Structure compression/resiliency

The contrasting structure of the plates and the separators is also relevant to the functioning of the battery. For example, the capillary pressures dictate that electrolyte fills the plates preferentially. This preferential filling appears to be the ideal situation since it can best support the electrochemical reaction, i.e., it leaves the separator partially saturated so that movement of electrolyte can provide pathways for gas transport. If, however, the overall saturation is too low or there is excessive loss of water, the separator will dry out and give rise to an increase in the internal resistance of the battery and the possibility of thermal runaway. An increase in internal resistance, and consequent low service-life, can also result if the compression between separators and battery plates relaxes over a period of time. Overcompression may cause fibres to fracture with a loss of resilience, i.e., the separators lose the ability to return to original thickness after a high pressure is applied and... 

The resrilting foam is conditioned at 60% R.H. at 20 C for one week. Mechanical tests, i.e. compressive testing and resilience testing, are performed according to the method described by Tatarka and Cutuiingham. The foam density was calculated by sand replacernent volumetric measurement. The cell structure was analyzed by Scanning Electron Microscopy. 

Mechanical testing on the foam is performed to measure the compressive stress and the resiliency. The results from diese tests are shown in table 2, in which the properties of extruded polystyrene foam (XPS) and commercial starch-based loose-frll foams (Eco-foam and Mater-Bi) together with EPS loose-fill foam (Pelaspan Pac) are added for conq>arison. The values of XPS are obtained from tests on typical XPS retail packaging trays. The table shows that the compressive stress reached with potato starch foam is comparable with that of XPS. Through the cell structure of the potato starch foam (high cell density, very small cells) a good resiliency can be obtained, although pure starch plastics exhibit brittle fracture behavior. This brittle fracture still is present on the microscopic scale of the individual cells but due to the cell density, the foam exhibits resiliency on macroscopic scale. 

As it can be seen, the structural layer coefficients for the granular base or sub-base layers may be derived from different laboratory tests including resilient modulus (Egg or sb)-Similarly, the structural layer coefficients for the cement-treated bases or bituminous-treated bases may be derived from unconfined compressive strength or Marshall stability, respectively, including elastic modulus. 

Flexible polyurethane foams are open-cell structures which are usually produced with densities in the range 1.5—3 Ib/ft The major interest in flexible foams is for upholstery applications and thus the load-compression characteristics are of importance. Typical load-deflection curves for polyether and polyester foams are shown in Figure 14.2. The most obvious difference between polyether and polyester foams is the lower resilience of the polyester materials. This feature has led to a preference for polyether foams in cushioning applications. Compared to polyether foams, polyester foams have higher tensile strength, elongation at break and hardness consequently polyester foams are preferred in such applications as textile laminates and coat shoulder pads. 

With regard to flooded lead-acid battery separators, the normal materials of construction are relatively noncompressible and they fix the electrode distance, providing a degree of compression on the electrodes, at least where the ribs contact the plate surface. In flooded designs, separators with a laminate layer are regularly utilized to provide more support of the active material that is likely to shed during deep discharge. Because the laminate thickness is normally a small portion, say, 10% to 20%, of the total structure thickness, the amount of compression or resiliency is minimized. 

Javni et al. (2011) studied the possibility of replacing polyol copolymers used in the preparation of flexible PU foams by the incorporation of unmodified and modified montmorillonites. While the addition of the unmodified MMT increased hardness, compression strength, and resilience of the foams, the incorporation of the organically modified MMT resulted in foams with lower modulus, hardness, and compression strength values, a direct result of the higher open-cell contents and poorer cellular structure of the resulting foams, apparently leading to the conclusion that in this specific case the addition of modified MMT led to a counterproductive result. 

In comparison to cotton, wool or silk, the poultry feather biomass is not a lot used relating to the complex the structure of the feathers. However, the secondary and the tertiary structures of the feathers, i.e. the barbs and the barbules have the morphology and properties that make them suitable for use as reinforcement or filler in composites for several applications [1,2]. Because of a very low density, excellent compressibility and resiliency, warmth retention and typical morphology, poultry feather barbs and barbules are preferable in comparison to other natural and synthetic fibers. In addition, poultry feather fibers are cheap, abundantly available and constitute a renewable source for animal fibers. The density of poultry feather is about 0.8 g/cc compared to about 1.3 g/cc for wool and about 1.5 g/cc for cellulose fiber [1-3]. 

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