Carboxyl Chemical resistance

When compounded to form ebonites they show improved chemical resistance especially to carboxylic acids and may be used for some oxidative chemicals depending on type and operating temperatures. Ebonites can be compounded to be suitable for working temperatures up to at least 100°C, but, due to brittleness, are not normally suitable for sub-zero temperatures. 

If the chemistry of polymer molecules were different from that of simple compounds resembling the repeating units (model compounds), the study of the chemical resistance of organic polymers would be difficult. Fortunately, Nobel laureate Paul Flory found that the rate of esterification of molecules with terminal hydroxyl and carboxyl groups is essentially independent of the size of the molecules. Thus it is customary to assume that the rates of most reactions of organic molecules are similar regardless of the size of the molecule. 

Carboxylic acids react with aryl isocyanates, at elevated temperatures to yield anhydrides. The anhydrides subsequently evolve carbon dioxide to yield amines at elevated temperatures (70—72). The aromatic amines are further converted into amides by reaction with excess anhydride. Ortho diacids, such as phthalic acid [88-99-3], react with aryl isocyanates to yield the corresponding N-aryl phthalimides (73). Reactions with carboxylic acids are irreversible and commercially used to prepare polyamides and polyimides, two classes of high performance polymers for high temperature applications where chemical resistance is important. Base catalysis is recommended to reduce the formation of substituted urea by-products (74). 

Epoxy-nitrile Nitrile-epoxy adhesives are composed of solid epoxy resin modified with carboxyl-terminated butadiene nitrile (CTBN) copolymer. The CBTN is introduced into die epoxy resin at elevated temperatures. The modification provides toughness and high peel strength without sacrificing heat and chemical resistance. The film adhesives are widely used in the aerospace industry in the construction of jetliners. 

Ionomers are used to prepare membranes for a variety of applications including dialysis, reverse osmosis, and in electrolytic cells for the chlor-alkali industry. This latter application needs materials that show good chemical resistance and ionomers based on perfluorinated backbones with minor amounts of sulfonic or carboxylic acids are ideal. They also show good ion-exchange properties. 

Epoxy modification provides the ability to cross-link with carboxyl-modified vinyl resins to give an all-vinyl reactive system that yields thermoset-like characteristics, most notably improved toughness, enhanced physical properties and superior chemical resistance (Union Carbide Corp., 19%). 

Ionomer membranes based on perfluorocarbon polymers became available In the late 196O s. These materials have excellent chemical resistance, thermal stability, mechanical strength and strong acid strength, A number of functionalities have been studied. Including carboxylate, sulfonate and sulfonamide, but only the first two are available as commercial materials. Ferfluorlnated lonomers have been evaluated as membranes In a variety of applications, such as water electrolysis, fuel cells, air driers, Donnan dialysis In waste metal recovery, and acid catalysts, but the primary interest in these materials is for the permselective membrane In electrochemical processes such as In the production of chlorine and caustic (58). 

A good measure of past and continuing interest in ionomer membranes issued from the development of perfluorinated ionomers, the first-announced being Nafion(44). These materials are characterized by remarkable chemical resistance, thermal stability and mechanical strength, and they have a very strong acid strength, even in the carboxylic acid form. The functionalities that have been considered include carboxylate, sulfonate, and sulfonamide, the latter resulting from the reactions of amines with the sulfonyl fluoride precursor. 

In many cases the use of epoxy materials in so-called field conditions (for industrial, construction sites, etc.) demand an increase in the reaction velocity, which is usually achieved by adding accelerators. At present, the widely used accelerators include alkyl-substituted phenols, benzyl alcohol, carboxylic acids (in particular, salicylic acid), and others. A major disadvantage of these accelerators is their tendency to migrate from the cured epoxy matrix during the exploitation, which could lead to a change in the physical properties of the polymer. They also act as a plasticizer of epoxy-based polymers, and as a result reduce the polymer s chemical resistance. Thus, there is a need for new accelerator-modifiers that can provide faster curing of epoxy-amine compositions without negative side effects, and also improve the properties of the finished product. 

The mechanical properties and chemical resistance of nano-coatings are significantly higher when using surfactants with terminal carboxyl groups. 

Commercial ionomers are ethylene-methacrylic acid copolymers and terpolymers in which the carboxylic acid moiety is partially neutralized with sodium or zinc, to promote interchain ionic bonding. Ionomers exhibit excellent low temperature toughness, chemical resistance and adhesion. However they lack in stiffness and heat resistance. Hence ionomer blends with polyolefins such as polyethylene have been developed which, upon reinforcing with suitable fillers, seem to give a unique combination of high strength, excellent low temperature toughness, and moderate stiff-... 

Nitrile rubbers are known for their oil and chemical resistance and addition of PVC improves the ozone resistance. Use of carboxylated NBR is believed to obviate the necessity of vulcanization. 

Vinyl chloride terpolymers containing carboxyl groups adhere extremely well to metals. Due to their speeial properties (outstanding adhesion to aluminum, good chemical resistance, heat-sealable from ca. 140""C—the sealing temperatures can be lowered by adding plasticizers) these copolymers are ideal binders for heat-sealable finishes of aluminum foils used in the packaging sector. 

If less stringent requirements with regard to chemical resistance, abrasion, and hardness are placed on the cross-linking density, carboxyl-containing acrylates can also be cross-linked by salt formation (e.g., with diamines [2.44] or metal complexes [2.61]). This procedure is widely employed, particularly for aqueous dispersions. Cross-linking with bisoxazolines has also been reported [2.45]. Epoxy groups can be incorporated into the binder via glycidyl (meth)acrylate and cross-linked with dicar-boxylic acids [2.40]. 

The presence of reactive sites such as double bonds, hydroxyl and carboxyl groups and phenyl rings in aromatic anhydride and ester linkages all provide tremendous potential for the modification of oil-modified polyester. Epoxy resins are considered to be polyols, which react with the carboxylic functions of polyester resin. The modification of oil-modified polyesters with epoxy resins results in products with excellent adhesion properties and improved water and chemical resistance. Epoxy modified polyesters are less expensive than epoxy resins. 

This paper reports on the synthesis, characterisation, and applications of novel flame retardant dibromostyrene-based latexes. They are copolymers of dibromostyrene with butadiene, alkyl acrylates and methacrylates, vinyl acetate, styrene and unsaturated carboxylic acids, which form a wide variety of flame retardant latexes via an emulsion polymerisation technique. Choice of monomer or monomer blend is based upon the final glass transition temperature of the copolymer desired. Other criteria include desired physical properties and chemical resistance. Dibromostyrene-based butadiene and acryUc latexes are shown to possess the desired physical properties for use in coatings, adhesives and sealants, and the bromine content of the latexes has enabled the material to pass six different flammability requirements for the end uses such as textile backcoating, latex-based paint, contact adhesive, latex sealant, nonwoven binder, and carpet backing. 18 refs. 

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