Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1997-03-24
1999-03-23
Housel, James C.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525106, 525464, 525474, 525477, 528 15, 528 25, 528 26, 528 27, C08F28300, C08F28302, C08G 7704, C08G 7706
Patent
active
058861114
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
This invention relates to gel sealing materials. More specifically this invention relates to a silicone gel sealing material having a high stress relaxation which enables it to effectively seal two wires entering the back end of a twin wire connector.
BACKGROUND OF THE INVENTION
Permanently sealing wires in the back end of the connector can be accomplished with epoxies or other fast curing adhesives. However, differences in thermal expansion properties of the adhesive and the wire jacket may cause hair line cracks or fractures which would permit moisture to enter the connector and cause corrosion. Sealing wires entering a connector where reentry is necessary creates additional problems. Mastics or greases can be used but these are messy and/or flow at higher temperatures.
Effective sealing where reentry is a requirement or desirable has been achieved through the use of gel sealing materials as described in U.S. Pat. Nos., 4,600,261; 4,680,233; 4,777,063 and 5,079,300. All these preceding patents are completely incorporated herein by reference for all purposes. These gel sealing materials are cross-linked polymer solids extended with a non reactive fluid extender. Alternatively, the gels may be a cross-linked system which includes an excess of a reactive fluid such as the vinyl group material so that it acts like an extender as exemplified by Sylgard 527.RTM. and as taught in U.S. Pat. No. 3,020,260, the disclosure of which is incorporated herein by reference for all purposes.
The gel material is a substantially dilute system which exhibits no steady state flow. As discussed by Ferry, a polymer gel is then a cross-linked solution whether linked by chemical bonds or crystallites or some other kind of junction. The absence of the steady state flow is the key definition of the solid like properties while the substantial dilution is necessary to give the relatively low modulus of gels. The solid nature is achieved by a microscopically continuous network structure formed in the material generally through crosslinking the polymer chains through some kind of junction or the creation of domains of associated substituents of various branch chains of the polymer. The crosslinking can be either physical or chemical as long as the crosslink sites are sustained at the use conditions of the gel.
Gels produced by mixing styrenic triblock copolymers such as styrene-ethylenebutylene-styrene (SEBS) and styrene-ethylene propylene-styrene (SEPS) etc. and parafinic oils are comprised of glassy styrenic micropheres interconnected by a fluid extended elastomeric phase. The microphase separated styrenic domains serve as the junction points in the systems. The SEBS and SEPS gels are examples of thermoplastic systems. Whereas, silicone gels of the present invention are examples of thermoset gels. This class of gels is chemically cross-linked through the use of a multifunctional cross linking agent.
Although the silicone gels described in the above referenced patents and brochures have been shown to effectively seal a wide variety of articles, difficulties often arise when trying to seal two fine wires generally in the gauge found in automotive connectors where the wires are located in close proximity such as the back end of a connector. Thus, it would be highly desirable to have the benefits and ease of use of a gel sealing material with preferred sealing characteristics for use with twin or multiple wires in for example an automotive connector wherein the gauges of wires are between 18 and 26 gauge wire.
SUMMARY OF THE INVENTION
The invention provides for the previously cited desirable features as well as many other advantages obvious to the ordinary skilled artisan. More specifically, it has been discovered that a silicone gel having a stress relaxation greater than about 50% provides an effective gel sealant for twin or multi-wire applications for example in the back end of automotive connectors. In particular, the gel sealing material should also have a Voland hardness of from about 6 gram
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Chiotis Achilles
Wojtowicz Janusz
Burkard Herbert G.
Chao Yuan
Housel James C.
Raychem Corporation
Swartz Rodney P.
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