Chemical saturation

The forces of attraction between neutral, chemically saturated molecules, postulated by van der Waals to explain non-ideal gas behaviour, also originate from electrical interactions. Three types of such inter molecular attraction are recognised ... 

Natural and synthetic rubbers are used as linings or as structural components for equipment in the chemical industries. By adding the proper ingredients, natural rubbers with varying degrees of hardness and chemical resistance can be produced. Hard rubbers are chemically saturated with sulfur. The vulcanized products are rigid and exhibit excellent resistance to chemical attack by dilute sulfuric acid and dilute hydrochloric acid. 

In polymers with chemically saturated structures, i.e. cr-bonded backbones, it is very difficult to observe any electronic conductivity at all, and what... 

Chemical Saturation of Enamel Minerals in Dental Plaque in... 

In appearance, HR resembles natural crepe rubber, since it is an aliphatic, hydrocarbon polymer the density being the minimum (0.91) attainable for elastic materials of this type. In HR, the original unsaturation is very small, and even this low unsaturation is greatly reduced and may even be entirely eliminated during the compounding and curing process. The fact that once vulcanised it is extremely resistant to chemical attack is understandable because it becomes, after vulcanisation, not only a nonthermoplastic strong elastic material, but also essentially a chemically saturated product as well. This means that whilst physically vulcanised HR resembles soft vulcanised natural rubber, chemically it may be considered most similar to ebonite almost devoid of any unsaturation. 

However the fear and anxiety of harm from synthetic chemicals saturates our psyches, and thus truth and realities are ignored in favor of the tenets of virtual toxicology. As the legal case history develops in support of this argument, it effectively becomes law. Is this the proper forum for risk assessment If hysteria and emotion are allowed to determine whether a chemical is toxic or not, society is doomed since the real hazards to our health, found in the natural world, are still there. I hope that this book can help dissuade this opinion. 

Two chemically saturated particles, such as two molecules of methane or two atoms of argon, are subject to attractive forces as they approach one another. The intermolecular forces are electrical in origin since they are responsible for the phenomena of gas imperfection and liquefaction, they are often called van der Waals forces. The energy of vaporization of a liquid provides a convenient measure of the strength of these forces, since it is the energy required to pull the molecules from the liquid, where they are in proximity, and bring them into the gas where they are widely separated. The energy of vaporization is simply related to the heat of vaporization of the liquid at constant pressure ... 

The corresponding adduct compounds for 3- and 6-valent actinides are An(N03)3S3 and An02(N03)2S2. These chemically saturated neutral conqx>unds are soluble to differmt extent in organic solvents like kerosene, and — in the case of hexone — by hexone itself. The process using hexone is referred to as the Redox process. 

The law of corresponding states can be deduced by statistical mechanics from certain assumptions concerning the mutual potential of pairs of molecules. It must be remarked, however, that, although the law is approximately valid for chemically saturated nonpolar real gases, it breaks down for polar molecules. 

Because of their chemically saturated structure, FKM exhibit excellent weathering resistance to sunlight and especially to ozone. After 13 years of exposure in Florida in direct sunlight, samples showed little or no change in properties or appearance. Similar results were experienced with samples exposed to various tropical conditions in Panama for a period of 10 years. Products made of this elastomer are unaffected by ozone concentrations as high as 100 ppm. No cracking occurred in a bent loop test after one year of exposure to 100 ppm of ozone in air at 100°F (38°C) or in a sample held at 356°F (180°C) for several hundred hours. This property is particularly important considering that standard tests, for example, in the automotive industry, require resistance only to 0.5 ppm ozone. 

Chemical Saturation Absence of double or triple bonds in a chain organic molecule such as that of most polymers, usually between carbon atoms. Saturation makes the molecule less reactive and polymers less susceptible to degradation and cross-linking. Also called Chemically Saturated Structure. 

Use of a chemically saturated rubber such as chlorobutyl, together with styrene as the monomer, with the rubber the predominant component by weight, results in a material similar in behavior to the thermoplastic elastomers (see Chapter 4). In all cases two glass transitions and other evidence suggested phase separation. 

Van der Waals forces are always present between molecules or between particles and maybe attractive or repulsive [1,2], depending on whether they are working between like materials or dislike materials. For like materials, the van der Waals forces are always attractive however, repulsive forces are predicted for certain dissimilar material combinations [3j. Van der Waals forces have been used to explain why neutral chemically saturated atoms congregate to form liquids and solids. These forces are a main reason for fouhng of membranes. Using AFM, repulsive van der Waals forces can be measured with higher precision than attractive van der Waals forces [3,4]. 

Most kinetics data in the literature suggest that gypsum dissolution is diffusion transport controlled. However, the work by Raines and Dewers (1997) shows that a mixed suiface reaction/transport control mechanism can operate over a range of hydrodynamic conditions and chemical saturation states for gypsum dissolution. Additionally, very little work can be found on gypsum dissolution kinetics at near equilibrium conditions where surface reaction controlled dissolution could be the dominated mechanism. Research on surface behavior of gypsum during dissolution is consistent with the conclusion that dissolution on the 010 surface is a lay-by-lay process and is not characterized by the formation of deep etch pits, even at conditions far fi om equilibrium. 

As a result of their chemically saturated structure, the fluoroelastomers display excellent weathering resistance to sunlight and especially to ozone. Samples exposed to various tropical conditions in Panama for 10 years showed little or no change in properties. Similar results were experienced after 13 years of exposure in direct Florida sunlight. 

Another clue about awareness comes from studies of brain activity with the anesthetic propofol. When this chemical saturates the brain and knocks you unconscious, all brain areas participate in a synchronized undulation. At the moment when awareness is lost, a low-frequency wave of firing neurons sweeps across the brain. Most brain areas continue to connect within their own area, but the connections between separate areas are lost. As consciousness fragments, so does the connectivity of the brain. 

Polyacrylic elastomer is a chemically saturated polymer of acrylic acid esters. Since esters are rather inert, other groups such as epoxy, halogen and carboxyl must be incorporated into the polymer to introduce sites for curing. We have studied the effect of various ammonium and phosphonium salt catalysts on the rate of crosslinking of polyacrylic elastomers which contain carboxyl and epoxy groups as cure-sites. We find that the catalytic activity of onium salts correlates with nucleophilicity of their anions. 

Polyacrylic elastomers contain chemically saturated backbones. Since these rubbers are not unsaturated, they cannot be vulcanized with conventional sulfur cure systems. Monomers with cure-sites must therefore be introduced into the polymer chain. 

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