Core-Shell Starch Nanoparticles Improve the Mechanical and Thermal Properties of Poly(propylene carbonate)

Poly(propylene carbonate) (PPC) is a green biodegradable polymer material, but its poor mechanical properties and thermal properties severely limit its wider application. PPC-based nanocomposites with improved mechanical properties and thermal properties were prepared by melt-blending of core-shell starch nanoparticles (CSS NPs) and PPC, in which a starch core covered by outer shell was formed in that process. The core was formed by synthesized CSS NPs as the product of gelatinization of the esterified starch; on the other hand, the outer shell was a poly(methyl acrylate) (PMA) produced in the soap-free emulsion copolymerization of methyl acrylate. The synergistic association of hard starch and soft PMA induces a significant increase in the mechanical and thermal properties of PPC. When the addition of CSS NPs was 20 wt %, the tensile strength and initial Young's modulus of PPC/CSS composite were 3.2 times and 50.4 times those of neat PPC, respectively, while the toughness increased by 44%. In addition, the glass transition temperature (T-g) increased by 6.2 degrees C and the thermal degradation temperature at 5% weight loss (T-5%) increased by 81.2 degrees C.