Viscous compounds

Acidic Cation-Exchange Resins. Brmnsted acid catalytic activity is responsible for the successful use of acidic cation-exchange resins, which are also soHd acids. Cation-exchange catalysts are used in esterification, acetal synthesis, ester alcoholysis, acetal alcoholysis, alcohol dehydration, ester hydrolysis, and sucrose inversion. The soHd acid type permits simplified procedures when high boiling and viscous compounds are involved because the catalyst can be separated from the products by simple filtration. Unsaturated acids and alcohols that can polymerise in the presence of proton acids can thus be esterified directiy and without polymerisation. 

The concept is simple, since the solid and carrier to be micronized do not have to be soluble in the SCF this favors the application of PGSS to a wide range of products. Polymers and generally highly viscous compounds, including waxes, resins, and sticky materials can, be preferentially treated by the PGSS process. 

Chemicals such as mustard (a blister agent) and sarin (a nerve agent) can form toxic vapors at room temperature. Agents that share this physical property could be employed in crude but still very deadly attacks without sophisticated dispersal devices. Other, more viscous compounds such as VX are much less prone to evaporation even at higher temperatures, and for this reason present more of a hazard as a skin contaminant. 

The C-chlorinated linear carbosilanes are liquids, while (Cl3Si—CCl2)2SiCl2 is a viscous compound which degrades on attempted distillation. 

Besides normal alkyl chains, alkenyl chains (-C H2 CH CHCH3) are also important because they exhibit particularly beneficial elastic constants and low rotational viscosities desirable for use in supertwisted nematic (STN) displays. Branched alkyl chains Iowct transition temperatures and increase the viscosity. Thus, chiral liquid crystal compounds, which usually incorporate a branched chain alcohol, e.g., 2-methyl butanol or 2-octanol, are relatively viscous. Compounds with two long alkyl chains favor smectic C phase formation (3, K-S, 48°C S.-S 122°C S -N 128°C N-I 166°C), especially when the core system contains some kind of nonlinear stmcture (such as a lateral substituent and/or este group) which aids the formation of tilted phases. 

It has more recently been found that amyrol, like santalol, is not a uniform body, but that by frequently repeated fractional distillation it can be separated into diPFereut alcohols. The higher boiling, very viscous compound has a faint, characteristic, fragrant odour its formula Specific gravity about Q 987 an = about + 3G ... 

CLOSED MIXING SYSTEMS FOR THE PRODUCTION OF HIGHLY VISCOUS COMPOUNDS... 

For pin-point gates, the transfer from the runner should always take the form of an accumulation base. The accumulation base prevents the highly viscous compound at the edge from being carried along, the plastic core of the runner is thus retained for longer (the gate does not freeze until later). 

Glycoproteins or mucoproieins. Compounds of proteins with carbohydrates. All glycoproteins contain a hexosamine and usually sulphate, ethanoate and glucuronic acid. The carbohydrate-protein linkages are, in some cases covalent and in others of the salt type. Aqueous solutions of glycoproteins are extremely viscous. 

Usually it is not easy to predict the viscosity of a mixture of viscous components. Certain binary systems, such as methanol and water, have viscosities much greater than either compound. 

Carry out this preparation precisely as described for the a-compound, but instead of zinc chloride add 2 5 g. of anhydrous powdered sodium acetate (preparation, p. 116) to the acetic anhydride. When this mixture has been heated on the water-bath for 5 minutes, and the greater part of the acetate has dissolved, add the 5 g. of powdered glucose. After heating for I hour, pour into cold water as before. The viscous oil crystallises more readily than that obtained in the preparation of the a-compound. Filter the solid material at the pump, breaking up any lumps as before, wash thoroughly with water and drain. (Yield of crude product, io o-io 5 g.). Recrystallise from rectified spirit until the pure -pentacetylglucose is obtained as colourless crystals, m.p- 130-131° again two recrystallisations are usually sufficient for this purpose. 

Sepro Conta.iner, The Sepro container consists of a collapsible plastic bag fitted into a standard three-piece, tin-plated container such as a 202 X 214, 202 x 406, or 202 x 509 can. The product is placed within the bag, and the propellant is added through the bottom of the container, which is fitted with a one-way valve. There is no limitation on the viscosity of the product but compatibiUty with the plastic bag must be considered. A free-dowing hquid can be dispensed either as a stream or a fine spray, depending on the type of valve employed. A viscous material is often dispensed as a stream. This system has been used for caulking compounds, postfoaming gels, and depilatories. 

Over the years, the term gums has been used to denote a wide range of compounds including polysaccharides, terpenes, proteins, and synthetic polymers. In the 1990s, the term more specifically denotes a group of industrially useful polysaccharides or their derivatives that hydrate in hot or cold water to form viscous solutions, dispersions, or gels (1). 

Chiral nematic Hquid crystals are sometimes referred to as spontaneously twisted nematics, and hence a special case of the nematic phase. The essential requirement for the chiral nematic stmcture is a chiral center that acts to bias the director of the Hquid crystal with a spontaneous cumulative twist. An ordinary nematic Hquid crystal can be converted into a chiral nematic by adding an optically active compound (4). In many cases the inverse of the pitch is directiy proportional to the molar concentration of the optically active compound. Racemic mixtures (1 1 mixtures of both isomers) of optically active mesogens form nematic rather than chiral nematic phases. Because of their twist encumbrance, chiral nematic Hquid crystals generally are more viscous than nematics (6). 

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