Micro-porous films

Grafting adds a monomeric or low molecular wieght moiety to a high molecular weight formed polymer, which can be a film, a non-woven, a micro-porous film or a bulk material, to affect various properties. Grafting can be defined as the ability to attach or grow a different material onto the backbone of another. With polymeric materials, the different material is most typically a monomer and the backbone a polymer or other solid. A chemical bond is then formed between the grafted moiety and the material. 

Jiang, X., Gu, J., Shen, Y., Wang, S., Tian, X. Formation of honeycomb-patterned micro-porous films based on a fluorinated poly(siloxane imide) segmented copolymer. J. Appl. Polym. Sci. 119, 3329-3337 (2011)... 

Micro-porous films with very high permeabilities have been developed and are also available commercially. Films using micro perforations, where the diameter of micro perforations generally range from 40 to 200 pm, ean offer very high gas transmission rates (Sandhya, 2010). 

In supported liquid membranes, a chiral liquid is immobilized in the pores of a membrane by capillary and interfacial tension forces. The immobilized film can keep apart two miscible liquids that do not wet the porous membrane. Vaidya et al. [10] reported the effects of membrane type (structure and wettability) on the stability of solvents in the pores of the membrane. Examples of chiral separation by a supported liquid membrane are extraction of chiral ammonium cations by a supported (micro-porous polypropylene film) membrane [11] and the enantiomeric separation of propranolol (2) and bupranolol (3) by a nitrate membrane with a A/ -hexadecyl-L-hydroxy proline carrier [12]. 

Fig. 7.6 Spectral dependence of the absorption coefficient for free-standing micro PS (72% porosity), meso PS (45% porosity), bulk Si and amorphous Si H at RT. While the meso porous film can be roughly fitted to a Bruggeman effective medium calculation for...

The third main class of separation methods, the use of micro-porous and non-porous membranes as semi-permeable barriers (see Figure 2c) is rapidly gaining popularity in industrial separation processes for application to difficult and highly selective separations. Membranes are usually fabricated from natural fibres, synthetic polymers, ceramics or metals, but they may also consist of liquid films. Solid membranes are fabricated into flat sheets, tubes, hollow fibres or spiral-wound sheets. For the micro-porous membranes, separation is effected by differing rates of diffusion through the pores, while for non-porous membranes, separation occurs because of differences in both the solubility in the membrane and the rate of diffusion through the membrane. Table 2 is a compilation of the more common industrial separation operations based on the use of a barrier. A more comprehensive table is given by Seader and Henley.1... 

Chemical damage occurs when a contaminant in the feed water is incompatible with the polymer comprising the membrane, the micro-porous support, or the fabric support. Besides oxidizers that degrade the crosslinking of a thin-film membrane, there are a variety of chemicals that swell or dissolve the polysulfone microporous support, including the following compounds. 

Hillhouse, H.W. van Egmond, J.W. Tsapatsis, M. Hanson, J.C. Larese, J.Z. The interpretation of X-ray diffraction data for the determination of channel orientation in mesoporous films. Micro-porous Mesoporous Mater. 2001, 44, 639-643. 

The PEC-1000 membrane, developed by Toray Industries, has many similarities to the NS-200 membrane. This membrane has been described by Kurihara and coworkers as a thin film composite membrane in which the barrier layer was formed by an acid-catalyzed condensation reaction on the surface of micro-porous polysulfone.7S The cross section of this membrane, under high magnification in a scanning electron microscope is quite similar in structure to the NS-200 membrane. The barrier layer is 300 angstroms thick. 

Following the work of Bloch and Vofsi, two other methods of producing immobilized liquid films were introduced. Both are still under development. In the first approach, the liquid carrier phase is held by capillarity within the pores of a microporous substrate, as shown in Figure 9.4. This approach was first used by Miyauchi14 and further developed by Baker et al15-17 and by Largman and Sifniades.18 The principal objective of this early work was the recovery of copper and other metals from hydrometallurgical solutions. Despite considerable effort on the laboratory scale, the first pilot plant was not installed until 1980.19-20 The principal problem is instability of the liquid carrier phase in the micro-porous membrane support. 

Gregorian, R.S. and C.C. Kirk, Process for forming crosslinked oriented, micro-porous polyolefin film. U.S. Patent 3376238, 1968. 

Immobilized Liquid Membranes. Facilitated transport liquid membranes for gas separations can be prepared In several configurations. The complexatlon agent solution can be held between two nonporous polymer films (2j1), Impregnated Into the pore structure of a micro-porous polymer film (25), or the carrier can be exchanged for the counterion In an Ion exchange membrane (it). 

Surface area and its accessibility are important both in catalysis and gas cleanup. Nano-structured micro-porous catalysts or catalyst supports offer intensified catalysis since they provide an enhanced surface area which is accessible to the reactants and products through a network of arterial channels feeding into the regions of catalytic activity. In non-structured catalysts, although the surface area might be large, as determined by gas adsorption, they are often not accessible as a result of surface fouling and the diffusion resistance can slow down the rates of reactions. Catalysts are either deposited as a thin film on a support or they are used as pellets. These two techniques have certain drawbacks in coated systems, catalyst adhesion can be non-uniform and weak while the accessibility of the active sites within the interior of the catalyst is hindered due to low porosity. 

Previous research aimed at removing pesticide residues from contaminated fabrics has been directed at removal of a particular pesticide chemical and/or formulation of pesticide, with no effect toward comparing the pesticide residue s composition to that of common soil. Fabric selection for this study allowed a comparison of both hydrophilic and hydrophobic fibers and the effect of fabric type on soil removal. Two fabrics were identified for the study. Denim was 100% cotton fabric of twill weave dyed with indigo dyes. This fabric was 14 ounce, comparable to the heavy weight denim found in jeans. The second fabric was Gore Tex, a three layer structure consisting of an outer layer of rip-stop nylon and an inner layer of nylon tricot laminated to a film. The film was a micro-porous, polymeric film or polytetrafluoroethylene (PTFE). Previous studies on pesticide penetration found Gore Tex to be impermeable to pesticides. Thermal comfort studies found it to be relatively comfortable, similar In comfort to the commonly worn denim jeans and a chambray shirt. 

An experiment sample is the polypropylene which is one of the four major general- purpose resin. It shows the different polypropylene (PP) of three kinds of proporties in Table 1. A polypropylene film as prep>ared (PPl) and the polypropylene drawn film (PP2) to two axes (Futamura Chemicals) were used as base polymers. The porous film containing pores of several micro meters in radius prep>ared (PP3) was drawn to the thickness of 75pun. 

GE-Osmonics (part of GE Water Technologies) commercializes the Desal 5 nanofiltration membranes, used for removal of hardness and other contaminants, alcohol recovery from aqueous solution and removal of salt from salt whey. The membrane has 4 layers, a polyester nonwoven, an asymmetric micro-porous polysulfone and two proprietary thin films, which might be based on sulfonated polysulfone and polypiperazineamide [34]. A comparison between DesaF 5 and NF270 for nanofiltration has been reported by [44] (Tab. 4.3). 

Escale, P., Save, M., Lapp, A., Rubatat, L., Billon, L. Hierarchical structures based on self-assembled diblock copolymers within honeycomb micro-structured porous films. Soft Matter... 

TFC Thin-film composite RO and NF membranes. A typical TFC membrane consists of three layers a polyester web structural support (120—150 pm thick), a micro-porous inter layer ( 40 pm thick), and an ultra-thin polyamide (or other polymer) top layer (0.2 pm thick). See Figure 6.15. 

This chapter will focus on the open cell PU foams, even though many general aspects and recent developments of the technology, dealing with films, getters and manufacturing processes, can be also applied, with minor changes, to other micro porous fillers. 

Figure 16.6 Average WVTR versus tensile modulus of micro porous stretched LLDPE/60% CaC03 films containing different filler grades [21],...

In most batteries, the separators are either made of nonwoven fabrics or micro-porous polymeric films. Batteries that operate near ambient temperatures usually use separators fabricated from organic materials such as cellulosic papers, polymers, and other fabrics, as well as inorganic materials such as asbestos, glass-wool, and Si02. In alkaline batteries, the separators used are either regenerated cellulose or microporous polymer films. The lithium batteries with organic electrolytes mostly use microporous polymer films. 

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