Enhanced Polyolefin Thin Film Properties with Polyolefin Grafted Cellulose Nanocrystals

Only 2% of plastic films and flexible packaging are recycled, presenting a significant challenge in sustainable waste management. A notable obstacle lies in the recycling of multilayer films, wherein each layer possesses distinct compositions and functionalities. Synergistic integration of high-strength nanomaterials into high-strength semi-crystalline polyolefins is a potential strategy to enhance nanomechanical and barrier thin film properties, reducing requisite layers in multilayer films, facilitating their recyclability. Cellulose nanocrystals (CNCs) represent a class of biobased nanoparticles that have the potential to confer such desirable properties to polyolefin films by virtue of their high aspect ratio (anisotropy) as well as surface chemistry suitable for functional modification. However, the integration of CNCs into non-polar polyolefins poses a significant challenge due to their unfavorable surface energies. This study addresses this by employing a grafting-to approach to attach polypropylene (PP) chains onto CNCs to improve their dispersion in a PP matrix. Adding grafted CNCs to PP thin films greatly enhanced the film’s Youngs bending modulus by as much as 760 % increase in ultrathin 16 nm films, which was attributed to increased nucleation by CNCs and their in-plane confinement.Additionally, the influence of undercooling on PP crystallization was noted to be significant. We conclude that PP grafted CNCs have significant potential for enabling polyolefin circularity.