Flocculation of cellulose fibre suspensions: the contribution of percolation and effective-medium theories- May 28, 2008 Abstract The concept of crowding factor applied to the flocculation of cellulose fibres is revisited through the application of percolation and effective medium theories. It is shown that, even if the crowding factor allows predicting the critical concentration of fibre suspension above which flocculation occurs, and indeed leads to acceptable results in most cases, percolation and effective medium theories are most rigorous and much less empirical. Examples of calculation are...http://www.springerlink.com/content/8235pp75055n4253/ Effects of temperature and molecular weight on dissolution of cellulose in NaOHurea aqueous solution- May 24, 2008 Abstract Dissolution of cellulose having different viscosity-average molecular weight (M ) in 7 wt%NaOH12 wt%urea aqueous solution at temperature from 60 to 12.6C was investigated with optical microscope, viscosity measurements and wide X-ray diffraction (WXRD). The solubility (Sa) of cellulose in NaOHurea aqueous solution strongly depended on the temperature, and molecular weight. Their Sa values increased with a decrease in temperature, and cellulose having M ..http://www.springerlink.com/content/vt72517224p1734g/ Simulation of X-ray diffractograms relevant to the purported polymorphs cellulose IVI and IVII- May 22, 2008 Abstract Diffractograms were simulated for model nanocrystals of cellulose I, using numerical summation of radiation scattered from all carbon and oxygen atoms in the nanocrystal. Diffractogram peaks were sometimes displaced by a few degrees from positions calculated by the Bragg equation, as predicted in a published study based on a different mathematical approach. Simulated diffractograms showed 2 or 3 peaks, depending on the cross-sectional size and shape of the model...http://www.springerlink.com/content/5767222j63x55483/ |