Cellulose temperature coefficient

Table I. Measured and Computed Room Temperature Characteristic Ratio and Temperature Coefficients for Cellulosic and Amylosic Chains...

Another similarity between amylose and cellulose is to be found in the variation of the limiting viscosity number with temperature. Cellulose derivatives are unique in having a large, negative, temperature dependence of viscosity. For amylose in dimethyl sulfoxide, it has been shown that the temperature coefficient of viscosity is again negative, although... 

When rubber swelled in benzene (49), or when paraffin (50 was absorbed by cured rubber and by rubber gum, the positive temperature coefficients of the sorption velocity suggested that in these and other organic solids vapours are sorbed by processes of activated diffusion. The occurrence of activated diffusion has already been established for gas-rubber (52), cellulose, -bakelite and similar systems (Chap. IX). In liquids also, diffusion constants (53) may be expressed by the equation D = although the values of E are usually smaller. 

The precipitation data for cellulose from diluted solutions of cadoxen have shown that the precipitation process has a positive temperature coefficient. The kinetics observed fitted a unidimensional nucleation rate law. The low crystallinity of the product suggests that dissociation of the cellulose-cadoxen complex rather than phase separation occurs. 

Solubility normally increases with rising temperature. However, negative temperature coefficients in some solvents are observed. This is particularly true for cellulose and poly(ethylene oxide)s. 

In this equation the temperature dependence of the persistence length is incorporated in the parameter n. The equation is used to calculate the best fit of the full lines in Fig. 16.29. We found for the parameters n the values PIPD n = 0.6 PPpPTA n = 1.2 PABI n = 1.2 and cellulose n = 5.6 (correlation coefficients 0.988-0.997). It shows that cellulose is indeed a relatively flexible polymer, whereas the other three polymers show rigid-rod behaviour, in particular PIPD. 

Lewin and coworkers [255-260] developed an accessibility system based on equilibrium sorption of bromine, from its water solution at pH below 2 and at room temperature, on the glycosidic oxygens of the cellulose. The size of the bromine molecule, its simple structure, hydrophobicity, nonswelling, and very slow reactivity with cellulose in acidic solutions, contribute to the accuracy and reproducibility of the data obtained. The cellulose (10 g/1) is suspended in aqueous bromine solutions of 0.01-0.02 mol/1 for 1-3 h, depending on the nature of the cellulose, to reach sorption equilibrium. The diffusion coefficients of bromine in cotton and rayon are 4.6 and 0.37 x 10 cm /min, respectively. The sorption was found to strictly obey the Langmuir isotherm, which enables the calculation of the accessibility of the cellulose as follows ... 

Xylan from birchwood decomposes over a broader temperature range than cellulose and the shape of the TGA curves suggests a mechanism with more than one reaction step. Consequently, one step formal models are not very successful. Applying multivariate regression, the best fit for this case is achieved with a single reaction of n order with the kinetic parameters logio (Ws ) = 19 63, Ea = 220.8 kJ/mol and n = 5.45. A correlation coefficient of 0,99423 and a mean of residues of 0.06806 were calculated for this fit. 

The model is one-dimensional over a spherical, dry cellulose panicle. The particle is supposed to expose to an inert, high-temperature environment of a fluidized-bed subject to an intense heating immediately. A typical constant overall heat transfer coefficient is adopted. 

FIG. 87. Rate of burning ( coefficient of vivacity, dp/dr ,x) of Ammon-pulver against the temperature of carbonization of cellulose, according to... 

These results indicate that conduction alone would not be sufficient to assure uniform temperatures within the 100 ym diameter Avicel cellulose particles for the high flux experiments. However, cellulose is not perfectly opaque, and it seems likely that entry of radiation into the body of the particle would tend to establish uniform temperatures. Clearly, the extinction coefficient of various biomass materials should be measured to provide for a more quantitative investigation of this phenomenon. 

I he simplest is the partition of a solute between two immiscible solvents. In this case [0] /[Z)], = K, where K is the partition coefficient. This equilibrium is often referred to as the Nernst distribution. When [Z)], is plotted against [Z)], at constant temperature the curve is a straight line which terminates at the point when both the fibre and the dyebath are saturated. There are slight deviations from the linearity of the curve, particularly as the solutions become more concentrated. This system is probably exhibited in its ideal form when dyeing cellulose acetate rayon from an alcoholic dye solution, but it is also essentially true in the case of the application of disperse dyes in aqueous suspension to cellulose acetate, because the dyes are all soluble in water to a very limited extent and the undissolved particles act as a reservoir to maintain the concentration of the solution. The curve for this isotherm is shown in Fig. 12.14. 

Bonds with plastics, 142 Calcium carbonate in, 112, 141 Cellulose in, 112 Chemical composition, 112 Cost of, 112 Granules, 141 Ingredients, 141 Kaolin clay in, 112 Mold shrinkage, effect on, 142 Oil absorption, 141 Porosity, 141 Shape of particles, 142 Speciflc gravity, 142 Tensile modulus, effect on, 142, 143 Thermal expansion-contraction coefficient, 142 Biodegradable plastics, 79 Biodegradable wood-plastic composites, 91 Bioresistance, 42 Biotite, 146 Black Algae, 426 Black mold, 29, 31, 424, 429 Black panel temperature, 41, 132 Black panel thermometer, 612 Black panel, 41, 132 Bleached cellulose, 11, 14, 180 Cost, 14... 

Another industrial application of gas-separation membranes is the removal of carbon dioxide from natural gas. The CO2/CH4, selectivity is about 20 to 30 for polycarbonate, polysulfone, and cellulose acetate membranes at 35°C and 40 atm. A selectivity of over 60 can be obtained with Kapton , but this polymer is much less permeable than the others. Increasing the temperature raises the permeability of most polymers but generally causes a. slight decrease in selectivity. The operating temperature is chosen to be somewhat above the dew point of the residue gas. There is considerable COj absorbed in the membranes at high CO2 partial pressures, and the plasticization effect of CO2 increases the effective diffusion coefficients for all gases and makes the selectivity less than that based on pure-gas data. Methods of allowing for such nonlinear effects have been presented. ... 

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