US20100320700A1

US20100320700A1 - Red Heat Exhaust System Silicone Composite O-Ring Gaskets and Method for Fabricating Same

Info

Publication number: US20100320700A1
Application number: US12/665,716
Authority: US
Inventors: William A Clarke
Original assignee: Flexible Ceramics Inc
Current assignee: Flexible Ceramics Inc
Priority date: 2007-06-19
Filing date: 2008-06-19
Publication date: 2010-12-23
Also published as: US20100324187A1; WO2008156840A1; WO2008156822A3; CN101903429A; US20100319656A1; EP2162478A4; WO2008156822A2; WO2008156821A1; JP2011506618A; JP5307804B2; US8347854B2; EP2162478B1; CN101903429B; ES2862460T3; EP2162478A1; US8293830B2

Abstract

This invention extends the elastic range of silicone composite gaskets from typically −40 to 300° C. (Reference I) to temperatures within the “red heat”, Le, 600 to 1000° C. applications The composite gaskets comprise a matrix of cured methyl and/or phenyl-silsesquioxane resins, boron oxide, boron oxide and silica additives and a reinforcing material that enables highly thermally stable elastic composites to be fabricated into durable composite exhaust system gaskets The invention offers the most economical and proven durable solution to the current high temperature sealing problems (Reference 2) and cost of current traditional multi-layer steel gaskets The method for making the composite gaskets comprises applying the above resin blend to continuous or discontinuous fiber reinforcing material and curing the resin

Description

RELATED APPLICATION DATA

The present application claims benefit from commonly owned, co-pending U.S. Application for Provisional Patent, Application No. 60/936,472, filed Jun. 19, 2007. The present application is related to commonly owned co-pending applications, Silicone Resin Composites for High Temperature Durable Elastic Composite Applications and Methods for Fabricating Same, application Ser. No. ______, and Internal Combustion (IC) Engine Head Assembly Combustion Chamber Multiple Spark Ignition (MSI) Fuel Savings Device and Methods of Fabrication Thereof, application Ser. No. ______, each filed on even day herewith.

BACKGROUND OF THE DISCOVERY

1. Field of the Invention
This invention discusses a new gasket technology to address the increasing demands of providing effective sealing solutions for exhaust systems in engines and power plant industries.
There is an increasing demand (Reference 2) for more effective exhaust system joints to meet environmental and emissions regulations. These hot-gas applications are especially difficult to seal (FIG. 2). With low-load joints, significant flange movement and distortion plus temperatures in excess of 850° C. (1550° F.), traditional gaskets (Reference 2) “often do not provide an effective seal, typically degrading or creeping at operating temperatures”. The exhaust manifold gas leakage occurs before passing through the catalytic converter.
Prior art in O-rings or “liquid” gaskets utilize organic materials that pyrolyze giving off noxious smoke by-products when subjected to temperatures greater than 300 to 400° C. where the majority of organic materials pyrolyze. Other silicone polymer pastes and cements do not retain elastic properties after heat curing at 400° C. These silicone prepreg materials are excellent for producing ceramic products which cannot perform as gaskets without elastic properties.
The current EPA pollution testing is currently limited to the tail pipe and inspection under the hood to make sure the pollution control equipment is properly installed which misses the underhood exhaust manifold gasket pollution. This invention solves this pollution problem economically at a significant cost savings to engine manufacturers which includes elimination of storage, inventory and costly tooling required for multilayer steel gaskets which weigh four times more than the composite O-rings applied as liquid gaskets.
2. Description of the Previously Published Art
The Beckley U.S. Pat. No. 5,552,466 is specific to teach methods of producing processable resin blends that produce high density silica ceramics in the red heat zone. The preferred catalyst, zinc hexanoic acid produces a high cross-link density polymer by the Beckley methods of processing that favor the formation of high yield ceramic composites compared the high temperature elastic silicone polymers produced by the Clarke methods of using boron nitride, silica and a preferred boron oxide catalyst. No mention is made of compression-recovery properties common to Clarke related composites.
The Boisvert, et al. U.S. Pat. No. 5,972,512 is specific to teach silanol-silanol condensation cured methylsilsesquioxane resins enabling the fabrication of non-burning composites with superior performance than organic laminates. No mention is made of producing a high temperature elastic silicone containing boron nitride and silica to produce the fire resistant elastic silicone laminate that slowly transforms into a flexible ceramic then ceramic with no burn through at 2000° F. after 15 minutes. Also, the fire resistance is specific to methyl resins overlooking the high thermal advantages of phenyl resins even when used sparingly. Also, elastic composites have dissimilar materials joining advantages not mentioned in the Boisvert patent.
The Clarke U.S. Pat. No. 6,093,763 is specific to teach the use of the zinc hexanoic acid catalyst for a specific ratio of 2:1 for two specific silicon resins with boron nitride as filler. The zinc hexanoic acid catalyst produces a different high cross-link density polymer than the preferred elastic composite produced from a reaction mixture of boron nitride, silica and boron oxide and controlled reaction methods. The amount of zinc catalyst required to enable the sealant to perform is also excessive in comparison to the boron oxide catalyst which is sparingly used to favor a slow reaction for producing elastic composites.
The Clarke U.S. Pat. No. 6,161,520 is specific to teach that the gasket materials derived from Clarke's copending U.S. patent application Ser. Nos. 08/962,782; 08/962,783 and 09/185,282, all teach the required use of boron nitride as the catalyst for condensation polymerization of the resin blend needed to produce the gaskets. Clarke has verified that boron nitride is not a catalyst as incorrectly claimed. Clarke verified the certainty that boron nitride is not a catalyst by attempting to repeat the 873 patent's FIG. 1 “gel” curve at 177° C. using the preferred CERAC, Inc. item #B-1084-99.5% pure boron nitride. Other research associates have also confirmed the certainty that boron nitride is not a silicone condensation catalyst. Numerous possible contaminates would need to be investigated to find the actual catalyst or combination of catalysts including the possibility of humidity. No mention of using boron nitride, silica and boron oxide as a reaction mixture processed in a rotating cylinder at ambient temperature to favor the production of a high temperature elastic composite. Neither is boron oxide mentioned as catalyst with boron nitride cost advantage addressed when boron oxide is used as a residual from the chemical processing (Reference 4) of boron nitride.
The Clarke U.S. Pat. No. 6,183,873 B1 is specific to teach the use of boron nitride as the catalyst in producing polysiloxane resin formulations for hot melt or wet impregnation of ceramic reinforcements. As stated above, boron nitride is not a catalyst as incorrectly claimed. The more costly and toxic hot melt and wet processing methods of the above described '873 patent are eliminated with the superior ambient temperature methods addressed by the inventor. No resin formulations using boron oxide as the catalyst are mentioned. Additionally, the methods of producing “flexible ceramic” high temperature elastic laminates are not addressed. Also, the use of laser processing (up to 16,500° C.) to increase the tensile strength by 25% and form ceramic sealed edges is not addressed. The economical advantage of using residual boron oxide contained in boron nitride as a source for the catalyst addition is not mentioned.
The Clarke SAE 2002-01-0332 paper (Reference 3) refers to high purity boron oxide as a Lewis acid catalyst with silica mentioned as an unobvious inhibitor for these silicone condensation polymerization catalysts. High cost boron nitride and boron oxide are added separately. No mention is made of producing resin formulations using boron nitride containing boron oxide residues as a source of boron oxide catalyst and cost savings advantage. Additionally, the methods of producing “flexible-ceramic” laminates capable of high-temperature elastic recovery (FIG. 3) are not addressed. Also, the use of laser processing (up to 16,500° C.) to increase the tensile strength by up to 25% and forming ceramic sealed edges is not addressed. The “self extinguishing” property of the elastic composite when heat is removed is also not mentioned. This is an essential requirement to prevent combustion pre-ignition in superior fuel saving flexible ceramic composite ignition devices.
The Zurfluh SAE 2007-01-1520 paper (Reference 2) refers to new alloys (HTAs) and an unique high temperature coating (undefined) for solving the exhaust systems multi-layer steel (MLS) gasket environmental and emissions problems where traditional MLS gaskets “often do not provide an effective seal, typically degrading or creeping at operating temperatures”. The high costs associated with the MLS gaskets are not eliminated by the proposed new metals and the coating cannot have sufficient compression-recovery to act as a gasket, so the MLS recovery from compression is needed to provide the gaskets recovery which is not the same as the more economical viscoelastic recovery provided by the composite gaskets.

REFERENCES CITED

U.S. Patent Documents

U.S. Pat. No. 5,552,466 Sep. 3, 1996 Beckley et al.
U.S. Pat. No. 5,972,512 Oct. 26, 1999 Boisvert et al.
U.S. Pat. No. 6,093,763 Jul. 25, 2000 Clarke
U.S. Pat. No. 6,161,520 Dec. 19, 2000 Clarke
U.S. Pat. No. 6,183,873 Feb. 6, 2001 Clarke

Published References

1. Sorenson W. R. and W. T. Campbell, Preparative Methods of Polymer Chemistry, John Wiley & Sons, (1968) p. 387.
2. Zurfluh, T. O., A New High Temperature Exhaust Sealing System, Federal-Mogul, SAE PAPER, 2007-01-1520 (April, 2007).
3. Clarke, W. A.; Azzazy, M and West, R., Reinventing the Internal Combustion Engine Head and Exhaust Gaskets, Clarke & Associates, SAE PAPER, 2002-01-0332, (Mar. 4, 2002) pp. 2-3.
4. Lenonis, D. A.; Tereshko, J. and C. M. Andersen, Boron Nitride Powder—A High-Performance Alternative for Solid Lubrication, Advanced Ceramics Corporation, A Sterling Publication (1994).
5. Rochow, E. G., Chemistry of the Silicones, Second Edition, Wiley, (1951).
6. Thompson, Raymond, The Chemistry of Metal Borides and Related Compounds, reprinted from PROGRESS IN BORON CHEMISTRY, Vol. 2, Pergamon Press, (1969) p. 200

SUMMARY OF THE INVENTION

Objectives of the Discovery

It is the objective of this discovery, derived from the above background experience to exploit the use of the liquid composite blend in producing emissions free exhaust system gaskets for assuring elimination of under hood pollution from exhaust systems particularly in front of the catalytic converter at significant cost savings to engine manufacturers.
It is the further objective of this discovery to provide options to exhaust systems engineers which allow. the same high temperature sealing capability with applied liquid gaskets or complex network beaded gaskets, molded O-rings and continuous braided fiber reinforced helical O-rings.
It is the further objective of this discovery to design the O-ring options so the compression of the ring provides a 10 to 1 minimum ratio of the compressed ring's land width to thickness, so engineers can restrict the flow of the compressed gasket within their desired design perimeters.
It is the further objective of this discovery to provide engine exhaust manifold liquid and molded O-rings that have successfully completed durability testing on Ford 460 V8 truck engine dynamometers for greater than 6000 hours fired by methane gas.
It is the further objective of this discovery to have exhaust manifold O-ring gaskets that have successfully completed over 350,000 miles cab fleet testing on Ford Crown Victoria 4.6 V8 engines.
It is the further objective of this discovery to have out performed the current Ford Crown Victoria 4.6 V8 engine MLS exhaust manifold gaskets with the composite gaskets measuring pressure decay from 30 psi at 300 to 400° C. flange temperatures with essentially no leakage.
It is the further objective of this discovery to have greater than 95% recovery from 15% compression of composites made with the invention's polymer matrix cured from 200 to 750° C. and densified with the invention's resin blend (see FIG. 3).
It is the further objective of this discovery to make the resin blend from the methyl and phenyl silsesquioxane resins and additives and apply the resin blend to reinforcing materials to provide a liquid composite that can be used to apply O-rings, mold O-rings or impregnate braided reinforcement to make “helical” O-rings (FIG. 1) or apply the liquid blend to make network gaskets. The applied prepreg or liquid composite is typically staged at 100 and cured at 150° C. prior to raising the temperature to the desired performance temperature (in exhaust manifold applications the firing of the engine completes the cure).
This invention extends the elastic range of silicone composite gaskets from typically −40 to 300° C. to temperatures within the “red heat”, i.e., 600 to 1000° C. applications. The composite gaskets comprise a matrix of cured methyl and/or phenyl-silsesquioxane resins, boron nitride, boron oxide and silica additives and a reinforcing material that enables highly thermally stable elastic composites to be fabricated into durable composite exhaust system gaskets. The high temperature composite gaskets are assembled as an O-ring or as a liquid bead forming an O-ring on engine exhaust manifolds just before assembly. High performance engine exhaust gas temperatures are typically 871° C. for sustained and 982° C. for spike temperatures. The heat from the hot gases contained within the compressed composite O-rings form a protective sealed ceramic barrier on the inside of the compressed edge that allows the compressed composite material to remain elastic. The applied composite O-ring gaskets invention enables the seals to control their flow within precise thickness and land width limits when compressed in assembly and durability tested. The method for making the composite gaskets comprises applying the above resin blend to continuous or discontinuous fiber reinforcing material and curing the resin.
The composite matrix materials contained in exhaust manifold composite gaskets have passed cab fleet durability testing (under confidentiality agreement) for over 350,000 miles (with 150,000 mile requirement). The economical “Liquid gaskets” applied as liquid bead formed “O” rings on 460 V8 truck engine exhaust manifolds before assembly performed for nine months on dynamometers (under confidentiality agreement) for over 6000 hours the equivalent of 400,000 miles on methane fired engines. Methane fires hotter than conventional fossil fuel. The composites have passed FAA fire penetration, burn through, heat release (<10 kW/m²), smoke density and Boeing toxicity testing per BSS 7239.

BRIEF DESCRIPTION OF THE DRAWING

FIGS. 1A and 1B is a helical polysiloxane O-ring seal braid constructed according to the principles of the present invention;

FIG. 2 is a is a graph illustrating pressure decay curves for flexible ceramic and multilayer steel gaskets;

FIG. 3 is a graph of laminate thickness recovery as a function of cure temperature; and

FIGS. 4A and 4B are braided cross-sections of the helical braid of FIG. 1

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Durability testing (under confidentiality agreement) of the resin blend used to make composite laminate internal combustion engine exhaust manifold gaskets has revealed that they can perform up to and exceeding 350,000 miles cab fleet durability testing (typical automotive requirement is 150,000 miles) with “spike” exhaust hot-gas temperatures up to 932° C. FIG. 3 shows the percent recovery from 15% compression is greater than 95% for composites cured from 200 to 750° C. and densified (vacuum impregnated) with the invention's resin blend.
To accomplish the above product performance, the resin blend additive materials are selected with high flexible and thermal resistant properties.
The unique resin blend is typically mixed from three silicone resins and two or more ceramic additives. To accomplish the elastic compression recovery performance (see FIG. 3) of composites made from the resin blend's “prepreg” several different composite elements are utilized, the most important being the resin blend composition and methods of processing. The resin blend is formulated from a high-molecular-weight “flake resin” and intermediate liquid silicone resin precursor and optionally a lower molecular weight silicone resin. These resins are selected to have different functionality such as listed in Table 1.

TABLE 1

(Reference 5)
Organosilicon preferred functionalities (where R = methyl or phenyl):

(RSiO_3/2)_n, silsesquioxane polymers, e.g., methylphenylsesquisiloxane

R₂Si—OH, silanol (hydroxyl) terminated, polydimethylsiloxane, e.g.,

HOSiMe₂O—(SiMe₂O)n—SiMe₂OH, and

Me₃SiO—, trimethylsilyl terminated, e.g., Me₃SiO—(SiMe₂O)_n—SiMe₃,

or

Dimethylpolysiloxane polymers containing methyl or phenyl

silsesquioxanes, with optional methoxy-termination, e.g.,

CH₃O—(SiMe₂O)_n—

A variety of polysiloxane oligomers are well known in the art that exhibit similar functionality; however, the discovery's most preferred organic groups are the methyl or phenyl because of their high thermal stability.
A typical resin blend with the preferred additive systems is given in Table 2.

TABLE 2

Typical Resin Blend

Parts by Weight

Resin Blend Formulation	In General	Preferred

(1)	Dimethylsiloxane polymers	40-70	65
	containing phenyl silsesquioxanes
(2)	Dimethylsiloxane polymers	5-25	10
	containing methyl silsesequioxanes.
(3)	silanol terminated, poly-	5-25	25
	dimethylsiloxane
(4)	boron nitride & residual boron oxide	5-40	20
(5)	boron oxide content of (4)	0.1-1.2	0.40
(6)	silica	3-15	6
	or other filler such as
	silica gel or	3-15
	silicon carbide or	15-25
	alumina or silica fiber	15-25
	reinforced polysiloxane rods

In Table 3, the formulation using preferred commercially available resins is set forth.

TABLE 3

Preferred Commercially Available Resins

Parts by Weight

Formulations Using

GE Silicones

Dow Corning

Commercial Resins	In General	Preferred	In General	Preferred

(1)	Dimethyl polymers	40-70	65 (SR 355)	40-70	65 (233)
	w/ phenyl silsesquioxanes,				(or 249)
	high MW
(2)	Dimethyl polymers	5-25	10 (TPR-179)	10-60	35 (3037)
	w/ methyl silsesquioxanes,				covers items
	methoxy				(2) and (3)
	terminated
(3)	Silanol terminated	5-25	25 (TPR-178)
	Polymethylsiloxane

Additives

The preferred resin blend additives are silica and boron nitride retaining 2±1.0 wt % residual boron oxide. These additives provide high thermal capabilities.

Silica/Boron Nitride:

Silica was discovered by Clarke (Reference 3) to slow down the time it takes for the silicone resin reaction mass catalyzed by boron oxide to reach “gel” at 177° C. (Table 1). Using this capability, the silicone reaction mass is slowly polymerized at ambient temperature in excess acetone favoring the formation of high molecular weight silicone polymers with high elastic increased linear chain (Si—O—Si) growth. Additionally, a mixture of silica and boron nitride added to the silicone resin reaction mass produces a superior flexible elastic polymer with high-temperature elastic properties than can not be produced using silica or boron nitride alone.
Silica alone will increase the polymer modulus causing it to become nonelastic above 300° C. Boron nitride alone at the suggested 16 wt % will produce an excessively plasticized soft low modulus weak polymer that will fail in interlaminar shear loading as a gasket. But when boron nitride and silica are in a 10/6 to 20/6 parts by weight ratio with 100 parts resin blend the elastic polymer produced by the boron oxide processing will become a thermally stable high-temperature flexible elastic polymer up to 500° C. because the silica is increasing the modulus to compensate for the plasticizing effect of the boron nitride which is thermally stable as a lubricant to 850° C. (Reference 6).

Boron Nitride and Residual Boron Oxide

Boron nitride retaining 2.0±1.0 wt. % boron oxide is available from the Momentive Performance Materials (grade SAM-140) and ZYP Coating (grade ZPG-18 and -19) Companies who can selectively provide this preferred residual boron oxide and within the boron nitride from their commercial synthesis and leaching production operations. This aggregate boron nitride retaining 2% residual boron oxide is superior to high purity boron nitride (requiring a separate catalyst addition) in processing efficiency and cost advantage.
The residual boron nitride containing the residual boron oxide is typically added up to 20 parts by weight for every 100 parts resin as shown in Table 3. The submicron boron nitride containing residual boron oxide is then about 16 wt. % of the resin blend and silica is added at 4.8 wt. %.

Prepreg

The preferred fiber for preparing the braid reinforced polysiloxane composite helical O-rings are S-glass and E-glass. Atkins & Pearce has worked with the inventor to develop a proprietary braid identified as 6×6×6 which essentially uses 6 yarn bobbins to braid a core braid that is then over braided with 2 layers of 6 yarns each that form a near hexagonal braid that is ideal for forming a high temperature helical O-rings (FIG. 4). The prepreg resin content is up to 40 weight % while the braid weight % is up to 70% with a preferred 33 weight % resin content. The dry braid is vacuum impregnated to form the prepreg with the excess resin removed. The impregnation is carried out cost effectively at ambient temperature not requiring solvents or heat. Heating the braid to 65 C makes the prepreg easily handled for preparing the helical O-rings or other desired network gaskets.
A simple right cylinder tooling mandrel at the desired O-ring inside diameter is used to apply the prepreg braided fiber around and heat cure by first staging for 30 minutes at 100° C. followed by 200° C. for exhaust manifold applications. The cured helical composite braid is removed from the tooling and cut with a 0.300 inch circumferential overlap as shown in FIG. 1. These composite helical O-rings are tested in tooling using the standard studs and nuts called out for Ford Crown Victoria 4.6 V8 exhaust manifold gaskets. FIG. 2 reveals the composite O-rings have essentially no leakage while the MLS gaskets at 300 to 400° C. leak significantly.
The fiber reinforcements can be selected from any of the glass (E-glass, S-glass, quartz or chemically altered variations of these), Nextel® or refractory (e.g., zirconia) high temperature fibers or advanced composite graphite or pitch fiber weaves or styles provided by the textile industry. When using graphite or pitch fabrics, electro-less metal (such as nickel or aluminum) coated fibers are preferred for producing these advance composite polysiloxane matrix composites with high performance mechanical properties. Nickel oxide activates the silicone resin blends just as aluminum oxide assuring increased bond strength.

Compressed O-Ring Thickness Control

It has been observed by the inventor that the thickness of the composite gaskets is the major cost and performance driver in making such products as automotive or aerospace gaskets have reliable durability. The laminate uniform thickness is the most critical quality control capability requirement for assuring high durability sealing of exhaust manifold gaskets operating at “spike” exhaust gas temperatures of 927° C. Pressure decay testing (Table 4) of laminate gaskets reveals the maximum thickness standard deviation should not be greater than ±0.45×10⁻³inches to assure extended durability. Laminates made to the composite gasket's composition requirements and molded to the above thickness standard deviation limits have performed well over 4 years in cab fleet testing (under confidentiality agreement) up to 350,000 miles (exceeding 150,000 mile test requirement).

TABLE 4

Decay in Exhaust Gas Pressure from 30 psi (measured in minutes)

	Decay in
Sample	pressure	Time	Average thickness	Standard. Deviation
#	(psi)	(minutes)	(inches) × 10⁻³	×10⁻³

T-1	29.4	40	30.83	±0.41
T-2	27.2	40	31.70	±0.45
T-3	27.0	40	31.25	±0.52
T-4	25.0	0.83	31.50	±0.55
T-5	25.0	1.17	31.50	±0.78

FIG. 3 reveals the laminate thickness recovery after 15% compression and 10,000,000 compression recovery cycles at different temperatures. Also, the hotter the steel bolted aluminum clamped laminate joint becomes, the greater the anisotropic thermal expansion sealing pressure exerted by the trapped polysiloxane matrix. In contrast, at the minimum automotive engine design operating temperature of −40° C., the elastic recovery of the matrix prevents cold start blow outs. Deep thermo-shock testing under pressures higher than exhaust manifold pressures is utilized to verify the thermal cycling capability.

Prototype Parts

All optional liquid gaskets have been made and extensively tested in exhaust manifold engine testing. The liquid gaskets require discontinuous fiber weight % of 50% with 50% resin blend. The molded O-rings use a preferred 40 to 50% discontinued fiber weight %. The helical O-rings are made with the Atkins& Pearce “6×6×6” braid reinforcement with the prepreg preferred resin content at 33±3%. The network applied liquid gasket is prepared the same as the liquid gasket. Many prototype parts have been made (under confidentiality agreement) which demonstrate that most engine components of diesel, internal combustion (IC) and turbine engines that operate from 500 to 1000° C. can be made with fiber reinforced composites made with the resin blend.

Testing

Examples include engine gaskets, multiple ignition fuel saving devices, turbine engine combustion liners, diesel engine head and exhaust gaskets, aircraft fire walls, and liquid exhaust gaskets, O-rings. Testing (under confidentiality agreement) has been extensive on IC engine dynamometers including cab fleet testing and deep thermal shock, steam testing of head gaskets and multispark ignition prototypes. Automotive, coolant, oil and combustion gas sealing has been tested and reviewed with major automotive companies (under confidentiality agreement) including fleet testing. Liquid exhaust gaskets and multiple ignition composite devices are recent developments which solves current costly pollution and fuel burning efficiency automotive IC engine CAFÉ standards capability requirements.
Fire protective testing of the inventions under FAA typical tests has proven the superior performance of the discoveries to pass the FAA major testing requirements for aircraft interior, cargo container, fire blankets and fire wall requirements. The composites have passed FAA fire penetration, burn through, heat release (<10 kW/m²), smoke density and Boeing toxicity testing per BSS 7239.
The inventions resin blend when used as composite exhaust gasket matrix material has been evaluated for a year (under confidentiality agreement) on Jasper Engine Company Generators powered with Ford 460 V8 truck engines. All engines performed without a problem for 6640 hours which is equivalent to 400,000 miles of truck engine durability. Cab fleet testing has confirmed the durability in performing over 350,000 miles in Crown Victoria 4.6 liter V8 engine exhaust manifold composite gasket testing.

Claims

1. A composite sealing device made up in the form of a “liquid gasket”, “helical O-ring”, molded O-ring, and complex network of beaded sealing gasket comprising

a) methyl and or phenylsilsesquioxane resin consisting essentially of the following commercial resins or from other commercial suppliers of essentially the same or similar resin composition are mixed at up to 100 parts by weight as follows:

Parts by Weight 5 to 35 Dow Corning flake 249 5 to 35 Dow Corning flake 233 2 to 15 Dow Corning intermediate liquid MR 2404 and 15 to 30 Dow Corning intermediate liquid 3037 and the following commercial additives at up to 26 parts by weight 5 to 30 Momentive boron nitride grade SAM-140 1 to 10 Silica (submicron) Note: the boron nitride may contain a residual boron oxide catalyst content from 0.1 to 5 weight percent of boron oxide.

b) the above 100 parts by weight resin is then mixed with a reinforcing material for the following types of composite seals:

Weight % Resin Mix Reinforcement Up to 50 up to 50 Liquid Gasket Up to 40 up to 80 Helical O-rings Up to 50 up to 50 Molded O-rings Up to 50 up to 50 Beaded Complex Net-Work Gaskets

2. The composite of claim 1, where the reinforcement is a braid, twisted yarn or tow made up of continuous E-glass, S-glass, quartz or chemically processed glass, carbon, pitch, Nextel, alumina, zirconia or vapor grown continuous carbon fibers.

3. The composite of claim 1, where the reinforcement is a discontinuous fiber, chopped resin impregnated and cured fibers, fused fibers, spheres and mixtures thereof.

4. The composite of claim 1 where the liquid gaskets are made from discontinuous glass fibers mixed at up to 50% of the resin mix.

5. The composite of claim 1 where the helical O-ring is made from a braid provided by The Atkins& Pearce Company identified as a 6×6×6 braid which is up to 70 weight % and the resin mix is up to 40% of the prepreg braid.

6. The composite of claim 1 where the helical O-ring is made from twisted (2 and ½ turns per inch) fibers (preferably glass fibers).

7. The composite of claim 1 wherein the molded O-ring is made from up to 50% discontinuous fibers (preferably glass fibers) and up to 50% resin mix.

8. The composite of claim 1 wherein the beaded complex net-work gaskets are made from discontinuous fibers (preferably glass fibers) applied by caulking, silk-screening, masking and spraying devices and computer controlled delivery systems.

9. The composite composition of the claim 1 sealing devices wherein the specifics of the sealing devices' composite composition for claims 2,3,4,5,6,7, and 8 have been incorporated.

10. The claim 2 braid, twisted yarn or tow vacuum impregnated with the claim 1 resin mix forming a prepregged braid or twisted yarn or tow.

11. The claim 10 prepreg at up to 35 weight percent resin mix is wrapped on a cylindrical mandrel and heat cured into a helical preform which is cut into helical O-rings as shown in FIG. 1.

12. The claim 11 heat cured helical O-ring is staged for ½ hour at 100° C. then raised to the desired performance temperature (typically 400 C for exhaust manifold applications and 550° C. for fire resistance applications).

13. The claim 12 cured helical O-ring is cut as shown in FIG. 1 with circumferentially overlapping ends which after being compressed under clamping pressure weld together to form a resin sealed joint.

14. The claim 12 cured helical O-ring is designed to have after being compressed flat under clamping pressure an extruded land width to thickness ratio of 10 to 1 to 20 to 1 to assure high temperature reliable sealing performance for the compressed O-ring. Typically a 0.090 inch diameter helical O-ring will compress under 175 inch-pounds bolt torque load to a land width of 0.250 inches and thickness of 0.025 producing a 10 to 1 ratio, which is common to engine exhaust manifold applications.

15. The liquid gasket, molded O-ring and beaded net-work sealing gaskets all are made up of a preferred 40 to 50 weight percent discontinuous fibers in 40 to 60% resin mix from claim 1 which needs to be evaluated and adjusted to assure the compressed reinforcement thickness is 1/10 the land width produced when the ring is flattened by the compression load generated by the bolt torque typically 175 inch-pounds wherein the preferred fiber loading typically satisfies this sealing performance requirement.

16. The molded O-rings are typically heat cured to 400° C. after staging at 100° C. when used for exhaust manifold high durability gasket applications wherein fire protection applications are heat cured to 550 C for satisfying FAA fire penetration and burn through requirements for aircraft interior fire resistance applications.

17. The helical O-ring circumferential over lap of claim 13 is increased to several circumferential turns when a packing is preferred in “packing” applications.

18. The claim 1 beaded net-work gasket can be made up to incorporate the helical and molded O-rings within the next work formed gasket designs.

19. The method of fabricating these high temperature sealing devices of claim 1 comprises applying the resin blend of claim 1 to a reinforcement material which may be a continuous fiber (up to 80 weight %) or discontinuous fiber (up to 50 weight %) with the resin mix content at 20 to 40 weight % for continuous fiber applications and up to 60% for discontinuous fiber applications wherein the cure is staged first at 100° C. followed by heat curing to the desired performance temperature.

20. The method of claim 19 where the catalyst will include boron oxide as a preferred catalyst at 0.1 to 5% of the boron nitride additive.

21. The composite seals of claim 1 wherein the composite char yield for helical O-rings is greater than 90%, the liquid gasket durability is greater than 6000 hours when applied to 460 V8 truck exhaust manifolds.