Solvent permeability

Dhinojwala A and Granick S 1997 Surface forces In the tapping mode solvent permeability and hydrodynamic thickness of adsorbed polymer brushes Macromoiecuies 30 1079-85... 

Many ceramic products are coated with a glassy coating called a glaze. The glaze increases the resistance of the material to gas and solvent permeability makes the surface smoother in art objects used for decoration. 

Strength, brittleness, and solvent permeability properties are limited because of lack of control of the ceramic composition on a macro- and microlevel. Even small particle sizes are large compared with the molecular level. There have been a number of attempts to produce uniform ceramic powders including the sol-gel synthesis in which processing involves a stable liquid medium, coprecipitation in which two or more ions are precipitated simultaneously. More recently, Carraher and Xu have used the thermal degradation of metal containing polymers to deposit metal atoms and oxides on a molecular level. 

The first, and currently only, successful solvent-permeable hyperfiltration membrane is the Starmem series of solvent-resistant membranes developed by W.R. Grace [40]. These are asymmetric polyimide phase-inversion membranes prepared from Matrimid (Ciba-Geigy) and related materials. The Matrimid polyimide structure is extremely rigid with a Tg of 305 °C and the polymer remains glassy and unswollen even in aggressive solvents. These membranes found their first large-scale commercial use in Mobil Oil s processes to separate lube oil from methyl ethyl ketone-toluene solvent mixtures [41-43], Scarpello et al. [44] have also achieved rejections of >99 % when using these membranes to separate dissolved phase transfer catalysts (MW 600) from tetrahydrofuran and ethyl acetate solutions. 

Set out the equation that governs the time needed for microfiUration. The equation is as follows, with Lp representing solvent permeability and n the number of moles of solute present ... 

In liquid filtration using micro-, ultra-, and nanofiltration porous membranes, the driving force for transport is a pressure gradient. Solvent permeability and separation selectivity are the two main factors characterizing membrane performance. Convective flux is predominant with macroporous and mesoporous membrane strucmres, the selectivity being controlled by a... 

Roth et al. [80] proposed a method to determine the state of membrane wear by analyzing sodium chloride stimulus-response experiments. The shape of the distribution of sodium chloride in the permeate flow of the membrane revealed the solute permeation mechanisms for used membranes. For new membranes the distribution of sodium chloride collected in the permeate side as well in the rejection side was unimodal. For fouled membranes they noted the presence of several modes. The existence of a salt leakage peak, as well as an earlier detection of salt for all the fouled membranes, gave evidence of membrane stmcture modification. The intensive use of the membranes might have created an enlargement of the pore sizes. Salt and solvent permeabilities increased as well. While this is a difficult paper to follow, it may be of use to those who want to develop new methods for measuring membrane degradation. 

In this technique, which is a combination of bubble pressure and solvent permeability methods, a liquid A wetting the membrane is displaced by a fluid B (non miscible liquid less wetting than A). The principle is based upon the Laplace equation determining the mechanical equilibrium at the interface... 

Wet samples. Combination of bubble pressure and solvent permeability methods. 

Figure 2. Mass-transfer coefficient with pure solvent permeability for O.lSta NaCl...

Solvent-based adhesives are adhesives with polymers dissolved or pasted in organic solvents. The solvents or solvent mixtures are only processing aids and have to be removed, either partly or completely, from the applied liquid adhesive layer through evaporation or penetration prior to the fixing of the adherends. The first case is necessary for solvent-impermeable materials (metals, glass, thermosetting plastics), the second case concerns porous and solvent-permeable materials (paper, cardboard, wood, leather). This process can be accelerated by heat supply. Solvents are mainly esters, ketones, if applicable, portions of different alcohols. The total solvent portion ranges between 75-85%. 

One-sided bonding (wet bonding) In this procedure, the adhesive is applied to one adherend only. This is recommendable for bonding of solvent-permeable, respectively, absorbent materials (leather, textiles, wood products). In this case, complete solvent evaporation is not required. 

Yasuda et a .25 have developed die concept of a homogeneous solvent-swollen membrane in which thermally induced movement of segments of randomly coiled polymer molecules leaves an interstitial free volume available for solute transport. They concluded that the permeability characteristics of highly swollen systems cannot he represented try a single coefficient. Values of solute ned solvent permeabilities depend ou the conditions of mnesurement, in particular, the magnitude of diffusive flux relative to convnetive flux. 

A liquid-liquid displacement technique (biliquid permporometry) was also found to be well adapted to the characterization of meso- and macroporous membranes [44]. It is based on the combined principles of bubble pressure and solvent permeability. In this case the applied pressure P and the flux J through the membrane are measured simultaneously. The recorded P and J values, introduced in the Laplace equation directly, give the pore equivalent radius and... 

Non-cross-linked polymers can be used in this way just as cross-linked polymers can. For example, we have used polyethylene supports with surface grafts to support Pd(0) catalysts [133,134]. In these cases, the polymer-immobilized catalyst is used in exactly the same way as an insoluble polymer-bound catalyst. Such supported catalysts do require that the insoluble polymer be swollen or permeable to substrates or that the catalysts be within a solvent-permeable, thin immobilized graft. While this approach can be useful, it takes no advantage of the polymer s solubility. It is an approach that conceptually is no different than that used with insoluble inorganic supports or with polymers that are by design insoluble by virtue of cross-linking, and is an approach to catalyst immobilization that is not further discussed since this review is focused on polymer-immobilized catalysts that are used under solution-state conditions. 

Bhanushali et al. [22] showed differences between porous UF polymer membranes and dense reverse osmosis/NF membranes. According to these authors, permeability can be correlated with the inverse of the solvent viscosity for UF membranes whatever the nature of the solvent. For reverse osmosis/NF membranes, a permeation model is proposed in which the flux relates to a solvent permeability coefficient, accounting for a number of solvent intrinsic parameters, like molar volume V , the viscosity p, the sorption value O, and to an intrinsic parameter of the membrane (the solid-vapor surface tension ysv). 

Araki, M. S., Coutinho, C. M., Gon9alves, L. A. G., Viotto, L. A. (2010) Solvent permeability in commercial ultrafiltration polymeric membranes and evaluation of the structural and chemical stability towards hexane. Separation and Purification Technology 71, 13-21. 

Monticciolo, A., P. Cassagnau, and A. Michel. 1998. Fibrillar morphology development of PE/PBT blends Rheology and solvent permeability. Polymer Engineering and Science 38 1882-1889. 

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