Improved Thermal Stability, Moisture Resistance, Oxygen Barrier Properties, and Interaction of Recycled Polypropylene/Ethylene Vinyl Alcohol Blends Using a Polypropylene Functionalized with a Maleinized Hyperbranched Polyester Polyol as a Compatibili

Polypropylene (PP) is widely used in the packaging industry. However, it has high oxygen permeability (PO2). Ethylene vinyl alcohol (EVOH) has been blended with PP to improve this property. However, these polymers are incompatible. In this study, PP functionalized with a maleinized hyperbranched polyester polyol (PP-g-MHBP) was used as a new compatibilization alternative for the recycled PP (rPP)/EVOH blend. The rPP/EVOH blends were prepared using a torque rheometer at 200°C. The weight proportions of rPP (80%) and EVOH (20%) were constant, whereas those of PP-g-MHBP were 0, 2.5%, 5.0%, 7.5%, and 10.0%. PP-g-MHBP improved the thermal stability of the rPP/EVOH blends by 16.79–18.36% for the EVOH-associated decomposition step and by 1.62–3.23% for the rPP-associated decomposition step in the blends. Additionally, it reduced the crystallinity of the rPP and EVOH in these blends. The rheological behavior of the blends was primarily pseudoplastic in nature. Scanning electron microscopy (SEM) analyses showed that the interaction between rPP and EVOH improved in the presence of PP-g-MHBP. Moreover, these blends exhibited a reduction in moisture content (MoC) and moisture absorption (MoA), and PO2 values (between 8.94% and 23.44%, between 7.69% and 23.08%, and between 4.10% and 28.39%, respectively). However, the tensile modulus increased by 13.57–41.49%.