Enhanced Barrier Properties and Tailored Biodegradation of Poly(Butylene Adipate‐Co‐Terephthalate) Composites With Expanded Graphite for Sustainable Packaging

ABSTRACT Poly(butylene adipate‐co‐terephthalate) (PBAT) is a biodegradable polymer widely used in various industries, including agriculture and medicine, due to its favorable physical and environmental properties. However, to reduce oxygen permeability, fillers, such as expanded graphite (EG) are used. EG is obtained by expanding graphite and is considered a suitable reinforcing agent for polymers because of its high specific surface area, good thermal and electrical conductivity, and low weight. In this study, PBAT/EG composites with different weight percentages were synthesized using the in situ polymerization method, in which PBAT monomers are polymerized in the presence of EG. This method improved EG dispersion and composite properties. Tensile testing revealed that the composite with 1 wt.% EG exhibited a unique mechanical response, characterized by an increase in elongation at break from 602% to 620% compared to neat PBAT, enhancing its ductility. This was accompanied by a reduction in tensile strength, a trade‐off that distinguishes the behavior of these in situ polymerized composites from conventionally melt‐mixed systems. The primary enhancement, however, was observed in the barrier properties. Hydrolytic biodegradation tests showed that increasing the EG content enhanced degradation by up to ~15 wt.%, while the soil degradation rate decreased. Additionally, the composites exhibited reduced oxygen and water vapor permeability.