Separators puncture resistance

Even though separation may not be the primary function for which the geotextde is instaded, in almost every case the geotextde does perform as a separator. For the separation function, the physical properties of concern are primarily strength-related, including wide width, puncture resistance, and tear resistance. 

The PE separators have excellent microporous structure for electrolyte flow with minimal lead particle deposits excellent ductility, strength, and toughness for envelopability and plate puncture resistance excellent oxidation, chemical and thermal resistance to resist premature deterioration and good manufacturability with high production efficiency and relatively low raw material cost, which reduces overall manufacturing costs. The PE pocket sepa-... 

On the other hand. AGM separators offer little control over the oxygen transport rate or the recombination process. The arrival of too much oxygen to the negative plate could result in overheating, hindrance of the battery s ability to recharge, or even a loss of capacity. Furthermore. AGM separators exhibit low puncture resistance. 

The Li-Ion cells used in consumer applications use thin microporous separators (< 25 pm). The separators being developed for EV/HEV appUcations will require thicker ( 40 pm) separators. The thicker the separator, the greater the mechanical strength and the lower the probability of punctures during cell assembly, but the smaller the amount of active materials that can be placed in the can. The thinner separators take up less space and permit the use of longer electrodes. This increased both capacity and, by increasing the interfacial area, rate capability. The thinness also makes it a low-resistance separator. 

The addition of rubber to polypropylene can lead to improvements in impact resistance. One of the most commonly added elastomers is ethylene-propylene rubber. The elastomer is blended with polypropylene, forming a separate elastomer phase. Rubber can be added in excess of 50 percent to give elastomeric compositions. Compounds with less than 50 percent added rubber are of considerable interest as modified thermoplastics. Impact grades of PP can be formed into films with good puncture resistance. 

The force required to create a short through a separator due to mix (electrode material) penetration defines mix penetration strength. In this test, force (with a Vi.-inch diameter ball) is applied on the positive electrode/separator/negative electrode sandwich and the force at which the mix penetrates through the separator and creates an electronic short is called mix penetration force. Mix penetration strength is used to indicate the tendency of separators to allow short circuits during battery assembly. The mix penetration resistance test is more closely related to particle penetration resistance compared to puncture resistance [45]. 

When the aggregate layer is subjected to loads, significant local stresses are created in the separator. The separator must therefore be of sufficient strength to withstand these stresses. The bursting strength, localised tensile strength properties, and puncture resistance are of specific importance to the separation function. 

Depending on the methods of assembly, a certain minimum level of puncture resistance is required in the separator otherwise, the electronic shorts are likely to decrease. To improve puncture resistance, the polymer concentration can be inaeased at the expense of silica. Also, work will continue to optimize the ribbing designs to prevent the potential of plate snagging, especially when performing side alignment of the elements. Increasing the polymer content will also serve to increase the oxidation resistance of the separator. 

Design the geotextile as a separator. This frmction is always required. The survivability design steps just described have direct applicability here. Burst strength, tensile strength, puncture resistance, and impact resistance all have significance in this particular application. 

Nonwoven geotextiles are produced mechanically or chemically, or by heat-bonding fibers together to form a stable network. Nonwoven geotextiles have higher flexibility and movement than do woven geotextiles. Because of this, they are ideal for use in separation applications where the earthen base may have irregularities to which the nonwoven can mold. The thickness and puncture resistance of a... 

Buoyancy. The low density, closed-ceUed nature of many ceUular polymers coupled with their moisture resistance and low cost resulted in their immediate acceptance for buoyancy in boats and floating stmctures such as docks and buoys. Since each ceU in the foam is a separate flotation member, these materials caimot be destroyed by a single puncture. 

The moisture resistance, low cost, and low-density closed-cell structure of many cellular polymers resulted in their acceptance for buoyancy in boats, floating docks, and buoys. Because each cell is a separate flotation unit, these materials cannot be destroyed by a single puncture. Foamed-in-place polyurethane between thin skins of high tensile strength is used in pleasure craft [98]. Other cellular polymers that have been used where buoyancy is needed are produced from polystyrene, polyethylene, poly(vinyl chloride), and certain types of rubber. Foams made from styrene-acrylonitrile copolymers are resistant to petroleum products [99,100]. 

Recently Nitto Denko developed a battery separator made by a wet process that had high puncture strength and high heat rupture resistance. They used a polyolefin resin with a high-molecular-weight rubber as its main component materials and cross-linked through oxidation in air. The melt rupture temperature, as measured by thermomechanical analysis, was over 200°C in this material. They also tried cross-linking UHMWPE with electron-beam and ultraviolet irradiation, but this had the... 

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