Amine solvent/chemical resistance

In general, polycarbonate resins have fair chemical resistance to aqueous solutions of acids or bases, as well as to fats and oils. Chemical attack by amines or ammonium hydroxide occurs, however, and aUphatic and aromatic hydrocarbons promote crazing of stressed molded samples. Eor these reasons, care must be exercised in the choice of solvents for painting and coating operations. Eor sheet appHcations, polycarbonate is commonly coated with a sihcone—sihcate hardcoat which provides abrasion resistance as well as increased solvent resistance. Coated films are also available. 

The chemical resistance of the linear polymers is also very good. Resistant to most acids, aqueous bases, hydrocarbons, most halogenated hydrocarbons, alcohols and phenols, they are attacked by concentrated sulphuric acid, formic acid, some amines, benzaldehyde, nitromethane and a few other reagents. They will dissolve in 1-chloronaphthalene at elevated temperatures but in general have excellent solvent resistance. The polymer is cross-linked by air oxidation at elevated temperatures. 

Primary and secondary aliphatic amines react relatively rapidly with epoxy groups at room or lower temperature to form three-dimensional crosslinked structures. The resulting cured epoxies have relatively high moisture resistance and good chemical resistance, particularly to solvents. They also have moderate heat resistance with a heat distortion temperature in the range of 70 to 110°C. Thus, short-term exposures of cured adhesive joints at temperatures up to 100°C can generally be tolerated. 

Structure 4.1) [7,8,42] as well as absence of unstable biuret and allophanate units [9] seem to be responsible for increased thermal stability and chemical resistance to nonpolar solvents. The reactivity of amine is shown in Scheme 4.2 [42],... 

Typically, a low molecular weight solid epoxy resin and latent curing agent, such as dicyandiamide dissolved in an appropriate solvent, are widely used in dry lay-up formulations for electrical laminates for computers, aerospace applications, and communications equipment. Wet lay-up systems are almost exclusively based on low-viscosity resins cured with aliphatic amines. These ambient cure resin systems are used primarily for manufacture of large chemical-resistant tanks, ducting, and scrubbers. Filament winding is used... 

In addition, the film has a long life and is resistant to the water, solvents, chemicals, acids, and alkali normally found in chemical and industrial environments. The epoxy-polyamide coatings have less resistance to strong solvents than do amine-cured systems, and their heat resistance tends to be somewhat lower. The properties of these coatings have been described in detail in several publications (32. 33). 

Polyamideimides (PAI) were obtained by polycondensation of imides with aromatic di-amines, [-N=(CO)2=(t)-CO-NH-R-NH-CO-(t)=(CO)2=N-] (Tg = 275°C, HDT = 265-280°C). The resin has high tensile and impact strength from T = -190 to T = 260°C, dimensional stability, good dielectric properties, solvent and chemical resistance, flame retardancy, good UV stability and low outgassing in high vacuum. To improve processability, PAI was blended with PA, PSF, or PEST [Toray Industries, Inc., 1979]. 

The chemical resistance of ECTFE is outstanding. It is resistant to most of the common corrosive chemicals encountered in industry. Included in this list of chemicals are strong mineral and oxidizing acids, alkalies, metal etchants, liquid oxygen, and practically all organic solvents except hot amines (aniline, dimethylamine, etc.). No known solvent dissolves or stress cracks ECTFE at temperatures up to 250°F (120°C). 

Polyvinylindene fluoride. Polyvinylindene fluoride (PVDF) is crystalline with a melting point near 170°C. The structure of PVDF is shown in Fig. 1.10. PVDF has good chemical and weather resistance, along with good resistance to distortion and creep at low and high temperatures. Although the chemical resistance is good, the polymer can be affected by very polar solvents, primary amines, and concentrated acids. PVDF has limited use as an insulator because the dielectric properties are frequency dependent. The polymer is important because of its relatively... 

Cycloalipatic amine Room temperature-curing, convenient handling, long pot life, better toughness and thermal properties of the resulting network compared with aliphatic amine-cured network High cost, can work at a service temperature <100 C poor chemical resistance poor solvent resistance... 

While epoxy resins are known for excellent chemical resistance properties, the development and commercialization of epoxy vinyl ester resins in the 1970s by Shell and Dow offered enhanced resistance properties for hard-to-hold, corrosive chemicals such as acids, bases, and organic solvents. In conjimction with the development of the structural composites industry, epoxy vinyl ester resin composites found applications in demanding environments snch as tanks, pipes and ancillary equipment for petrochemical plants and oil refineries, automotive valve covers, and oil pans. More recently, epoxy and vinyl esters are used in the construction of windmill blades for wind energy farms. Increasing requirements in the composite industries for aerospace and defense applications in the 1980s led to the development of new, high performance multifunctional epoxy resins based on complex amine and phenolic structures. Examples of those products are the trisphenol epoxy novolacs developed by Dow Chemical and now marketed by Huntsman (formerly Ciba). 

Polyamide resins can be reacted with epoxies to form durable protective linings with a temperature resistance of 225°F/107°C dry and 150°F/60°C wet. The chemical resistance of epoxy polyamides is inferior to that of the amine cured epoxies. They are partially resistant to acids, acid salts, alkaline and organic solvents and resistant to moisture. Refer to Table 6.5 for the compatibility of epoxy polyamides with selected corrodents and to Ref. 1 for a more comprehensive listing. 

Epoxies Epoxy binders are made of relatively low molecular weight resins in which the epoxy group is at the end of each molecule. The epoxy resins are then reacted with amines of various molecular weight and cured to form high molecular weight binders with good solvent and chemical resistance. 

Chemical resistance in ECTFE is excellent. ECTFE is resistant to mineral acids, oxidizing acids, inorganic bases, and all solvents it is not resistant to hot amines [86]. 

Glue can be modified by a variety of chemical reactions, including acetylation of the hydroxyl groups, alcoholysis to yield amino acid esters, and aryl sulfonation to give complexes insoluble in water but soluble in organic solvent. Reaction with fatty amines improves water resistance. Quatemization yields cationic molecules. The literature abounds with ideas for modification. 

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