Tailoring compatibility, morphology, and functional properties of polyester-based biodegradable blends: a review

Understanding how thermodynamic compatibility, phase morphology, interfacial interactions, and processing conditions influence the performance and biodegradation of biodegradable polyester blends remains important and underreported. Thus, this review examines how compatibility and phase morphology govern the mechanical, barrier, and rheological properties and the underlying thermodynamics of PBS-, PBSA-, PHA-, and PBAT-based blends. The review starts by explaining the thermodynamic principles of polymer blends. An understanding of these principles is needed to interpret the immiscibility of biodegradable blends and its influence on phase behaviour, morphology, and functional properties. Thereafter, recent studies on polyester-based blends are discussed, focusing on the factors governing their mechanical, barrier, and rheological properties. Mechanical performance depends on the evolution of suitable phase morphology and interfacial adhesion which can facilitate stress transfer throughout the material. Reactive compatibilizers, interfacial crystallites, and nanostructures can improve toughness and strength by enhancing compatibility between the blend polymers. Barrier properties are governed by the degree of crystallinity, interface, and the tortuous diffusion pathways created by compatibilizers and nanoscale fillers. Rheological behaviour of the blends provides insight into molecular interactions, melt elasticity, and processability. In general, chain extension and filler-network formation improve melt strength and viscoelasticity. Excessive plasticization or phase separation tends to reduce melt elasticity and make processing more difficult. The effects of compatibilization, chain extension, and filler incorporation on biodegradation are non-linear. Thus, phase morphology, crystallinity, interfacial structure, and polymer accessibility need to modify and maintain the biodegradability of the blends. The insights from this review is essential for developing high-performance biodegradable polyester blends.