Effect of polymer microspheres on selected properties of injection-molded shapes based on thermoplastic starch

Microporous products were obtained by injection molding. The effect of adding 1-5 wt% of a foaming agent (Expancel® FG92 MB 120) on selected properties of TPS/PBAT blend compatibilized with maleic anhydride-grafted PLA (MPLA) was investigated. The addition of a foaming agent did not significantly affect the wetting properties or the energetic character of the surface. SEM analysis showed that, unlike blow molding, injection molding, due to the high flow rate, high pressure, and rapid cooling, leads to the formation of closed but deformed pores. Significant structural variability and increased surface roughness occur along the flow direction, which is not fully correlated with internal porosity. This structure results in only minor changes in mechanical properties compared to the solid material. Density, hardness, tensile strength and elongation at break gradually decrease and moisture absorption increases with increasing foaming agent content.