Polyethylene microporous

Polypropylene and polyethylene microporous films obtained by this method are available from Cel-gard48.5o,54,55 Ube. The dry process is technologically convenient because no solvents are required. However, only a uniaxial stretching method has been successful to date, and as a result, the pores are slitlike in shape and the mechanical properties of films are anisotropic. The tensile strength in the lateral direction is relatively low. 

Producing polyethylene microporous film with a porosity of 20 to 80% for battery separators. ... 

Solid electrolytes for lithium-ion batteries are expected to offer several advantages over traditional, nonaqueous liquid electrolytes. A solid electrolyte would give a longer shelf life, along with an enhancement in specific energy density. A solid electrolyte may also eliminate the need for a distinct separator material, such as the polypropylene or polyethylene microporous separators commonly used in contemporary liquid electrolyte-based batteries. Solid electrolytes are also desirable over liquid electrolytes in certain specialty applications where bulk lithium-ion batteries as weU as thin-film lithium-ion batteries are needed for primary and backup power supplies for systems, devices, and individual integrated circuit chips. 

In the case of POM synthesis, for example, it was necessary to control the moisture content in the solution of raw materials to a very low level (a few ppm)2 and I could turn this technique to advantage when I made up nonaqueous electrolytes in which water content must be as low as possible. Biaxially drawn polyethylene microporous fihn was adopted as a separator and this material was analogous to superdrawn polyethylene fibers described above. As a binder for active electrode materials, PVdF was used, which was familiar to me as a piezoelectric speaker material. 

Biaxially drawn polyethylene microporous film was adopted as a separator this material is analogous to superdrawn polyethylene fibers described above. As a binder for active electrode materials, PVDF was used which was familiar to me as a piezoelectric material. 

M. Bleha, V. Kudela, E. Y. Rosova, G. A. Polotskaya, A. G. Kozlov, and G. K. Elyashevich. Synthesis and characterization of thin polypyrrole layers on polyethylene microporous films. European Polymer Journal 35,613-620 (1999). 

The separator must be stmcturaHy sound to withstand the rigors of battery manufacturing, and chemically inert to the lead—acid cell environment. Numerous materials have been used for separators ranging from wood, paper, and mbber to glass and plastic. The majority of separators used are either nonwoven—bound glass or microporous plastic such as PVC or polyethylene. 

The microporous polyethylene pocket has succeeded worldwide more than 70 percent of all starter batteries use this form of separation. Whereas in the USA and Western Europe the transition is essentially complete, a similar development in the Asia-Pacific area and Latin America, and in the medium term also in Russia and China, is expected [3],... 

In the second half of the 1960s, at the same time but independently, three basically different plastic separators were developed. One was the polyethylene separator [16] already referred to in starter batteries, used only rarely in stationary batteries, but successful in traction batteries. The others were the microporous phenolic resin separator (DARAK) [18] and a microporous PVC separator [19], both of which became accepted as the standard separation for stationary batteries. They distinguish themselves by high porosity (about 70 percent) and thus very low electrical resistance and very low acid displacement, both important criteria for stationary batteries. 

The alternative is hexane, which because of the explosion hazard requires a more expensive type of extractor construction. After the extraction the product is dull gray. The continuos sheet is slit to the final width according to customer requirements, searched by fully automatic detectors for any pinholes, wound into rolls of about 1 m diameter (corresponding to a length of 900-1000 m), and packed for shipping. Such a continuous production process is excellently suited for supervision by modern quality assurance systems, such as statistical process control (SPC). Figures 7-9 give a schematic picture of the production process for microporous polyethylene separators. 

Because of the increased shedding with these alloys, pure leaf separation is hardly suitable. Separations with supporting glass mats or fleeces as well as microfiber glass mats provide technical advantages, but are expensive and can be justified only in special cases. Also under these conditions of use the microporous polyethylene pocket offers the preferred solution [40]. Lower electrical properties at higher temperatures, especially decreased cold crank duration, are battery-related the choice of suitable alloys and expanders gains increased importance. 

Without any doubt the microporous polyethylene pocket will meet all requirements of modern starter batteries for the foreseeable future. Whether and to what extent other constructions, such as valve-regulated lead-acid batteries, other battery systems, or even supercapacitors, will find acceptance, depends — besides the technical aspects — on the emphasis which is placed on the ecological or economical factors. 

Polyethylene separators Rubber separators Phenol formaldehyde-resorcinol separators Microporous PVC separators... 

Table 12 shows the physicochemical data of separators used in open stationary batteries. Since the emphasis is on low acid displacement, low electrical resistance, and high chemical stability, the phenolic resin-resorcinol separator is understandably the preferred system, even though polyethylene separators, especially at low backweb, are frequently used. For large electrode spacing and consequently high separation thickness, microporous as well as sintered... 

Polyethylene separators Phenol-Formal dehyde-resorcinol Separators Microporous PVC separators Sintered PVC separators Rubber separators... 

Among the separator varieties described, the phenol-formaldehyde-resorcinol separator (DARAK 2000) [60] as well as the microporous PVC separator [86] have proven effective for this construction. For applications without deep discharges, concessions may be made with the respect to porosity and pore sizes of the separator therefore polyethylene separators or a spe-... 

One version of the microporous, filled polyethylene separator ( PowerSep ) [113], which is so successful in the lead-acid battery, is also being tested in nickel-cadmium batteries. This separator is manu-... 

We experienced no safety problems during the external short tests because of the Polyswitch inside the cell. We confirmed that even if the Polyswitch fails to operate, the short-circuit current stops flowing before thermal runaway occurs because the micropores are closed by the polyethylene separator, which melts at 125 °C ("separator shutdown"). 

Currently, all commercially available, spirally wound lithium-ion cells use microporous polyolefin separators. In particular, separators are made from polyethylene, polypropylene, or some combination of the two. Polyolefins provide excellent mechanical properties and chemical stability at a reasonable cost. A number of manufacturers produce microporous polyolefin separators (Table 1.)... 

Lower-density E-plastomers have found alternate use in cast film processes to make elastic film laminates with good breathability which contain laminates of liquid impermeable extensible polymeric films with extensible-thermoplastic-polymer-fiber nonwovens and nonwoven webs of polyethylene-elastomer fibers as the intermediate layers. The development relates to a breathable film including an E-plastomer and filler that contributes to pore formation after fabrication and distension of the film. The method and extent of distension is designed to produce a breathable film by stretching the film to form micropores by separation of the film of the E-plastomer from the particulate solids. This film is useful for manufacture of absorbent personal-care articles, such as disposable diapers and sanitary napkins and medical garments. In detail, these constructions comprise a liquid impermeable extensible film comprising polyolefins. The outer layer contains extensible-thermoplastic-polymer-fiber nonwovens, and an elastic intermediate layer contains nonwoven webs of fiber E-plastomers. The intermediate layer is bonded to the film layer and the outer... 

Other microporous materials have been synthesized using the porogen polyethylene glycol in polyethylene oxide-urethane gels [27]. Micropores were formed in the gel, and it was found that the diffusion of larger species, vitamin B12, was enhanced relatively more than that of a smaller species, proxyphylline. This result is in qualitative agreement with that found for electrophoretic transport by RiU et al. [322] discussed earher, where the mobility of larger species was preferentially enhanced in the templated media. 

Testa and Staccioli [70] used Microthene-710 (microporous polyethylene) as a support material for bis-(2-ethylhexyl) hydrogen phosphate in the determination of 55 iron in environmental samples. 

They are fabricated from a variety of inorganic, organic, and naturally occurring materials and generally contain pores that are greater than 50—100 A in diameter. Materials such as nonwoven fibers (e.g. nylon, cotton, polyesters, glass), polymer films (e.g. polyethylene (PE), polypropylene (PP), poly(tetrafluo-roethylene) (PTFE), poly (vinyl chloride) (PVC)), and naturally occurring substances (e.g. rubber, asbestos, wood) have been used for microporous separators in batteries that operate at ambient and low temperatures (<100 °C). The microporous polyolefins (PP, PE, or laminates of PP and PE) are widely used in lithium based nonaqueous batteries (section 6.1), and filled polyethylene separators in lead-acid batteries (section 7.3), respectively. 

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