Fabrication and Properties of Polyethylene/Cellulose Nanocrystal Composites

The preparation of nanocomposites of low-density polyethylene (LDPE) and cellulose nanocrystals (CNCs) isolated from cotton or produced in situ by the dispersion of microcrystalline cellulose (MCC) is reported. The hydrophobic matrix polymer and the rather polar filler particles appear to be difficult to mix, but it is shown here that composites with significantly improved mechanical characteristics and of homogeneous appearance can be produced using an organic-solvent-free two-step process. This is achieved by first mixing an aqueous slurry of an LDPE powder with an average particle size of <600 mu m with aqueous suspensions of CNCs or MCC and removing most, but not all, of the water. Compounding such water-plasticized mixtures in a roller-blade mixer and subsequent compression-molding afford highly transparent films, whose room-temperature storage modulus is increased by a factor of 2.5 upon incorporation of 15% w/w CNCs or MCC. The results demonstrate that LDPE/nanocellulose composites with improved mechanical properties can be produced by an organic solvent-free process that appears to be scalable to industrial production scale.