Microstructure Development and Its Effect on the Properties of Melt-Processed Biodegradable Polylactide/Poly(ε-Caprolactone) Blends

The relationship between structure and properties in polymeric materials explores how variations in polymer blend composition affect their microstructure and alter rheological, thermal and mechanical characteristics. This study focuses on polylactide (PLA)/poly(ε-caprolactone) (PCL) blend, which is selected for its biodegradable and biocompatible properties, enabling applications ranging from packaging to biomedical fields. PLA/PCL blends with different PCL loadings were processed in a twin-screw extruder. We assessed the correlation between blend microstructure and properties to analyse mechanical performance under various loading conditions. The blend with 10 wt% PCL exhibited droplet-matrix morphology with well-dispersed PCL particles, strong interfacial adhesion and notable crystallinity, as shown through scanning electron microscopy (SEM), rheological analysis, dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The high PLA content, excellent dispersion and significant crystallinity resulted in elevated tensile strength and toughness, as well as reduced brittleness in tests. However, the material exhibited low notched Charpy impact strength. This indicates that it can deform under tensile and repetitive loads, yet exhibits poor resilience to sudden impacts under notched conditions. The droplet-matrix morphology is validated as the experimental tensile modulus aligns with Takayanagi model predictions. These findings emphasise the importance of blend microstructure in property development and how service conditions affect polymeric product performance.