Material imparting special functions

Fully Encapsulating Suit (FES) Sometimes referred to as a Moon Suit, personal protective clothing diat provides complete skin, eye, and respiratory proteetion, and includes positive-pressure SCBA. The reader should refer to Chapter 2 for detailed discussions. Refer to Protective Materials. Fumes Solid particles formed by the condensation of vaporized solids, usually molten metals. Particles are much smaller than dusts with typical size ranges between 0.01 and 1.0 microns. Functional Group An atom or group of atoms, bound together chemically, that has an unpaired electron, which when it attaches itself to the hydrocarbon backbone, imparts special properties to the new compound thus formed. 

Synthesis parameters are modified, as with the PFs, to alter resin properties. Molar ratio, catalyst system, raw material concentration and their rate of addition, target nonvolatiles, a dehydration step and additives may all be varied to modify and impart special properties to a resin. Properties monitored may include molecular weight, molecular weight distribution, functional groups, cure rheology, viscosity, and cure speed. 

Besides reinforcement for rubber, the principal functions that carbon black imparts to a compoimd material are color, ultraviolet damage resistance, electrical conductivity, nondegradation of polymer physical properties, and ease of dispersion. The carbon blacks used for these purposes are classified as special-grade blacks. Smaller volume applications exploit other principal attributes, such as chemical inertness, thermal stability, and an open porous structure. The secondary attributes include chemical and physical purity, low affinity for water adsorption, and ease of transportation and handling. 

In many cases latex products are composed of more than one monomer. In copolymerisation two or more monomers are built-in into the polymer chains. The copolymer chains are produced by simultaneous polymerisation of two or more monomers in emulsion. Emulsion copolymerisation allows the production of materials with properties which cannot be obtained by latex products consisting of one monomer, that is, homopolymer latexes, or by blending homopolymers. The properties of the materials required are usually dictated by the market. Nowadays, most of the material properties are achieved by combination of more than two monomers in the copolymer product. Typical industrial emulsion polymerisation formulations are mixtures of monomers giving hard polymers, and monomers leading to soft polymers. Styrene and methyl methacrylate are examples of monomers giving hard polymers, that is, polymers with a high glass transition temperature, Tg. Soft polymers, that is, polymers with a low Tg, are, for example, formed from -butyl acrylate. The industrial emulsion polymerisation formulations also contain small amounts of functional monomers such as acrylic and methacrylic acid to impart improved or special characteristics to the latex product. Note that the colloidal stability of the latex product can be seriously improved by acrylic and methacrylic acid. Furthermore, some applications may demand for the addition of other specialty monomers that make the kinetics of the copolymerisation even more complex. 

Miscellaneous Sulfoester and Amide Surfactants The sulfoesters and amides discussed in the preceding section are those in which the two functionalities were located on adjacent carbon atoms, a situation that imparts some special properties to the resultant surfactant molecules. A second class of related materials is that in which the two groups are more widely separated. General examples of such compounds would be... 

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