PAN/PVC

Alginate-polylysine has been used to encapsulate hepatocytes (32-34), parathyroid cells (35) and growth hormone transfected fibroblasts (36). Poly (acryl-onitrile/vinyl chloride) (PAN/PVC) macrocapsules have been used with PC12 (37, 38), embryonic mesencephalon tissue (39), thymic epithelial cells (40), adrenal chromaffin cells (41) and islets (25) using preformed hollow fibers or more recently coextrusion techniques (41) similar to those we have developed microcapsules cannot be made since DMSO is used as the solvent. All these studies have concluded from the maintenance of viability of the islets or cells that immunoprotection provided by the capsule membrane was compatible with... 

Broadhead and Tresco studied the effects of fabrication conditions on the structures and performances of membranes formed from poly(acrylonitrile-vinylchloride) (PAN-PVC) by using the phase inversion process [85]. They reported the relationship of the fine-surface structure of PAN-PVC membranes to the membrane performance and membrane fabrication method. The fine-surface structure of nodular elements and the size of these elements could be altered by changing the precipitation conditions. Membranes were prepared at 22 on 55 mm diameter polished silicon wafers by spinning at 1500 rpm for 20 s with a spin coater [86]. The film was immediately precipitated in one of the four different precipitation media. The first three media consisted of deionized water at 4,22, and 54 °C. These membranes were referred to as Type 1 , Type 2 , and Type 3 , respectively. The fourth medium was a 50/50 mixture of deionized water and N,iV-dimethylformamide (DMF) at 54 °C and coded as Type 4 . Figure 4.53 shows the histograms of the nodule size distributions observed at the skinned surface of the membranes made under four different precipitation conditions. The sizes of these nodular elements became smaller and more uniform with milder precipitation conditions, which supports the theory that nodules are formed through spinodal decomposition under these conditions. In addition, the size of these nodules could be related to water permeability. Hence, water transport occurred through the interstitial spaces where the pores could be situated. 

Ashallow plastic pan (PVC) at least 12 14" 1" and a half pint plastic container (PVC) with tightly closing lid. 

Such synthesis processes may be also exemplified for CEL triacetate-CEL [351], and, respectively, PAN-PVC mixtures [693]. 

Bridge, M. J., Broadhead, K. W., Hlady, V, and Tresco, P. A. (2002). Ethanol treatment alters the ultrastructure and permeability of PAN-PVC hollow fiber cell encapsulation membranes. J. Membr. Sci. 195, 51-64. 

PAN, PVC, and PVdF have been broadly used as matrix polymers in plasticized polymer electrolytes with a room temperature ionic conductivity in the order of 10 S/cm. However, they cannot completely satisfy the requirements for the high mechanical strength, long-term phase stability, and good adhesion to the electrode. As for this aspect, the copolymerization or blending with polymers has been proposed to improve the performance of polymer electrolytes. Blending is more useful because of the ease of preparation and control of polymer electrolytes by changing the composition of blended polymer matrices. 

Reduction or even complete compensation of birefringence by mixing polymers with positive birefringence (PC, PVC, PETP, PPE, PVDF, etc) with polymers with negative birefringence (PMMA, PS, PAN, etc) has been the consistent strategy. 

Polymer Solvent. Sulfolane is a solvent for a variety of polymers, including polyacrylonitrile (PAN), poly(vinyhdene cyanide), poly(vinyl chloride) (PVC), poly(vinyl fluoride), and polysulfones (124—129). Sulfolane solutions of PAN, poly(vinyhdene cyanide), and PVC have been patented for fiber-spinning processes, in which the relatively low solution viscosity, good thermal stabiUty, and comparatively low solvent toxicity of sulfolane are advantageous. Powdered perfluorocarbon copolymers bearing sulfo or carboxy groups have been prepared by precipitation from sulfolane solution with toluene at temperatures below 300°C. Particle sizes of 0.5—100 p.m result. 

Heterogeneous polymerization is characteristic of a number of monomers, including vinyl chloride and acrylonitrile. A completely satisfactory mechanism for these reactions has not been deterrnined. This is tme for VDC also. Earlier studies have not been broad enough to elucidate the mechanism (26,30,31). Morphologies of as-polymerized poly(vinyl chloride) (PVC) and polyacrylonitrile (PAN) are similar, suggesting a similar mechanism. 

Figure 2. Polymerization temperature vs. limiting conversion for different monomer-polymer systems (4) ( 7) PMMA ( ) PAN (x) PS (O) PVC.

In 1968, a French Patent issued to the Sumitomo Chemical Company disclosed the polymerization of several vinyl monomers in C02 [84], The United States version of this patent was issued in 1970, when Fukui and coworkers demonstrated the precipitation polymerization of several hydrocarbon monomers in liquid and supercritical C02 [85], As examples of this methodology, they demonstrated the preparation of the homopolymers PVC, PS, poly(acrylonitrile) (PAN), poly(acrylic acid) (PAA), and poly(vinyl acetate) (PVAc). In addition, they prepared the random copolymers PS-co-PMMA and PVC-co-PVAc. In 1986, the BASF Corporation was issued a Canadian Patent for the preparation of polymer powders through the precipitation polymerization of monomers in carbon dioxide at superatmospheric pressures [86], Monomers which were polymerized as examples in this patent included 2-hydroxyethylacrylate and iV-vinylcarboxamides such as iV-vinyl formamide and iV-vinyl pyrrolidone. 

Fig. 1 Chemical structures of the polymers commonly used for preparation of beads poly (styrene-co-maleic acid) (=PS-MA) poly(methyl methacrylate-co-methacrylic acid) (=PMMA-MA) poly(acrylonitrile-co-acrylic acid) (=PAN-AA) polyvinylchloride (=PVC) polysulfone (=PSulf) ethylcellulose (=EC) cellulose acetate (=CAc) polyacrylamide (=PAAm) poly(sty-rene-Wocfc-vinylpyrrolidone) (=PS-PVP) and Organically modified silica (=Ormosil). PS-MA is commercially available as an anhydride and negative charges on the bead surface are generated during preparation of the beads...

PBDEs are used in different resins, polymers, and substrates at levels ranging from 5 to 30% by weight (EU 2001). Plastic materials that utilize PBDEs as flame retardants include ABS polyacrylonitrile (PAN) polyamide(PA) polybutylene terephthalate (PBT) polyethylene (PE) cross-linked polyethylene (XPE) polyethylene terephthalate (PET) polypropylene (PP) polystyrene (PS) high-impact polystyrene (HIPS) polyvinyl chloride (PVC) polyurethane (PUR) and unsaturated polyester (UPE). These polymers and examples of their final products are summarized inTable 5-2 (Hardy 2002 WHO 1994a). 

ABS = Acrylonitrile Butadene Styrene PA = Polyamide PAN = Polyacrylonitrile PBT = Polybbutylene Terephthalate PE= Polyethylene PET = Polyethylene Terephthalate PP = Polypropylene PUR = Polyirethane PVC = Polyvinyl chloride UPE = Un saturated polyester XPE = Cross-linked polyethylene ... 

Eq. (5) in conjunction with Eqs. (8) and (9) have, so far, provided adequate representation of experimental isotherms6 32, which are characterized by an initial con vex-upward portion but tend to become linear at high pressures. Values of K, K2 and s0 have been deduced by appropriate curve-fitting procedures for a wide variety of polymer-gas systems. Among the polymers involved in recent studies of this kind, one may cite polyethylene terephthalate (PET) l2 I4), polycarbonate (PC) 19 22,27), a polyimide l6,17), polymethyl and polyethyl methacrylates (PMMA and PEMA)l8), polyacrylonitrile (PAN)15), a copolyester 26), a polysulphone 23), polyphenylene oxide (PPO)25), polystyrene (PS) 27 28), polyvinyl acetate 29) and chloride 32) (PVAc and PVC), ethyl cellulose 24) (EC) and cellulose acetate (CA) 30,3I>. A considerable number of gases have been used as penetrants, notably He, Ar, N2, C02, S02 and light hydrocarbons. 

In 2.6 we have looked at the types of interaction forces which can occur between chains. The strongest of these are the dipole forces. Their effect on Tg is illustrated by the series PP, PVC and PAN, in which the chain mobility hardly varies because the side groups are of about equal size, but in which, in the order of sequence mentioned, the dipole interactions increase. 

Middle Polarity Acrylonitrile (PAN) Polystyrene (PS) Polyvinyl chloride (PVC) Polyethylene lerephthalate (PET) Polycarbonate (PC)... 

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