Tensile strength membranes

Membrane tensile strength increased by a factor of 1.5 and hydration expansion rednced by 50% compared to NR-211 membranes. 

The presence of macrovoids in hoUow-fiber membranes is a serious drawback since it increases the fragUity of the fiber and limits its abUity to withstand hydrauhc pressures. Such fibers have lower elongation and tensile strength. 

Films of the copolymers are, as with Nafion, saponified and used for permselective membranes. They have a much higher tensile strength than the Du Pont material and are also claimed to have a higher ion exchange capacity. 

The processes for manufacturing microporous membranes can be broadly divided into wet processes and dry processes. Both processes usually employ one or more orientation steps to impart porosity and/or increase tensile strength. Figure 2 shows scanning electron micrographs of surfaces of separators made by each process. 

Superficially phosphorylated chitosan membranes prepared from the reaction of orthophosphoric acid and urea in DMF, showed ionic conductivity about one order of magnitude larger compared to the unmodified chitosan membranes. The crystallinity of the phosphorylated chitosan membranes and the corresponding swelling indices changed pronouncedly, but these membranes did not lose either tensile strength or thermal stability [234]. 

PVA has also been extensively used for immobilization of biocatalysts in a membranous form. As compared to PAAm, PVA is more hydrophilic and having adhesive property with better tensile strength in dry conditions. But it has high swelling index and dissolves readily in water when not cross-linked. PVA can be cross-linked using a variety of reagents including... 

For the purification of the membranes, the common treatment with 0.1-2.0 N aqueous sodium/potassium hydroxide solutions has been compared with the purification of raw BC membranes using aqueous sodium/ potassium carbonate. Whereas hydroxide purification leads to a decrease of the tensile strength and an elongation of the material this effect is lower in the case of carbonate treatment. Moreover, the oxygen transmission rate is higher after carbonate washing. 

P.M. Biesheuvel and H. Verweij, Ceramic Membrane Supports, Permeability, Tensile Strength and Stress , J. Membrane Sci. 156 141-52 (1999). 

Mechanical functions. Proteins often fulfill structural roles. The protein collagen provides tensile strength in skin, teeth, and bone. The membranes surrounding cells and cell organelles are also partly composed of proteins, having both functional and structural roles. 

Figure 14.17. Young s modulus and tensile strength of SWNT membrane as a function of irradiation dose.

Details are given of the preparation of PVC membranes containing dialkylphthalate. The tensile strength and percent elongation of these membranes as a function of concentration of the phthalate plasticisers, their size and ageing period were performed. Applications in the controlled release of agrochemicals are mentioned. 19 refs. 

The tonoplast does not have an appreciable difference in hydrostatic pressure across it. A higher internal hydrostatic pressure would cause an otherwise slack (folded) tonoplast to be mechanically pushed outward. The observed lack of such motion indicates that AP is close to zero across a typical tonoplast. If the tonoplast were taut, AP would cause a stress in the membrane, analogous to the cell wall stresses discussed in Chapter 1 (Section 1.5C) namely, the stress would be rAPI2t for a spherical vacuole (see Eq. 1.15). However, the tensile strength of biological membranes is low—membranes can rupture when a stress of 0.2 to 1.0 MPa develops in them. For a tonoplast 7 nm thick with a maximum stress before rupturing of 0.5 MPa surrounding a spherical vacuole 14 pm in radius, the maximum hydrostatic pressure difference across the tonoplast is... 

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