Crystallization and Enzymatic Degradation of Maleic Acid-Grafted Poly(butylene adipate-co-terephthalate)/Organically Modified Layered Zinc Phenylphosphonate Nanocomposites

Abstract

Biodegradable nanocomposites were successfully synthesized using the maleic acid-grafted poly(butylene adipate-co-terephthalate) (g-PBAT) and organically modified layered zinc phenylphosphonate (m-PPZn), containing covalent linkages between g-PBAT and m-PPZn. Differential scanning calorimetry, wide-angle X-ray diffraction (WAXD), and transmission electron microscopy (TEM) were used to determine the crystallization behavior and morphology of g-PBAT/m-PPZn nanocomposites. The isothermal crystallization kinetics of g-PBAT/m-PPZn nanocomposites was determined using the Avrami equation. It was found that the half-time for the crystallization of the neat g-PBAT matrix is larger than that of g-PBAT/m-PPZn nanocomposites. This result suggests that the incorporation of m-PPZn can improve the crystallization rate of nanocomposites. The WAXD and TEM data illustrate that most of the m-PPZn layered materials are partially intercalated or exfoliated in the g-PBAT matrix. As the enzyme, lipase from Pseudomonas sp. was used for the enzymatic degradation tests. The degradation rates of the neatly fabricated g-PBAT copolymers using the heat pressing technique increase in the order of g-PBAT-80 > g-PBAT-50 > g-PBAT-20. The growing degradation rate of g-PBAT-80 is due to the growing amount of the adipate acid group and the increasing chain flexibility of the polymer backbone. Moreover, the increasing loading of m-PPZn enhances the weight loss of nanocomposites, suggesting that the existence of m-PPZn enhances the degradation of g-PBAT copolymers. The degradation rate of the freeze-drying samples containing a highly porous structure is greater than those prepared using the heat pressing technique.