Polyacrylonitrile polytetrafluoroethylene

A list of typical commercial pervaporation membranes [23] is given in Table 3.1. Commercial hydrophilic membranes are very often made of polyvinyl alcohol (PVA), with differences in the degree of crosslinking. Commercial hydrophobic membranes often have a top layer in polydimethyl siloxane (PDMS). However, a wide variety of membrane materials for pervaporation can be found in the literature, including polymethylglutamate, polyacrylonitrile, polytetrafluoroethylene, polyvinylpyrrolidone, styrene-butadiene rubber, polyacrylic acid, and many others [24]. A comprehensive overview of membrane materials for pervaporation is given by Semenova et al. [25],... 

Graft copolymer of A -vinylpyrrolidone with such polymers as dextran, poly(acrylate esters), polyacrylonitrile, polytetrafluoroethylene, poly(methyl methacrylate) films, polyester films, and polyolefins have been reported [24]. 

There is much evidence that weak links are present in the chains of most polymer species. These weak points may be at a terminal position and arise from the specific mechanism of chain termination or may be non-terminal and arise from a momentary aberration in the modus operandi of the polymerisation reaction. Because of these weak points it is found that polyethylene, polytetrafluoroethylene and poly(vinyl chloride), to take just three well-known examples, have a much lower resistance to thermal degradation than low molecular weight analogues. For similar reasons polyacrylonitrile and natural rubber may degrade whilst being dissolved in suitable solvents. 

Various polymeric materials were tested statically with both gaseous and liquefied mixtures of fluorine and oxygen containing from 50 to 100% of the former. The materials which burned or reacted violently were phenol—formaldehyde resins (Bakelite) polyacrylonitrile—butadiene (Buna N) polyamides (Nylon) polychlor-oprene (Neoprene) polyethylene polytrifluoropropylmethylsiloxane (LS63) polyvinyl chloride—vinyl acetate (Tygan) polyvinylidene fluoride—hexafluoropro-pylene (Viton) polyurethane foam. Under dynamic conditions of flow and pressure, the more resistant materials which burned were chlorinated polyethylenes, polymethyl methacrylate (Perspex) polytetrafluoroethylene (Teflon). 

Other polymeric materials (Figure 3.7) including polystyrene, polyvinylchloride (PVC), polytetrafluoroethylene (PTFE), polyvinylenedifluorate (PVDF), polyacrylonitrile (PAN), polycarbonates, polyacrylates and polymethacrylates, polyetherur-ethane, as well as various inorganic materials have been used as chromatographic supports. 

Polytetrafluoroethylene Polyacrylonitrile Poly(vinyl alcohol) Poly(vinyl acetate)... 

The objects of our investigations were four kinds of elastomers, of different structure and polarity, viz. cis-1,4-polybutadiene (BR)> butadiene-acrylonitrile copolymer (NBR), isobutylene-isoprene copolymers (IIR) and ethylene-propylene-diene terpolymer (EPT). They were mixed with plastomers low density polyethylene (PE] ), polystyrene (PS), polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), polycaproamide (PCA) and polyacrylonitrile (PAN) (Table 1). The concentration of the plastomers in the mixtures was changed in the range from 0 to 50 pph of the elastomer. The polymers were blended at temperature T = 423 K by means of the micromill of the Plasti--Corder apparatus. After 24 hours, crosslinking substances, dicurayl peroxide (DCP) or sulphur and diphenylguanidine (S, DPG), were added at room temperature. The composition of the mixtures is given in Table 2. 

This process is used in the production of sodium polyacrylate, a superabsorbent polymer and neoprene used in disposable diapers and wetsuits, respectively. The polymers produced using this method are generally polyacrylonitrile (PAN), polyacrylic acid, and polytetrafluoroethylene. 

Solubility parameter (SP, 8) n. The square root of the cohesive energy density of a polymer, solvent, or adhesive. For solvents, SP equals the square root of the heat of vaporization per unit volume (J/cm )°. Values for polymers (which do not vaporize) are found by indirect methods. If the solubility parameters of a polymer and solvent differ by 3 (J/cm )° or less, the polymer will probably dissolve in the solvent differ by (J/cm )° or less, the polymer will probably dissolve in the solvent. SPs for organic solvents range from 13 for neopentane to 30 methanol for polymers, from 13 for polytetrafluoroethylene to 32 for Polyacrylonitrile. Wypych G (ed) (2001) Handbook of solvents. Chemtec Publishing, New York. Barton AFM (1983) Handbook of solubility parameters and other cohesion parameters. CRC Press, Boca Raton, FT. Brandrup J, Immergut EH, Elias HG (eds) (1975) Polymer handbook. Interscience Publishers Inc., New York. 

An important example of a polymer is that of polyvinylchloride, shown in Figure 9.15. This polymer is synthesized in large quantities for the manufacture of water and sewer pipe, water-repellant liners, and other plastic materials. Other major polymers include polyethylene (plastic bags and milk cartons), polypropylene (impact-resistant plastics and indoor-outdoor carpeting), polyacrylonitrile (Orion and carpets), polystyrene (foam insulation), and polytetrafluoroethylene (Teflon coatings and bearings) the monomers from which these substances are made are shown in Figure 9.16. 

In precipitation polymerization, the reaction mixture is initially homogeneous, as in solution polymerization, but it is a precipitant for the polymer. Thus, the initially formed macromolecules collapse and coagulate to create particle nuclei, which gradually flocculate into irregularly shaped and polydisperse particles. Such a process concerns for instance the synthesis of polytetrafluoroethylene in water or polyacrylonitrile in bulk. 

PMG polymethyiglutamate PDMS polydimethylsiloxane PVA polyvinylalcohol CA cellulose acetate PAN polyacrylonitrile PTFE Polytetrafluoroethylene PVP poly vinylpyrrolidbne SBR styrene-butadiene rubber NBR nitrile-butadiene rubber CTP cellulose tripropionate PAA polyacrylic acid ... 

Polymers resistant to hydrolysis in all media include polyolefins, hydrocarbon rubbers, polystyrene, polytetrafluoroethylene, and implasticized poly(vinyl chloride). Polymers sensitive to hydrolysis in both alkaline and acidic media are, eg, cellulose esters, plasticized poly(vinyl chloride), polyCmethyl methacrylate), polyacrylonitrile, polyoxymethylene, polyamides, polyesters, polycarbonates, and polysulfones. Polymers sensitive to alkalis but not acids are imsaturated polyester resins and phenol-formaldehyde resins. 

Figure 1 Polymer interpretation chart. PAI, polyamideimide PC, polycarbonate UP, unsaturated polyester PDAP, diarylate phtalate resin VC-VAc, vinyl chloride-vinyl acetate copolymer PVAc, polyvinyl acetate PVFM, polyvinyl formal PUR, polyurethane PA, polyamide PMA, methacrylate ester polymer EVA, ethylene-vinyl acetate copolymer PF, phenol resin EP, epoxide resin PS, polystyrene ABS, acrylonitrile-butadiene-styrene copolymer PPO, polyphenylene oxide P-SULFONE, poly-sulfone PA, polyamide UF, urea resin CN, nitrocellulose PVA, polyvinyl acetate MC, methyl cellulose MF, melamine resin PAN, polyacrylonitrile PVC, polyvinyl chloride PVF, polyvinyl fluoride CR, polychloroprene CHR, polyepichlorohydrin SI, polymethylsiloxane POM, polyoxy-methylene PTFE, polytetrafluoroethylene MOD-PP, modified PP EPT, ethylene-propylene terpolymer EPR, ethylene-propylene rubber PI, polyisoprene BR, butyl rubber PMP, poly(4-methyl pentene-1) PE, poly(ethylene) PB, poly(butene-l). (Adapted from Ref. 22, p. 50.)...

Fig. 18 Activation energy of p-relaxation in (a) low-molecular weight glasses and (b) linear polymers vs the cohesion energy or cohesion energy of Kuhn statistical segment, respectively [86, 88,103]. (a) (1) Pentanol (2) isopropylbenzene (3) 5-methyl-3-heptanol (4) decalin (5) 1,1-diphenylpropane (6) diethyl phthalate (7) glycerol (8) 6>-terphenyl (9) hexamethyl disolox-ane (10) tetra-a-methylstyrene (11) pentastyrene. (b) (1) Polyethylene (2) polyisoprene (3) poly(dimethylsiloxane) (4) poly(diethylsiloxane) (5) poly(phenylene oxide) (6) poly(ethylene terephthalate) (7) polytetrafluoroethylene (8) polycarbonate (9) polyamide (10) polypropylene (11) polymethacrylate (12) poly(vinyl fluoride) (13) poly(vinyl acetate) (14) poly(vinyl chloride) (15) poly(vinyl alcohol) (16) poly(methyl methacrylate) (17) poly(diphenyl oxypheny-lene) (18) poly(butyl methacrylate) (19) polystyrene (20) polyacrylonitrile (21) poly(a-methylstyrene) (22) poly(cyclohexyl methacrylate) (23) polyimide I (24) polyimide II (25) poly(metaphenylene isophthalamide) (26) polyisobutylene...

MF and UF membranes can be polymeric or inorganic. Membrane materials must be chemical resistant to both feed and cleaning solutions, mechanically and thermally stable, and characterized by high selectivity and permeability. Polysulfone (PS), polyethersulfone (PES), polyamide (PA), cellulose acetate (CA), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), poly(vinylidene F ) (PVDF) and polypropylene (PP) are typical materials commonly used to cast the membrane. Alumina, zirconia and ceramic materials are usually used as inorganic materials. 

Synthetic and man-made Cellulose Fibers Regenerated cellulose (rayon fabric, cellophane) Polyacrylonitrile, polyamides (aliphatic (nylon), aromatic (aramid) fibers), polyester (PET), polytetrafluoroethylene, polyvinyl alcohol... 

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