Functional chemicals, additives

Oilfield operations can be classified into several categories drilling and exploration, oil and gas production, reservoir stimulation, and enhanced oil recovery. All of these require the use of complex fluids containing a range of functional chemical additives. 

In addition, many grades of paper and paperboard are used in direct or indirect contact with foods. Thus, many mills only use paper chemicals that have been cleared for use by the U.S. Pood and Dmg Administration (PDA) (3), so that it is not necessary to segregate machine broke (off-grade paper and edge clippings that are reclaimed for their fiber value) and white water. Most of the chemicals discussed in this article are approved by the PDA for use in paper and paperboard that are intended for appHcations in food processing and packaging. However, there are various restrictions on both the specific functional uses and amounts of paper chemical additives which can be used, so the PDA status should be confirmed by the suppHer before use. 

Defoamers. Foam is a common problem in papermaking systems (27). It is caused by surface-active agents which are present in the pulp slurry or in the chemical additives. In addition, partially hydrophobic soHd materials can function as foam stabilizers. Foam can exist as surface foam or as a combination of surface foam and entrained air bubbles. Surface foam usually can be removed by water or steam showers and causes few problems. Entrained air bubbles, however, can slow drainage of the stock and hence reduce machine speed. Another serious effect is the formation of translucent circular spots in the finished sheet caused by permanently entrained air. 

In addition to full- or part-treatment formulations (boiler compounds), the art and science of BW treatment usually requires the application of certain primary functional chemicals and secondary functional chemicals (adjuncts) to provide a comprehensive program, as outlined below ... 

A great many additives can be used to impart desired properties to the drilling fluid. In general, the deeper and hotter the well, the more chemical additives are needed to obtain the desired fluid properties. These additives can be classified into different types by function. These include ... 

Auhom WJ (2008) Retention agents and stock deaerators in the production of mechanical printing papers. In Chemical additives for the production of pulp paper functionally essential - ecologically beneficial. ZELLCHEMEMG Technical Committee Chemical Additives CHAD, Deutscher Fachverlag, Frankfurt, p. 45-59... 

In practice, the primary objective of chemical thermodynamics is to estabhsh a criterion for determining the feasibility or spontaneity of a given physical or chemical transformation. For example, we may be interested in a criterion for determining the feasibility of a spontaneous transformation from one phase to another, such as the conversion of graphite to diamond, or the spontaneous direction of a metabohc reaction that occurs in a cell. On the basis of the first and second laws of thermod5m-amics, which are expressed in terms of Gibbs s functions, several additional theoretical concepts and mathematical functions have been developed that provide a powerful approach to the solution of these questions. 

The generalized Fisher theorems derived in this section are statements about the space variation of the vectors of the relative and absolute space-specific rates of growth. These vectors have a simple natural (biological, chemical, physical) interpretation They express the capacity of a species of type u to fill out space in genetic language, they are space-specific fitness functions. In addition, the covariance matrix of the vector of the relative space-specific rates of growth, gap, [Eq. (25)] is a Riemannian metric tensor that enters the expression of a Fisher information metric [Eqs. (24) and (26)]. These results may serve as a basis for solving inverse problems for reaction transport systems. 

Children, as well as the unborn child, have in some cases appeared to be uniquely vulnerable to chemical s toxic effects because periods of rapid growth and development render them more susceptible to some specific toxic endpoints when compared to adults. Furthermore, there may be windows of vulnerability or periods of development when chemical exposures may substantially alter organ stmcmre and function. In addition to such toxicodynamic factors, differences in toxicokinetics may contribute to an increased susceptibility during these periods. The greatest differences in comparison with adults occur in neonates and infants (<1 year). However,... 

The dynamic mechanical behavior of most homogeneous and heterogeneous solid and molten polymeric systems or composite formulations can be determined by DMA. These polymeric systems may contain chemical additives, including fillers, reinforcements, stabilizers, plasticizers, flame retardants, impact modifiers, processing aids, and other chemical additives, which are added to the polymeric system to impart specific functional properties and which could affect the process-ability and performance. 

What we are trying to emphasize here is that plastics of themselves are quite functional materials but they can sometimes be made more so through the addition of fillers, reinforcing agents, and chemical additives. Perhaps the most important contribution of fillers is the reduction in cost which they impart. The more expensive reinforcing agents, on the other hand, are used because of the desirable properties they impart to the plastic and such reinforced... 

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