Polyacrylonitrile diameter

Fig. 13. Scanning election micrograph of polyacrylonitrile fibrils formed by spraying a 0.05 wt % polyacrylonitrile in dimetbylform amide solution into CO2 through a 50-//m inner diameter, 18-cm-long no22le at a temperature of 40°C, density of 0.66 g/mL, and solution flow rate of 0.36 ml,/min (118).

Bead Polymerization Bulk reaction proceeds in independent droplets of 10 to 1,000 [Lm diameter suspended in water or other medium and insulated from each other by some colloid. A typical suspending agent is polyvinyl alcohol dissolved in water. The polymerization can be done to high conversion. Temperature control is easy because of the moderating thermal effect of the water and its low viscosity. The suspensions sometimes are unstable and agitation may be critical. Only batch reaciors appear to be in industrial use polyvinyl acetate in methanol, copolymers of acrylates and methacrylates, polyacrylonitrile in aqueous ZnCh solution, and others. Bead polymerization of styrene takes 8 to 12 h. 

The produced cationic and anionic exchange fibroid sorbents on the base of polyacrylonitrilic fiber were used to produce household water filters. The cloths of cationic and anionic exchange sorbents with mass of 50 g each one were reeled on a perforated cylinder with diameter of 10 mm and length of 15 mm. This cartridge could be easily replaced. Initial tap water... 

Martin and coworkers tried to prepare carbon tubes from the carbonization of polyacrylonitrile (PAN) in the channels of anodic oxide film (10). A commercially available film with a pore diameter of 260 nm was immersed in an aqueous acrylonitrile solution. After adding initiators, the polymerization was carried out at acidic conditions under N2 flow at 40°C. The PAN formed during the reaction was deposited both on the pore walls and on both sides of the film. Then the Film was taken from the polymerization bath, followed by polishing both faces of the film to remove the PAN deposited on the faces. The resultant PAN/alumina composite film was heat-treated at 250°C in air, and then it was heat-treated at 600°C under Ar flow for 30 min to carbonize the PAN. Finally, this sample was repeatedly rinsed in I M NaOH solution for the dissolution of the alumina film. The SEM observation of this sample indicated the formation of carbon tubes with about 50 xm long, which corresponds to the thickness of the template film. The inner structure of these tubes was not clear because TEM observation was not done. The authors claim that it is possible to control the wall thickness of the tubes with varying the polymerization period. 

Carbon fiber electrode - Edison produced the first carbon fibers by carbonization of cotton threads in 1879. Today polyacrylonitrile (as well as Rayon and various other organic precursors) is the most common precursor for carbon fiber formation [i]. Carbonization of polyacrylonitrile is carried out at 1500 °C to give highly electrically conducting fibers with 5-10 pm diameter. Fibers carbonized at up to 2500 °C are more graphitic with a carbon content of >99%. Carbon fiber-based materials have found many applications due to their exceptionally high tensile strength. In electrochemistry carbon fiber -> micro electrodes are very important in analytical detection [ii] and for in vivo electrochemical studies [iii]. Carbon fiber textiles are employed in - carbon felt electrodes. 

Carbon molecular sieve membranes. Molecular sieve carbons can be produced by controlled pyrolysis of selected polymers as mentioned in 3.2.7 Pyrolysis. Carbon molecular sieves with a mean pore diameter from 025 to 1 nm are known to have high separation selectivities for molecules differing by as little as 0.02 nm in critical dimensions. Besides the separation properties, these amorphous materials with more or less regular pore structures may also provide catalytic properties. Carbon molecular sieve membranes in sheet and hollow fiber (with a fiber outer diameter of 5 pm to 1 mm) forms can be derived from cellulose and its derivatives, certain acrylics, peach-tar mesophase or certain thermosetting polymers such as phenolic resins and oxidized polyacrylonitrile by pyrolysis in an inert atmosphere [Koresh and Soffer, 1983 Soffer et al., 1987 Murphy, 1988]. 

The hollow fibre is the most crucial part of the microdialysis probe. It acts as a membrane, and its characteristics affect performance in the sampling step as well as the probe s suitability for the selected application. Hollow fibres are commercially available in different materials, the most common being polycarbonate (PC), regenerated cellulose (Cuprophan, CU), cellulose acetate (CA), polyacrylonitrile (PAN), polyethersulphone (PES), polysulphone (PE), and polyamide (PA). Generally, the fibres have an outer diameter between 200... 

ID, internal diameter ED, external diameter CA, cellulose acetate CTA, cellulose triacetate PA, polyamide PAN, polyacrylonitrile PC, polycarbonate PE, polyethylene PES, polyethersulfone PP, polypropylene PS, polysulfone PVDF, polyvinylidene fluoride PVP, polyvinyl pyrrolidone RC, regenerated cellulose. 

The MSC membranes are produced by carbonization of polyacrylonitrile, polymide, and phenolic resins [30]. They contain nanopores (typically <5 A in diameter) that allow some of the molecules of a feed gas mixture to enter the pores at the high-pressure side, adsorb, and then diffuse to the low-pressure side where they desorb into the gas phase. The other molecules of the feed gas are excluded from entering the pores and they are enriched in the high-pressure side. Thus the separation is based on the differences in the molecular sizes and shapes of the feed gas components. The smaller molecules preferentially diffuse through the membrane as schematically depicted by Fig. 22.7(a). Table 22.7 gives the permeance and the permselectivity of the smaller species (component 1) of several binary gas mixtures by the MSC membrane [25, 26, 30]. 

PbS/polyacrylonitrile nanocomposite which consists of quasi-spherical PbS particles of 8nm in diameter, homogeneously dispersed and well separated in the polymer matrix. The polyacrylonitrile was chosen, being a good heat-insulator and an aging-resistive material. To provide an homogeneous system, in which the reactants are well mixed at the molecular lever, and to ensure the presence of solvated electrons, absolute ethanol was used as solvent [2] ... 

T. Jimbo, M. Higa, N. Minoura and A. Tanioka, Surface characterization of polyacrylonitrile) membranes graft-polymerized with ionic monomers as revealed by potential, Macromolecules, 1998, 31, 1277-1284 C. Molina, L. Victoria, A. Arenas and J. A. Ibanez, Streaming potential and surface charge density of microporous membranes with pore diameter in the range of thickness, J. Membr. Sci., 1999,163,239-255. 

Tavanai, H. Jalili, R. and Morshed, M. Effects of fiber diameter and CO activation temperature on the pore characteristics of polyacrylonitrile based activated carbon nanofibers. Surface Interface Analy. 2009, 41(10), 814-819. 

The third is a fiber with an easy fibrillation. The fiber is spun by gelation-spinning of a mixture of PVA and another polymer, such as polyacrylonitrile, which is soluble in dimethyl sulfoxide. Phase-separated fibers are produced the continuous phase consists of PVA, and the noncontinuous phase consists of polyacrylonitrile. The fiber can be fibrillated with physical strengths such as milling in rubber, stirring in water, and jet-streamed water, to result in fibrillated fibers with diameters less than 1 pm (0.01 den). 

Pakalapati et al [115] investigated some carbon/thermoplastic laminates. The materials were pultruded and they consisted of 50 v/o unidirectional continuous polyacrylonitrile-based carbon fibres in DuPont J-2 aromatic polyamide-based thermoplastic matrix. They were subjected to anodic and cathodic currents in sea water. Dynamic mechanical analysis was carried out in situ to measure the shear storage modulus (G ) and shear loss modulus (G") of 1.27mm diameter rod shaped samples, subjected to small amplitude torsional oscillations. The moduli were constant with time in air. 

Average fiber diameter Central composite design Contact angle Dimethylformamide Nanofibers Polyacrylonitrile... 

Electrospun carbon precursor fibers, based on polyacrylonitrile (PAN] and mesophase pitch, having diameters in the range from 100 nm to a few microns, were stabilized and carbonized. These carbon nanofibers had a very high aspect ratio. Nanopores were produced in CNFs made from PAN by a high-temperature reaction with water vapor carried in nitrogen gas by increasing the surface area per unit mass of carbon black. For conductive CNT/polymer composite fibers, CNTs were incorporated into poly(vinylidene fluoride) (PVDF) in iV,iV-dimethylformamide [DMF] solutions and electrospun to form CNT/PVDF fiber mats.The thinnest fiber was obtained as 7 0 nm in diameter. 

Figure 8.6 shows the TEM images of silver/polypyrrole/ polyacrylonitrile composite nanofibrous mats prepared. It was reported that low AgN03 content could decrease the diameters of the Ag/PAN fibers and higher AgNOs concentration led to increase in the diameters of the hybrid fibers due to the high content of the solute in the electrospinning solution. ... 

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