Efficient Compatibilization of iPP and HDPE Blends

Current approaches to plastic recycling are limited in their ability to reconstitute functional components, elements, and materials for use in high-value applications. Although iPP and PE constitute nearly two-thirds of the plastic produced worldwide, efforts to recycle them are challenged by their immiscible properties that lead to low-quality blended products. This has led to the investigation of compatibilizers additives, which can be added to such iPP/PE mixtures to improve their structural integrity for future use. However, existing compatibilizers require high additive loadings (5-10 wt%), resulting in plasticization, which deteriorates the physical properties of produced blends and effectively relegates them to limited or downcycling purposes. To overcome the significant challenges associated with recycling PE and iPP from mixed waste streams, Intermix is developing cost-efficient methods to generate novel tapered block copolymers (TPBs) for the compatibilization of PE and iPP, resulting in blends with desired tensile strength characteristics. Enabling upcycling processes, copolymer blocks will be developed to create structures with well-controlled, enhanced properties. Intermix’s proposed research will be comprised of three objectives: 1) Optimization of tapered block copolymer compatibilization additives, 2) Scale-up of optimized tapered block copolymers, and 3) Testing of larger-scale batches for end polymer qualities. Intermix’s non-reactive compatibilization approach allows for PE and iPP to be recycled together via simple melt blending. The adjustability of these components’ molecular weights and architectures support the precise manipulation of mixed plastic waste streams to develop robust blended plastics with distinct properties, facilitating application to a broad range of PE/iPP recycling applications, as well as the development of new blends with properties rivaling those of virgin plastics. Intermix’s approach will allow PE and iPP polyolefins to be efficiently compatibilized, forming recycled polymers with mechanically desirable properties (e.g., tensile toughness, impact strength), at low additive loadings (~1 wt%). Because the recycled PE/iPP polymers will exhibit greater structural durability, ductility, and industrial utility, incorporating these TPBs will open the door for these plastics to be up- rather than down-cycled, enabling extreme cost-efficiency in the recycling industry and supporting higher recycling rates overall. The ability of this technology to not only improve the mechanical properties of PE/iPP blended polymers but do so at significantly lower additive loadings is an overwhelming advantage over existing compatibilizers. By facilitating cost-efficient production of mechanically valuable blended plastics, continued development of this innovative technology will support increased recycling rates and, in concert, advance efforts toward a more sustainable, circular economy.