Compatibilizers support high-value recycling of mixed polymers
A new series of DuPont Entira EP compatibilizers is designed for the valueadding recycling of difficult to separate mixtures of polymers. First grades have now become available in the market. These are optimized for the converting of PP-PE-mixtures, providing easy-to-process re-granulates with significantly improved low temperature toughness.
Compounding of reground mixed polymers together with Entira EP in an efficiently mixing twin-screw extruder or in a single screw extruder with good mixing performance provides re-granulates in pellet form with excellent mechanical and processing properties, meeting high demands even with high degrees of contamination.
The re-compounding process itself is more economical, because using Entira EP significantly reduces the need for melt filter cleaning operations. Depending on the selected compatibilizer formulation, the re-compounded materials can reach almost the same level of low temperature toughness as the major blend fraction.
Due to their excellent processing properties, the regranulates are highly suitable for injection moulding, extrusion or blow-moulding. Typical applications include their use as blending partner in new materials or as core layer surrounded by new product. Under certain conditions they can even be processed directly.
– As plastic processors increasingly recycle plastic waste in-house, the amount of singlecomponent and therefore easy-to-process material available to the recycling industry is going down, comments Michel Decodts, Market Segment Leader at DuPont.
– At the same time, incompatible plastic mixtures have become more readily available. These have to be segregated at relatively high cost and therefore make it more difficult to achieve specified recycling rates. Entira EP compatibilizers now offer manufacturers of re-compounds cost-efficient new opportunities, as they significantly boost the range of ready-to-use raw materials for high-performance applications.
Typical sources for mixed PP-PE waste streams include packaging applications, such as screw-caps made of PP and fitted with sealing inserts made of foamed PE. Products resulting from mixing and jointly processing such incompatible plastics in an extruder will always consist of a continuous phase (the matrix), created by the higher fraction material, and inclusions of the other component dispersed in this matrix. Adhesion between the matrix and the inclusions is poor, cracks may easily propagate along their interfaces, and mechanical properties are therefore on a very low level.
The new PE-PP-specific Entira EP formulations are ethylene-copolymers, exhibiting high compatibility – and hence adhesion – to either one or to both polyolefins. Even at low concentrations of around 4%, these new compatibilizers act highly efficient, promoting a firm bond between matrix and dispersed material. Best results will derive from an advanced formulation