Polyacrylate permeability

Polyacrylates are often added to drilling fluids to increase viscosity and limit formation damage. The filter-cake is critical in preventing reservoir invasion by mud filtrate. Polymer invasion of the reservoir has been shown to have a great impact on permeability reduction [98]. The invasion of filtrate and solids in drilling in fluid can cause serious reservoir damage. 

Hydration of polymeric membranes may be influenced by the chemical identity of the polymers. A hydrophilic polymer has a higher potential to hydrate than a hydrophobic one. Sefton and Nishimura [56] studied the diffusive permeability of insulin in polyhydroxyethyl methacrylate (37.1% water), polyhydroxy-ethyl acrylate (51.8% water), polymethacrylic acid (67.5% water), and cupro-phane PT-150 membranes. They found that insulin diffusivity through polyacrylate membrane was directly related to the weight fraction of water in the membrane system under investigation (Fig. 17). 

Figure 17 Effect of weight fraction of water on insulin permeability of highly swollen polyacrylate membranes. (Reprinted with permission from Ref. 56.)...

MV Sefton, E Nishimura. Insulin permeability of hydrophilic polyacrylate membranes. J Pharm Sci 69(2) 208-209, 1980. 

Instead of packed columns, monolithic (continuous bed), analytical, or capillary columns in the form of a rod with flow-through pores offer high porosity and improved permeability. Silica-based monolithic columns are generally prepared by gelation of a silica sol to a continuous sol-gel network, onto which a Cjg or another stationary phase is subsequently chemically bonded. Such columns provide comparable efficiency and sample capacity as conventional columns packed with 5-pm particle materials, but have three to five times lower flow resistance, thereby allowing higher flow rates and fast HPLC analyses. Rigid polyacrylamide, polyacrylate, polymethacrylate, or polystyrene monolithic columns are prepared by in sim polymerization. 

Technology for preparing nanocomposites directly via compounding has been investigated by Vaia, Ishii, and Giannelis. Industrial R D efforts have focused on process technology (e.g., melt or monomer exfoliation processes), as there are a number of polymers (e.g., polyolefins) that do not lend themselves to a monomer process. Nanocomposites with a variety of polymers, including polyacrylates or methacrylates, polystyrene, styrene-butadiene rubber, epoxy, polyester, and polyurethane, are amenable to the monomer process. The enhancement of mechanical properties, gas permeability resistance, and heat endurance are the primary objectives for the application of PCN, and their success will establish PCNs as a major commercial product. 

As may be seen from Table I, concentrations of SO2 in the atmosphere are subjected to considerable variations. Moreover, SO2 concentrations used in corrosion tests are larger by several orders of magnitude. Therefore, it becomes highly questionable whether data obtained at high SO2 concentration levels may be also applied to practical exposure conditions. SO2 permeabilities of a series of polymer films like polyethylene, polycarbonate. polyamide 2 gg well as polyacrylate and cellulose triacetate have been shown to depend on SO2 pressure, especially at higher SO2 concentration levels. In the case of organic coatings such data are not available. It is therefore recommended to study SO2 permeability at low SO2 concentrations comparable to practical exposure conditions. 

Contrary to other atmospheric gases like N2, O2 or CO2, the permeability of polymer films for SO2 is very high (Table III). Obviously the molecular size of SO2 is not the dominating factor for its permeation rate. As the permeability coefficient P is defined by the product of the diffusion coefficient, D, and the solubility, S, the SO2 solubility of the polymer films plays an Important role. In fact the few data published on solubility of SO2 in polymers corroborate this expectation. Equilibrium solubility of SO2 in polyacrylate was found to be as high as 21.5% by weight at 760 mmHgl. In case of a bisphenol A polycarbonate. 

The encapsulation experience with EUDRAGIT RL lead to the conclusion that EUDRAGIT RL, while appropriate for demonstrating in a general sense that water insoluble polyacrylates could be used to microencapsulate live mammalian cells, was not suitable for the particular problem of encapsulating cells because of its limited biocompatibility and permeability. To address both of these limitations (and especially the former one), a series of noncrosslinked... 

After 5 min, during which the alamethicin equilibrated with the lipid bilayer and its CD spectrum did not change, different amounts of 0.1 N (normality equals molarity in monomeric units) of degree of polymerization 100,000, sodium polyacrylate (PA-) solution were added. Free alamethicin in the presence of salt tends to interact with PA- to form gels. Lack of gelation with added PA- indicates that the alamethicin is incorporated into the membranes. The final polyacrylate concentrations were between 0 and 0.1 N. The concentrations of Na+ and glucose added up to 0.1 M to maintain isotonicity. Due to the permeability of alamethicin channels to small ions, different polyacrylate concentrations resulted in different Donnan potentials across the membrane. 

Figure 9-33. Selectivity of different polymer membranes to He-N2 separation as a function of nitrogen permeability (n, incm /(cm x atm x s)) (1) polyvinylidenechloride (2,4)polyethylene terephthalafe (3) polyvinylfluoride (5) polyvinylchloride (6) polyamide (7) plasfified polyvinylidene chloride (8) cellulose nitrate (9) polypropylene (lO)fluoroplast (26) (ll)co-polymer of isoprene (74%) and acryl-nitryl (26%) (12, 18, 20) different co-polymers of butadiene and acryl-rritryl (13) polyacrylate (14) polycarbonate (15) polyisobutylene (16) bulyl latex (17) co-polymer of vinyl chloride and vinyl acetate (19, 37) butyl acetate of cellulose (21) polyethylene vinyl acetate (22) polybutadiene (23) special polymer SKI-3 (24) natural latex (25) nitryl silicon latex (26) dimethyl silicon latex (27) special polymer SKS-30 (28) special polymer SKMS-50 (29) special polymer SKMS-30 (30, 34, 35) high-density, medium-densily, and low-density polyethylene (31) polyethylene with 5% soot (32) co-polymer of ethylene (90%) and propylene (10%) (33) co-polymer of ethylene (96.5%) and vinyl acetate (3.5%) (36) triacetate of cellulose (38) acetate cellulose (39) polystyrene.

In the study of Marx-Tibbon and Willner [88], membranes from the photo-reactive polyacrylate/amide system, in the zwitter-ionic state imprinted with tryptophan, showed a specific tryptophan permeability which could be erased by light irradiation of the membrane inducing an isomerization of the functional groups to the uncharged spiropyrane form. According to the solution-diffusion mechanism, this could be taken as evidence that specific sorption in the membrane can yield specific transport through the membrane. 

Certain biodegradable superabsorbent materials, such as those composed of crosslinked polysaccharides, tend to exhibit lower absorbency properties, particularly absorbency under load and gel bed permeability, in comparison to the conventional non biodegradable polyacrylate superabsorbents. 

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