Microcellular Foaming Behaviors of Poly (Lactic Acid)/Low-Density Polyethylene Blends Induced by Compatibilization Effect

A facile methodology for improving the crystallization ability, rheological properties and microcellular foaming behaviors of poly (lactic acid)/low-density polyethylene (PLA/LDPE) blends through compatibilization was proposed. Poly (ethylene octene) grafted with glycidyl methacrylate (GPOE) as reactive compatibilizer was introduced into PLA/LDPE blends and the resultant PLA/LDPE/GPOE blends were foamed by supercritical CO₂. Torque curves and Fourier transformation infrared spectroscopy results confirmed that GPOE reacted with PLA successfully. The crystallization ability and rheological properties of PLA was promoted obviously by the addition of LDPE and GPOE. The size of LDPE dispersion phase in PLA/LDPE blends decreased from 4.4 ± 0.1 to 1.2 ± 0.1 µm, owing to the compatibility effect. When the content of GPOE reach 8 phr, microcellular structure appeared in the PLA/LDPE/GPOE blending foam. An interesting flower-like cellular structure was observed in PLA/LDPE/GPOE blending foams, with the foaming temperature at 85 and 90 °C. Finally, the microcellular foaming mechanism for various PLA foams was proposed and clarified using schematic diagram.