3. RESULTS AND DISCUSSION
A uniformly mixed polysiloxane-LDPE-polymer microbead blend was achieved using a counter-rotating twinscrew
extruder. When the blend was foamed using gaseous CO2, the polysiloxane was foamed in the blends. Figure 1 shows typical fracture surfaces of the foamed specimens using gaseous CO2. When depressurized, cellular structures
were formed due to the plasticizing effect of gaseous CO2 dissolved in polysiloxane [11]. Homogeneous cellular structures
with open-cells were obtained after foaming. The cell densities of the foamed specimens were 1.8×108
cells/cm3 for SiOC1, 4.5×107 cells/cm3 for SiOC2, and 2.6×107 cells/cm3 for SiOC3 (Fig. 2). It was observed that the
addition of LDPE resulted in a lower cell density when foaming was performed at a constant concentration of
microbeads with the same size. Furthermore, the use of a larger microbead resulted in a foamed body with a lower cell
density when the same content of LDPE was added. Since the glass transition temperature of LDPE was much
higher than room temperature even when saturated with high pressure CO2 [9], the dispersed LDPE phase in the blends