Polymer blends constitute a strategy for tailoring the properties of commercial polymers, leading to the development of materials designed for specific applications. In this work, the effect of the mixing sequence of the reactive compatibilizer styrene–acrylonitrile functionalized with epoxy groups (SAN-g-Epoxy) on the performance of poly(butylene terephthalate) (PBT)/acrylonitrile–butadiene–styrene (ABS) blends was investigated. PBT/ABS blends (60/40 wt%) were prepared by reactive extrusion in a twin-screw extruder followed by injection molding, incorporating five parts per hundred resin (phr) of SAN-g-Epoxy through different mixing sequences, aiming to understand how the processing order influences interfacial reactions, morphology, and the final properties of the material. The results indicated that SAN-g-Epoxy promotes reactive compatibilization between PBT and ABS, as evidenced by a significant increase in torque and complex viscosity, as well as by an increase in the intensity of the carbonyl band in the Fourier transform infrared spectroscopy (FTIR) spectra. By scanning electron microscopy (SEM), the presence of the compatibilizer resulted in a pronounced morphological refinement of the dispersed ABS phase, reducing the average particle size from approximately 4.34 µm to about 0.47–0.54 µm. Among the processing strategies, the route (PBT/SAN-g-Epoxy) + ABS exhibited the best mechanical performance under impact, reaching 206.7 J/m. However, the simultaneous mixing sequence PBT/ABS/SAN-g-Epoxy showed the best balance of properties, with gains of 203% in impact strength, 8.8% in elastic modulus, and 40.1% in heat deflection temperature (HDT) compared to neat PBT. The results indicate that PBT can be improved and tailored for engineering applications.

Poly(lactic acid) (PLA) is a renewable and biodegradable polymer that has attracted considerable attention for sustainable packaging applications. However, its inherent brittleness limits its use in flexible films. In this study, PLA/poly(vinyl alcohol) (PVA) blend films were prepared by a single-solvent-casting rout at PLA/PVA weight ratios of 80/20, 70/30, 60/40, and 50/50 to investigate the influence of composition on their thermal, chemical, morphological, mechanical, optical, and water vapor barrier properties. Increasing the PVA content progressively modified the molecular organization of the system, the crystallization ability of the PLA phase and promoting a more homogeneous phase distribution. These structural changes resulted in a transition from a brittle behavior to increasingly ductile films, with the PLA/PVA 50/50 composition exhibiting the most favorable combination of tensile toughness, transparency, and morphological homogeneity, reaching an elongation at break of approximately 60%. In contrast, the increase in the hydrophilic phase led to higher water vapor permeability, highlighting the trade-off between mechanical performance and moisture barrier properties. Overall, the results demonstrate that controlling the PLA/PVA ratio provides an effective strategy for tailoring the morphology and functional properties of solvent-cast PLA/PVA films, contributing to a better understanding of the composition–structure–property relationships in biopolymer blends.