Room-temperature vulcanized elastomers

For example, in heat-cured mbber systems a common loading with synthetic silica is around 30%. For economic reasons, precipitated silicas are used in increasing volumes in silicone elastomers such as high-consistency mbber (HCR), liquid silicone mbber (LSR), and two-component room temperature vulcanized elastomers (RTV2). The reinforcement provided by precipitated silicas is only slightly lower than that provided by fumed silicas. However, fumed silicas are necessary in silicone sealants and other high-end applications because of their desirable properties like low moisture content. 

The room temperature vulcanizing elastomers described above are two-pack ... 

Liquid silicone elastomers should not be confused with two-pack room temperature vulcanizing elastomers. The former cure only on heating. Blended liquid silicone components can be stored for at least 24 hours at room temperature the shelf-life of the separate components is approximately 1 year. 

Dibutyltin and dioctyltin diacetate, dilaurate, and di-(2-ethylhexanoate) are used as catalysts for the curing of room-temperature-vulcanized (RTV) sihcone elastomers to produce flexible siUcone mbbers used as sealing compounds, insulators, and in a wide variety of other appHcations. Diorganotin carboxylates also catalyze the curing of thermosetting siHcone resins, which are widely used in paper-release coatings. 

One-part moisture condensation cure. The one-part condensation cure system is a room-temperature vulcanizing (RTV) system that is based on a reactive PDMS polymer that undergoes hydrolysis on contact of air moisture, followed by condensation to yield a crosslinked elastomer. The most common systems [3,12,14,33] are based on the reactions shown in Scheme 5. 

Like the 1-RTV systems, the two-part room temperature vulcanization systems (2-RTV) cure to produce flexible elastomers that resist humidity and other harsh environments. Interestingly, they display primerless adhesion property to many substrates, and are used in silicone adhesives, sealants, seals, and gaskets, to name a few. 

Improved Room-Temperature Vulcanized (RTV) Silicone Elastomers as Integrated Circuit (IC) Encapsulants... 

Indirect tooling methods are many. Examples include cast aluminum, investment metal cast, cast plastics, cast kirksite, sprayed steel, spin-castings, plaster casting, electroforming, room temperature vulcanizing (RTV) silicone elastomer (Chapter 2 Silicone Elastomer), elastomer/ rubber, reaction injection, stereolithography,338 344 (Table 17.4), direct metal laser sintering, and laminate construction. 

These are silicones in liquid or paste form that can be transformed into cross-linked elastomers at or near room temperature. There are two basic types, one component and two component. The one-component room temperature vulcanizing (RTV) elastomers cure upon exposure to air. A typical material of this type is synthesized from a dihydroxy-terminated siloxane oligomer and methyltriacetoxysilane (Scheme 2). The resulting tetraacetoxy compound will flow as a paste and so can be molded into shape. Hydrolysis of the acetoxy groups takes place over a period of hours. Condensation of the resulting silanols gives a highly cross-linked end product. 

When silicone adhesives react with air moisture they are called RTV-1 silicone adhesives (RTV room temperature vulcanization). The RTV adhesives have a rubber-Uke character. The term vulcanization is not technically correct, but is rather an historical reference. Silicones are elastomers and were at first crosslinked like other elastomers, albeit not with sulfur. In the integrated state, silicones contain blocked crosslinking agents that lose their blocking function upon contact with moisture. There are various different types of crosslinking agents with different... 

Silicone elastomers are either room-temperature vulcanization (RTV) or heat-cured silicone rubbers, depending on whether cross-linking is accomplished at ambient or elevated temperature. [The term vulcanization (see Chapter 1 and Chapter 2) is a synonym for cross-linking. While curing is also a synonym for cross-linking, it often refers to a combination of additional polymerization plus cross-linking.] RTV and heat-cured silicone rubbers typically involve polysiloxanes with degrees of polymerizations of 200-1500 and 2500-11,000, respectively. 

RTV n. Abbreviation for room-temperature vulcanizing, a characteristic of some elastomers that do not require heating to cure. 

RTV elastomers n. Room-temperature vulcanizing (RTV) elastomer is an elastomer that does not require heating to cure. 

Silicone polymers may be filled or unfilled, depending on the properties desired and the application. They can be cured by several mechanisms, either at room temperature by room-temperature vulcanization (RTV) or at elevated temperatures. Their final form may be fluid, gel, elastomer, or rigid plastic. There are three primary types of silicone resins (1) flexible two-part, (2) flexible one-part, and (3) rigid silicones. Silicone rubber resins for casting, potting, and other liquid processes are available from Dow Coming (Silastic) and GE Silicones. 

The third area for casting is the use of cast elastomer products, particularly for industrial and medical products. Polyurethane and polyester based formulations are generally used, as is the room temperature vulcanizing silicone (RTV) material. These formulations can be cured at room temperature or at low oven temperatures and they... 

RTV silicone elastomer, an organosiloxane, is one of the most effective encapsulants used for temperature cycling and moisture protection of IC devices. Since World War II, silicones (organosiloxane polymers) have been used in a variety of applications where properties of high thermal stability, hydrophobicity, and low dielectric constant are necessary, e.g., as encapsulants or conformal coatings for integrated circuits. In 1969 it was demonstrated that room temperature vulcanized (RTV) silicones exhibited excellent performance as moisture protection barriers for IC devices and a number of different RTV silicone have been adapted For use in the elec-tronics industry... 

The major use of silicone elastomers is in aircraft where high and low temperature properties and electrical insulation characteristics are utilized, e.g., gaskets, sealing strips, ducting and cable insulation. Liquid room-temperature vulcanizing silicone elastomers are used for the encapsulation of electronic and electrical equipment. 

Whilst several processes are known for vulcanizing elastomers at common ambient temperatures the room temperature vulcanizing silicone rubbers (RTV rubbers) have proved of considerable value where elaborate processing equipment is not available. The rubbers are low molecular weight liquid silicone polymers filled with reinforc-... 

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