[OPEN ACCESS] Hard and transparent films formed by nanocellulose-TiO2 nanoparticle hybrids

http://dx.doi.org/10.1371/journal.pone.0045828

PLoS ONE 2012, 7, e45828

Christina Schütz, Jordi Sort, Zoltán Bacsik, Vitaliy Oliynyk, Eva Pellicer, Andreas Fall, Lars Wågberg, Lars Berglund, Lennart Bergström, German Salazar-Alvarez

DOI: 10.1371/journal.pone.0045828

Abstract

The formation of hybrids of nanofibrillated cellulose and titania nanoparticles in aqueous media has been studied. Their transparency and mechanical behavior have been assessed by spectrophotometry and nanoindentation. The results show that limiting the titania nanoparticle concentration below 16 vol% yields a homogeneous hybrids with a very high Young’s modulus and hardness, of up to 44 GPa and 3.4 GPa, respectively, and an optical transmittance above 80 %. Electron microscopy shows that higher nanoparticle contents result in agglomeration and an inhomogeneous hybrid nanostructure with a concomitant reduction of hardness and optical transmittance. Infrared spectroscopy suggests that the nanostructure of the hybrids is controlled by electrostatic adsorption of the titania nanoparticles on the negatively charged nanocellulose surfaces.

High strength, flexible and transparent nanocellulose/vermiculite biohybrid films with tunable oxygen and water vapor permeability

http://pubs.rsc.org/en/content/articlelanding/2012/NR/C2NR31726E

Nanoscale, 2012, Accepted Manuscript
DOI: 10.1039/C2NR31726E

Christian Aulin , German Salazar-Alvarez and Tom Lindström

Abstract

A novel, technically benign procedure to combine vermiculite nanoplatelets with nanocellulose fibre dispersions into functional biohybrid films is presented. Nanocellulose fibres of 20 nm diameters and several µm in length are mixed with high aspect ratio exfoliated vermiculite nanoplatelets through high-pressure homogenization. The resulting hybrid films obtained after solvent evaporation are stiff (tensile modulus of 17.3 GPa), strong (strength up to 257 MPa), and transparent. Scanning electron microscopy (SEM) shows that the hybrid films consist of stratified nacre-like layers with a homogenous distribution of nanoplatelets within the nanocellulose matrix. The oxygen barrier properties of the biohybrid films outperform commercial packaging materials and pure nanocellulose films showing an oxygen permeability of 0.07 cm3·μm/m2·day·kPa at 50 % relative humidity. The oxygen permeability of the hybrid films can be tuned by adjusting the composition of the films. Furthermore, the water vapor barrier properties of the biohybrid films were also significantly improved by the addition of nanoclay. The unique combination of excellent oxygen barrier behavior and optical transparency suggest the potential of this biohybrid materials as an alternative in flexible packaging of oxygen sensitive devices like thin-film transistors or organic light-emitting diode displays, gas storage applications and as barrier coatings/laminations in large volume packaging applications.