Microporous polyethylene films

There are several options for preparing a solid sample for IR spectroscopy. These include the preparation of solutions, castings, KBr pellets, and microporous polyethylene films, or the use of an accessory for obtaining attenuated total reflectance... 

Microporous Polyethylene Films. Disposable IR cards are available to which samples can be directly applied for infrared analysis (Fig. 8.8). These convenient IR cards have two 19-mm circular apertures containing a thin microporous film of chemically resistant polyethylene. Cards having microporous polytetrafluoroethylene are also available for special applications. The cards with polyethylene films may be used for infrared analysis from 4000-400 cm except for the region of aliphatic C-H stretching that occurs between 3000-2800 cm In this region of an FT-IR spectrum, there are several sharp... 

Lin, C. H., Tsai, I. S., Chu, W. C. (2009). Influence of calcium oxide (quickhme) on the hydrostatic pressure resistance of microporous polyethylene films. Journal of Plastic Film and Sheeting, 25, 251—269. 

Sakai, Y, Sadaoka, Y, Matsuguchi, M., Rao, VL., and Kamigaki, M. (1989). A humidity sensor using graft copolymer with polyelectrol3de. Polymer 30 1068. Sakai, Y. and Sadaoka, Y. (1985). Humidity sensors using sulfonated microporous polyethylene films. Denki Kagaki 53 150. 

G. K. Elyashevich, L. Terlemezyan, I. S. Kuryndin, V. K. Lavrentyev, P. Mokreva, E. Y. Rosova, and Y. N. Sazanov. Thermochemical and deformational stability of microporous polyethylene films with polyanihne layer. Thermochimica Acta 374, 23-30 (2001). 

To achieve the mechanical strength needed for use as a membrane, a microporous polyethylene support was used. The support, obtained from 3M (Minneapolis, MN), was approximately 20 microns in thickness and was 83% porous. The liquid monomer mixtures were applied to the support with a wiped film method and subsequently polymerized with UV irradiation at 365 nm and 2.0 mW/cm2 for 2 hours. After polymerization, a solid transparent film was obtained. To allow unreacted monomer and oligomer to leave the film, it was placed into chloroform for three days, with fresh chloroform exchanges once per day. After the chloroform exchanges, the film was allowed to dry in the chemical hood. 

The authors would like to thank NSF for its support of this work through a graduate Student Fellowship to KLT and both the I/U CRC Center for Separations Using Thin Films and the Colorado Advanced Technology Institute for their financial support of the project. The authors would also like to acknowledge 3M for donation of the microporous polyethylene support used in this work. 

LDPE Low-density polyethylene film Mesoporous and microporous material... 

Yu TH (1996) Processing and structure-property behavior of microporous polyethylene -from resin to final film. Ph.D. Dissertation, Virginia Polytechnic Institute and Stale University, Virginia... 

Microporous polypropylene film Microporous polypropylene film Microporous filled UHMW polyethylene separator Sintered PVC separator... 

LIB separators must provide electrical insulation between the positive and negative electrodes while permitting imi transport between them. They are microporous polyolefin films 10-30 pm thick with pores of 0.01-0.1 pm diameter. Most LIB separators are made of high-density polyethylene, although polypropylene is also used to a certain extent... 

Microporous polyethylene (PE) membranes with various pore diameters and porosities and microporous polytetrafluoroethylene (PTFE) membrane were used as substrates for the plasma graft polymerization (Table II). Besides these porous substrates, homogeneous poly[ l-(trimethyl si lyl)-l-propyne] (PTMSP), which has the highest gas permeability among polymeric materials, was used as the substrate. The poly[l-(trimethylsilyl)-l-propyne] was synthesized from l-(trimethylsilyl)-l-propyne according to the literature procedure (19). Films were prepared by casting polymers from toluene solutions. Hereafter, the respective substrate membranes will be abbreviated as shown in Table II. 

The electrochemically active electrode materials in Li-ion batteries are a lithium metal oxide for the positive electrode and lithiated carbon for the negative electrode. These materials are adhered to a metal foil current collector with a binder, typically polyvinylidene fluoride (PVDF) or the copolymer polyvinylidene fluoride-hexafluroropropylene (PVDF-HFP), and a conductive diluent, typically a high-surface-area carbon black or graphite. The positive and negative electrodes are electrically isolated by a microporous polyethylene or polypropylene separator film in products that employ a liquid electrolyte, a layer of gel-polymer electrolyte in gel-polymer batteries, or a layer of solid electrolyte in solid-state batteries. 

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... 

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. 

The materials used in nonwoven fabrics include a single polyolefin, or a combination of polyolefins, such as polyethylene (PE), polypropylene (PP), polyamide (PA), poly(tetrafluoroethylene) (PTFE), polyvinylidine fluoride (PVdF), and poly(vinyl chloride) (PVC). Nonwoven fabrics have not, however, been able to compete with microporous films in lithium-ion cells. This is most probably because of the inadequate pore structure and difficulty in making thin (<25 /rm) nonwoven fabrics with acceptable physical properties. 

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. ... 

Figure 2.29 Scanning electron micrographs at approximately the same magnification of four microporous membranes having approximately the same particle retention, (a) Nuclepore (polycarbonate) nucleation track membrane (b) Celgard (polyethylene) expanded film membrane (c) Millipore cellulose acetate/cellulose nitrate phase separation membrane made by water vapor imbibition (Courtesy of Millipore Corporation, Billerica, MA) (d) anisotropic polysulfone membrane made by the Loeb-Sourirajan phase separation process...

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. 

Virtually the entire membrane manufacture today is based on laminate structures comprising a thin barrier layer deployed upon a much thicker, highly permeable support. Most are formed of compositionaUy homogeneous polysulfone, cellulose acetate, polyamides, and various fluoropolymers by phase inversion techniques in which ultrathin films of suitably permselective material are deposited on prefabricated porous support structures. Hydrophobic polymers as polyethylene, polypropylene, or polysulfone are often used as supports. A fairly comprehensive hst of microporous and ultrafiltration commercial membranes and produced companies are presented in Refs [107-109]. A review on inorganic membranes has been given in Ref. [110]. 

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