Preparation And Supercritical CO₂ Foaming Of PLA/PBS/ZnO Nanocomposites

In this paper,PLA/PBS composites were prepared and the compatibility between PLA and PBS was discussed.The effects of different PBS contents on the mechanical properties,degradation properties and rheological properties of the composites were studied.The effects of different ZnO contents on the mechanical properties,crystallization properties and dynamic rheological properties of PLA/PBS/ZnO composite system were studied by melt blending ZnO with PLA/PBS?75/25?.The PLA/PBS/ZnO microporous plastic was prepared by supercritical CO₂ foaming method.The effects of foaming temperature,saturated pressure and pressure release rate on foaming performance were studied.The specific conclusions are as follows:PLA/PBS compositeswere partially compatible system.PBS improves the brittleness of the composites.When the content of PBSwas 25%,the comprehensive mechanical properties were the best.With the increase of PBS content,the crystallization performance and degradation performance of PLA were improved.PLA/PBS was a viscous dominated viscoelastic system,which exhibits a significant "shear thinning" phenomenon at high shear rates and was a typical non-Newtonian fluid.PLA/PBS/ZnO composites were prepared by melt blending extrusion,and ZnO was better dispersed in PLA/PBS matrix.When the content of ZnO was 0.5wt%,the tensile strength,elongation at break,flexural strength and impact strength reach the maximum of 40.9MPa,4.0%,71.6MPa and 8.8kJ/m² respectively.With the addition of ZnO,the fusion enthalpy ?Hm and the crystallization temperature Tc of the composites were increased and then decreased,and the crystallinity was improved,which was consistent with the change of mechanical properties.In addition,the rotational rheological test shows that when the content of ZnO was 0.5wt%,the storage modulus G'and the loss modulus G''of the composite were the maximum,and the side reflects the internal hydrogen bond and The most perfect cross-linking network,synergistic effect to achieve the best condition,so the mechanical performance was also optimal.When the foaming temperature of the system is 90?,the average cell diameter of PLA/PBS/ZnO porous foaming material is the smallest,the cell density is the largest,reaching 1.96×10⁹cell/cm³,and the cell size distribution is the most concentrated.When the saturation pressure is increased from 12 MPa to 16 MPa,the PLA/PBS/ZnO microporous foaming material with the smallest cell diameter,the largest cell density and the largest cell size distribution can be obtained.With the increase of the rate of release,the average cell diameter of PLA/PBS/ZnO microporous foaming material decreased,the cell density increased significantly,the number of cells increased and the size distribution was more concentrated.In addition,the foaming experiment showed that the foam density of the foaming material with 0.5wt% ZnO was an order of magnitudehigher than that of the non-added foams at the temperature of 90?,the saturated pressure was 16 MPa and the pressure rate was-160MPa/s,the cell size distribution was more concentrated,the volume expansion rate was higher.