To improve their strength, toughness, and other mechanical properties, we have reinforced polyolefins using polyethylene-grafted cellulose nanocrystals. As the most widely used plastics, polyolefins such as polyethylene and polypropylene are extremely diverse. Various structures and molecular weights span a large range of mechanical properties. In order to reinforce polyolefins with a versatile and sustainably-sourced material, we have synthesized polyethylene-grafted cellulose nanocrystals. CNCs are rod-like particles with excellent stiffness and strength, and previously proven potential to reinforce polymers. Asymmetric nanoparticles with high aspect ratio have significant potential for mechanical reinforcement, as demonstrated by clay-platelet dispersed nanocomposites in literature. Prior literature studies using CNCs were mainly conducted with water-soluble polymers, as the polar cellulose can be dispersed in water relatively easily. For their dispersion in nonpolar polyolefin systems, we have modified the CNC surface energy by grafting functionalized polyethylene to the hydroxyl groups on the CNC surface. With surface energy similar to that of polyethylene, these polymer-grafted nanoparticles can be more easily dispersed in polyethylene and similar nonpolar systems. The dispersion of polyethylene-grafted CNCs in polyethylene films was confirmed with atomic force microscopy and X-ray scattering. AFM studies revealed the details of CNC structure, dispersion and crystallization aspects of the functionalized polyethylene, results that will be discussed in more detail. Mechanical reinforcement of the films through addition of polyethylene-grafted CNCs was quantified through tensile testing. Ultimately, we will systematically examine the correlation between the molecular parameters of the asymmetric nanoparticles and polyolefins, and the associated macroscopic properties that emerge in such systems.

Reinforcement of polyolefins with polymer-grafted cellulose nanocrystals

ACS Spring Meeting 2021

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