Rheological Assessment of Compatibility and Hydrolytic Degradation of Poly(glycolic Acid)/Poly(butylene succinate) (PGA/PBS) Blends

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With the growing applications of biodegradable polyesters in packaging and biomedical devices, the performance enhancement and well-controlled degradation profile are equally important for sustainable polyester product development. Among these biodegradable polymers, poly(glycolic acid) (PGA) stands out as a fully environmentally compostable, high-performance biopolyester with exceptional barrier properties and mechanical strength. However, its rapid hydrolysis rate significantly compromises its stability and service life. This work presents a detailed rheological study to evaluate the hydrolytic degradation of compatibilized poly(glycolic acid)/poly(butylene succinate) (PGA/PBS) blends. Reactive extrusion with epoxy-functionalized Joncryl as the compatibilizer, together with the inclusion of carbodiimide (CDI) as a hydrolysis stabilizer, significantly enhanced the mechanical integrity and hydrolytic resistance of PGA/PBS blends. The hydrolysis degradation profiles of the blends were quantitatively investigated using an intrinsic material parameter G N 0 , i.e., the terminal rubbery plateau modulus of the polymer determined by oscillatory shear rheology. Four distinct hydrolysis stages were identified according to the G N 0 vs. frequency (ω) relationship, which interestingly corresponds to the mechanical degradation results. The rheology method offers a more efficient tool in diagnosing the hydrolysis progression of polymers, compared with conventional methods, such as tracking the molecular weight changes, weight loss, and or mechanical performance over time, thus overcoming sampling challenges and analytical limitations. The phase angle and plateau modulus relationship determined through oscillatory shear measurement can be applied as rheological fingerprints for quantifying the hydrolysis of compatibilized polyester blends.