Polymerization polyamids

Nanofiltration membranes usually have good rejections of organic compounds having molecular weights above 200—500 (114,115). NF provides the possibility of selective separation of certain organics from concentrated monovalent salt solutions such as NaCl. The most important nanofiltration membranes are composite membranes made by interfacial polymerization. Polyamides made from piperazine and aromatic acyl chlorides are examples of widely used nanofiltration membrane. Nanofiltration has been used in several commercial applications, among which are demineralization, oiganic removal, heavy-metal removal, and color removal (116). 

Ring-Opening Polymerization. Polyamides can be formed by ringopening reactions as in the polymerization of caprolactam. The polymerization may be carried out at high temperature with water, amino acid, or amine carboxylate salt as Initiator. The predominate ring-opening mechanism with these initiators is carboxyl-catalyzed aminolysls. In the case of water initiation, hydrolysis occurs (Reaction 10) to form small amounts of the amino acid. The amino acid then reacts with lactam amide groups (Reaction 11). 

Figure 9.14 Steady shear viscosity at 235°C for polyamide, in-situ polymerized polyamide nanocomposites and melt-blended polyamide nanocomposites. Reprinted from [61] with permission from Elsevier.

The clay platelets may not exfoHate fully in melt blending technique. Homogeneously exfoliated clay platelets can be obtained in in-situ polymerized polyamide nanocomposites [54]. These structrues can be observed only from transmission electron micrographs, since the XRD patterns may... 

A semicOTitinuous manufacturing process in which two liquid compmients are metered in the calculated ratio by high pressure piston pumps, mixed by impingement mixing and injected into a mold cavity or cavities, where the reactants are polymerized or cured. The process has been used to polymerize polyamides, elastomeric polyurethanes, and polyurethane foams. 

Xu, X. and Kirkpatrick, R.J. 2006. NaCl interaction with interfacially polymerized polyamide films of reverse osmosis membranes A solid-state Na NMR study. J. Membr. Sci. 280 226-233. 

Nucleophilic addition of RuH2(PPh3)4 to nitrile proceeds under neutral conditions or near neutral conditions [66a], Nitrile reacts with water in the presence of RuH2(PPH3)4 catalysts to afford amide in high yield and nitrile reacts with amine in the presence of water to afford amide in a high yield by an addition condensation as shown in eq. (16.28a). Further, dinitrile reacts with diamine to afford a polymeric polyamide by an addition condensation as shown in eq. (16.28b) [66a,79a]. 

The most important chain-growth polymers are polyolefins and other vinyl polymers. Examples of the former are polyethylene, and polypropylene, and examples of the latter are poly(vinyl chloride), polystyrene, poly(vinyl alcohol), polyacrylonitrile, and poly(methyl acrylates). The most common stepwise reactions are condensation polymerizations. Polyamides, such as nylon 6-6, which is poly(hexamethylene adipamide), and polyesters, such as poly(ethylene terephthalate), are the most important commercial condensation polymers. These polymers were originally developed for use in fiber manufacture because of their high melting points but are now used also as thermoplastics. Polycarbonate is an engineering plastic that is made from bisphenol A and phosgene by a stepwise reaction. 

The field of step-growth polymers encompasses many polymer structures and polymerization reaction types. This chapter attempts to cover topics in step-growth polymerization outside of the areas reviewed in the other introductory chapters in this book, i.e., poly(aryl ethers), dendritic polymers, high-temperature polymers and transition-metal catalyzed polymerizations. Polyamides, polyesters, polycarbonates, poly(phenylene sulfides) and other important polymer systems are addressed. The chapter is not a comprehensive review but rather an overview of some of the more interesting recent research results reported for these step-growth polymers, including new polymerization chemistries and mechanistic studies. 

Yoon, K., Hsiao, B., Chu, B., 2009, High flux nanofiltration membranes based on inter-facially polymerized polyamide barrier layer on polyacrylonitrile scaffolds, 7 Afemfc Sci 326(2) 484-492. 

I.J. Roh, A.R. Greenberg, V.P. Khare, Synthesis and characterization of interfacially polymerized polyamide thin films. Desalination, 191 (2006) 279-290. 

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