Diisocyanate-induced dynamic vulcanization and interfacial compatibilization toward mechanically robust PPC-P/PLA blends with enhanced foamability

Poly(propylene carbonate-co-phthalate) (PPC-P), limited by inferior melt strength and heat resistance, exhibits poor foamability and thermal stability. This study enhances PPC-P through biodegradable PLA incorporation and HDI-induced dynamic vulcanization of terminal hydroxyl groups, improving the interfacial compatibility. The gel contents, rheological properties, crystallization behaviours, mechanical properties, compatibility and microstructures of the PPC-P/PLA blends are investigated in detail. By adjusting the compatibilizer-NCO dosage and PLA contents, the melt strength and viscoelasticity of the blends are effectively enhanced and regulated. Enhanced interfacial compatibility among PPC-P and PLA phases, improves the tensile strength and elongation at break of PPC-P/PLA composites, with values of 48.2 MPa and 12.9%, respectively. By using the sub-critical CO 2 as blowing agent, light weight and low-shrinkage PPC-P/PLA foams with well refined cell structures are successfully obtained, which can be attributed to the improved melt strength and the induced thermal stability. The relationship between the crosslinked-crystalline network and the foam quality are established, including CO 2 solubility, cell microstructure, and dimensional stability. PPC-P/PLA foams show refined microstructures (cell size < 50 μm, cell density > 1.5×10 9 cells/cm 3 , VER > 20), and low shrinkage (< 25%). Here, the crosslinks and crystals play multiple essential roles in increasing the melt strength and foamability of PPC-P, providing a widely applicable low-shrinkage strategy, which is crucial for the biodegradable foams.