Fluorosilicone selectivity

A classification by chemical type is given in Table 1. It does not attempt to be either rigorous or complete. Clearly, some materials could appear in more than one of these classifications, eg, polyethylene waxes [9002-884] can be classified in both synthetic waxes and polyolefins, and fluorosilicones in silicones and fluoropolymers. The broad classes of release materials available are given in the chemical class column, the principal types in the chemical subdivision column, and one or two important selections in the specific examples column. Many commercial products are difficult to place in any classification scheme. Some are of proprietary composition and many are mixtures. For example, metallic soaps are often used in combination with hydrocarbon waxes to produce finely dispersed suspensions. Many products also contain formulating aids such as solvents, emulsifiers, and biocides. 

Fluorosilicone. By fluorinating the silicone polymer molecule it is possible to improve the solvent, fuel, and oil resistance of this already heat-resistant class of elastomers. The resulting polymers are especially useful in select automotive seals and gaskets as well as military and downhole oilfield parts. 

Another use of this system is to select columns which have unique characteristics. The fluorosilicones, such as SP-2401, are the only phases for which the z value is greater than the y value, which indicates that ketones would be eluted after alcohols. With polyglycols such as Carbowax 20M, the reverse is... 

Most commercial fluorocarbon elastomers have brittle points between -25°C (-13°F) and -40°C (-40°F). The low-temperature flexibility depends on the chemical structure of the polymer and cannot be improved markedly by compounding. The use of plasticizers may help somewhat, but at a cost of reduced heat stability and worsened aging. Peroxide-curable polymers may be blended with fluorosilicones, but such blends exhibit considerably lower high-temperature stability and solvent resistance and are considerably more expensive than the pure fluorocarbon polymer. Viton GLT is a product with a low brittle point of -51°C (-59°F) [48]. Tecnoflon for containing a stable fluorinated amide plasticizer reportedly exhibits improved low-temperature hardness, brittle point, and compression set without sacrificing physical properties [66]. Low-temperature characteristics of selected fluorocarbon elastomers are listed in Table 5.13 [9]. 

Fluorosilicones have low snrface energy, in fact lower than polytetraflnoroethylene of polydimethylsiloxane [95], Valnes of selected polymers measnred at room temperature are shown in Table 5.18. 

Silicones and fluorosilicones have traditionally been classified as high performance materials due to their suitability for use under extreme conditions and their processability has been particularly interesting as a result of the very flexible siloxane chain. The present paper discusses selected examples where more recent advances in science and technology have broadened the understanding and uses. Emphasis is given to relating the molecular chemistry and physics to the characteristics of the bulk materials. 

The range of values given for the siloxyimides covers three different materials tested of that type. Fluorosilicone demonstrated various anomalies which did not permit application of the given equation. The silastyrene showed no detectable moisture solubility. This material was selected as potentially hydrophobic due to its apparent low polarity. It contains methyl groups bonded to a silicon backbone. Although silastyrene has potential,... 

Table 1. Selected Properties of Linear PFCB Fluorosilicones from Figure 5.

Table 3. Selected Thermal Properties of Fluorosilicone Networks.

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