Nylon solution

Ede [56] has also examined the limitations of m-cresol as the mobile phase in the SEC of nylon. He noted that Waters Inc. had recommended that the instrument be operated at 130°C to reduce the pressure drop across the columns and to improve the resolution of the chromatogram, and suspected that degradation of nylon was occurring under these conditions. Accordingly, the relative viscosities of the nylon m-cresol solutions were determined after heating for various times at 130°C. Three nylon solutions were prepared and examined by SEC. The solutions were also held in the injection loop of the SEC for 3 h prior to injection. In each case the sample which had been held in the sample loop eluted later. The retention time in the SEC was 2-4 h, and it was concluded that degradation definitely occurred during this time. 

The determination of [17] from measurements of nylon solutions at a single concentration is also found in the literature. Of coune, the accuracy of such determination, which depends of the validity of certain assunqptions, is much lower than the determination by extrapolation methods. Thus, some authors calculate [17] from measurements at a single concentration using the equation... 

In some solvents, e. g. in anhydrous formic and sulphuric add, nylon solutions exhibit anomalous concentration dependences of reduced viscosity jraranKters ovnng to the polyelectrolyte effea. In an add medium capable of dissociation the amide group imy add a proton... 

Add 40 ml. of ethyl alcohol to 21 -5 g. of 70 per cent, ethylenediamine solution (0 -25 mol) dissolve 36 -5 g. of adipic acid (0 -25 mol) in 50 ml. of a 6 1 mixture of ethyl alcohol and water. Mix the two solutions, stir and cool. Filter off the resulting salt and recrystalliae it from 60 ml. of a 6 1 ethyl alcohol - water mixture, and dry the salt in the air. Heat the salt in an atmosphere of oxygen-free nitrogen or of carbon dioxide in an oil bath until it melts (ca. 160°) the product will sohdify after a short time. Reduce the pressure to 15 mm. of mercury or less and raise the temperature of the oil bath until the product remelts (about 290°) and continue the heating for 4r-5 hours. Upon coohng, a nylon type polymer is obtained. 

Add 10 ml. of concentrated sulphuric acid cautiously to 45 ml. of water contained in a 200 ml. round-bottomed flask, introduce 3 g. of Nylon 66 polymer into the hot solution, and heat under reflux for 6 hours. Allow to stand for 1 hour and cool in ice for a further hour. Filter off the solid and keep the filtrate. Recrystalhse the sohd (adipic acid) from water m.p. 152°. 

Nylon 6 and 6/6 possess the maximum stiffness, strength, and heat resistance of all the types of nylon. Type 6/6 has a higher melt temperature, whereas type 6 has a higher impact resistance and better processibility. At a sacrifice in stiffness and heat resistance, the higher analogs of nylon are useful primarily for improved chemical resistance in certain environments (acids, bases, and zinc chloride solutions) and for lower moisture absorption. 

As with polyesters, the amidation reaction of acid chlorides may be carried out in solution because of the enhanced reactivity of acid chlorides compared with carboxylic acids. A technique known as interfacial polymerization has been employed for the formation of polyamides and other step-growth polymers, including polyesters, polyurethanes, and polycarbonates. In this method the polymerization is carried out at the interface between two immiscible solutions, one of which contains one of the dissolved reactants, while the second monomer is dissolved in the other. Figure 5.7 shows a polyamide film forming at the interface between an aqueous solution of a diamine layered on a solution of a diacid chloride in an organic solvent. In this form interfacial polymerization is part of the standard repertoire of chemical demonstrations. It is sometimes called the nylon rope trick because of the filament of nylon produced by withdrawing the collapsed film. 

Would you expect solutions C and E or B and D to contain the higher molecular weight polymer Briefly explain. Outline a strategy for nylon fractionation based on steps (a)-(c). Some steps may be repeated as needed. 

Amidation. Heating of the diammonium salt or reaction of the dimethyl ester with concentrated ammonium hydroxide gives adipamide [628-94-4] mp 228°C, which is relatively insoluble in cold water. Substituted amides are readily formed when amines are used. The most industrially significant reaction of adipic acid is its reaction with diamines, specifically 1,6-hexanediamine. A water-soluble polymeric salt is formed initially upon mixing solutions of the two materials then hea ting with removal of water produces the polyamide, nylon-6,6. This reaction has been studied extensively, and the hterature contains hundreds of references to it and to polyamide product properties (31). 

Solutions of fluorosihcones impart oil and water repeUent finishes to nylon—cotton fabrics. One series of C-1 through C-9 perfluoroalkyl substituents with varying stmctures were attached to siHcon through amide or ether linkages. The fluorosihcones having perfluorinated straight-chain... 

The second difficulty, degradation, required the development of a two-step polyamidation process following salt formation (157). During salt formation, tetramethylenediammonium adipate salt is formed in water solution at approximately 50% concentration or at a higher concentration in a suspension. As in nylon-6,6 manufacture, this salt solution, when diluted, permits easy adjustment of the stoichiometry of the reactants by means of pH measurement. 

The solution (pad bath) contains one or more of the amino resias described above, a catalyst, and other additives such as a softener, a stiffening agent, or a water repeUant. The catalyst may be an ammonium or metal salt, eg, magnesium chloride or ziac nitrate. Synthetic fabrics, such as nylon or polyester, are treated with amino resias to obtaia a stiff finish. Cotton (qv) or rayon fabrics or blends with synthetic fibers are treated with amino resias to obtain shrinkage control and a durable-press finish. 

Repellents on Cloth. Each candidate repellent is appHed to a knit cotton stocking or cloth patch at 3.3 g/m cloth, usually as a 1% solution of active ingredient (AI) ia acetone. Two hours later, the stock or cloth patch is placed over an untreated nylon stocking on the arm of a subject, the hand covered, and the arm exposed to 1500 female mosquitoes for one minute. If fewer than five bites are counted, the test is repeated at 24 h, then weekly until failure, which is, by definition, five bites per minute. The standard mosquitoes used are Piedes aegppti Anopheles quadrimaculatus or M. albimanus. Candidate repellents ia cloth tests are ia one of the foUowiag classes class 1, effective 0 d class 2, 1—5 d class 3, 6—10 d class 4, 11—21 d and class 5, >21 d. 

Synthetic Fibers. Most synthetic fibers are sufficientiy white and do not requite bleaching. For white fabrics, unbleached synthetic fibers with duorescent whitening agents are usually used. When needed, synthetic fibers and many of theit blends are bleached with sodium chlorite solutions at pH 2.5—4.5 for 30—90 min at concentrations and temperatures that depend on the type of fiber. Solutions of 0.1% peracetic acid are also used at pH 6—7 for 1 h at 80—85°C to bleach nylon. 

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