Hydrolytic resistance

Aromatic polyamide (aramid) membranes are a copolymer of 1-3 diaminobenzene with 1-3 and 1-4 benzenedicarboxylic acid chlorides. They are usually made into fine hollow fibers, 93 [Lm outer diameter by 43 [Lm inner diameter. Some flat sheet is made for spirals. These membranes are widely used for seawater desalination and to some extent for other process applications. The hollow fibers are capable of veiy high-pressure operation and have considerably greater hydrolytic resistance than does CA. Their packing density in hoUow-fiber form makes them veiy susceptible to colloidal fouling (a permeator 8 inches in diameter contains 3 M fibers), and they have essentially no resistance to chlorine. 

Polycarbonates based on tetramethylbisphenol A are thermally stable and have a high Vicat softening point of 196°C. On the other hand they have lower impact and notched impact resistance than the normal polymer. Blends with styrene-based polymers were introduced in 1980, and compared with PC/ABS blends, are claimed to have improved hydrolytic resistance, lower density and higher heat deflection temperatures. Suggested applications are as dishes for microwave ovens and car headlamp reflectors. 

Determination of Hydrolytic Resistance of Glass Grains at 98°C, ISO R719 1968... 

Should the substrate to be oxidized and its oxidation product be hydrolytically resistant and thermally persistent, the oxidation with in-situ-generated dioxirane is recommended. The advantages include that more ketone catalyst is available, the generation of the... 

The hydrolytic resistance of the products was investigated quantitatively in 0.4 N potassium hydroxide and 0.5 N sulfuric acid solutions by mixing powdered materials (40 mg) in a suitable solvent (20 mL) at 50 0.1°C for 24 h. 

High hydrolytic resistance against aqueous acid and base The modified lignins were found not to consume more alkali than the parent lignin (i.e., 50-80 mg KOH/g of derivative as compared to 85 mg KOH/g of parent lignin) ... 

Some results of the modification of lignin sulfonate Ultra B002 by reaction with terephthaloyl chloride are summarized in Table VI. The total hydroxyl content of the lignosulfonates as well as their derivatives are presented in Table VII. The hydrolytic resistance of selected products is evaluated in Table VIII. The results presented in Tables VI-VIII stress several advantages of the derivatives with terephthaloyl chloride. The modified lignin sulfonates were insoluble, or only very slightly soluble, in organic solvents. They were, however, soluble in dimethyl sulfoxide. Ordered structures were identified by X-ray studies (16,17). 

Table VIII. Hydrolytic Resistance of the Lignins Modified with Terephthaloyl Chloride...

The hydrolytic resistance test described in this chapter is the powdered glass test and not the water attack test as described above see Appendix <661>, USP 27 [1]. 

Bohrer, D., do Nascimento, P. C, Becker, E., Bortoluzzi, F, depoi, E, and de Carvalho, L. M. (2004), Critical evaluation of the standard hydrolytic resistance test for glasses used for containers for blood and parenteral formulations, PDA J. Pharm. Sci. Technol, 58, 96-105. 

Fully aromatic, thermally (up to 250°C) and hydrolytically resistant films of PODs have been realized from polyhydrazides (56). Films of these polymers are useful as seawater desalination membranes. 

Whenever there is a chemical erosion of glass, water or its dissociation products, H+ or OH ions will be involved. Because of this, a distinction is made between the resistance of glass to water (its hydrolytic resistance) and to alkali or acid. Under attack from water or acids, small numbers of cations, particularly monovalent and divalent, are released. On resistant types of glass, a very thin layer of silica gel forms in this way on the glass surface and usually inhibits further erosion. In contrast, hydrofluoric acid, alkaline solutions and, under certain circumstances, phosphoric acid will slowly remove the inhibitor layer and thus the entire surface. Nonaqueous solutions (organic solutions), however, are practically nonreactive with glass. 

SPS is entirely different from conventional amorphous styrenics in chemical and physical properties. In addition to characteristics such as low specific gravity, excellent electrical properties, hydrolytic resistance and good mold-ability similar to those of existing styrenics, SPS has heat resistance, chemical resistance and the characteristics inherent to crystalline polymers that make it a new engineering plastic. SPS is finding new applications and is expected to bring out new horizons in the application areas of engineering thermoplastics. 

EP describes Type I glass as neutral glass with high hydrolytic resistance owing to the chemical composition of the glass itself. Type I is suitable for all preparations whether or not for parenteral use and for human blood and blood components. ... 

EP Soda-lime silica glass with high hydrolytic resistance resulting from suitable treatment of the surface. These containers are suitable for acidic and neutral aqueous preparations for parenteral use. ... 

EP These are soda-lime glasses with only moderate hydrolytic resistance. They are suitable for non-aqueous preparations for parenteral use, for powders for parenteral use, and for preparations not for parenteral use. ... 

These glass containers for pharmaceutical use have to comply with relevant tests such as tests for hydrolytic resistance for EP, and tests chemical resistance for Usp.[ 2] (gg procedure and methods are slightly... 

Table 4 Limit values in the test for surface hydrolytic resistance...

Type I Borosilicate Very high hydrolytic resistance, low thermal expansion Acidic and neutral parenteral preparations alkaline preparations if qualified... 

Type NP Soda-lime (general purpose) Very low hydrolytic resistance Non-parenteral use only (oral, topical, etc.)... 

Covers density, tensile voperties, tear, hardness, compression set, compression deflection, resilience, surface and core abrasion, heat aging, hydrolytic resistance, cut-growth resistance, impact strength, flexural modulus, ash, flexural recovery, and high-temperature sag. 

Interestingly, metal derivatives of di- and polyhydroxy alcohols are comparatively more hydrolytic resistant than their alkoxide analogues. Some of these compounds are even stable in alkaline solutions. The chelating nature of the alcohols and coordinative saturation achieved by the central metal atoms in the final products appear to be the main factor for their hydrolytic stability. 

Phenalkamine properties are positioned roughly between those of the polyamines and polyamides. They combine the best properties of each of these familiar types of curing agents. The phenal kamines have an intermediate viscosity, the chemical and hydrolytic resistance of the polyamines, and the low toxicity of the polyamides. They have the fast cure and ability to cure at reduced temperatures of the polyamines while exhibiting better compatibility than either the polyamines or the polyamides. The phenalkamines also provide flexibility comparable to the polyamides with similar easy-to-use, relatively non-critical mix ratios. 

One paradoxical characteristic with the slow addition procedure is observed for the most hydrolytically resistant alkenes, where the reaction proceeds faster the slower the reagent is added. As can be deduced from the discussion above, the slow addition and the acetate effect are not mutually exclusive, and can be used in combination for the most arduous alkenes (Table 3, entries 2 and 6). With the mechanistic insight into the details of the asymmetric dihydroxylation, and the remedies to maintain the enantioselectivity in the addition step, the enanti-oselectivity in the chiral selectors (DHQD-CLB and DHQ-CLB) became limiting factors in the AD process. 

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