Polyvinyl chemical modification

Nitrile rubber adhesives. The main application corresponds to laminating adhesives. PVC, polyvinyl acetate and other polymeric films can be laminated to several metals, including aluminium and brass, by using NBR adhesives. NBR adhesives can also be used to join medium-to-high polarity rubbers to polyamide substrates. The adhesive properties of NBR rubbers can be further improved by chemical modification using polyisocyanate or by grafting with methyl methacrylate. 

Chemical Modification of Polyvinyl Chloride and Related Polymers... 

Widespread chlorine-containing polymers would include, 1) stable molding material for practical use such as polyvinyl chloride (PVC), polyvinylidene chloride and poly(epichlorohydrin)(PECH) and, 2) reactive polymers capable to introduce additional functional groups via their active chlorines such as chloromethyl polystyrene, poly (3-chloroethyl vinyl-ether) and poly (vinyl chloroacetate). While the latter, especially the chloromethyl polystyrene, has been widely used recently for the synthesis of variety of functional polymers, we should like to talk in this article about the chemical modification of the former, mainly of PVC and PECH, which was developed in our laboratory. 

The second group already contains donor groups (usually oxygen or nitrogen) and, thus, requires no further chemical modification. These include polyacrylic acid (82, 83), polyvinyl alcohol (60), polymeric Schiff s bases (65), poly-L-methylethylenimine (52), poly-2-vinylpyridine (78, 79, 98), poly-4-vinylpyridine (24), and polyvinylamine (54, 59). 

Chemical modification of polymers continues to be an active field of research [1-5]. It is a common means of changing and optimising the physical, mechanical and technological properties of polymers [5-7]. It is also a unique route to produce polymers with unusual chemical structure and composition that are otherwise inaccessible or very difficult to prepare by conventional polymerisation methods. For example, hydrogenated nitrile rubber (HNBR) which has a structure which resembles that of the copolymer ethylene and acrylonitrile, is very difficult to prepare by conventional copolymerisation of the monomers. Polyvinyl alcohol can only be prepared by hydrolysis of polyvinyl acetate. Most of the rubbers or rubbery materials have unsaturation in their main chain and/or in their pendent groups. So these materials are very susceptible towards chemical reactions compared to their saturated counterparts. 

Water-dispersible lecithins are made by chemical modification, or by mixing ordinary lecithin with nonionic surfactants. Many of the products recommended in the literature and technical brochures for water-based compositions include such chemically modified, water-dispersible, lecithin compounds (e.g., hydroxy-lated, acylated, fractionated, and refined grades) (428, 431 33). Usually 0.5% to 1% modified lecithin is recommended in polyvinyl acetate-based paints, acrylic emulsions, and in butadiene—styrene emulsion paints. 

Very often used in various applications are the monoliths whose preparation routes involve chemical modifications with ethylenediamine, diethylamine or periodate, as well as grafting of monolithic pore surface via attachment of glucose, polyvinyl alcohol, dextran, ethyl cellulose, or 1,3-di-trimethylolpropane [122,128,164—167]. 

Synthesis. The polyvinyl block [polybutadiene or polystyrene) is synthesized by anionic polymerization, then the chemical modification of the living ends provides a polymer terminated by a primary amine function which is used to initiate the polymerization of the NCA of the desired a amino acid [7,8). 

Amination of the living end. At the end of the polymerization of the polyvinyl block we carry out a chemical modification of the living end in order to obtain a polymer terminated by a primary amine function. To perform this modification we have followed two different ways in the first way an intermediary hydroxyl function is involved while in the second way an intermediary carboxyl function is used. 

The chemical modification of homopolymers such as polyvinylchloride, polyethylene, poly(chloroalkylene sulfides), polysulfones,poly-chloromethylstyrene, polyisobutylene, polysodium acrylate, polyvinyl alcohol, polyvinyl chloroformate, sulfonated polystyrene block and graft copolymers such as poly(styrene-block-ethylene-co-butylene-block-styrene), poly(1,4-polybutadiene-block ethylene oxide), star chlorine-telechelic polyisobutylene, poly(lsobutylene-co-2,3-dimethy1-1,3-butadiene), poly(styrene-co-N-butylmethacrylate) cellulose, dex-tran and inulin, is described. 

Chlorinated Polyvinyl Chloride. As implied by its name, chlorinated polyvinyl chloride (CPVC) is a chemical modification of PVC. CPVC has properties very similar to PVC but the extra chlorine in its structure extends its temperature limitation by about 50°F (28°C), to nearly 200°F (93°C) for pressure uses and about 210°F (99°C) for nonpressure applications. ASTM D 1784, the rigid PVC materials specification, also covers CPVC which it classifies as Class 23477-B. By the older designation system, it is known as Type IV, Grade 1 PVC. CPVCs for pressure pipe are designated CPVC 4120 [i.e.. Type IV, Grade 1 CPVC with a maximum recommended hydrostatic design stress of 2000 Ib/in (13.8 MPa) for water at 73.4°F (23°C)]. At 180°F (82°C) the maximum recommended hydrostatic design stress for CPVC is 500 Ib/in (3.4 MPa). 

The first section, Chemical Reactions on Polymers, deals with aspects of chemical reactions occurring on polymers—aspects relating to polymer size, shape, and composition are described in detail. One of the timely fields of applications comprises the use of modified polymers as catalysts (such as the immobilization of centers for homogeneous catalysis). This topic is considered in detail in Chapters 2, 3, 8, 9, and 11 and dealt with to a lesser extent in other chapters. The use of models and neighboring group effect(s) is described in detail. The modification of polymers for chemical and physical change is also described in detail in Chapters 2 (polystyrene) 4 (polyvinyl chloride) 5 (polyacrylic acid, polyvinyl alcohol, polyethyleneimine, and polyacrylamide) 6 (polyimides) 7 (polyvinyl alcohol) 8 (polystyrene sulfonate and polyvinylphosphonate) 10 (polyacrylamide) and 12 (organotin carboxylates). 

With the war years, polyvinyl chloride (PVC) resins came under study, and plasticized PVC compounds, based on these resins, became available as calendered sheet lining materials-the material of choice for stainless steel pickling and for chrome plating and other exposure employing mixtures of chemicals including such strong oxidants as nitric and chromic acid which rapidly attack natural rubber. (A higher temperature limit modification now seldom seen is PVDC, for which the continuous temperature limit is said to be 170°-180°F.)... 

Polypropylene, polyethylene, and its copolymers, including polyvinyl alcohol-co-ethylene (EVAL) and polyethylene-co-maleic anhydride, are often reported in the literature as affinity supports for different ligand chemistries (Figure 6.5). Bare polyethylene and polypropylene membranes have good thermal, mechanical, and chemical resistance but are inert and show a too high nonspecific adsorption of biomolecules. Therefore, an additional surface modification step... 

The main use for phenolic resins is in oleoresinous varnishes. Apart from the chemical-resistant finishes produced with epoxy resins (Chapter 14), other outlets include modification of alkyds to improve resistance to water and alkali, combination with U/F resins (Chapter 13) to provide metal coatings and combination with polyvinyl formal or butyral resins to produce wire enamels. 

In nature as well as in technology, polymeric emulsifiers and stabiUzers play a major role in the preparation and stabiUzation of emulsions. Natural materials such as proteins, starches, gums, cellulosics, and their modifications, as well as synthetic materials such as polyvinyl alcohol, polyacryhc add, and polyvinylpyrrolidone, have several characteristics that make them extremely useful in emulsion technology. By the proper choice of chemical composition, such materials can be made to adsorb strongly at the interface between the continuous and dispersed phases. By their presence, they can reduce interfacial tension and/or form a barrier (electrostatic and/or steric) between drops. In addition, their solvation properties serve to increase the effective adsorbed layer thickness, increase interfacial viscosity, and introduce other factors that tend to favor the stabilization of the system. 

Here advantage is taken of modification by swelling and adsorption of chemically reactive modifiers and catalysts into the polymer to generate different functional groups. It has been shown that the pendant hydroxyl groups of polyvinyl alcohol (PVA) and poly-2-hydroxy propyl methacrylate can partially be reacted with acetic or benzoic anhydride or phenyl isocyanate to form new structures [44], to form side groups with ester linkages. As a result a copolymer of is produced ... 

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