Relationship Between Rheological Properties and Morphology in Determining the Foamability of PLA/LDPE blends

Polymer blending is an effective approach to overcome the inherent limitations of individual polymers and to tailor their properties for specific processing applications. However, most previous studies have focused on improving the compatibility and mechanical performance of polymer blends, while the foaming behavior of immiscible systems and correlation with rheological and morphological properties remain poorly understood.
To address this issue, a biodegradable polymer blend system composed of polylactic acid (PLA) and low-density polyethylene (LDPE) was developed to clarify these relationships. LDPE, which possesses a long-chain branched structure, exhibits strain-hardening behavior that significantly affects melt processability. Moreover, fillers with different shapes and surface hydrophobicities were incorporated to control interfacial tension and improve blend compatibility. The effects of filler-induced interfacial modifications on viscoelastic properties related to foaming were evaluated using small-amplitude oscillatory shear (SAOS) and uniaxial extensional viscosity measurements. The blend morphology and phase structures were observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Furthermore, correlations among rheological behavior, morphological characteristics, and foaming performance were analyzed to assess foam density, expansion ratio, cell morphology, and foam stability.
Overall, this study demonstrates that interfacial morphology plays a critical role in determining the rheological behavior and foam processing characteristics of PLA/LDPE blends, providing a fundamental understanding for the design of biodegradable polymer systems with enhanced foaming performance.