Enhancing Polyolefin Recycling with Cellulose Nanocrystals

Recycling and reuse of polyolefin waste are limited due to loss of properties after recycling and complicated by the presence of differing polymers which are not compatible and differing microstructures (e.g., high- and low-density polyethylenes or varying types of polypropylenes). Hence, upcycling of polyolefin waste to engender new properties that are retained during multiple recycling cycles is a major challenge and interest. Here, cellulose nanocrystals (CNCs), nanoparticles derived from cellulose, were functionalized and investigated as compatibilizers for immiscible polyethylene and polypropylene blends. CNCs were functionalized in the melt with grafted polypropylene chains and the polymer functionalization and grafting density were quantified with chemical and thermogravimetric analyses. Preliminary morphology characterization showed droplet size reduction with the addition of functionalized CNCs to the polyethylene/polypropylene blend. Nanoparticle compatibilization mechanisms are currently under exploration, such as droplet coalescence suppression and interfacial tension reduction.