U.S. patent application number 12/494951 was filed with the patent office on 2010-12-30 for bonded part with laminated rubber member and method of making.
This patent application is currently assigned to Gates Corporation. Invention is credited to Paul N. Dunlap, Yuding Feng, Yahya Hodjat, Lin Zhu.
Application Number | 20100330352 12/494951 |
Document ID | / |
Family ID | 42634793 |
Filed Date | 2010-12-30 |
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United States Patent
Application |
20100330352 |
Kind Code |
A1 |
Feng; Yuding ; et
al. |
December 30, 2010 |
Bonded Part with Laminated Rubber Member and Method of Making
Abstract
A bonded part with a press-fit, vulcanized rubber member
residing in compression between two rigid members and bonded
thereto. The rubber member is a laminate with a core layer
sandwiched between and bonded to two self-bonding rubber layers.
The bonded part may be, for example, a vibration damper, isolator
or absorber. The core layer and the self-bonding layers may have
the same primary elastomer and cure system type, and the
self-bonding layers have an adhesion promoter not present in the
core layer. The adhesive layers may be from 0.05 to 1 mm thick or
from 5% to 10% of the laminate thickness. The method includes
forming a rubber core layer, curing it, applying a rubber adhesive
layer on each side to form a laminate, inserting the laminate
between two rigid members under compression, and post-curing to
form a bonded part. The adhesive layers may be partially cured
before inserting.
Inventors: |
Feng; Yuding; (Rochester
Hills, MI) ; Zhu; Lin; (Rochester Hills, MI) ;
Hodjat; Yahya; (Oxford, MI) ; Dunlap; Paul N.;
(Englewood, CO) |
Correspondence
Address: |
THE GATES CORPORATION
IP LAW DEPT. 10-A3, 1551 WEWATTA STREET
DENVER
CO
80202
US
|
Assignee: |
Gates Corporation
Denver
CO
|
Family ID: |
42634793 |
Appl. No.: |
12/494951 |
Filed: |
June 30, 2009 |
Current U.S.
Class: |
428/220 ;
156/244.24; 156/325; 428/519 |
Current CPC
Class: |
B32B 27/18 20130101;
B32B 37/24 20130101; B32B 2037/1253 20130101; B32B 15/18 20130101;
B32B 27/365 20130101; B32B 37/185 20130101; B32B 3/263 20130101;
B32B 27/20 20130101; B32B 2605/08 20130101; C08J 5/124 20130101;
B32B 25/14 20130101; B32B 9/005 20130101; B32B 37/153 20130101;
B32B 9/043 20130101; B32B 2250/248 20130101; B32B 37/10 20130101;
B32B 7/12 20130101; B32B 2307/50 20130101; B32B 38/0012 20130101;
C08J 2323/16 20130101; B32B 27/34 20130101; B32B 37/1284 20130101;
B32B 25/08 20130101; B32B 2037/243 20130101; B32B 25/042 20130101;
B32B 2605/00 20130101; B32B 15/20 20130101; C08J 2323/08 20130101;
B32B 25/02 20130101; B32B 2307/546 20130101; B32B 15/06 20130101;
B32B 2307/712 20130101; C08J 2319/00 20130101; B32B 2307/306
20130101; C08J 3/24 20130101; C08J 2323/26 20130101; B32B 27/28
20130101; Y10T 428/31924 20150401; B32B 38/0036 20130101; B32B
2307/56 20130101; B32B 27/281 20130101 |
Class at
Publication: |
428/220 ;
156/325; 156/244.24; 428/519 |
International
Class: |
B32B 27/32 20060101
B32B027/32; B32B 37/12 20060101 B32B037/12; B32B 37/14 20060101
B32B037/14 |
Claims
1. A bonded part comprising a vulcanized rubber member residing in
compression between two rigid members and bonded thereto, wherein
the rubber member is a laminate comprising a rubber core layer
sandwiched between and bonded to two self-bonding rubber
layers.
2. The bonded part of claim 1 in the form of vibration damper,
isolator or absorber.
3. The bonded part of claim 1 wherein the rigid members are metal
members, and the amount of said compression is from 10% to 50%.
4. The bonded part of claim 3 wherein the core layer and the
self-bonding layers comprise the same primary elastomer type and
the same cure system type, and said self-bonding layers comprise an
adhesion promoter which is not present in said core layer.
5. The bonded part of claim 4 wherein the rubber core layer
comprises a peroxide cured elastomer composition and the
self-bonding rubber layers comprise a peroxide cured elastomer
composition comprising an adhesion promoter.
6. The bonded part of claim 5 wherein the primary elastomer type is
an ethylene-alpha-olefin elastomer and the adhesion promoter is a
metal salt of an alpha-beta unsaturated organic acid.
7. The bonded part of claim 1 wherein the self-bonding layers are
each from about 0.05 mm to about 1 mm in thickness.
8. The bonded part of claim 1 wherein the self-bonding layers are
each from about 5% to about 10% of the total laminate
thickness.
9. The bonded part of claim 1 wherein the core comprises at least
one surface with hills and valleys, and the self-bonding layer
fills the valleys.
10. A method comprising: a) forming a rubber core layer from an
elastomer composition comprising a primary elastomer and a cure
system; b) curing said core layer at least partially; c) applying a
rubber adhesive layer on each side of said core layer to form a
rubber laminate; d) inserting said rubber laminate between two
rigid members where it resides under compression to form a
composite article; e) post-curing said composite article to effect
a bond between the rubber adhesive layers and the rigid members to
form a bonded part.
11. The method of claim 10 wherein further comprising: (f) curing
said rubber adhesive layer no more than 70% of full cure according
to ASTM D-5289 or equivalent method before said inserting.
12. The method of claim 10 wherein the extent of said curing of
said core layer is from 80% to 100% of full cure according to ASTM
D-5289 or equivalent test method.
13. The method of claim 10 wherein the extent of said curing of
said core layer is substantially fully cured.
14. The method of claim 10 wherein each adhesive layer is 0.05 mm
to 1.0 mm in thickness.
15. The method of claim 10 wherein the adhesive layers are each
from about 5% to about 10% of the total laminate thickness.
16. The method of claim 10 wherein the adhesive layer is applied
under pressure and then partially cured to from 30% to 80% of full
cure.
17. The method of claim 10 wherein said applying is by extrusion
coating with a self-bonding rubber composition.
18. The method of claim 10 wherein said forming and said applying
is by co-extrusion.
19. The method of claim 10 wherein said applying is by insert
molding (either injection, compression or transfer) and includes
partially curing the adhesive layers no more than 70% of full
cure.
20. The method of claim 10 wherein said applying is by solution
coating with a drying step which also partially cures the rubber
adhesive layer no more than 70% of full cure.
21. The method of claim 10 wherein the primary elastomers of the
core and adhesive rubber layers are of same type and selected from
the group consisting of ethylene-alpha-olefin elastomer, EPM, EPDM,
SBR, NBR, NR, EVM, EAM, ECO, and blends thereof, and wherein the
cure systems of the rubber layers are compatible and co-cure for
adhesion there between; and wherein the adhesive layers comprise an
adhesion promoter not present in the core layer.
22. The method of claim 21 wherein the core layer comprises EPDM as
the primary elastomer and a peroxide cure system; and the adhesive
layer comprises EPDM as primary elastomer, a peroxide cure system,
and a metal salt of an unsaturated organic acid as the adhesion
promoter.
23. The method of claim 22 wherein the rigid members are metal
members.
24. The method of claim 23 wherein said adhesive layer includes two
peroxides with different cure activation temperatures at least
5.degree. C. apart.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates generally to a method of making a
bonded rubber-metal article with a laminated rubber member under
compression, more particularly to vibration control devices with a
laminated rubber member bonded between two rigid members, and
specifically to a torsional vibration damper with annular laminated
rubber member directly bonded to the inner and outer rigid or metal
members and under compression.
[0003] 2. Description of the Prior Art
[0004] As vehicle engine technology develops, engines are producing
high drive torques and more demanding requirements on crankshaft
dampers which have a rubber member connecting two rigid, for
example metal, members. As a consequence, reliance on friction is
not sufficient, and the rubber member must be bonded to the metal
surfaces to sustain the high drive torque and improve the
durability. Current approaches to bond the rubber to the metal
include using a rubber-metal adhesive applied to the rigid or metal
members for subsequent vulcanization bonding, or injection molding
of a self-bonding rubber composition. These approaches generally
permit the rubber to go into a state of tension upon cooling from
the vulcanization temperature, resulting in decreased durability
and premature part failures at low temperatures. To avoid rubber in
tension and maintain the rubber in a state of compression,
post-vulcanization bonding may be used with various rubber-metal
adhesives applied to the metal bonding surfaces. These bonding
technologies generally require a number of expensive process steps
to prepare the metal and/or rubber surfaces for bonding, to apply
adhesives, to deal with chemicals or emissions, and so forth. A
two-step cure method has been disclosed in U.S. Pat. Nos. 7,078,104
and 7,291,241 which disclose self-bonding rubber formulations that
eliminate conventional adhesives and a two-step cure method to form
the rubber member and bond it to the metal, thus retaining some
degree of compression on the rubber. However, in practice, given
the competing constraints on formulating and processing the rubber
to optimize a tradeoff between bonding and retained compression
while tuning rubber modulus, damping, heat resistance, etc., it has
yet proven difficult to retain sufficient compression to achieve
desired durability targets for crankshaft dampers. The same
concerns arise for any kind of bonded rubber composite article or
part in which the rubber member is bonded between rigid members and
held under compression to enhance durability.
[0005] What is needed is a process for bonding rubber to rigid
parts with a greater degree of flexibility to achieve higher states
of compression over the life of the composite part without
sacrificing adhesion or any desired tuning of rubber properties and
without using conventional adhesives with their demanding surface
preparation requirements.
[0006] Mention is made of the applicants' co-pending applications
Ser. No. 12/340,864 and Ser. No. 11/890,163.
SUMMARY
[0007] The present invention is directed to systems and methods
which provide a process for bonding rubber to rigid parts with the
process flexibility to achieve high states of compression over the
life of the composite part without sacrificing adhesion or the
ability to tune the rubber properties and without using
conventional adhesives.
[0008] The invention is directed to a bonded part with a press-fit,
vulcanized rubber member residing in compression between two rigid
members and bonded thereto, wherein the rubber member is a laminate
with a core layer sandwiched between and bonded to two self-bonding
rubber layers. The bonded part may be, for example, a vibration
damper, isolator or absorber, or any part which holds a bonded
rubber layer in compression. The core layer and the self-bonding
layers may have the same primary elastomer and cure system type,
and the self-bonding layers have an adhesion promoter not present
in the core layer. The adhesive layers may be from about 0.05 to
about 1 mm thick or from about 5% to about 10% of the laminate
thickness. The rigid members may be metal. The amount of said
compression may be from about 10% to about 50%.
[0009] In an embodiment of the invention the rubber core layer may
be a peroxide cured elastomer composition and the self-bonding
rubber layers may be a peroxide cured elastomer composition with an
adhesion promoter. The primary elastomer type may be an
ethylene-alpha-olefin elastomer and the adhesion promoter may be a
metal salt of an alpha-beta unsaturated organic acid.
[0010] In another embodiment of the invention the core may have at
least one surface with hills and valleys, and the adhesive layer
may reside in or fill up the valleys.
[0011] The invention is also directed to a method which includes
forming a rubber core layer, curing the core layer, applying a
rubber adhesive layer on each side of the core layer to form a
laminate rubber member, inserting the laminate between two rigid
members under compression, and post-curing the assembly to form a
bonded part. The adhesive layers may be partially cured before
inserting. The curing of the core layer may be from 80% to 100% of
full cure according to ASTM D-5289 or equivalent test method. The
extent of the curing of the core layer may be substantially fully
cured.
[0012] In an embodiment of the invention the adhesive layer may be
applied under pressure and then partially cured to from 30% to 80%
of full cure. The applying step may be by extrusion coating. The
forming and applying steps may be by co-extrusion. The applying may
be by insert molding (either injection, compression or transfer)
and may include partially curing the adhesive layers. The applying
may be by solution coating with a drying step which may also
partially cure the rubber adhesive layer.
[0013] In embodiments of the invention the primary elastomers of
the core and adhesive layers may be of same type and may be
selected from the group consisting of ethylene-alpha-olefin
elastomer, EPM, EPDM, SBR, NBR, NR, EVM, EAM, ECO, and blends
thereof. The cure systems of the rubber layers may be compatible
and co-cure for adhesion there between; and the adhesive layers may
have an adhesion promoter not present in the core layer. The core
layer may have EPDM as the primary elastomer and a peroxide cure
system; and the adhesive layer may have EPDM as primary elastomer,
a peroxide cure system, and a metal salt of an unsaturated organic
acid as an adhesion promoter. The adhesive layer may include two
peroxides with different cure activation temperatures, at least
5.degree. C. apart.
[0014] The foregoing has outlined rather broadly the features and
technical advantages of the present invention in order that the
detailed description of the invention that follows may be better
understood. Additional features and advantages of the invention
will be described hereinafter which form the subject of the claims
of the invention. It should be appreciated by those skilled in the
art that the conception and specific embodiment disclosed may be
readily utilized as a basis for modifying or designing other
structures for carrying out the same purposes of the present
invention. It should also be realized by those skilled in the art
that such equivalent constructions do not depart from the spirit
and scope of the invention as set forth in the appended claims. The
novel features which are believed to be characteristic of the
invention, both as to its organization and method of operation,
together with further objects and advantages will be better
understood from the following description when considered in
connection with the accompanying figures. It is to be expressly
understood, however, that each of the figures is provided for the
purpose of illustration and description only and is not intended as
a definition of the limits of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The accompanying drawings, which are incorporated in and
form part of the specification in which like numerals designate
like parts, illustrate embodiments of the present invention and
together with the description, serve to explain the principles of
the invention. In the drawings:
[0016] FIG. 1 is a partially fragmented perspective view of a
torsional vibration damper constructed according to the present
invention;
[0017] FIG. 2 is a cross section of a rubber laminate according to
an embodiment of the invention;
[0018] FIG. 3 is a flow chart of a method of making a bonded rubber
part according to an embodiment of the invention;
[0019] FIG. 4 is a side view of a lap shear adhesion test
configuration; and
[0020] FIG. 5 is a cross section of a rubber laminate according to
another embodiment of the invention.
DETAILED DESCRIPTION
[0021] In one embodiment, the invention uses extrusion to apply a
thin layer of self-bonding rubber over a substantially fully cured
rubber core. The core and self-bonding rubber layers are compatible
in terms of curing so that the self-bonding rubber layer will bond
to the core layer. The self-bonding rubber layer includes an
adhesive promoter which need not be present in the rubber core so
that the resulting laminated rubber member will bond to the rigid
or metal members of the final composite article. The invention
provides a number of advantages over the conventional bonding
methods including: no adhesive is required; no special treatment is
required on the metal surfaces; the process cost is therefore
relatively low; there is excellent bonding without sacrificing the
rubber properties; and excellent rubber compression can be
maintained.
[0022] FIG. 2 shows a cross-sectional view of a typical extruded
rubber laminate according to the invention. In FIG. 2, laminated
rubber member 8 includes core layer 12, and self-bonding adhesive
rubber layers 14 and 16. The core layer makes up the majority of
the thickness of the rubber member and therefore provides the
required elastomeric properties for the application, such as
modulus, damping, flexibility, toughness, strength, compression set
resistance, and the like. The adhesive rubber layers are relatively
much thinner and are there to provide a strong, durable bond
between the core layer and the rigid members. Using a laminate
rubber member permits more flexibility in design and formulation of
the rubber, since each portion can now be optimized for its
specific purposes, instead of having to optimize one formulation to
do everything. In an embodiment of the invention, the adhesive
layers may each make up about 5% to about 10% of the total laminate
thickness. Alternately, the adhesive layers may each range in
thickness from about 0.05 mm (0.002 inch) to about 1 mm (0.04
inch), or from about 0.1 mm to about 0.5 mm.
[0023] "Compression" means a decrease in thickness in a principal
direction under application of a compressive force in that
direction. "Compression" does not refer to bulk compression or
volumetric compression under hydrostatic pressure herein. For
example, press-fitting a rubber laminate into a gap between two
rigid plates results in a reduction in thickness of the laminate,
i.e. compression, in the direction normal to the surfaces of the
plates, and an increase in dimension in the plane parallel to the
surface of the plates. Compression is expressed as a percent
deformation or deflection based on the original thickness in that
direction, as described for example in ASTM D-395. Rubber under
some degree of compression is more durable when subjected to
dynamic stresses than rubber in a neutral state or under tension.
The amount of compression may be from about 1% to about 60%, or
from about 5% to about 50%, or preferably from about 10% to about
40%.
[0024] "Rigid" means stiff enough to maintain its shape while
holding the rubber member in a state of compression. Stiffness is a
function of the material properties (such as modulus) and the
dimensions of the rigid member. The anticipated use or application
of the composite article may also place stiffness requirements on
the rigid members. Suitably rigid materials may include: metals,
such as steel, brass, aluminum, iron, and their alloys; and high
performance thermosets or thermoplastics, such as phenolics,
epoxies, polyesters, polyimides, polyamides,
polyaryleneetherketones, polyarylenesulfides, polysulfones,
polycarbonates, and the like, including those with various
reinforcements, fillers, or other additives; and materials based on
metal oxides, such asglass or ceramics; and various rigid
composites of the foregoing.
[0025] "Cure," "vulcanization," and "cross-linking" are generally
used interchangeably herein to describe the formation of chemical
bonds or crosslinks between polymer chains, regardless of crosslink
type, generally as a result of the application of heat, radiation,
and/or pressure to a rubber composition, and generally indicated by
a decrease in plasticity and increase in elasticity of the rubber
composition. State of cure or extent of cure may be determined or
characterized for a given rubber composition by use of any of the
cure meters or rheometers well-known in the rubber industry, and
then inferred for a given part made from that rubber composition
from the actual cure conditions and/or processing history applied
to that part. For example, percent cure may be determined according
to ASTM D-5289, ASTM D-2084, ISO 6502, or the like. "Substantially
fully cured" is used herein in the practical sense, meaning the
rubber part can be handled, stretched repeatedly, is fully
functional, and/or has substantially reached an optimum level of
one or more physical properties which depend on cure, such as
elongation, tensile and tear strength, compression set, durometer,
and the like, any of which may also be used to characterize the
extent or state of cure. As a non-limiting example, according to
ASTM D-5289, cure to "t90" or more, or to "maximum torque", or to
"highest torque" in a specified period of time, or the like may be
considered substantially fully cured. In a preferred embodiment the
core may be cured from t80 to t90, or 80 to 90% of full cure or a
maximum value of a property.
[0026] Within the present context, the terms "bonded" and "adhered"
unless specifically noted otherwise, are used interchangeably as
well recognized in the art, to denote a strong or substantial
fixation brought about by chemical reaction. This condition is
characterized by any increased force required to separate the
relevant substrates compared to that force required to separate the
substrates in the absence of such fixation. Bonding strength may
exceed rubber tear strength in the practice of the present
invention, resulting in cohesive failure of the rubber, but
cohesive failure is not necessary to establish that some bonding is
achieved within the context of the present invention.
[0027] "Self-bonding" or "adhesive" rubber means a rubber
composition that will cure and bond to a substrate upon application
of heat, radiation, and/or pressure or other suitable cure
conditions. The substrate need not have any other type of
conventional primer, adhesive, adhesive coating, or adhesive
treatment since the self-bonding rubber composition "itself" bonds
to the substrate. Generally the applicable substrate is metal or
other rigid structural material, but any substrate may be intended
depending on the context.
[0028] FIG. 1 shows an exemplary article according to an embodiment
of the invention in the form of a torsional vibration damper.
Referring to FIG. 1, dual ring damper 10 includes inner ring 20 and
inertial outer ring 30 and laminated rubber member 8, which is the
rubber laminate described above and shown in FIG. 2 in the form of
an elastomeric ring. Inner ring 20 includes hub 1 and web 2 and rim
3. Hub 1 is sized to attach to a shaft (not shown, but
conventional) such as a crankshaft. The configuration shown in FIG.
1 is for a press fit of hub 1 to a shaft, although a flange, or
keyway, or other arrangement known in the art may also be used to
secure the hub to a receiving shaft. Inertial outer ring 30
includes rim 6 and belt receiving portion 4. Belt receiving portion
4 may comprise any belt profile known in the art including a flat
belt, a V-belt, a toothed belt, or multi-V-ribbed belt profile 5 as
shown in FIG. 1. Other composite devices contemplated within the
scope of this invention include vibration mounts such as engine
mounts, bushings, shaft dampers, isolators, isolation couplings,
and the like. The invention is especially suited for devices
wherein a rubber member is sandwiched between and bonded to two
rigid members in a state of compression, for example to connect or
couple the two rigid members with a certain degree of flexibility
and/or with some vibration damping, absorption, or isolation.
[0029] Rims 3 and 6 describe an annular space in the gap between
them. This annular space is fixed in thickness because of the rigid
nature of the generally cylindrical rims. Rims 3 and 6 may be flat
and/or smooth. Alternatively, rims 3 and 6 may each have a complex
shape that allows the rubber member 8 to be mechanically fixed in
the annular space such as the wavy shape shown in FIG. 1. Rims 3
and 6 may comprise knobs, surface roughness, or any other form of
random surface irregularity or friction producing form to enhance
adhesion between rim and elastomer. Generally cylindrical devices
with annular gaps are one kind of vibration control device that may
have a compressed rubber layer inserted therein which may benefit
from the present invention. Other devices may be rectangular with
some outer frame and an inner rigid member separated by rubber
member(s). The invention is most useful for such devices where the
rubber compression is maintained by the rigid members themselves,
not by some external force.
[0030] The rubber laminate includes a core layer with the
self-bonding adhesive layers on each side. The core layer and the
adhesive layers may comprise any desired rubber or elastomeric
composition, suitably chosen to meet the requirements of the
application, such as heat resistance, flexibility, modulus,
damping, environmental resistance, and the like. The rubber
compositions of the core layer and the adhesive layers include a
base elastomer or primary elastomer component, which may be any
desired elastomer which preferably can be co-cured or otherwise
compatible with the self-bonding rubber layers. It is preferable
that both the core rubber layer and the adhesive rubber layers have
the same, or similar or at least compatible, primary elastomer, for
improving the bonding compatibility between the layers. Suitable
primary elastomers include natural rubber (NR),
ethylene-alpha-olefin elastomers (such as ethylene propylene
copolymers (EPM), ethylene propylene diene terpolymers (EPDM),
ethylene octene copolymers (EOM), ethylene butene copolymers (EBM),
ethylene octene terpolymers (EODM); and ethylene butene terpolymers
(EBDM)); ethylene/acrylic elastomer (AEM), polychloroprene rubber
(CR), acrylonitrile butadiene rubber (NBR), hydrogenated NBR
(HNBR), styrene-butadiene rubber (SBR), chlorosulfonated
polyethylene (CSM, ACSM), epichlorohydrin (ECO), polybutadiene
rubber (BR), polyisoprene-based elastomers (IR, IIR, CIIR, BIIR),
chlorinated polyethylene (CPE), brominated polymethylstyrene-butene
copolymers, styrene-butadiene-styrene- (S-B-S) and
styrene-ethylene-butadiene-styrene(S-E-B-S) block copolymers,
acrylic rubber (ACM), ethylene vinyl acetate elastomer (EVM, EAM),
and silicone rubber, or a combination of any two or more of the
foregoing or blends thereof. See ASTM D-1418 for other suitable
elastomers and abbreviations. In the case of elastomer blends,
"primary" elastomer may be used to refer to the blend or to the
major elastomer component of the blend. Preferably the core layer
has good compression set resistance as measured by ASTM D-395 or
equivalent. This helps the rubber member retain the initial
compression applied at assembly of the device over the life of the
assembly.
[0031] The cure system of the core layer rubber composition and/or
the self-bonding rubber composition may, for example, be the
sulfur-based type with accelerators, sulfur, and the like, or the
peroxide-based type with one or more peroxides, coagents and the
like, or any other suitable cure system type. Preferably, both core
layer and adhesive layers have similar cure systems, or at least
compatible systems, to ensure good bonding between the materials
upon final cure. Suitable peroxide curatives include, without
limitation, 1,1-di-(t-butylperoxy)-3,3,5-trimethylcyclohexane,
2,5-dimethyl-2,5-di-(t-butylperoxy) 3-hexyne, dicumyl peroxide,
bis-(t-butylperoxy-diisopropyl benzene),
.alpha.-.alpha.-bis(t-butylperoxy)diisopropyl benzene, di-t-butyl
peroxide, 2,5-dimethyl-2,5-di-t-butylperoxyhexane, and
t-butylperbenzoate. Peroxides are conventionally incorporated at
about 2 to 10 parts weight per hundred parts of rubber ("phr").
Sulfur may optionally be added to the peroxide as part of the cure
system at about 0.1 to 1 phr
[0032] The core layer and the adhesive rubber layer may include any
other combination of ingredients known in the art including
fillers, fibers, oils, antioxidants, antiozonants, process aids,
accelerators, crosslinking aids, coagents, friction modifiers, and
the like. The self-bonding rubber layers, at least, also include an
adhesion promoter to assure good bonding between the rubber and
rigid members of the assembly. The suitable adhesion promoter may
be a single ingredient or a combination or system of ingredients.
Any known adhesion promoter or adhesion system may be utilized as
long as the capability of bonding to both the rigid members and the
core rubber layer are achieved. Generally the optimum adhesion
system will depend on the choice of primary elastomer, cure system,
and rigid material.
[0033] Adhesion promoters which can be used include for example,
maleated resins, metal salts of alpha-beta unsaturated organic
acids, cobalt salts with sulfur, copper and zinc salts,
organo-nickel salts, resorcinol-aldehyde resins, phenolic resins,
polymaleimides and bismaleimides, isocyanates, silica, silanes, and
the like, and various combinations thereof. Maleated or maleinized
resins include, for example, maleated polybutadiene or SBR,
maleated polyisoprene, maleated vegetable oil, maleated
ethylene-alpha-olefin polymer, and the like, for example as
described in U.S. Pat. No. 5,300,569, which is hereby incorporated
herein by reference. Metal salts of alpha-beta unsaturated organic
acids include, for example, metal salts of an
alpha,beta-ethylenically unsaturated carboxylic acid as described
for example in U.S. Pat. No. 5,776,294, which is hereby
incorporated herein by reference. The metal for salts of acrylic
and methacrylic acids include, without limitation, zinc, magnesium,
sodium, potassium, calcium, barium, cobalt, copper, aluminum and
iron. Zinc diacrylate (ZDA) and zinc dimethacrylate (ZDMA) are
preferred adhesion promoters for peroxide-cured rubber compositions
because of their effectiveness and commercial availability.
[0034] Useful polymaleimides and bismaleimides include N,N'-linked
bismaleimides containing maleimide groups that are either joined
directly at the nitrogen atoms without any intervening structure or
in which the nitrogen atoms are joined to and separated by an
intervening divalent radical such as alkylene, cycloalkylene,
oxydimethylene, phenylene (all 3 isomers),
2,6-dimethylene-4-alkyphenol, or sulfonyl. Preferred maleimide
compounds include those formed conventionally by a condensation of
maleic anhydride and a diamine compound which has a double bond
originating from maleic anhydride at each terminus. A preferred
bismaleimide resin employable in the present invention is a
reaction product of two moles of maleic anhydride and one mole of
an aromatic diamine. Examples of the aromatic diamine employable
for this purpose include, but are not limited to, diaminobenzene,
4,4'-diamino-3,3'-dimethylbiphenyl, 1,4-diaminodiphenyl ether,
1,4-diaminodiphenylmethane, 2,2-bis(4-aminophenyl)propane,
1,4-diaminodiphenylsulfone, 1,3-bis(4-aminophenoxy)benzene,
1,4-bis(3-aminophenoxy)benzene, and
bis(4-(3-aminophenoxy)phenyl)sulfone. M-phenylene-bis-maleimide is
a presently preferred compound. Polymaleimide compounds include
aliphatic or aromatic polymaleimide. Aromatic polymaleimides having
from about 1 to 100 aromatic nuclei wherein the maleimide groups
are directly attached to each adjacent aromatic ring are
preferred.
[0035] The invention is also directed to a method of making a
rubber-metal bonded part. The rubber member is made by forming a
rubber core of predetermined shape and curing it, preferably to a
substantially fully cured extent. Then, the self-bonding rubber
layer is applied to both sides of the cured core to form a rubber
laminate, preferably in a process whereby it is applied under
pressure and heat, such as an extrusion or lamination process or in
a closed mold. The self-bonding rubber layers may optionally be
partially cured if desired for improved handling and/or to initiate
bonding to the core rubber. The rubber laminate is then inserted
between two rigid members and the final assembly is post cured to
complete the cure of the self-bonding layers and effect a bond
between them and the rigid members and to the core. The rubber
laminate is generally thicker than that gap or space into which it
is inserted, resulting in a press fit and in the laminate residing
in a state of compression. The insertion process also can generate
considerable stress on the laminate, which is why the laminate is
preferably formed under pressure and heat and may include partial
cure of the adhesive layer, i.e., to improve the integrity and
handling of the laminate and prevent delamination during
assembly.
[0036] FIG. 3 shows one embodiment of the inventive process, using
extrusion to form the core and to apply a thin layer of the
self-bonding rubber to each side of the core rubber. In FIG. 3, the
core rubber goes through first extruder 110 first die 112 forms raw
core 114 into a predefined shape and/or dimension. Then, the raw
core goes through a first cure in first curing oven 120, preferably
till substantially fully cured. Cured core rubber 124 may be kept
at a predetermined temperature as it goes through coating die 132
of second extruder 130 to facilitate bonding with the next layer.
The second extruder 130 will apply the thin layer of self-bonding
rubber to both sides of the core rubber surface to make raw
laminate 134, which may be partly cured in optional second curing
oven 140. Finished laminate 144 is cooled in cooling stage 142
before going through cutter 150 to complete the production of
laminate rubber member 8, with its core 12 and self-bonding layers
14 and 16. The rubber laminate may be bent to form rubber ring 108,
which may be assembled into the annular gap between a damper hub
162 and inertia or pulley ring 164 in assembly operation 160. The
assembled damper goes through post-curing in final curing oven 170,
i.e., a post-cure step, to activate the bonding of the rubber to
the rigid or metal parts.
[0037] In another embodiment, the first and second extruders may be
combined into a coextrusion step, thus eliminating first cure oven
120. Then the cure of the core layer occurs after lamination, for
example in second curing oven 140. For this embodiment, the core
layer must have a different cure system from the adhesive layers,
which permits substantially full cure of the core before the
self-bonding layer cures more than about 70%, preferably no more
than about 50% to 70%, when exposed to the same vulcanization
conditions in oven 140. Then the resulting finished laminate 144
may continue through the process as described above.
[0038] The assembly step includes compressing the laminate into the
gap, and may require a lubricant. It has been found that some
lubricants may advantageously improve the bonding. Preferably the
lubricant is based on a compatible oil or soap which absorbs into
the self-bonding layers and/or the rubber core. Thus, the lubricant
may be selected from an oil, an aqueous emulsion, a lubricant
suspension, a soap solution or the like.
[0039] The optional step of partly curing the self-bonding layers
in second curing oven 140 may be facilitated by use of two
curatives or cure systems with different activation temperatures.
Thus, at least two separate curatives or cure systems (i.e.,
wherein the cure system may include a single curative or blends or
mixtures of two or more individual curatives), may be employed to
cure the elastomer composition. Such curatives may moreover be
advantageously selected such that each such curative or cure system
possesses an activation temperature range distinct from the other.
In a further embodiment, two such curatives are employed in the
elastomer compositions of the present invention, activation of each
of which being triggered by exposure to a set of conditions,
including temperature, pressure and/or exposure period, different
from the other. For substantially equal exposure periods and
pressures, activation temperatures of such two curatives according
to an embodiment at least five (5) degrees Centigrade apart from
one another; more preferably at least fifteen (15) degrees
Centigrade apart from one another; and most preferably at least
twenty five (25) degrees Centigrade apart from one another may be
beneficially employed. Exemplary materials exhibiting respective
activation temperatures beneficial in the practice of the present
invention include as the first curative,
1,1-Di-(t-butylperoxy)-3,3,5-trimethylcyclohexane such as that
available under the trademark VAROX 231XL by R. T. Vanderbilt; and
as the second curative, 2,5-dimethyl-2,5-Di-(t-butylperoxy)
3-hexyne such as that available under the trademark VAROX 130XL by
R. T. Vanderbilt.
[0040] When the optional partial cure of the laminated adhesive
layer is used, the degree of cure may be any amount that provides a
handling advantage without preventing bonding to the rigid parts
during the post-cure step. For example, the degree of cure may be
from 20 to 95%, or from 40% to 80%, and preferably the degree of
cure is from 50% to 70%.
[0041] Other methods of forming the core layer and/or applying the
thin layer of adhesive rubber may be used in various embodiments of
the invention. For example, one could mold a core rubber ring
first, using injection, compression or transfer molding, preferably
substantially fully curing it. Then the core rubber ring could be
put into a second mold cavity as an insert, wherein the
self-bonding elastomer could be applied by injection, or transfer
or other molding technique, onto the both inner and outer surface
of the core rubber ring, optionally with some degree of partial
cure. The self bonding elastomer will act as a bonding agent to
bond the rubber onto rigid or metal surfaces during the final
curing stage (or "post-curing" after assembly.
[0042] As another example of a useful applying step, one could dip
the cured rubber core layer into a bonding agent solution to apply
a coating layer of adhesive rubber. Multiple dips may be used to
achieve the desired layer thickness. The assembly and post-cure
(i.e., final cure) steps may be as described above.
[0043] In another embodiment of a laminated rubber member 58,
illustrated in FIG. 5, core layer 52 could be formed, for example
by molding a ring or extruding a profile with a ribbed or toothed
shape (i.e., hills and valleys) on one or both sides and then
substantially fully curing the core elastomer. The ring or profile
may then have applied to it the self-bonding rubber by one of the
application methods mentioned above. The self-bonding rubber may
then just fill the valleys 56 or fill the valleys and cover the
hills 54. The valleys can serve to provide areas with a much
greater depth or thickness of adhesive, while the hills provide
thinner areas where the fully cured core is closer to, or even
exposed 57 to, the rigid members of the final part. This
distribution of thicknesses may provide better combination of
adhesion and compression stability. The hills and valleys may also
help retain adhesive during assembly or other handling. As
described above, in another embodiment, the ribbed laminate could
be made by coextrusion of two materials with different cure
systems, the core being curable faster, at a lower temperature, or
the like, relative to the adhesive rubber layers.
[0044] Other laminate combinations are also possible. For instance,
a core that is layered in its horizontal plane with alternative or
alternating elastomer layers may be designed to have a particular
set of physical or dynamic properties not possible with a single
layer. With a self-bonding outer layer for bonding to the rigid
members of the final part, such variations give the dual,
heretofore competing benefits of maintaining compression from the
bulk of the rubber being a fully cured elastomer and the bonding to
rigid surfaces of a self-bonding elastomer.
EXAMPLES
[0045] To demonstrate embodiments of the invention, a number of
example rubber compositions were mixed for use as core and adhesive
layers of the rubber laminate. The examples were based on various
EPDM elastomers with carbon black or silica filler and peroxide or
sulfur curatives. The mixing was done according to conventional
practice for rubber materials, i.e., using an internal mixer of the
Banbury type. The compounds were generally mixed in two stages,
with curatives added in the second stage. Thin adhesive layers of
examples H thru N were calendered to a thickness of 0.25 mm, and
example O was extruded at 0.5 mm in thickness. Core layers were
generally injection molded in the form of annular rings about five
inches in diameter, about one inch long, and about 3/16 of an inch
thick. The rings were cut into one-inch squares for lap shear
adhesion tests and used whole for testing in dampers, as further
described below.
[0046] A number of core layer rubber compositions (A thru G) for
use in embodiments of the invention are described in Table 1. A
number of adhesive layer rubber compositions (H thru O) for use in
embodiments of the invention are described in Table 2. Core
compositions A thru F were used in combinations with adhesive
compositions H thru N for lap shear adhesion testing to confirm
that the invention had broad applicability to a wide range of
laminate combinations and assembly options. The combinations and
results are shown in Table 3. Table 3 shows a first series of
examples. Inventive examples are designated "Ex.", while
comparative examples are designated "Comp. Ex."
[0047] A number of comparative examples are included in Table 3,
wherein the adhesive composition was used to make a partially cured
core and the core then fully cured in contact with metal lap shear
tabs with no additional adhesive layer. Lap shear adhesion results
provided in the following tables were obtained using steel tabs 72,
74 each measuring 25.4 mm (1 inch) by 63.5 mm (2.5 inches), and
molded rubber core slabs 70 measuring 4.8 mm ( 3/16 of an inch) in
thickness by 25.4 mm (1 inch) square laminated with rubber adhesive
layers 76 measuring 0.25 mm (10 mil) thick by 1 inch square,
assembled according to the method of ASTM D-816, "Type 1 Lap
Specimen," such that the rubber laminate sample was substantially
fully covered on both relevant surfaces by the metal slab, as
illustrated in FIG. 4, under an applied force sufficient to achieve
about 25% rubber compression. Thus, the lap shear test evaluated
the integrity of the rubber laminate and the entire bonded
metal-rubber part.
[0048] For many of the examples, various lubricants were applied to
the steel and or laminate surfaces to simulate a lubricated
assembly operation. "P-80" is an assembly lubricating oil available
from International Products Corp., and "R" was a grade of process
oil from Clark Oil and Refining Corporation applied in a thin layer
to the steel slab surfaces. In most cases, the lap shear specimens
were allowed to sit for 1, 4 or 24 hours in contact with the
lubricating oil-coated slabs and then cured, as indicated in the
footnotes related to assembly details. Finally, the specimens were
pulled at a rate of 2 inches per minute to a point of failure. Hot
adhesion tests were done at 100.degree. C. The results are reported
as peak load in pounds, which also is equivalent to pounds per
square inch of bond area. It may be noted that rubber tear is
generally a dominant mode of failure for specimens with a peak load
of 200 pounds or more, and adhesive failure is generally dominant
for peak loads less than 200 pounds, with considerable variation
depending on the composition.
[0049] For some examples as noted in Tables 3 and 4, the steel
parts were grit blasted and/or alkali washed utilizing conventional
techniques prior to the application of the assembly lubricant and
the insertion of the rubber laminate. The optional step of
partially curing the rubber laminate before assembly was not
carried out in these examples.
[0050] The lap shear results in Table 3 show a number of
advantageous results. Comp. Ex. 25-27 may be used as a baseline for
the adhesion level attainable pure self-bonding elastomer to metal.
Similar levels of adhesion are observed for the inventive
combinations. Thus, good results may be obtained for sulfur-cured
cores (B and D) or peroxide-cured cores (A, C, and E-F) with a
variety of peroxide-cured self-bonding layers. Examples 1-9 and
13-15 illustrate that a variety of core rubber layers (A-E) may be
bonded to metal parts with the same adhesive rubber composition
(H). This makes the present invention much more flexible than the
prior art two-step cure method based on a single rubber
formulation. The particular examples cited include both
sulfur-cured and peroxide-cured formulations, with various levels
of compression set resistance as indicated by the test results in
Table 1. The results in Table 3 also illustrate that some
combinations of core and adhesive are better than others, and that
other variables may be important, such as the details of assembly,
lubrication, cure, etc.
[0051] Core compositions A, D, and E were laminated with adhesive
composition I and the laminate inserted into mock torsional dampers
to test the resulting adhesion in a torque to turn test. The
combinations and results are shown in Table 4. It can be seen from
Table 4 that either a sulfur-cured core (D) or peroxide-cured core
(A and E) may be used with the peroxide-cured self-bonding
composition I. However, the chemically better-matched combination
where both core and adhesive are peroxide-cured gives the strongest
TTT result. It may be noted that some of these examples were not
tested because they popped apart during post-curing. This was more
likely to occur with the machined (smooth) surfaces than with the
grit-blasted surfaces.
[0052] Core composition G was used with adhesive composition O to
make exemplary assembled parts in the form of crank dampers to
confirm the performance advantages of embodiments of the invention
over a conventional approach based on the comparative example
rubber composition ("Comp. Ex. 51") shown in Table 1. Comp. Ex. 51
composition was formed and partially cured, assembled into a crank
damper, and post cured according to a two-step cure process, as
disclosed in U.S. Pat. No. 7,078,104, which is incorporated herein
by reference. In these examples, the crank damper was similar to
that shown in FIG. 1.
TABLE-US-00001 TABLE 1 Core Layer Compositions COMP. A B C D E F G
EX. 51 Keltan K7441A.sup.1 175 175 175 175 175 175 Nordel MG
47130.sup.2 110.5 Nordel IP 4725P.sup.2 15.0 Royaltherm 1411.sup.3
100 HiSil 233 (Silica) 6 HiSil 243LD (Silica) 8 Carbon Black N293
36 Carbon Black N550 3 62 62 65 79 Carbon Black N358 47 47 Carbon
Black N472 89 Triethanolamine 0.6 0.6 0.6 0.6 0.6 1 1 Paraffin Oil
(Sunpar 2280) 10 5 10 5 30 50 6 Antioxidant TMQ.sup.4 1 1.5 1.5 1.5
Zinc Oxide 5 5 5 5 5 5 5 Stearic Acid 1.5 1.5 1.5 1.5 Zinc Stearate
1.5 1.5 Zinc Dimethacrylate.sup.5 3 33
N-N'-m-phenylenebismaleimide.sup.6 0.8 1 1 Vestenamer 8012 (process
aid 2 from Evonik) VUL-CUP 40KE 3 9 9 10 5 VAROX 130XL 1 VAROX
231XL 5.4 N-Cyclohexyl-2-benzothiazole 0.8 0.8 sulfenamide
Tetramethylthiuram disulfide (75%) 2.45 2.45 Sulfur 0.64 0.24 0.64
0.24 Comp. Set 22 h/100.degree. C. (%) 18.6 7 16.9 8.2 Comp. Set 22
h/150.degree. C. (%) 71.9 49.2 20.6 48.7 20.3 14.5 28.2 31-40 Comp.
Set 22 h/150.degree. C. - post cured (%) 12.8 .sup.1EPDM from DSM
Elastomers. .sup.2EPDM from Dow Chemical. .sup.3Silicone-modified
EPDM from Lion Copolymer. .sup.4polymerized
1,2-dihydro-2,2,4-trimethylquinoline. .sup.5SR-634 from Sartomer.
.sup.6HVA-2 from DuPont.
TABLE-US-00002 TABLE 2 Adhesive Layer Compositions H I J K L M N O
Nordel MG 47130 110.5 Nordel IP 4725P 15.0 Engage 8180.sup.1 100
Engage 8150.sup.1 100 100 100 100 ROYALTHERM 1411 100 VISTALON
606.sup.2 80 TRILENE CP80 DLC.sup.3 20 ZEOPOL 8745 (Silica) 40 40
HI-SIL 190G (Silica) 60 60 HI-SIL 233 (Silica) 40 Carbon Black N330
50 50 Carbon Black N293 25 Carbon Black N550 5 45 Paraffin Oil
(Sunpar 2280) 55 Antioxidant TMQ 1 1 1 1.5 Antioxidant ZMTI.sup.4 1
1 1 1 Antioxidant NAUGARD 44.sup.5 1 1 Antioxidant ETHANOX
702.sup.6 0.5 0.5 0.5 0.5 Zinc Oxide 5 5 5 5 5 5 5 Zinc Stearate
1.5 1.5 Zinc Dimethacrylate 15 15 5 30 30 33 Zinc Diacrylate.sup.7
30 30 N-N'-m-phenylenebismaleimide 0.8 Ricon 154.sup.8 0.2 VUL-CUP
40KE 6 8 8 8 8 VAROX 130XL 2 VAROX 231XL 4.4 .sup.1EOM from Dow
Chemical. .sup.2EPM from ExxonMobile Chemical. .sup.3Liquid EPM
from Lion Copolymer. .sup.4Zinc 2-mercaptotolylimidazole.
.sup.5Substituted diphenylamine.
.sup.64,4'-methylenebis-(2,6,di-t-butyl phenol). .sup.7SR-633 from
Sartomer Company. .sup.8Liquid Polybutadiene resin from Sartomer
Company.
[0053] To make a crank damper, the elastomeric composition for the
core layer, "G" in Table 1, was molded into a strip about 4-mm
thick by about 25-mm wide by compression molding for about 80
seconds at about 175.degree. C., enough to substantially fully cure
the composition. The self-bonding adhesive composition, "O" in
Table 2, was extruded as a film 0.5 mm thick and applied to both
sides of the core strip. The resulting laminate was heated for 50
seconds at 160.degree. C. to partially cure the adhesive layers and
then was force fit into the damper gap with the aid of an alkali
soap lubricant. The metal bonding surfaces were wiped with a rag to
remove excess residue from the machining operations, but no further
cleaning or surface preparations were carried out. The gap of the
dampers used was about 3.5 mm in spacing, and the laminated
elastomeric member was thus about 5 mm thick, including two
adhesive layers each about 0.5 mm thick. Thus, the elastomer was
compressed about 30% upon insertion into the gap, and the adhesive
layers were each about 10% of the total thickness. The damper
assembly was placed in an oven for 60 minutes at 190.degree. C.,
activating the self-bonding layer, causing it to bond to the core
and to the metal damper parts (hub and ring).
[0054] The torque-to-turn test ("TTT") was carried out on the
damper examples at room temperature by rotating the hub with the
outer ring fixed at a rate of 1 degree/second until the laminate
rubber element and/or the bond failed and recording the peak
torque. For some examples, the TTT test was done after a durability
test involving a predetermined period of time (generally 40 hours
was the target time) on a vibrating rotational shaker test at
resonant frequency in a 100.degree. C. environment with a hub
excitation amplitude of 0.2 or 0.3 degrees double amplitude
("DDA"). When reported, tensile tests followed ASTM D-412 using
dumbbells cut from molded plates. Compression set tests followed
ASTM D-395 Method B with 25% compression. Other aspects of the
examples will be explained below.
[0055] Comparative damper assemblies were made according to the
two-step cure method of U.S. Pat. Nos. 7,078,104 and 7,291,241, the
entire contents of which are hereby incorporated herein by
reference. The rubber used was composition "Comp. Ex." in Table
1.
[0056] The results of the damper testing show the advantage of the
current inventive method. The Ex. 50 damper with the laminated
rubber exhibited sufficient original adhesion, as indicated by a
TTT result of 1732 N-m with rubber tear as the failure mode. After
a 40-hour durability test at 0.2 DDA, the TTT result was 1454 N-m
(a retained torque to turn of about 84%). By comparison, the Comp.
Ex. 51 dampers had original TTT values of 3448 N-m, but only
retained about 22% of that torque strength after 40 hours at 0.2
DDA. After a more severe test of 40-hours at 0.3 DDA, Ex. 50
dampers still retained 73% of their original torque, while Comp.
Ex. 51 only survived for 10 hours with adhesive failure at the hub
surface.
TABLE-US-00003 TABLE 3 RT Assembly Adh. Hot Adh. Ex. No. Core
Adhesive Lube Details (psi) (psi) Ex. 1 B H None 1 136 2 Ex. 2 C H
None 1 246 23 Ex. 3 A H None 1 229 9 Ex. 4 B H P-80 1 203 1 Ex. 5 C
H P-80 1 234 12 Ex. 6 A H P-80 1 218 6 Ex. 7 B H R 1 193 6 Ex. 8 C
H R 1 431 89 Ex. 9 A H R 1 259 27 Ex. 10 D I None 1 22 4 Ex. 11 E I
None 1 80 31 Ex. 12 A I None 1 23 28 Ex. 13 D H None 1 386 19 Ex.
14 E H None 1 536 114 Ex. 15 A H None 1 233 13 Ex. 16 D J None 1
262 40 Ex. 17 E J None 1 262 98 Ex. 18 A J None 1 116 30 Ex. 19 D J
P-80 1 47 5 Ex. 20 E J P-80 1 88 23 Ex. 21 A J P-80 1 120 30 Ex. 22
D J R 1 202 36 Ex. 23 E J R 1 237 91 Ex. 24 A J R 1 169 43 Comp.
Ex. 25 I -- None 1 165 -- Comp. Ex. 26 H -- None 1 238 -- Comp. Ex.
27 J -- None 1 166 -- Ex. 28 F K P-80 2 201 -- Ex. 29 F L P-80 2
162 -- Ex. 30 F M P-80 2 233 -- Ex. 31 F N P-80 2 384 -- Comp. Ex.
32 H -- P-80 2 353 -- Ex. 33 F K R 2 374 -- Ex. 34 F L R 2 619 --
Ex. 35 F M R 2 295 -- Ex. 36 F N R 2 570 -- Comp. Ex. 37 H -- R 2
447 -- .sup.1Assembly details: clean, grit-blasted steel, 20
min./175.degree. C. post-cure. .sup.2Assembly details: clean,
grit-blasted steel, 1-hr. wait, 45 min./171.degree. C.
post-cure.
TABLE-US-00004 TABLE 4 Assembly TTT Ex. No. Core Adhesive Lube
Details (ft-lbs) Ex. 38 D I P-80 3M -- Ex. 39 D I P-80 3G 239 Ex.
40 E I P-80 3M 583 Ex. 41 E I P-80 3G 273 Ex. 42 A I P-80 3M 432
Ex. 43 A I P-80 3G 344 Ex. 44 D I R 4M -- Ex. 45 D I R 4G -- Ex. 46
E I R 4M 881 Ex. 47 E I R 4G 459 Ex. 48 A I R 4M 615 Ex. 49 A I R
4G 496 .sup.3 M = machined bonding surfaces, G = grit-blasted
bonding surfaces; 24-hr. wait, then post cured 20 min./175.degree.
C.; .sup.4 M and G have same meaning; 4-hr. wait, then post cured
30 min./177.degree. C..
TABLE-US-00005 TABLE 5 Comp. Ex. Damper Durability testing Ex. 50
51 TTT original (N-m) 1732 3448 TTT after 40 hrs@0.2 DDA (N-m) 1454
766 (% of original) 84% 22% TTT after 40 hrs@0.3 DDA (N-m) 1260
.sup. 1243.sup.1 (% of original) 73% 36% .sup.1This test only ran
10 hours due to adhesion failure.
[0057] Although the present invention and its advantages have been
described in detail, it should be understood that various changes,
substitutions, and alterations can be made herein without departing
from the spirit and scope of the invention as defined by the
appended claims. Moreover, the scope of the present application is
not intended to be limited to the particular embodiments of the
process, machine, manufacture, composition of matter, means,
methods, and steps described in the specification. As one of
ordinary skill in the art will readily appreciate from the
disclosure of the present invention, processes, machines,
manufacture, compositions of matter, means, methods, or steps,
presently existing or later to be developed that perform
substantially the same function or achieve substantially the same
result as the corresponding embodiments described herein may be
utilized according to the present invention. Accordingly, the
appended claims are intended to include within their scope such
processes, machines, manufacture, compositions of matter, means,
methods, or steps. The invention disclosed herein may suitably be
practiced in the absence of any element that is not specifically
disclosed herein.
* * * * *