Compatibilization of PE/PS and PE/PP blends. I. Effect of processing conditions and formulation

Abstract

The objective of this work was to study the effectiveness of low-cost commercial compatibilizers and several processes (internal mixer, single- and twin-screw extruders) for two types of plastic blends: high-density poly-ethylene/polypropylene and high-density polyethylene/polystyrene blends, to gain insight into the recycling of wastes from those frequently encountered mixed plastics. Blends going from a pure A to a pure B component, with and without a compatibilizer, were prepared using an internal mixer, a corotating twin-screw extruder, as well as a single-screw extruder to follow an industrial-convenient process. In both cases, the analyses of blend morphologies highlighted the poor adherence between the two phases in the uncompatibilized blends. Compatibilized blends display better adherence between phases and the ability to process blends made from both single- and twin-screw extruders. When adding a compatibilizer, the viscosity of each blend (PE/PP or PE/PS) increased due to a better adhesion of the phases. Charpy impact tests showed that the presence of the compatibilizer in PE/PS blends increased their impact properties. Indeed, the improvement of the adhesion between the two phases enabled stress transfer at the interface. A single-screw extruder seems to be efficient as a processing method on an industrial scale when a compatibilizer is used.