Interfacial properties of polyethylene/poly(lactic acid)/maleic anhydride-grafted polyethylene ternary blends and its relationship with rheology, morphology and mechanical properties

Abstract

The performance of incompatible blends is strongly depended on their morphology and interfacial properties that can be controlled by proper compatibilizers. This research systematically investigates the interfacial properties of the binary and the ternary blends based on low-density polyethylene (LDPE), poly(lactic acid) (PLA) and maleic anhydride-grafted polyethylene (PE-g-MAH) through the melt linear viscoelastic rheological behavior of the blends and neat components analyzed by proper rheological models. Moreover, the relationship between rheology, phase morphology and mechanical properties of LDPE/PLA ternary blends with different amounts of PE-g-MAH was studied. In the rheological analyses via the additive rule indicated in the molten state, no consistent interfacial interaction between LDPE and PLA phases is made due to the presence of PE-g-MAH at the interface of the blend. However, the analyses based on the Palierne’s model implied that the interfacial tension of compatibilized blends decreases. This not only resulted in improving PLA dispersed phase morphology in the compatibilized blends, but also forming in situ fibrillar composites where the compatibilizer amount was relatively high (5 and 7.5 wt.%). Unlike the molten state, because of the strong interactions between PE and PLA phases of compatibilized blends in the solid state, the tensile mechanical properties, including Young’s modulus, strength and elongation-at break, could be reinforced up to 24%, 25% and 90%, respectively. Overall, findings make a profound realization of the amount depended performance of PE-g-MAH as the most common compatibilizer for PE/PLA blends, very helpful not only from scientific viewpoints but also in terms of the blend industry applications.