Accelerating the Coupling of Maleated Polyolefins with Polyesters via Tin Compounds

Novel sustainable materials from waste plastics: compatibilized blend from discarded bale wrap and plastic bottles

This work studies a novel sustainable polymeric material made from a reactive blend of two agri-food waste plastics, with the new material showing strong promise for value-added industrial uses. Discarded bale wrap destined for landfill that was originally made from linear low density polyethylene (LLDPE) and used polyethylene terephthalate (PET)-based plastic bottles were melt mixed in a twin-screw extruder. The miscibility of such recycled LLDPE (rLLDPE) in recycled PET (rPET) is enhanced by the incorporation of a compatibilizer and the PET molecular architecture is maintained using a chain extender, which governs its melt strength. Microscopic analysis of the blends with the compatibilizer and chain extender confirms the enhanced interaction of rPET and rLLDPE chains and the formation of co-continuous morphologies. The efficient interaction of a soft phase (rLLDPE) with a hard phase (rPET) leads to prolonged fracture propagation by an appropriate impact energy transfer mechanism, which ultimately enhances the impact resistance and elongation at break of the resulting blend. The incorporation of a compatibilizer and chain extender in the rPET/rLLDPE blend makes it a toughened blend (with 60 J m⁻¹ notched Izod impact strength) with ∼80% elongation at break in comparison to ∼3% for the blend without a compatibilizer or chain extender. Around ∼36% enhancement is observed in the tensile strength without affecting the tensile and flexural modulus in comparison to the blend without a compatibilizer or chain extender. Applications of the developed materials can extend from rigid packaging applications to the production of filaments for 3D printing.

This work studies a novel sustainable polymeric material made from a reactive blend of two agri-food waste plastics, with the new material showing strong promise for value-added industrial uses.

Multiblock Copolymers for Recycling Polyethylene-Poly(ethylene terephthalate) Mixed Waste

Plastic pollution is one of the most pressing global environmental issues we face today, in part due to the continued rise in production and use of disposable plastic products. Polyolefins and polyesters are two of the most prevalent polymers in the world accounting for ∼80% of total nonfiber plastic production. Recycling, despite being intrinsically environmentally friendly and sometimes economically viable, remains at a surprisingly low level (<9% in the U.S.) with most plastic waste ending up in landfills. One reason for this low rate of recycling stems from the challenge of recycling mixed waste streams and multicomponent plastics. In mixed waste streams, physical presorting of components prior to recycling requires significant effort, which translates to added cost. For multicomponent plastics (e.g., multilayer films such as food wrappers), the individual plastic components cannot be efficiently physically separated, and they are immiscible with poor interfacial adhesion when melt reprocessed. Thus, direct recycling of mixed plastics by melt reprocessing results in products that lack desired end-use properties. In this study, we describe the synthesis of novel poly(ethylene terephthalate)-polyethylene multiblock copolymers (PET-PE MBCPs) and evaluate their utility as adhesive tie layers in multilayer films and compatibilizer additives for melt reprocessed blends. PET and PE are targeted because they are two of the most prevalent commercial polymers in the world and are high volume waste streams. The work described here demonstrates two key findings. First, the PET-PE MBCPs serve as effective adhesive tie layers between neat PET/PE films with adhesive strength comparable to that of commercially available adhesives. Second, PET/PE (80/20 wt %) blends containing ∼0.5 wt % PET-PE MBCP were melt mixed to mimic recycling mixed plastic waste, and they were found to exhibit mechanical properties better than neat PET. Overall, this study demonstrates that PET-PE MBCPs could significantly enhance the ability to recycle PET/PE mixed waste streams by serving the role as both an adhesive promoting layer and a compatibilizer additive.