Polypropylene fibers diffusion

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... 

Radicals, generated in polypropylene fibers during irradiation as well as the transition frcan these reidicals (R ) to peroxy radicals (ROa ) are monitored by electron spin resonance spectroscopy. Experimental data exhibit an anomaly in the temperature dependence of RO, concentration, around the glassy transition temperature (Tq). The dependence of RO, concentration on temperature, around T, is described by a Hil-liam-Landel-Perry equation rather than by an Arrhenius one. Consequently, the transition consists of two steps the first is associated with diffusion processes and the second with the proper chemical reaction. 

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). 

In the membrane introduction ion trap MS (MIMS) technique, a membrane composed of a microporous polypropylene hollow support fiber coated with an ultrathin ca 0.5 p,m) polydimethylsiloxane layer serves as the interface between the sample and the vacuum chamber of the mass spectrometer. The simultaneous diffusion of volatile and semivolatUe compounds through the ultrathin polydimethylsiloxane MIMS membrane is one of the method s strengths, in that all the analytical information is obtained in a relatively short time (in the order of seconds to minutes). Lead and nickel / -diketonates could be detected by the MIMS technique. ... 

Thermal diffusivity measurements have been reported for fiber-reinforced phenol formaldehyde resins, nylon 6,6, polypropylene, polymethyl methacrylate [81], and trifluoroethylene nanocomposites [82]. 

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