.