Cellulose fibers resulting measurements

Corrections of the apparent crystallinity values of fibers materials have been carried out by taking into account a disorder parameter k, following Ruland s method. Peculiar care was taken about samples preparation (cutting and pelleting of fibers), data collection and reduction, which will be briefly described. Crystallinity and disorder parameter measurements have been performed on main textile fibers (polyester, polyamide, aramid, polypropylene, cellulosic fibers) and the results will be discussed comparatively, with those got by more conventional x-ray crystallinity determinations. The complementarities of these different approaches will be illustrated with several examples. For instance,... 

More recentfy Mohlin and Gray (9J) determined adsorption isotherms on cellulose fibers for a variety of adsorbates (solutes). From the experimental type II isotherms specific surface areas of the fibers were computed, for eadi solute, with the results en in Table 11. The agreement observed between the different solutes is quite remarkable considering that the area of the solute molecule on the potymer surface must be known or estimated. Hie sirface area determined by nitrogen adsorption measurements at —196° was included for the purpose of comparison. The sli t di arity could possibly indicate that the area available to the smaller nitrogen molecule may be somewhat larger (1.9 compared to 1.6 m g" ). 

Table III shows the results of the resolution of all carbon and oxygen species on the 13 samples studied. Values in the table are based on the overall atomic concentration of the two elements in the sample ratioed to the fractional area contribution of each component to the region. The expected error in the resolution result is anticipated to be less than 10% of the value of each species. Continued fitting of the data did not yield a significantly better result. Based on the Auger parameter listed in Table IV for all the samples, Wagner s measurement of the Auger parameter for cellulose,(13) and Gray s work on cellulose fibers,(6, 7, 8) it is possible to assign the prime constituent of all the samples as being anhydroglucose (cellulose or starch).

The measured normalized wetting rates for various test liquids (for cellulose fibers Fig. 23) ean be transformed into the cosine of the contact angle (cos0) and plotted as a function of the liquid surface tension (Fig. 24). The resulting linear relationship cos 0=1 b(yi — yc) was established empirically by Zisman and Fox [120] and found to hold for solid with low surface tensions. The eritical surface tension yc corresponds to the surface tension of the liquid that will just spread over/wet eompletely the soUd. The constant C reflects the eapillary geometry of the porous solid and may change in a non-predictable manner during the penetration proeess of different test liquids. It was concluded from the experiments performed [112] that there is no need to determine the constant C in order to obtain solid-surface tensions, because the position of the maximum in the C yiv cos 6 vs. yiv plot, which is expected to... 

The results of the contact force measurements, p, between cellulosic fibers in the presence of PEI are shown in Figure 2.23. The observed trends are similar to those shown in Figure 2.21 for the friction coefficient measurements and are also in good agreanent with the patch model of flocculation by the PEI, and the previously mentioned electrokinetic studies, as reflected by the maximum in the cohesive force at low concentrations of PEI. As expected, after reaching the maximum, the cohesive forces decrease with a further increase in the PEI concentration. This corresponds to the decrease in the fraction of available negatively charged patches for interaction with PEI and the increase in the electrostatic repulsion due to a continued adsorption of PEI. 

FIGURE 2.26 Cohesive force measured in the contact between two bleached cellulose fibers in a solution of papermaking cationic polyacrylamide. The effect of sequential rupturing and reformation of contacts between the same fibers is shown. (Zelenev, A.S. and Shchukin, E.D., unpublished results.)... 

The aim of this work has been to show that the phase partition technique has great potentials for characterizing cellulosic fibers. The results above clearly show that the method gives a good measure of... 

The properties of cellulosic graft copolymers have been studied to a considerable extent but mainly in the form of grafted fibers or films of ill-defined composition. However, a few properties have been measured on well defined grafts (147). It was found that solutions of cellulose acetate-polystyrene grafts in dimethyl formamide are less tolerant to the addition of polystyrene than cellulose acetate itself. This result was attributed to the greater coil expansion in the case of the graft copolymer. On the other hand, the tolerance of the grafts to each homo-... 

QF samples contained 15% (w/w) starch and 17% cellulose (Table 1). The total carbohydrate composition was 65%. Protein and oils accounted for 12%. The components measured account for 78% of the dried material, the residual material (not tested for) includes ash, extractables, lignin, and lipids. The composition of the QF was, as expected, similar to that found for corn fiber. Corn fiber and QF are both derived from the pericarp and tip portions of the kernel. Most notably, the QF contained approx the same amount of residual starch, which suggests that the modified milling process is as effective at separating starch from the pericarp as a full steeping protocol. Starch recovery is significantly improved compared to previous results for which the starch content of the QF was 42-46% w/w (2). The current study used an improved process that included an additional starch washing step. 

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