Resistance solvent

At room temperature there are no known solvents for SPS. Even though the good solvents for atactic polystyrene such as toluene, benzene, tetrahydrofuran and dichloroethane can swell SPS at room temperature. Some of these solvents dissolve SPS at elevated temperatures, close to their boiling point. For example, a 5-10% by weight solution can be prepared by heating the polymer with trichlorobenzene at 160 °C with agitation. 

Solvent and chemical resistant engineering polymers are of particular importance in applications such as storage containers, chemical plants and vehicles. Polymers with particularly good solvent resistance include PEEK, epoxy resins, polymethylpentene, PP, HDPE, LDPE, PI, PA 4,6, PA 11, PAI, polyether sulfone, PPS and PTFE. 

Polymer Detergent resistance Hydrolytic stability Water absorption 

Acrylate-styrene-acrylonitrile terpolymer Very good Very good Poor (0.5%) 

Alky resins (mineral filled) Very good Poor Good (0.20%) 

Chlorinated PVC Excellent Very good Very good (0.01%) 

A wide range of solvents and chemicals can potentially be used when laying down the different layers in a display, depending on the processing steps involved. Amorphous polymers usually have poor solvent resistance compared with semicrystalline polymers (Table 7.1). 

This deficiency is overcome by application of a hard coat to the amorphous resins this substantially improves resistance to the solvents and chemicals such as NMP, IPA, acetone, methanol, THF, ethyl acetate, 98% sulfuric acid, glacial acetic acid, 30% hydrogen peroxide, and saturated bases such as sodium hydroxide [13]. With poly(ethylene terephthalate) and of poly(ethylene naphthalate) films a hard coat is not required for solvent resistance. 

The residual shrinkage of TeonexQ65 after 30 min at 150 °C is of the order of 500 ppm but can be reduced to below 200 ppm or better by careful process control. Dimensional reproducibility down to 25 ppm is being requested for the more demanding applications such as inorganic AM backplanes on flexible substrates and it has been shown that it is possible to achieve this level of shrinkage with Teo- 

Ester Ethyl acetate Good Good (Fair) (Good) 

At 150 °C the film takes 6 min to reach an equilibrium moisture level of 5 ppm but at 90 °C the film takes 30 min to reach an equilibrium level of 40 ppm. 

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Hexamethylolmelamine can further condense in the presence of an acid catalyst ether linkages can also form (see Urea Eormaldehyde ). A wide variety of resins can be obtained by careful selection of pH, reaction temperature, reactant ratio, amino monomer, and extent of condensation. Eiquid coating resins are prepared by reacting methanol or butanol with the initial methylolated products. These can be used to produce hard, solvent-resistant coatings by heating with a variety of hydroxy, carboxyl, and amide functional polymers to produce a cross-linked film. 

The polymer can be vulcanized to give a rubber with very good chemical (solvent) resistance, excellent resistance to aging and weathering, and good color retention in sunlight. 

Reinforced furan resias have been used for many years in process piping and in underground sewer or waste-disposal systems. With a wide range in pH acceptability and good solvent resistance, furan piping has been a logical choice for many services. 

Crystallinity. The crystallinity of the parylenes determines two of their most important practical characteristics mechanical strength at elevated temperatures (see Fig. 5) and solvent resistance. 

Solvent Resistance. At temperatures below the melting of the crystallites, the parylenes resist all attempts to dissolve them. Although the solvents permeate the continuous amorphous phase, they are virtually excluded from the crystalline domains. Consequently, when a parylene film is exposed to a solvent a slight swelling is observed as the solvent invades the amorphous phase. In the thin films commonly encountered, equilibrium is reached fairly quickly, within minutes to hours. The change in thickness is conveniently and precisely measured by an interference technique. As indicated in Table 6, the best solvents, specifically those chemically most like the polymer (eg, aromatics such as xylene), cause a swelling of no more than 3%. 

The polymers dissolve in l,l,l,3,3,3-hexafluoro-2-propanol [920-66-1/, hot phenols, and /V, /V- dim ethyl form am i de [68-12-2] near its boiling point. The excellent solvent resistance notwithstanding, solvents suitable for measurement of intrinsic viscosity, useflil for estimation of molecular weight, are known (13,15). 

Useflil properties of acrylonitrile copolymers, such as rigidity, gas barrier, chemical and solvent resistance, and toughness, are dependent upon the acrylonitrile content in the copolymers. The choice of the composition of SAN copolymers is dictated by their particular appHcations and performance requirements. The weU-balanced and unique properties possessed by these copolymers have led to broad usage in a wide variety of appHcations. 

Acrylonitrile has contributed the desirable properties of rigidity, high temperature resistance, clarity, solvent resistance, and gas impermeabiUty to many polymeric systems. Its availabiUty, reactivity, and low cost ensure a continuing market presence and provide potential for many new appHcations. 

Solvent Resistance. Elastomeric fibers tend to swell in certain organic solvents mbber fibers swell in hydrocarbon solvents such as hexane. Spandex fibers become highly swollen in chlorinated solvents such as tetrachloroethylene [127-18-4] (Perclene). Although the physical properties of spandex fibers return to normal after the solvent evaporates, considerable amounts of its stabilizers may have been extracted. Therefore, the development of stabilizers that are more resistant to solvent extraction has become important as solvent scouring during mill processing replaces aqueous scouring at many mills, especially in Europe (26). 

Acrylonitrile—Butadiene—Styrene. Available only as sheet, ABS has good toughness and high impact resistance. It is readily therm oform able over a wide range of temperatures and can be deeply drawn. ABS has poor solvent resistance and low continuous-use temperature. It is often used in housings for office equipment (see Acrylonitrile polymers). 

The presence of carbon—fluorine bonds in organic polymers is known to characteristically impart polymer stabiUty and solvent resistance. The poly(fluorosibcones) are siloxane polymers with fluorinated organic substituents bonded to siUcon. Poly(fluorosibcones) have unique appHcations resulting from the combination provided by fluorine substitution into a siloxane polymer stmcture (see Silicon compounds, silicones). 

The incorporation of a singlecarbon—fluorine bond into a polymer cannot provide the stabiUty and solvent resistance offered by multiple bonds or clusters ofcarbon—fluorine bonds available with substituents like the CF, 2 5 3 7 Therefore, commercially interesting po1y(fluorosi1icones)... 

Low Temperature Properties. The property of solvent resistance makes fluorosihcone elastomers usefiil where alternative fluorocarbon elastomers cannot function. The abiHty to retract to 10% of their original extension after a 100% elongation at low temperature is an important test result. Eluorosihcones can typically pass this test down to —59°C. The brittle point is approximately —68°C. 

Polyphenols. Another increa singly important example of the chemical stabilization process is the production of phenoHc foams (59—62) by cross-linking polyphenols (resoles and novolacs) (see Phenolic resins). The principal features of phenoHc foams are low flammabiUty, solvent resistance, and excellent dimensional stabiUty over a wide temperature range (59), so that they are good thermal iasulating materials. 

Halogenated hydrocarbons that are inexpensive sometimes are used alone or in blends with phosphate esters as fire-resistant hydrauHc fluids. Other halogenated fluids are used for oxygen-compressor lubricants, lubricants for vacuum pumps that are in contact with corrosive materials, solvent-resistant lubricants, and other lubricant appHcations where highly corrosive or reactive materials are being handled. 

The transparency, solvent resistance, and attractive feel of ionomer mol dings have resulted in a substantial European market in stoppers for botdes containing expensive perfumes. This is a demanding appHcation since no loss of perfume ingredients can be tolerated. 

Post-curing and chemical modification improves chemical and solvent resistance (20). Paraformaldehyde and acetylene diurea are added to a hot borax solution. Toluenesulfonamide (p and o), a few drops of phosphorous acid. Brilliant Yellow 6G [2429-76-7] Rhodamine E3B, and Rhodamine 6GDN [989-38-8] are added. After heating, the mass is cured in an oven at 150°C. The resulting cured resin is thermoset but can be ground to fine particle sizes. 

Ceramic, Metal, and Liquid Membranes. The discussion so far implies that membrane materials are organic polymers and, in fact, the vast majority of membranes used commercially are polymer based. However, interest in membranes formed from less conventional materials has increased. Ceramic membranes, a special class of microporous membranes, are being used in ultrafHtration and microfiltration appHcations, for which solvent resistance and thermal stabHity are required. Dense metal membranes, particularly palladium membranes, are being considered for the separation of hydrogen from gas mixtures, and supported or emulsified Hquid films are being developed for coupled and facHitated transport processes. 

Solubility and Solvent Resistance. The majority of polycarbonates are prepared in methylene chloride solution. Chloroform, i7j -l,2-dichloroethylene, yy -tetrachloroethane, and methylene chloride are the preferred solvents for polycarbonates. The polymer is soluble in chlorobenzene or o-dichlorobenzene when warm, but crystallization may occur at lower temperatures. Methylene chloride is most commonly used because of the high solubiUty of the polymer (350 g/L at 25°C), and because this solvent has low flammabiUty and toxicity. Nonhalogenated solvents include tetrahydrofuran, dioxane, pyridine, and cresols. Hydrocarbons (qv) and aUphatic alcohols, esters (see Esters, organic), or ketones (qv) do not dissolve polycarbonates. Acetone (qv) promotes rapid crystallization of the normally amorphous polymer, and causes catastrophic failure of stressed polycarbonate parts. 

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. 

Polycarbonate—polyester blends were introduced in 1980, and have steadily increased sales to a volume of about 70,000 t. This blend, which is used on exterior parts for the automotive industry, accounting for 85% of the volume, combines the toughness and impact strength of polycarbonate with the crystallinity and inherent solvent resistance of PBT, PET, and other polyesters. Although not quite miscible, polycarbonate and PBT form a fine-grained blend, which upon analysis shows the glass-transition temperature of the polycarbonate and the melting point of the polyester. 

Polyester elastomers are resistant to a variety of common solvents including aqueous acids or bases. The chemical resistance of copolyesterether elastomers is shown in Table 13 (193) which gives examples of solvent resistance and is not inclusive. 

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