Theoretical and experimental investigation of the compatibilization agent contribution to the interactions of polymer blend (PP/LDPE): Thermal, morphological, and DFT insights

Abstract

In this research, we looked at the impact of (styrene-ethylene/butylene-styrene) SEBS 5 % wt and (maleic anhydride grafted SEBS) SEBS-g-MA 5 % wt as compatibilizer agents of polypropylene (PP)/low-density polyethylene (LDPE) blends. Compression molding was used after mixing the melts in a Brabender internal mixer to create the blends. Scanner electron microscopy (SEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) were used to characterize the structural and surface behaviors of the blends and their morphology. FTIR analysis showed a weak and broad absorption peak at 1650 cm−1 for PP, LDPE and their blend, which signals the presence of carbonyl groups, and therefore oxidation of the blend. Upon addition of SEBS (styrene ethylene/butylene styrene) and SEBS-g-MA (SEBS grafted with maleic anhydride), the absorption of the carbonyl group decreases, so the peak at 1650 cm−1 becomes smaller. SEM analysis showed an improvement in the morphology and interfacial adhesion of the mixtures with the use of SEBS and SEBS-g-MA. These results suggest that the use of compatibilizers can lead to improved properties for PP/LDPE blends in various applications. Molecular modeling was also used to infer the effects of the compatibilizing agent on the properties of PP-LDPE blends. According to molecular dynamics simulations, the inclusion of SEBS dramatically increases the binding interaction energies for the 3PP/3PE and 3PP-3PE-1SEBS-g-MA systems, going from 440 kcal/mol to 880 kcal/mol, respectively. Density functional theory calculations further confirm the compatibilization role of SEBS-g-MA on the blend. In particular, Quantum molecular descriptors and the density of states demonstrate SEBS-g-MA's involvement as an intermediate in promoting PP and LDPE compatibility. Overall, our results suggest that SEBS-g-MA is a potential PP-LDPE compatibilizer.