Polyurethane membrane

Polystyrene (PS) and polyethylene (PE) Polysulphone ultrafiltration membranes Polyurethanes... 

Woven Weft knitted Warp knitted Membrane Polyurethane polymer... 

First, we consider the experimental aspects of osmometry. The semiperme-able membrane is the basis for an osmotic pressure experiment and is probably its most troublesome feature in practice. The membrane material must display the required selectivity in permeability-passing solvent and retaining solute-but a membrane that works for one system may not work for another. A wide variety of materials have been used as membranes, with cellophane, poly (vinyl alcohol), polyurethanes, and various animal membranes as typical examples. The membrane must be thin enough for the solvent to pass at a reasonable rate, yet sturdy enough to withstand the pressure difference which can be... 

In the mid-to-late 1980s, growth estimates of the use of polystyrene and polyurethane ceUular plastic insulation materials and products were a healthy 10% per year and greater for phenoHc (40,41). The principal appHcation where strongest growth was forecast for these types was for roofing, especially single-membrane systems (42). 

Propylene glycol, glycolysis of polyurethanes with, 572 Propylene oxide (PO), glycolysis of polyurethanes with, 572-573 Propylene oxide (PO) polyols, 211, 223 Proton exchange membrane fuel cells (PEMFCs), 272-273 Proton NMR integrations, 386. See also H NMR spectroscopy Protonic acids, reactions catalyzed by, 67-68... 

Chitosan has been associated with other biopolymers and with synthetic polymer dispersions to produce wound dressings. Biosynthetic wound dressings composed of a spongy sheet of chitosan and collagen, laminated with a gentamicyn sulphate-impregnated polyurethane membrane, have been produced and clinically tested with good results. 

Liquid membranes consist of an organic phase, which by its hydrophobic nature is relatively impermeable to ions. Originally organic solvents such as decanol were used in conjunction with a porous hydrophobic membrane. These have been replaced by plasticized polyvinyl chloride membranes which behave like liquids yet have improved mechanical properties Other polymers such as silicone, polyurethane and ururshi, a... 

Figure 19 Free volume plot for co(polyether)polyurethane membranes at 37°C for model drugs. D is the diffusion coefficient in cm2/sec, and H is the hydration expressed as (wet volume — dry volume)/wet volume. (Reproduced with permission from Ref. 59.)...

WA Hunke, LE Matheson. Mass properties of Co(polycthcr) polyurethane membranes. Part 2. Permeability and sorption characteristics. Int J Pharm 1313-1318, 1981. 

Akabori, K. Fujimoto, H. A Method for Measuring Cell Membrane Thickness of Polyurethane Foam, International Progress in -Urethanes. 1980, 2, 1-61. 

MJ. Berrocal, I.H.A. Badr, D. Gao, and L.G. Bachas, Reducing the thrombogenicity of ion-selective electrode membranes through die use of a silicone-modified segmented polyurethane. Anal. Chem. 73, 5328-5333 (2001). 

Polymer-based pH sensors are not suitable for continuous in-vivo measurements due to the poor biocompatibility of plasticizers used in the polymer membrane. To minimize such a problem, surface treatment or using a reduced amount of plasticizers has been proposed [71]. In order to improve stability and adhesion, polyurethane has been used as an alternative to PVC membranes in the construction of pH sensing membranes [72, 73],... 

Yoon el al. [112] reported an all-solid-state sensor for blood analysis. The sensor consists of a set of ion-selective membranes for the measurement of H+, K+, Na+, Ca2+, and Cl. The metal electrodes were patterned on a ceramic substrate and covered with a layer of solvent-processible polyurethane (PU) membrane. However, the pH measurement was reported to suffer severe unstable drift due to the permeation of water vapor and carbon dioxide through the membrane to the membrane-electrode interface. For conducting polymer-modified electrodes, the adhesion of conducting polymer to the membrane has been improved by introducing an adhesion layer. For example, polypyrrole (PPy) to membrane adhesion is improved by using an adhesion layer, such as Nafion [60] or a composite of PPy and Nafion [117],... 

Ciobanu, G., Carja, G., and Ciobanu, O. (2008) Structure of mixed matrix membranes made with SAPO-5 zeolite in polyurethane matrix. Micropor. Mesopor. Mater., 115 (1-2), 61-66. 

Ciosek, P., Kraszewska, Z., and Wroblenski, W. (2009). Polyurethane membranes used in integrated electronic tongue for the recognition of tea and herbal products. Electroanalysis 21(17-18), 2036-2043. 

A great many different materials have been used in osmotic pressure experiments. Various forms of cellophane and animal membranes are probably the most common membrane materials. Various other polymers, including polyvinyl alcohol, polyurethane, and polytrifluorochl-oroethylene, have also been used along with such inorganic substances as CuFe(CN)6 precipitated in a porous support. 

However, we will not ignore physical properties. A section of the book will focus on structure-property relationships. PURs fonn devices that have chemical and physical features. The great value of polyurethanes as we will show in this book is the freedom to take advantage of their chemical and physical features and efficacies. While much of the book focuses on foams, we will also discuss coatings, membranes, elastomers, and their application to the problems addressed. 

Entrapping an enzyme within a gel is a common technique, but washout and membrane diffusion are important issues. The most effective system would be an enzyme that attaches covalently to a flow-through medium of high surface area to create a system that would represent an optimal balance of both chemical and engineering attributes. This optimal balance is the basis of several applications for polyurethane and its composites. 

Tuerker and Mavituna immobilized Trichoderma reesei within the open porous networks of reticulated polyurethane foam matrices. Growth pattern, glucose consumption, and cellulase production were compared with those of freely suspended cells. The method of immobilization was simple and had no detrimental effect on cell activity. Hundreds of similar projects could be cited. Not all rated the use of polymethane as the preferred technique. If a statistical analysis were conducted on aU the immobilization literature, we are sure that no single technique would be dominant. However, the combination of ease of immobilization, cost of materials, flow-through properties, control of flux rate through the immobilizing membrane, high surface-to-volume ratio, and other factors make polymethane a viable substratum for the continuous production of proteins. 

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