Cellulose fibers friction forces

Separator structures fall into four main categories microporous films, nonwovens, gel polymers, and solid polymers. Microporous films contain small pores (5 to 10 nm in diameter) and are often used for low temperature applications. They are made from nonwoven fibers such as cotton, polyester, glass, polyolefins (PP and PE), PTFE, and PVC. Microporous separators are commonly used with organic electrolytes and in acidic systems. Nonwovens are manufactured as mats of fibers and bind through frictional forces. They exhibit consistent weight, thickness, and degradation resistance but they show inadequate pore order and are difficult to make thinner than 25 pm. Nonwovens are generally made from cellulose, PTFE, PVC, PVdF, or a combination of polyolefins and receive preference in alkaline systems [114]. 

Contacts between Cellulose Fibers The Evaluation of Friction Forces and Contact Strength The Effect of Common Papermakinc Chemicals... 

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 2.24 The molecular component of the shear friction force between cellulosic fibers in water as a function of the PEI concentration. (Redrawn from Amelina, E.A. et al., Kolloidnyi Zh., 63, 132, 2001.)... 

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