Diffusion polypropylene

Kazayawoko M, Balatineoz J J and Woodhams R T 1997 Diffuse refleotanoe Fourier transform infrared speotra of wood fibers treated with maleated polypropylenes J. Appl. Polymer Sci. 66 1163-73... 

For the separation of D,L-leucine, Ding et al. [62] used poly(vinyl alcohol) gel-coated microporous polypropylene hollow fibers (Fig. 5-11). An octanol phase containing the chiral selector (A-n-dodecyl-L-hydroxyproline) is flowing countercur-rently with an aqueous phase. The gel in the pores of the membrane permits diffusion of the leucine molecules, but prevents convection of the aqueous and octanol phase. At a proper selection of the flow ratios it is possible to achieve almost complete resolution of the D,L-leucine (Fig. 5-12). 

To avoid this damage great efforts were made to improve the cultivation systems. Feder and Tolbert [5] developed special stirrers with low shear damage and Lehmann et al. [6] replaced gas bubbling through indirect aeration by diffusion of oxygen through porous polypropylene membranes. 

Fig. 2 shows the liquid product distributions over catalysts. Main product over ferrierite is C5 hydrocarbon, while products were distributed over mainly C,-C, over HZSM-5. Table 4 shows the effect of mixing ratio on product distribution. While HZSM-5/PP ratio does not affect product distribution, higher amount of gas is obtained with increasing ferrierite/PP ratio. This is ascribed to the increased possibility of polypropylene diffusion into pore as the amount of ferrierite is increased. 

Several manufacturers introduced products amenable for this solid-supported LLE and for supported liquid extraction (SLE). The most common support material is high-purity diatomaceous earth. Table 1.8 lists some commercial products and their suppliers. The most widely investigated membrane-based format is the supported liquid membrane (SLM) on a polymeric (usually polypropylene) porous hollow fiber. The tubular polypropylene fiber (short length, 5 to 10 cm) is dipped into an organic solvent such as nitrophenyl octylether or 1-octanol so that the liquid diffuses into the pores on the fiber wall. This liquid serves as the extraction solvent when the coated fiber is dipped... 

In an effort to optimize the solvent-containing passive sampler design, Zabik (1988) and Huckins (1988) evaluated the organic contaminant permeability and solvent compatibility of several candidate nonporous polymeric membranes (Huckins et al., 2002a). The membranes included LDPE, polypropylene (PP), polyvinyl chloride, polyacetate, and silicone, specifically medical grade silicone (silastic). Solvents used were hexane, ethyl acetate, dichloromethane, isooctane, etc. With the exception of silastic, membranes were <120- um thick. Because silicone has the greatest free volume of all the nonporous polymers, thicker membranes were used. Although there are a number of definitions of polymer free volume based on various mathematical treatments of the diffusion process, free volume can be viewed as the free space within the polymer matrix available for solute diffusion. 

Coughlin and Canevari (1%9) have published experimental data on two systems at a variety of operating conditions the extraction of xylene from polypropylene and the extraction of methanol from polypropylene. These studies were conducted in a single screw extruder at low pressures and w was assumed to be small in comparison with w. Coughlin and Canevari developed a model which they used in conjunction with their experimental data to obtain a value for the diffusion coefficient. The values that they computed were of the order of 10 mVsec, which obviously means that the model is incorrect. Coughlin and Canevari also computed values for the mass transfer coefficient and found it to be independent of screw speed. This observation is particularly noteworthy since they saw no evidence of bubble formation. 

The mechanism of transport of GPG using SLM has been studied at the authors laboratory [56]. GPG could be permeated from alkaUne feed of carbonate buffer into an acidic stripping solution of acetate buffer across the membrane comprising Aliquat-336 in -butyl acetate immobiUzed in a polypropylene (Gelgard 2400) support. The transport mechanism is a case of counter transport exhibiting overall rate dependence on solute diffusion in the membrane phase as well as the mass transfer across the aqueous boundary films. 

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. 

Based on the research of Dr. E. D. Palmes (1) at New York University s Institute of Environmental Medicine and on additional study supported by a contract from the United States Bureau of Mines, a unique personal sampler has been designed to passively collect N0X. This is accomplished by way of molecular diffusion and subsequent trapping of the molecules onto a matrix coated with triethanolamine (TEA) at the closed end of the sampler. Constructed of polypropylene, the tubular sampler shown in Figure 1 is small, lightweight, unbreakable and can be easily worn in the breathing zone of the employee whose exposure is to be monitored. No pumping mechanism is required. The components of N0X diffuse at constant, known rates towards the sealed end of... 

Dyrstad, K., Veggeland, J., and Thomassen, C. (1999), A multivariate method to predict the water vapour diffusion rate through polypropylene packaging, Int. J. Pharm., 188,... 

Cage Effect in Solid Polymers Migration of Free Valence in Solid Polymers Initiated Polymer Oxidation Diffusion of Dioxygen in Polymer Diffusion Regime of Polymer Oxidation Isomerization of Alkyl and Peroxyl Radicals of Polypropylene... 

Excellent spectrum of polypropylene down toAv = 268cm-1. Melt also examined — spectrum similar to solid. Spiral structure assumed to decay on melting. No spectral evidence Adequate spectrum using arc excitation but results nearer than 800 cm-1 from the exciting line diffuse. Preliminary results only... 

Several graft copolymerizations were described by Ballantine (17, 64), Henglein (104, 105) and coworkers. Different monomer-polymer systems were examined styrene on polymethyl methacrylate, poly-2, 5-dichlorostyrene, polytetrafluoroethylene, polyethylene, polypropylene and polyisobutylene, acrylonitrile on polyethylene, rubber, polymethyl methacrylate and dimethyl polysiloxane, vinylpyrrolidone and acroleine on polymethyl methacrylate. The results agree with the preceding ones moreover they show the influence of the swelling and diffusion of the monomer into the polymer. 

The films of organic polymers like polypropylene orpolyethyleneterephta-late, when subjected to mechanical tensions, develop systems of micro- and mesopores that make them transparent for the diffusion of solutions in solvents not dissolving the polymers itself. The counterflow diffusion of solutions ofM02(0C2H40Me)2 (M = Mo, W) in MeOC2H4OH (from one side) and water solutions (from the other side) permitted composites to be obtained where the metal (Mo, W) oxohydroxide particles were formed in situ inside such organic polymer films and remained there after the removal of the solvents [171],... 

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