Cellulose-Based Anisotropic Composites
In an attempt to improve the mechanical properties of an all-cellulose based composite we made solid flexible films containing microcrystalline cellulose fibres produced by a shearing casting technique. To an anisotropic (liquid crystalline) solution of 2-hydroxypropylcellulose (HPC) in N,N – dimethylacetamide (60 w/w %) were added AVICEL fibres (0, 2, 4, 6, 10, 12 w/wHPC %). After homogenization these solutions were poured into a Teflon plate and sheared at a constant rate of 5 mm/s. The cellulosic microfibres in the liquid crystalline polymer medium were partially aligned by shear flow. Mechanical and morphological properties of the films were investigated using tensile tests, polarized optical microscopy and scanning electron microscopy. The mechanical properties of these films, as expected, are higher than those of the films produced from an isotropic solution of HPC. The results show that the orientation of the microfibres, and the mesoscopic properties, can be tuned by adjusting the topography of the nematic matrix in the micro-nano scale.
António Torres Marques, António Fernando Silva, António Paulo Monteiro Baptista, Carlos Sá, Fernando Jorge Lino Alves, Luís Filipe Malheiros and Manuel Vieira
J. P. Borges and M.H. Godinho, "Cellulose-Based Anisotropic Composites", Materials Science Forum, Vols. 587-588, pp. 604-607, 2008