Hydrophobic polypropylene

This simple mass transfer model based on simplified film theory has been proposed to describe the process of facilitated transport of penicillin-G across a SLM system [53]. In the authors laboratory, CPC transport using Aliquat-336 as the carrier was studied [56] using microporous hydrophobic polypropylene membrane (Celgard 2400) support and the permeation rate was found to be controlled by diffusion across the membrane. 

As an example, results on the adsorption of human serum albumin (HSA) at a hydrophobic polypropylene (PP) film, which was modified by PEI/PAC multilayers are shown in Fig. 10 [111]. Based on ATR-FTIR spectra in the amide I region of the adsorbed protein layer the medium kinetic course... 

Very well known commercially available block copolymers showing micellar behavior are polymers of the Pluronic type. Pluronic-type copolymers are symmetric triblock copolymers with the central block of hydrophobic polypropylene... 

Microscopic foam films have been used to study the steric interaction between two liquid/gas interfaces [130]. Two ABA triblock copolymers of the Synperonic PE series were employed P85 and F108. These commercial non-ionic surfactant were used as obtained from ICI Surfactants, Witton, UK. Blocks A are hydrophilic polyethylene oxide (PEO) chains, while block B is a hydrophobic polypropylene oxide (PPO) chain. The molecular masses and average EO contents are known from the manufacturer and yield approximate chemical formulae (Table 3.3). Data about the surface tension of electrolyte-free aqueous copolymer solutions can be seen in Fig. 3.31 [130]. It was additionally checked that NaCl (up to 510 2 mol dm 3) had no influence on these values. 

High soil-release performance, excellent softness and combinability with fluorocarbon finishes may be achieved by special silicone/polyalkylene oxide copolymers. The silicone segments contain hydrophobic dimethylsiloxane structures and hydrophilic silicone modifications with ethoxylated or amino group-containing side groups. The different hydrophilic-lipophilic balance (HLB) of the polyalkylene blocks is adjusted by the ratio of hydrophobic (polypropylene oxide) and hydrophilic (polyethylene oxide) components. 

VOCs can also be removed by applying vacuum and using composite membranes as, for example, in the VaporSep process commercialized by the MTR, where a porous support is used for a silicone membrane coating in a spiral wound configuration. Hydrophobic polypropylene hollow fibers with an ultrathin and highly VQC-permeable plasma-polymerized nonporous silicone skin on the outer surface can be also effective [31-33]. 

The last example shows that it is also feasible to use SLMs to remove and recover efficiently radioactive metals from nuclear process effluent. By using a microporous hydrophobic polypropylene hoUow-fiber supported Hquid membrane (HFSLM) consisting of extractant, tri-w-butyl phosphate (TBP) as carrier diluted with w-dodecane, actinides such as uranium (U) and plutonium (Pu) were removed [188]. It was concluded after modeling and evaluation of the process conditions that it is possible to remove more than 99% of U(VI) and Pu(IV) from process effluent in the presence of fission products when stripping reagent 0.1 M hydroxylamine hydrochloride in... 

Nielsen and Edrusick [29] evaluated the effect of five kinds of knit structures, all made from 100% polypropylene were evaluated. On subjects exercising for 40 minutes at 5°C followed by 20 minutes at rest, and then repeated. The thickest knit, a fleece, caused the greatest total sweat production, retained the most moisture, and wetted skin the most. They stated that the hydrophobic polypropylene prevented extensive sweat accumulation in the underwear (10 to22%) causing the sweat to accumulate in the outer garments. 

Nunez, 1999). Surfactants and lipids are effective for the separation of biomolecules such as proteins (Bucak et al, 2003), while hydrophobic polypropylene oxide side chains have a high affinity for synthetic organic compounds (Moeser et al, 2002). The selectivity of copper phthalocyanine dye for organic compounds, specifically polycyclic organic dyes, has also been demonstrated (Safarik, 1994). 

Ciszewski, A., Kunicki, J. and Gancarz, I. 2007. Usefulness of microporous hydrophobic polypropylene membranes after plasma-induced graft polymerization of acrylic acid for high-power nickel-cadmium batteries. Electmchim. Acta 52 5207-5212. 

Qin et al. (2003) used SLMs for the separation of acetic acid and butyric acid from their aqueous solution. Polypropylene hfs and silicon-coated, microporous hydrophobic polypropylene membranes were used as support. In another study, Qin et al. (2002) demonstrated PV by using a liquid membrane consisting of nonvolatile hydrocarbons immobilized in the micropores of hydrophobic hfs on the outer surface of the fibers. TCE was separated and concentrated from its aqueous solution at 25°C and essentially atmospheric pressure. The feed TCE concentration was varied between 50 and 950 ppm the permeate pressure range was 0.6-70 mmHg. A 78-flber, 30-33 cm long module could achieve as much as 98% removal of TCE. It was reported by them that the hexadecane SLM was permselective for TCE the experimental selectivity was 30,000 and the intrinsic selectivity could be as high as 2 x 10 much higher than the values obtained by any solid membranes. 

A great deal of research has been performed into the use of poloxamers for the controlled release of active substances [24]. Poloxamers, also referred to as Pluronics or Lutrols, consist of triblock copolymers having a central hydrophobic polypropylene oxide block and on both sides a hydrophilic polyethylene oxide block (Fig. 18.9). 

Significant progress in this area has been made. It has been shown recently that the polarity of the casting substrate may provide an avenue for surface wetting without surface treatment. The casting of silicone-based formulations from polar mold materials results in a surface rich character. For example, a copolymer based on a fiuorinated silicone and the hydrophilic monomer, DMA was cast against the hydrophilic mold resin Barex (copolymer of acrylonitrile and styrene). X-ray photoelectron spectroscopy analysis of the surface showed a threefold increase in surface nitrogen concentration as compared with the same formulation cast from a hydrophobic polypropylene resin. The Barex cast material resulted in... 

We have then washed the surface by rinsing with chloroform and dichloromethane, which are good solvents of the additives. This washed surface (Fig. 6) shows a remarkable change in adhesion from the PPis surface. The average adhesion force obtained in water with a -CH3 tip is equal to 15 nN. The surface behaves thus like a hydrophobic polypropylene surface. 

Papadopoulos and Sirkar (27) employed symmetric microporous hydrophobic polypropylene hollow fibers with a thin nonporous plasma-polymerized skin of silicone on the outside surface. For species like N2, O2, CO2, H2S, SO2 which have high permeability through a thin silicone skin, the extra skin resistance on top of the liquid membrane resistance is limited. Yet, it eliminates liquid membrane breakthrough when Pm exceeds Ppo or P q by 100 psi. Unless the silicone coating is ruptured or the composite fibers break, the membrane liquid remains contained... 

Another interesting example of surface modification is represented by the modification of hydrophobic polypropylene surfaces by carbon dioxide plasma [23] and carbon tetrachloride plasma [24] treatment to convert them into hydrophilic surfaces. This technique has potential applications in coatings and adhesion to other materials such as polymers, metals, and ceramics [24]. Radiation-induced reactions for LDPE/PP blends have also been recently reported [25]. 

Solvent extraction of p-nitrophenol (PNP) from a high-salt aqueous solution into 1-octanol acting as solvent was considered in Problem 5.2.9. After the extraction of the pollutant PNP into 1-octanol, the solvent is regenerated by contacting the solvent containing PNP with another aqueous solution the solution may be basic or is amenable to biodegradation of PNP (Tompkins et al., 1992). Microporous hydrophobic polypropylene membranes (Figure 3.4.10) were used by these authors to back extract PNP from 1-octanol into the aqueous back extraction phase. 

Figure 27.9 Tr5fpsin (A, from Drioli et al., 2005) and lysozyme (B, from Di Profio et al., 2003) crystals grown on hydrophobic polypropylene (PP) membranes.

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