Resistance-to-flow analysis in low density polyethylene/plasticized starch blends containing compatibilizers with attractive and repulsive interactions

Processing of polymer blends is mainly controlled by the behaviour of their components, interfacial area and strength. Therefore, many experimental and theoretical investigations have been devoted to elucidating their basic governing principles. Nonetheless, there are only limited data in the literature about the effect of compatibilizers on the rheological properties of blends. The resistance-to-flow of low density polyethylene/plasticized starch blend and their compatibilized versions with poly(ethylene-r-vinyl acetate), maleated poly(styrene-ethylene-butadiene-styrene) and maleated polyethylene was investigated with a capillary rheometer at different temperatures. Furthermore, the melt elasticity enhancement of the aforementioned alloys was compared with their non-compatibilized polyethylene/thermoplastic starch blend via rheomechanical spectroscopy at 190 degrees C and 500 Hz as an index of their interfacial strength. The results showed that by lowering the temperature of the melt alloys, the compatibilizer was directed toward interfacial localization and led to concomitant elasticity enhancement in comparison with their virgin blends. In addition, the resistance-to-flow of the blend and their alloys through capillary rheometer were enhanced and distinctively differentiated. This was attributed to the blend positive X parameter which pushes compatibilizers localization at the interface with different adsorption densities and conformational resistance against flow of the system. In other words, a quasi core/shell structure formation at the dispersed phase/matrix interface was proposed as the origin of resistive capillary flow, leading to a viscoelastic loss enhancement. In analogy with Gent-Schultz equation governing the joint adhesion energy of polymers, the energy loss during capillary flow of a multicomponent blend was correlated for the first time to their interfacial strength. Interestingly, the calculated energy loss for the investigated melt blend and its compatibilized alloys in capillary flow was proportional to the solid state deformation loss during peeling of a corresponding joint interfaces reported by our group.