Cellulose fiber network

In the following section, a new bulk conductivity cell is described that significantly reduces the contact resistance to a level where the measurements of paper bulk conductivity can be made with an accuracy that is limited primarily by the anisotropic structure of the paper itself. A small uncertainty in the measured conductivity arises from compaction ( 10%) of the paper sample in the apparatus caused by the application of 13-8 MPa pressure to the stainless steel electrode system in the cell. This pressure is used to eliminate contact resistance. Despite this uncertainty, measurement errors in the new cell are significantly less than the spread in the conductivity values ( 200)t) determined at different points in a single paper sheet. The variability arises from inhomogeneities in the cellulose fiber network within the sheet. 

Shown in Figure 8 is a plot of conductivity as a function of the pressure applied to the paper samples. In the low-pressure range, up to approximately 5000 psi (3 1.5 MPa), the paper conductivity appears to increase linearly. Above 5000 psi (3 1.5 MPa), there is a distinct increase in the bulk conductivity, followed by another linear region which has a much steeper slope than the dependence found in the low-pressure region. A precise measurement of the paper thickness as a function of pressure 16) showed that the paper sample starts with a thickness of 70 fia prior to the application of pressure and then decreases in thickness to 50 jun at 15,000 psi (103 MPa) in an essentially linear manner. The change in conductivity shown in Fig. 8 is most probably associated with the compression of the cellulose fiber network in the paper. 

The speed of mobile phase development of paper depends upon the density and strength of the cellulose fiber network. Rapid flow rates due to a looser fiber network are achieved on Whatman 4 and 31ET and on S and S 2043A. Whatman... 

Advances in Liquid Repellent Cellulose Fiber Networks... 

I. S. Bayer, D. Fragouli, A. Attanasio, B.Sorce, G. Bertoni, R. Brescia, R.Di Corato, T. Pellegrino, M. Kalyva, S.Sabella, P. P. Pompa, R. Cingolani, and A. Athanassiou, Water-repellent cellulose fiber networks with multifunctional properties ACS Appl. Mater. Interfaces 3,4024-4031 (2011). 

As Figure 25 8 shows the glucose units of cellulose are turned with respect to each other The overall shape of the chain however is close to linear Consequently neigh boring chains can pack together m bundles where networks of hydrogen bonds stabilize the structure and impart strength to cellulose fibers... 

In Section III, it was mentioned that cell wall is a complex structure formed by different polysaccharides connected to glycoproteins. Hydroxy-L-proline-rich glycoproteins, such as extensin, have been found in almost all plants surveyed, and in some algae.203,281 A network of protein, pectic polymers, and xyloglucan, serving to cross-link the cellulose fibers of the cell wall, has been proposed.282,283 However, covalent links between the different components have not been demonstrated moreover, some of them can be extracted separately,284 and some associations may be artificial.285 Nevertheless, results are consistent with interactions through dipole-dipole (such as hydrogen bonds) or hydrophobic bonds. 

The elastomers exhibited rubber-like behavior. From an examination of electron photomicrographs of cross sections of the elastomers, the fibrillar structure of the cellulose fibers apparently formed a network, and poly (ethyl acrylate) was distributed uniformly among the fibrils. The rigid crystalline regions of the cellulose fibers apparently stabilized the amorphous, grafted poly (ethyl acrylate) to determine the mechanical properties of the elastomers (43, 44). For example, typical elastic recovery properties for these elastomers are shown in Table X. 

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