Synthesis and compressive behaviors of PMMA microporous foam with multi-layer cell structure

The polymeric microporous foams with multi-layer cell structure is prepared via the combination of multi-layer hot melt pressing and supercritical carbon dioxide(SCCO2) foaming method. The morphology and compression properties of such foams were detailed studied. The results show that nucleation and directional growth of the cells are promoted by the introduction of multi-layer interface into the polymer matrix. When the distance of the multi-layer interface is smaller than the critical nucleation size of the cell, the microcellular foams with uniform, continuously and directionally multi-layer cell structure can be prepared, and the unit cell shape is well controlled. In addition, the compressive properties of the foams with multi-layer cell structure are different in vertical and horizontal loading direction. The compression strength of the multi-layer foam is up to 20.27 MPa and 11.84 MPa in horizontal and vertical loading direction, respectively, which is much higher than that of the uniform foam.