Potting compounds silicone

Additions of BN powder to epoxies, urethanes, silicones, and other polymers are ideal for potting compounds. BN increases the thermal conductivity and reduces thermal expansion and makes the composites electrically insulating while not abrading delicate electronic parts and interconnections. BN additions reduce surface and dynamic friction of rubber parts. In epoxy resins, or generally resins, it is used to adjust the electrical conductivity, dielectric loss behavior, and thermal conductivity, to create ideal thermal and electrical behavior of the materials [146]. 

Room temperature cured (RTV) silicones are used as potting compounds and as in situ formed gaskets. These compositions are toughened by the addition of styrene or butyl acrylate which form minute strands of fiber in situ when they polymerize.21 Silicone sealants and coatings are being used in the NASA space shuttles.22 Paintable, fast curing-octoate-cured silicone sealants are also available. Simple tests for utility, based on a filled glass tube, have been described.22... 

A. Christou, Reliability Aspects of Moisture and Ionic Contamination Diffusion Through Hybrid Encapsulants, in Proceedings of the Technical Program—International Microelectronics Conference (1978) p. 237, Industrial Scientific Conference Management, Inc., New York. Electric insulators and dielectrics Silicone/epoxy-polyurethane interpenetrating networks, moisture, and ion diffusion through potting compounds. 

DETA is an ideal technique for monitoring the cure of silicone potting compounds because the unreacted material (with its low viscosity) can be directly applied to the dielectric sensor and continuous measurement made as the material transforms from a low molecular weight liquid to a high molecular weight crosslinked rubber. 

Figure 10.3 Study of cure of silicone potting compound by dielectric thermal analysis (a) Lot A (b) Lot B Source Author s own files)...

Table 92. Extent of cure of silicon potting compounds...

Encapsulants are usually characterized as either potting compounds, glob-tops, or underfills, depending on the end use. Potting compounds are materials that are used to protect final assemblies (relays, component terminals, electrical contact assemblies, etc.). Glob-tops and underfills are specifically used for silicon die protection. 

Early two-part RTV silicones were relatively low-strength materials with generally nonreinforcing filler systems. Most of these were used as potting compounds for protection of electrical devices where strength and elastomeric behavior were of little importance. 

RTV silicones are used by the automotive, appliance, and aerospace industries for electronic potting compounds and formed-in-place gaskets, to form molds for the manufacture of plastic parts, and widely in construction adhesives, sealants, roof coatings, and glazing. 

The combination of carbonylate dianions with silicon tetrachloride leads in high yields to the p-Si compounds 22-24. As already mentioned, the reaction can be performed either stepwise with isolation of the dichlorosilylene complex or in a one-pot procedure. The resulting products show a surprisingly high thermal... 

Compounds containing the Si-N-P linkage combine the structural and stereochemical diversity of phosphorus with the reactivity of the silicon-nitrogen bond. Indeed, much of the derivative chemistry and synthetic potential of these compounds, especially the (silylamino)phosphines such as (Me3Si)2NPMe2, is based on this difunctional character. We report here a general, "one-pot" synthesis of (silylamino)phos-phines and describe their use in the preparation of several types of phosphorus-containing materials. 

Because of their monofiinctionality, the title compounds may be used as a silicone offset for many organic molecules and additives. While the monosilanol oil is prone to spontaneous condensation reactions and has limited pot life, the amino- and chlorofiinctional fluids will confer the silicone haptics, surface tension, weatherability, and other sought-after siloxane properties onto the organic formulation. 

From a synthetic point of view, asymmetric synthesis at silicon in dihydrosilanes has proved to be useful. It provided the basis for a one-pot synthesis of Sommer s compound, R-(+)- or S-(-)-l-NpPhMeSiH, in 96% e.e. with a 51% chemical yield starting from 1 -NpPhSiH2 (83). The synthesis of a new optically active oxasilacycloalkane has also been realized in this way (84). Moreover, the stereochemistry of a cleavage reaction of a silicon-carbon bond has been determined using asymmetric synthesis (85). The configurations of the pertinent compounds could not be correlated in any other way. 

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