U.S. patent application number 17/440976 was filed with the patent office on 2022-05-26 for curable compositions, articles therefrom, and methods of making and using same.
The applicant listed for this patent is 3M INNOVATIVE PROPERTIES COMPANY. Invention is credited to Jeremy M. Higgins, Adrian T. Jung, Michael A. Kropp, Matthew J. Kryger, Ying Lin, Wayne S. Mahoney, Mario A. Perez, Ahmad Shaaban, Lingjie Tong, Shuang Wu, Li Yao.
Application Number | 20220162376 17/440976 |
Document ID | / |
Family ID | |
Filed Date | 2022-05-26 |
United States Patent
Application |
20220162376 |
Kind Code |
A1 |
Yao; Li ; et al. |
May 26, 2022 |
CURABLE COMPOSITIONS, ARTICLES THEREFROM, AND METHODS OF MAKING AND
USING SAME
Abstract
A curable composition includes a first part comprising an epoxy
resin; and a second part comprising a multifunctional, functional
thiol containing compound. The curable composition further includes
an inorganic filler present in an amount of at least 20 weight %,
based on the total weight of the curable composition. The
multifunctional, functional thiol containing compound comprises an
ether in the backbone thereof.
Inventors: |
Yao; Li; (Woodbury, MN)
; Kropp; Michael A.; (Cottage Grove, MN) ; Kryger;
Matthew J.; (Hudson, WI) ; Mahoney; Wayne S.;
(St. Paul, MN) ; Perez; Mario A.; (Burnsville,
MN) ; Wu; Shuang; (Shanghai, CN) ; Tong;
Lingjie; (Shanghai, CN) ; Shaaban; Ahmad;
(Koln, DE) ; Jung; Adrian T.; (Kaarst, DE)
; Higgins; Jeremy M.; (Roseville, MN) ; Lin;
Ying; (Woodbury, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
3M INNOVATIVE PROPERTIES COMPANY |
St. Paul |
MN |
US |
|
|
Appl. No.: |
17/440976 |
Filed: |
March 25, 2019 |
PCT Filed: |
March 25, 2019 |
PCT NO: |
PCT/CN2019/079523 |
371 Date: |
September 20, 2021 |
International
Class: |
C08G 59/66 20060101
C08G059/66; C08G 59/24 20060101 C08G059/24; C08K 5/37 20060101
C08K005/37; C08K 3/22 20060101 C08K003/22; C08K 7/18 20060101
C08K007/18; C08K 9/06 20060101 C08K009/06; C09J 163/00 20060101
C09J163/00; H01M 50/233 20060101 H01M050/233; H01M 10/653 20060101
H01M010/653 |
Claims
1. A curable composition comprising: a first part comprising an
epoxy resin; and a second part comprising a multifunctional,
functional thiol containing compound; and an inorganic filler
present in an amount of at least 20 weight %, based on the total
weight of the curable composition wherein the multifunctional,
functional thiol containing compound comprises an ether in the
backbone thereof.
2. (canceled)
3. (canceled)
4. (canceled)
5. The curable composition of claim 1, wherein the epoxy resin
comprises an internally flexible bisphenol epoxy resin.
6. The curable composition of claim 5, wherein the internally
flexible bisphenol epoxy resin is represented by the following
formula: ##STR00012## where Ar is bisphenol A, bisphenol F,
bisphenol Z, or a mixture thereof.
7. The curable composition of claim 1, wherein the epoxy resin
comprises a phosphonic acid group in the backbone thereof.
8. (canceled)
9. The curable composition according to claim 1, further comprising
a silane coupling agent, wherein the silane coupling agent
comprises an amine terminated silane coupling agent.
10. The curable composition according to claim 1, further
comprising a silane coupling agent, wherein the silane coupling
agent comprises a mercaptan terminated silane coupling agent.
11. The curable composition according to claim 1, further
comprising a silane coupling agent, wherein the silane coupling
agent comprises an epoxy terminated silane coupling agent.
12. The curable composition according to claim 1, further
comprising a catalyst.
13. The curable composition according to claim 12, wherein the
catalyst comprises a basic catalyst.
14. The curable composition according to claim 13, wherein the
basic catalyst is represented by one of the following formulas:
##STR00013##
15. The curable composition according to claim 12, wherein the
catalyst comprises a Lewis acid catalyst.
16. The curable composition according to claim 15, wherein the
Lewis acid catalyst comprises calcium triflate, calcium nitrate, or
a tin catalyst.
17.-25. (canceled)
26. The curable composition according to claim 1, wherein the
inorganic filler present in an amount of at least 50 wt. %, based
on the total weight of the curable composition.
27. (canceled)
28. The curable composition according to claim 1, wherein the
inorganic filler comprises spherical alumina particles and
semispherical alumina particles.
29. The curable composition according to claim 1, wherein the
inorganic filer comprises silane surface-treated particles.
30. The curable composition according to claim 1, wherein the
inorganic filler comprises ATH.
31. (canceled)
32. The article of claim 31, wherein the cured composition has a
thickness between from 5 microns to 10000 microns.
33. (canceled)
34. The article of claim 33, wherein the substrate is a metal
substrate.
35. (canceled)
36. A battery module comprising a plurality of battery cells
connected to a first base plate by a first layer of the reaction
product of the curable composition according to claim 1.
37. A method of making a battery module comprising: applying a
first layer of a curable composition according to claim 1 to a
first surface of a first base plate, attaching a plurality of
battery cells to the first layer to connect the battery cells to
the first base plate, and curing the curable composition.
Description
FIELD
[0001] The present disclosure generally relates to curable
compositions that include an epoxy composition and a thiol
composition. The curable compositions may be used, for example, as
thermally conductive gap fillers, which may be suitable for use in
electronic applications such as battery assemblies.
BACKGROUND
[0002] Curable compositions based on epoxy or polyamide resins have
been disclosed in the art. Such curable compositions are described
in, for example, U.S. Pat. No. 9,926,405, U.S. Pat. App. Pub.
2013/0165600, and EP Patent 1291390.
SUMMARY
[0003] In some embodiments, a curable composition is provided. The
composition includes a first part comprising an epoxy resin; and a
second part comprising a multifunctional, functional thiol
containing compound. The curable composition further includes an
inorganic filler present in an amount of at least 20 weight %,
based on the total weight of the curable composition. The
multifunctional, functional thiol containing compound comprises an
ether in the backbone thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 illustrates the assembly of an exemplary battery
module according to some embodiments of the present disclosure.
[0005] FIG. 2 illustrates the assembled battery module
corresponding to FIG. 1.
[0006] FIG. 3 illustrates the assembly of an exemplary battery
subunit according to some embodiments of the present
disclosure.
DETAILED DESCRIPTION
[0007] Thermal management plays an important role in many
electronics applications such as, for example, electric vehicle
(EV) battery assembly, power electronics, electronic packaging,
LED, solar cells, electric grid, and the like. Certain thermally
conductive materials (e.g., adhesives) may be an attractive option
for these applications due to good electrical insulative
properties, feasibility in processing for integrated parts or
complex geometries, and good conformability/wettability to
different surfaces, especially the ability to efficiently dissipate
the heat away while having good adhesion to different substrates
for assembly.
[0008] Regarding applications in EV battery assemblies, currently,
one such application that utilizes a thermally conductive material
is the gap filler application. Generally, requirements for the gap
filler application include high thermally conductivity, good
overlap shear adhesion strength, good tensile strength, good
elongation at break for toughness, and damping performance, and
good hydrolytic stability, in addition to having low viscosity
before curing. However, to achieve high thermal conductivity,
typically, a large amount of inorganic thermally conductive filler
is added to the composition. The high loading of thermally
conductive fillers, however, has a deleterious impact on adhesion
performance, toughness, damping performance, and viscosity.
[0009] Furthermore, compositions useful for the gap filler
application should have relatively fast curing profiles to
accommodate the automated processing requirements of the industry.
For example, thermally conductive materials that attain adequate
green strength after room temperature cure of about 10 minutes or
less may be particularly advantageous.
[0010] A filled curable composition that includes an epoxy resin, a
polyamide composition, an amino functional compound, and a
multi-functional (meth)acrylate provides many of the above
discussed attributes but does not provide, in some applications,
sufficient hydrolytic stability. Another filled curable composition
that includes an epoxy composition and a polyamide composition, the
polyamide composition including a polyamide having one or more
tertiary amides in the backbone thereof, also provides many of the
above discussed attributes but does not provide, in some
applications, sufficient green strength.
[0011] In order to solve the above-discussed problems associated
with high loadings of inorganic thermally conductive filler, a
curable composition providing a good balance of the above discussed
desired properties has been discovered that includes an epoxy
composition and a thiol composition. Specifically, in addition to
exhibiting all of the desired attributes discussed above, the
curable compositions of the present disclosure also exhibit good
hydrolytic stability and green strength.
[0012] As used herein:
[0013] The term "room temperature" refers to a temperature of
22.degree. C. to 25.degree. C.
[0014] The terms "cure" and "curable" refer to joining polymer
chains together by covalent chemical bonds, usually via
crosslinking molecules or groups, to form a network polymer.
Therefore, in this disclosure the terms "cured" and "crosslinked"
may be used interchangeably. A cured or crosslinked polymer is
generally characterized by insolubility, but may be swellable in
the presence of an appropriate solvent.
[0015] The term "unfilled" when used in connection with a component
or a composition refers to all the materials that make up that
component or composition except for inorganic fillers (e.g.,
thermally conductive fillers).
[0016] The term "backbone" refers to the main continuous chain of a
polymer.
[0017] The term "aliphatic" refers to C1-C40, suitably C1-C30,
straight or branched chain alkenyl, alkyl, or alkynyl which may or
may not be interrupted or substituted by one or more heteroatoms
such as O, N, or S.
[0018] The term "cycloaliphatic" refers to cyclized aliphatic
C3-C30, suitably C3-C20, groups and includes those interrupted by
one or more heteroatoms such as O, N, or S.
[0019] The term "alkyl" refers to a monovalent group that is a
radical of an alkane and includes straight-chain, branched, cyclic,
and bicyclic alkyl groups, and combinations thereof, including both
unsubstituted and substituted alkyl groups. Unless otherwise
indicated, the alkyl groups typically contain from 1 to 30 carbon
atoms. In some embodiments, the alkyl groups contain 1 to 20 carbon
atoms, 1 to 10 carbon atoms, 1 to 6 carbon atoms, 1 to 4 carbon
atoms, or 1 to 3 carbon atoms. Examples of "alkyl" groups include,
but are not limited to, methyl, ethyl, n-propyl, n-butyl, n-pentyl,
isobutyl, t-butyl, isopropyl, n-octyl, n-heptyl, ethylhexyl,
cyclopentyl, cyclohexyl, cycloheptyl, adamantyl, norbornyl, and the
like.
[0020] The term "alkylene" refers to a divalent group that is a
radical of an alkane and includes groups that are linear, branched,
cyclic, bicyclic, or a combination thereof. Unless otherwise
indicated, the alkylene group typically has 1 to 30 carbon atoms.
In some embodiments, the alkylene group has 1 to 20 carbon atoms, 1
to 10 carbon atoms, 1 to 6 carbon atoms, or 1 to 4 carbon atoms.
Examples of "alkylene" groups include methylene, ethylene,
1,3-propylene, 1,2-propylene, 1,4-butylene, 1,4-cyclohexylene, and
1,4-cyclohexyldimethylene.
[0021] The term "aromatic" refers to C3-C40, suitably C3-C30,
aromatic groups including both carbocyclic aromatic groups as well
as heterocyclic aromatic groups containing one or more of the
heteroatoms, O, N, or S, and fused ring systems containing one or
more of these aromatic groups fused together.
[0022] The term "aryl" refers to a monovalent group that is
aromatic and, optionally, carbocyclic. The aryl has at least one
aromatic ring. Any additional rings can be unsaturated, partially
saturated, saturated, or aromatic. Optionally, the aromatic ring
can have one or more additional carbocyclic rings that are fused to
the aromatic ring. Unless otherwise indicated, the aryl groups
typically contain from 6 to 30 carbon atoms. In some embodiments,
the aryl groups contain 6 to 20, 6 to 18, 6 to 16, 6 to 12, or 6 to
10 carbon atoms. Examples of an aryl group include phenyl,
naphthyl, biphenyl, phenanthryl, and anthracyl.
[0023] The term "arylene" refers to a divalent group that is
aromatic and, optionally, carbocyclic. The arylene has at least one
aromatic ring. Optionally, the aromatic ring can have one or more
additional carbocyclic rings that are fused to the aromatic ring.
Any additional rings can be unsaturated, partially saturated, or
saturated. Unless otherwise specified, arylene groups often have 6
to 20 carbon atoms, 6 to 18 carbon atoms, 6 to 16 carbon atoms, 6
to 12 carbon atoms, or 6 to 10 carbon atoms.
[0024] The term "aralkyl" refers to a monovalent group that is an
alkyl group substituted with an aryl group (e.g., as in a benzyl
group). The term "alkaryl" refers to a monovalent group that is an
aryl substituted with an alkyl group (e.g., as in a tolyl group).
Unless otherwise indicated, for both groups, the alkyl portion
often has 1 to 10 carbon atoms, 1 to 6 carbon atoms, or 1 to 4
carbon atoms and an aryl portion often has 6 to 20 carbon atoms, 6
to 18 carbon atoms, 6 to 16 carbon atoms, 6 to 12 carbon atoms, or
6 to 10 carbon atoms.
[0025] Repeated use of reference characters in the specification is
intended to represent the same or analogous features or elements of
the disclosure. As used herein, the word "between", as applied to
numerical ranges, includes the endpoints of the ranges, unless
otherwise specified. The recitation of numerical ranges by
endpoints includes all numbers within that range (e.g. 1 to 5
includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5) and any range within
that range.
[0026] It should be understood that numerous other modifications
and embodiments can be devised by those skilled in the art, which
fall within the scope and spirit of the principles of the
disclosure. All scientific and technical terms used herein have
meanings commonly used in the art unless otherwise specified. The
definitions provided herein are to facilitate understanding of
certain terms used frequently herein and are not meant to limit the
scope of the present disclosure. As used in this specification and
the appended claims, the singular forms "a", "an", and "the"
encompass embodiments having plural referents, unless the context
clearly dictates otherwise. As used in this specification and the
appended claims, the term "or" is generally employed in its sense
including "and/or" unless the context clearly dictates
otherwise.
[0027] In some embodiments, the present disclosure provides a
highly filler loaded thermally conductive curable composition
formulated by blending an epoxy composition and a thiol
composition.
[0028] In some embodiments, the epoxy compositions may include one
or more epoxy resins. Suitable epoxy resins may include aromatic
polyepoxide resins (e.g., a chain-extended diepoxide or novolac
epoxy resin having at least two epoxide groups), aromatic monomeric
diepoxides, aliphatic polyepoxide, ormonomeric diepoxides. A
crosslinkable epoxy resin typically will have at least two epoxy
end groups. The aromatic polyepoxide or aromatic monomeric
diepoxide typically contains at least one (in some embodiments, at
least 2, in some embodiments, in a range from 1 to 4) aromatic ring
that is optionally substituted by a halogen (e.g., fluoro, chloro,
bromo, iodo), alkyl having 1 to 4 carbon atoms (e.g., methyl or
ethyl), or hydroxyalkyl having 1 to 4 carbon atoms (e.g.,
hydroxymethyl). For epoxy resins containing two or more aromatic
rings, the rings may be connected, for example, by a branched or
straight-chain alkylene group having 1 to 4 carbon atoms that may
optionally be substituted by halogen (e.g., fluoro, chloro, bromo,
iodo).
[0029] In some embodiments, examples of aromatic epoxy resins
useful in the epoxy compositions disclosed herein may include
novolac epoxy resins (e.g., phenol novolacs, ortho-, meta-, or
para-cresol novolacs or combinations thereof), bisphenol epoxy
resins (e.g., bisphenol A, bisphenol F, halogenated bisphenol
epoxies, and combinations thereof), resorcinol epoxy resins,
tetrakis phenylolethane epoxy resins and combinations of any of
these.
[0030] In some embodiments, useful epoxy compounds include
diglycidyl ethers of difunctional phenolic compounds (e.g.,
p,p'-dihydroxydibenzyl, p,p'-dihydroxydiphenyl,
p,p'-dihydroxyphenyl sulfone, p,p'-dihydroxybenzophenone,
2,2'-dihydroxy-1,1-dinaphthylmethane, and the 2,2', 2,3', 2,4',
3,3', 3,4', and 4,4' isomers of dihydroxydiphenylmethane,
dihydroxydiphenyldimethylmethane,
dihydroxydiphenylethylmethylmethane,
dihydroxydiphenylmethylpropylmethane,
dihydroxydiphenylethylphenylmethane,
dihydroxydiphenylpropylphenylmethane,
dihydroxydiphenylbutylphenylmethane, dihydroxydiphenyltolylethane,
dihydroxydiphenyltolylmethylmethane,
dihydroxydiphenyldicyclohexylmethane, and
dihydroxydiphenylcyclohexane.) In some embodiments, the adhesive
includes a bisphenol diglycidyl ether, wherein the bisphenol (i.e.,
--O--C.sub.6H.sub.5--CH.sub.2--C.sub.6H.sub.5--O--) may be
unsubstituted (e.g., bisphenol F), or either of the phenyl rings or
the methylene group may be substituted by one or more halogens
(e.g., fluoro, chloro, bromo, iodo), methyl groups, trifluoromethyl
groups, or hydroxymethyl groups.
[0031] In some embodiments, examples of aromatic monomeric
diepoxides useful in the epoxy compositions according to the
present disclosure include the diglycidyl ethers of bisphenol A and
bisphenol F and mixtures thereof. Bisphenol epoxy resins, for
example, may be chain extended to have any desirable epoxy
equivalent weight. Chain extending epoxy resins can be carried out
by reacting a monomeric diepoxide, for example, with a bisphenol in
the presence of a catalyst to make a linear polymer. Other aromatic
epoxy resins may include difunctional epoxy resins that have a
polysulfide polymer backbone such as block coplymer of Thiokol LP
and bisphenol F epoxy resin (e.g. FLEP-60 available from Toray Fine
Chemicals Co., Ltd., Tokyo, Japan.
[0032] In some embodiments, the aromatic epoxy resin (e.g., either
a bisphenol epoxy resin or a novolac epoxy resin) may have an epoxy
equivalent weight of at least 150, 170, 200, or 225 grams per
equivalent. In some embodiments, the aromatic epoxy resin may have
an epoxy equivalent weight of up to 2000, 1500, or 1000 grams per
equivalent. In some embodiments, the aromatic epoxy resin may have
an epoxy equivalent weight in a range from 150 to 2000, 150 to
1000, or 170 to 900 grams per equivalent. In some embodiments, the
first epoxy resin has an epoxy equivalent weight in a range from
150 to 450, 150 to 350, or 150 to 300 grams per equivalent. Epoxy
equivalent weights may be selected, for example, so that the epoxy
resin may be used as a liquid or solid, as desired.
[0033] In some embodiments, in addition or as an alternative to
aromatic epoxy resins, the epoxy resins of the present disclosure
may include one or more non-aromatic epoxy resins. In some cases,
non-aromatic epoxy resins can be useful as reactive diluents that
may help control the flow characteristics of the compositions.
Non-aromatic epoxy resins useful in the curable compositions
according to the present disclosure can include a branched or
straight-chain alkylene group having 1 to 20 carbon atoms
optionally interrupted with at least one --O-- and optionally
substituted by hydroxyl. In some embodiments, the non-aromatic
epoxy can include a poly(oxyalkylene) group having a plurality (x)
of oxyalkylene groups, OR.sup.1, wherein each IV is independently
C.sub.2 to C.sub.5 alkylene, in some embodiments, C.sub.2 to
C.sub.3 alkylene, x is 2 to about 6, 2 to 5, 2 to 4, or 2 to 3. To
become crosslinked into a network, useful non-aromatic epoxy resins
will typically have at least two epoxy end groups. Examples of
useful non-aromatic epoxy resins include glycidyl epoxy resins such
as those based on diglycidyl ether compounds comprising one or more
oxyalkylene units. Examples of these include resins made from
ethylene glycol diglycidyl ether, propylene glycol diglycidyl
ether, diethylene glycol diglycidyl ether, dipropylene glycol
diglycidyl ether, polyethylene glycol diglycidyl ether,
polypropylene glycol diglycidyl ether, glycerol diglycidyl ether,
glycerol triglycidyl ether, propanediol diglycidyl ether,
butanediol diglycidyl ether, and hexanediol diglycidyl ether. Other
useful non-aromatic epoxy resins include a diglycidyl ether of
cyclohexane dimethanol, a diglycidyl ether of neopentyl glycol, a
triglycidyl ether of trimethylolpropane, and a diglycidyl ether of
1,4-butanediol. Crosslinked aromatic epoxies (that is, epoxy
polymers) as described herein can be understood to be preparable by
crosslinking aromatic epoxy resins. The crosslinked aromatic epoxy
typically contains a repeating unit with at least one (in some
embodiments, at least 2, in some embodiments, in a range from 1 to
4) aromatic ring (e.g., phenyl group) that is optionally
substituted by one or more halogens (e.g., fluoro, chloro, bromo,
iodo), alkyl groups having 1 to 4 carbon atoms (e.g., methyl or
ethyl), or hydroxyalkyl groups having 1 to 4 carbon atoms (e.g.,
hydroxymethyl). For repeating units containing two or more aromatic
rings, the rings may be connected, for example, by a branched or
straight-chain alkylene group having 1 to 4 carbon atoms that may
optionally be substituted by halogen (e.g., fluoro, chloro, bromo,
iodo).
[0034] In some embodiments, the epoxy resins of the present
disclosure may be liquid at room temperature. Several curable epoxy
resins useful in the epoxy compositions according to the present
disclosure may be commercially available. For example, several
epoxy resins of various classes and epoxy equivalent weights are
available from Olin Corporation, Clayton Mo.; Hexion Inc.,
Columbus, Ohio; Huntsman Advanced Materials, The Woodlands, Tex.;
CVC Specialty Chemicals Inc. Akron, Ohio (acquired by Emerald
Performance Materials); and Nan Ya Plastics Corporation, Taipei
City, Taiwan. Examples of commercially available glycidyl ethers
include diglycidylethers of bisphenol A (e.g. those available under
the trade designations "EPON 828", "EPON 1001", "EPON 1310" and
"EPON 1510" from Hexion Inc. Columbus Ohio, those available under
the trade designation "D.E.R." from Olin Corporation (e.g., D.E.R.
331, 332, and 334), those available under the trade designation
"EPICLON" from Dainippon Ink and Chemicals, Inc. (e.g., EPICLON 840
and 850) and those available under the trade designation "YL-980"
from Japan Epoxy Resins Co., Ltd.); diglycidyl ethers of bisphenol
F (e.g. those available under the trade designation "EPICLON" from
Dainippon Ink and Chemicals, Inc. (e.g., "EPICLON 830"));
polyglycidyl ethers of novolac resins (e.g., novolac epoxy resins,
such as those available under the trade designation "D.E.N." from
Olin Corporation. (e.g., D.E.N. 425, 431, and 438)); and flame
retardant epoxy resins (e.g., "D.E.R. 560", a brominated bisphenol
type epoxy resin available from Olin Corporation). Examples of
commercially available non-aromatic epoxy resins include the
glycidyl ether of cyclohexane dimethanol, available from Hexion
Inc., under the trade designation "HELOXY MODIFIER 107".
[0035] In some embodiments, aromatic epoxy resins useful in the
epoxy compositions disclosed herein may include a flexible
bisphenol A, bisphenol F, or bisphenol Z epoxy resin represented by
the following structural formula:
##STR00001##
where Ar is an aromatic group (which can include bisphenol A,
bisphenol F, or bisphenol Z) having from 10 to 20 carbon atoms and
from 0 to 5 substituents selected from aliphatic hydrocarbon
groups, ether groups, or combinations thereof.
[0036] Examples of suitable aromatic epoxy resins include those
available under the trade designation ARALDITE PY-4122 available
from Huntsman (Woodlands, Tex.), SE-4125P available from SHIN-A
T&C and Epon 872 available from Hexion (Columbus, Ohio).
[0037] In some embodiments, the epoxy compositions of the present
disclosure may include epoxy resin in an amount of between 5 wt. %
and 40 wt. %, 10 wt. % and 30 wt. %, 15 wt. % and 30 wt. %, or 20
wt. % and 30 wt. % (or may be even higher (up to 95%, 99%, or 100%)
for curable compositions that do not include fillers), based on the
total weight of the epoxy composition. In some embodiments, the
epoxy compositions of the present disclosure may include epoxy
resin in an amount of at least 10 wt. %, at least 20 wt. %, at
least 30 wt. %, at least 40 wt. %, or at least 50 wt. %, based on
the total weight of the epoxy composition.
[0038] In some embodiments, the thiol composition may include one
or more multifunctional, functional thiol containing compounds. As
used herein, a thiol refers to an organosulfur compound that
contains a carbon-bonded sulfhydryl or mercapto (--C--SH) group. In
some embodiments, the multifunctional, functional thiol containing
compounds may include at least two functional thiols. In some
embodiements, one or more of the functional thiols in the
multifunctional, functional thiol containing compounds may be a
terminal thiol. In some embodiments, the multifunctional,
functional thiol containing compounds may include an ether in the
backbone thereof. In some embodiments, in additional to functional
thiols, the multifunctional, functional thiol containing compounds
may include, for example, one or more alcohol or amine functional
functional groups. In some embodiments, the multifunctional,
functional thiol can be a di-functional thiol, tri-functional
thiol, tetra-functional thiol, or a polyfunctional thiol.
[0039] In some embodiments, the multifunctional, functional thiol
containing compounds may include a compound represented by the
following structural formula:
##STR00002##
where R is a aliphatic hydrocarbon having from 3 to 11 or 5 to 9
carbon atoms, n is 0 to 20 or 1 to 10, and m is 2 to 4, or 2 to
3.
[0040] In some embodiments, the multifunctional, functional thiol
containing compounds may include a compound represented by the
following structural formula:
##STR00003##
where each R1, R2 and R3 is, independently, an alkyl groups having
1 to 4 or 1 to 3 carbon atoms or hydrogen, and n is 0 to 20 or 1 to
10.
[0041] Examples of suitable commercially available multifunctional,
functional thiol containing compounds include those available under
the trade designation GPM-800LO, GPM-800 and Capcure 3-800
available from Gabriel Chemical (Akron, Ohio), and tetra(ethylene
glycol)dithiol, DMDO (1,8-Dimercapto-3,6-dioxaoctane) from Sigma
Aldrich (Saint Louis, Mo.).
[0042] In some embodiments, the multifunctional, functional thiol
containing compounds may be used alone or as a mixture of two or
multiple different thiol-functionalized compounds. In some
embodiments, the multifunctional, functional thiol containing
compounds of the thiol composition may be liquid (e.g., a viscous
liquid having a viscosity of about 500-50,000 cP) at room
temperature.
[0043] In some embodiments, the epoxy and thiol compositions may be
present in the curable compositions based on stoichiometric ratios
of the functional groups of the respective components. Employing
such relative amounts may be advantageous in that it can reduce the
amount of residual unreacted thiol or epoxy in the cured
composition, which residual components can migrate or provide
environmental or health challenges.
[0044] In some embodiments, the curable compositions of the present
disclosure may be provided (e.g., packaged) as a two-part
composition, in which a first part includes the epoxy composition
(hereinafter "the first part") and a second part includes the thiol
composition (hereinafter "the second part"). In some embodiments,
the first part may include epoxy resin in an amount of at least 50
wt. %, at least 60 wt. %, or at least 68 wt. %; or between 50 and
90 wt. %, between 60 and 80 wt. %, or between 65 and 70 wt. %,
based on the total weight of the unfilled first part. In some
embodiments, the second part may include multifunctional,
functional thiol containing compounds in an amount of at least 50
wt. %, at least 60 wt. %, at least 70 wt. %, or at least 76 wt %;
or between 50 and 90 wt. %, between 65 and 88 wt. %, or between 73
and 78 wt. %, based on the total weight of the unfilled second
part. In some embodiments, the curable composition may include
epoxy resin in an amount of at least 20 wt. %, at least 30 wt. %,
or at least 35 wt. %; or between 20 and 60 wt. %, between 35 and 45
wt. %, or between 37 and 40 wt. %, based on the total weight of the
unfilled curable composition. In some embodiments, the curable
composition may include multifunctional, functional thiol
containing compounds in an amount of at least 10 wt. %, at least 20
wt. %, or at least 30 wt. %; or between 20 and 60 wt. %, between 35
and 45 wt. %, or between 33 and 35 wt. %, based on the total weight
of the unfilled curable composition.
[0045] In addition to the above-described materials, the first part
and the second part may, independently, include one or more
additives such as inorganic fillers, coupling agents, tougheners,
dispersants, catalysts, antioxidants, and the like, which are
described in further detail below. The present disclosure further
provides a dispenser comprising a first chamber and a second
chamber. The first chamber comprises the first part and the second
chamber comprises the second part.
[0046] In some embodiments, the curable compositions may include
one or more inorganic fillers (e.g. thermally conductive inorganic
fillers). Inorganic fillers may be provided to the curable
compositions via the first part, the second part, both parts, or
following mixing of the first and second parts. Generally, the
selection and loading levels of the inorganic fillers may be used
to control the thermal conductivity of the curable composition. In
some embodiments, inorganic filler loadings may be at least 20 vol.
%, at least 30 vol. %, at least 40 vol. %, at least 50 vol. %, at
least 60 vol. %, at least 70 vol. %, at least 80 vol. %, based on
the total volume of any or all of the epoxy composition, the thiol
composition, or the curable composition. In some embodiments,
inorganic filler loadings may be between 20 and 90 vol. %, between
30 and 80 vol. %, between 50 and 70 vol. %, or between 60 and 65
vol. %, based on the total volume of any or all of the epoxy
composition, the thiol composition, or the curable composition.
[0047] Generally, any known thermally conductive fillers may be
used, although electrically insulating fillers may be preferred
where breakthrough voltage is a concern. Suitable electrically
insulating, thermally conductive fillers include ceramics such as
oxides, hydroxides, oxyhydroxides, silicates, borides, carbides,
and nitrides. Suitable ceramic fillers include, e.g., silicon
oxide, aluminum oxide, aluminum trihydroxide (ATH), boron nitride,
silicon carbide, and beryllium oxide. In some embodiments, the
thermally conductive filler includes ATH. It is to be appreciated
that while ATH is not generally used in the polyurethane based
compositions commonly employed in thermal management materials
because of its reactivity with isocyanate species and the resultant
formulation difficulties, the curable compositions of the present
disclosure are able to incorporate such inorganic fillers without
drawback. Other thermally conducting fillers include carbon-based
materials such as graphite and metals such as aluminum and
copper.
[0048] Thermally conductive filler particles are available in
numerous shapes, e.g. spheres, irregular, platelike, &
acicular. Through-plane thermal conductivity may be important in
certain applications. Therefore, in some embodiments, generally
symmetrical (e.g., spherical or semi-spherical) fillers may be
employed. To facilitate dispersion and increase filler loading, in
some embodiments, the thermally conductive fillers may be
surface-treated or coated. Generally, any known surface treatments
and coatings may be suitable, including those based on silane,
titanate, zirconate, aluminate, and organic acid chemistries. For
powder handling purposes, many fillers are available as
polycrystalline agglomerates or aggregates with or without binder.
To facilitate high thermal conductivity formulations, some
embodiments may include mixtures of particles and agglomerates in
various size and mixtures.
[0049] In some embodiments, the curable compositions of the present
disclosure may include one or more silane coupling agents. Silane
coupling agents were discovered to meaningfully improve overlap
shear strength, after aging, of the cured curable compositions. In
some embodiments, silane coupling agents may be provided to the
curable compositions via the first part, the second part, both
parts, or following mixing of the first and second parts. Sutiable
silane coupling agents may include silane thiols, silane amines
(e.g., silane secondary amines), or silane epoxies.
[0050] In some embodiments, suitable silane coupling agents may
include those described in E. P. Plueddemann, Silane Coupling
Agents, 2nd ed., Springer US, New York, 1991, which is herein
incorporated by reference in its entirety. In some embodiments,
suitable silane coupling agents may be described as organosilicone
compounds having two functional groups with different
reactivity--one of the two functional groups reacts with inorganic
materials and the other generally reacts with organic materials. In
some embodiments, the silane coupling agents may have the following
general structural formula:
##STR00004##
where Y is a functional group that is compatable with, or links
with, organic materials, e.g. a vinyl, epoxy, amino, thiol,
isocyanate group, or the like; R is an aliphatic group (typically,
an aliphatic group having from 2-6 carbon atoms); and X is a
functional group that undergoes hydrolysis by water or moisture to
form silanol (e.g., a chlorine, alkoxy, or acetoxy group), and n is
1-3 or 1-2.
[0051] Example of suitable silane coupling agents including
3-glycidoxypropyltriethoxysilane, 5,6-epoxyhexyltriethoxysilane,
2-(3,4-epoxycyclohexyl)ethyltriethoxysilane,
gamma-mercaptopropyltrimethoxysilane, mercaptoproyltriethoxysilane,
s-(octanoyl)mercaptopropyltriethoxysilane,
hydroxy(polyethyleneoxy)propyltriethoxysilane,
N-(n-butyl)-3-aminopropyltrimethoxysilane, or combinations
thereof.
[0052] In some embodiments, the first part may include a silane
epoxy and the second part may include either or both of a silane
thiol and a silane amine.
[0053] In some embodiments, silane coupling agents may be present
in the curable composition in an amount of at least 0.1 wt. %, at
least 10 wt. %, or at least 15 wt. %; or between 0.1 and 60 wt. %,
between 9 and 20 wt. %, or between 14 and 17 wt. %, based on the
total weight of the unfilled curable composition. In some
embodiments, silane coupling agents may be present in the first
part in an amount of at least 0.1 wt. %, at least 15 wt. %, or at
least 20 wt. %; or between 50 and 90 wt. %, between 60 and 80 wt.
%, or between 65 and 70 wt. %, based on the total weight of the
unfilled first part. In some embodiments, silane coupling agents
may be present in the second part in an amount of at least 0.1 wt.
%, at least 5 wt. %, or at least 10 wt. %; or between 0.1 and 40
wt. %, between 5 and 16 wt. %, or between 9 and 11 wt. %, based on
the total weight of the unfilled second part.
[0054] In some embodiments, the curable compositions according to
the present disclosure may include one or more catalysts.
Generally, the catalysts may act to accelerate the cure of the
curable composition. Suitable catalysts according to the present
disclosure may include basic catalysts, Lewis acid catalysts, or a
combination thereof.
[0055] In some embodiments, the suitbale basic catalyst may include
nitrogen-containing catalysts. In some embodiments, the
nitrogen-containing catalysts may include amine-containing
catalysts. In some embodiments, the amine-containing catalysts may
include at least two groups of formula-NR.sup.1R.sup.2, where
R.sup.1 and R.sup.2 are, independently, selected from hydrogen,
alkyl, aryl, alkaryl, or aralkyl. Suitable alkyl groups often have
1 to 12 carbon atoms, 1 to 8 carbon atoms, 1 to 6 carbon atoms, or
1 to 4 carbon atoms. The alkyl group can be cyclic, branched,
linear, or a combination thereof. Suitable aryl group usually have
6 to 12 carbon atoms such as a phenyl or biphenyl group. Suitable
alkylaryl group can include the same aryl and alkyl groups
discussed above. In some embodiments, the amine-containing
catalysts may be an imidazole, an imidazole-salt, and imidazoline,
or a combination thereof. Aromatic tertiary amines may also used as
a catlyst, including those having the structure formula:
##STR00005##
Where R.sup.4 is hydrogen or an alkyl group; R.sup.5, R.sup.6 and
R.sup.7 are, independently, hydrogen or CHNR.sup.8R.sup.9, wherein
at least one of R5, R6 and R7 is CHNR.sup.8R.sup.9, and R.sup.8 and
R.sup.9 are, independently, alkyl groups. In some embodiments, the
alkyl groups of R.sup.4, R.sup.8, and/or R.sup.9 are methyl or
ethyl groups. In some embodiments, the amine-containing catalysts
may include tris-2,4,6-(dimethylaminomethyl)phenol, commercially
available under the tradename ANCAMINE K54 from Evonik Corporation
(Parsippany, N.J.), as the structural formula:
##STR00006##
[0056] In some embodiments, the nitrogen-containing catalysts may
include cyclic or bridged nitrogen containing compounds, including
amidine compounds such as 1,5-diaza-bicyclo[4.3.0] non-5-ene (DBN)
and 1,8-diaza-bicyclo[5.4.0]undec-7-ene (DBU), and also
diazabicyclo[2.2.2]octane (DABCO) from Sigma Aldrich (Saint Louis,
Mo., US) with the structural formula:
##STR00007##
[0057] In some embodiments, the catalysts may be present in the
curable composition (or either or both of the first part and the
second part) in an amount between 100 and 10,000 ppm or 200 and
5,000 ppm, based on the total weight or volume of any or all of the
unfilled curable composition, the unfilled first part, or the
unfilled second part. It was discovered that use of cyclic-type
nitrogen containing catalysts (such as DABCO) can meaningfully
reduce the cure time of the curable compositions of the present
disclosure (e.g., by up to 6 times) relative to cure times using
non-cyclic nitrogen containing catalysts (such as K54).
[0058] In some embodiments, basic catalysts may be present in the
curable composition in an amount of at least 1 wt. %, at least 2
wt. %, or at least 3 wt. %; or between 1 and 20 wt. %, between 2
and 10 wt. %, or between 3 and 5 wt. %, based on the total weight
of the unfilled curable composition. In some embodiments, the
second part may include a basic catalyst. In some embodiments,
basic catalysts may be present in the second part in an amount of
at least 0.5 wt. %, at least 5 wt. %, or at least 7 wt. %; or
between 0.5 and 30 wt. %, between 5 and 15 wt. %, or between 7 and
10 wt. %, based on the total weight of the unfilled second part. In
some embodiments, the second part may include a Lewis acid
catalyst. In some embodiments, Lewis acid catalyst may be present
in the curable composition in an amount of at least 1 wt. %, at
least 2 wt. %, or at least 3 wt. %; or between 1 and 20 wt. %,
between 2 and 10 wt. %, or between 3 and 5 wt. %, based on the
total weight of the unfilled curable composition. In some
embodiments, Lewis acid catalysts may be present in the second part
in an amount of at least 0.5 wt. %, at least 5 wt. %, or at least 7
wt. %; or between 0.5 and 30 wt. %, between 5 and 15 wt. %, or
between 7 and 10 wt. %, based on the total weight of the unfilled
second part.
[0059] In some embodiments, the curable compositions according to
the present disclosure may include one or more dispersants.
Generally, the dispersants may act to stabilize the inorganic
filler particles in the composition--without dispersant, the
particles may aggregate, thus adversely affecting the benefit of
the particles in the composition. Suitable dispersants may depend
on the specific identity and surface chemistry of filler. In some
embodiments, suitable dispersants according to the present
disclosure may include at least a binding group and a
compatibilizing segment. The binding group may be ionically bonded
to the particle surface. Examples of binding groups for alumina
particles include phosphoric acid, phosphonic acid, sulfonic acid,
carboxylic acid, and amine. The compatibilizing segment may be
selected to be miscible with the curable matrix. For epoxy resin
matrices, useful compatibilizing agents may include polyalkylene
oxides, e.g., polypropylene oxide, polyethylene oxide, as well as
polycaprolactones, and combinations thereof. Commercially available
examples include BYK W-9010 (BYK Additives and Instruments), BYK
W-9012 (BYK Additives and Instruments), Disberbyk 180 (BYK
Additives and Instruments), and Solplus D510 (Lubrizol
Corporation). In some embodiments, the dispersants may be present
in the curable composition in an amount between 0.1 and 10 wt. %,
0.1 and 5 wt. %, 0.5 and 3 wt. %, or 0.5 and 2 wt. %, based on the
total weight of the filled curable composition. In some
embodiments, the dispersants may be present in the unfilled curable
composition (or the first part or the second part) in an amount
between 0.1 and 30 wt. %, 1 and 20 wt. %, 5 and 15 wt. %, or 7 and
10 wt. %, based on the total weight of the total weight of the
unfilled first part, the unfilled second part, or the unfilled
curable compostions.
[0060] In some embodiments, the dispersant may be pre-mixed with
the inorganic filler prior to incorporating into any or all of the
first part, the second part, or the curable composition. Such
pre-mixing may facilitate the filled systems behaving like
Newtonian fluids or enable shear-thinning effects behavior.
[0061] In addition to the above discussed additives, further
additives can be included in one or both of the first and second
parts. For example, any or all of antioxidants/stabilizers,
colorants, abrasive granules, thermal degradation stabilizers,
light stabilizers, conductive particles, core-shell tougheners,
tackifiers, flow agents, bodying agents, flatting agents, inert
fillers, binders, blowing agents, fungicides, bactericides,
surfactants, plasticizers, flame retardants, and other additives
known to those skilled in the art. These additives, if present, are
added in an amount effective for their intended purpose.
[0062] In some embodiments, upon curing, the curable compositions
of the present disclosure may exhibit thermal, mechanical, and
rheological properties that render the compositions particularly
useful as thermally conductive gap fillers. For example, it is
believed that that curable compositions of the present disclosure
provide an optimal blend of tensile strength, elongation at break,
and overlap shear strength (even after aging) for certain EV
battery assembly applications.
[0063] In some embodiments, the cured compositions may have an
elongation at break that ranges from 0.1 to 100%, 0.5 to 80%, 1 to
50%, or 8 to 15%, with the pulling rate between 0.8 and 1.5 mm/min
for fully cured systems (for purposes of the present application,
elongation at break values are as measured in accordance with ASTM
D638-14, "Standard Test Method for Tensile Properties of
Plastics."); or at least 1%, at least 3%, at least 7%, at least
10%, at least 15% with the pulling rate between 0.8 and 1.5 mm/min
for fully cured systems.
[0064] In some embodiments, the cured compositions may have an
overlap shear strength on a bare aluminum substrate ranging from
1-30 N/mm.sup.2, 1-25 N/mm.sup.2, 4-20 N/mm.sup.2, 6-20 N/mm.sup.2,
2-16 N/mm.sup.2, or 3-8 N/mm.sup.2, for fully cured systems (for
purposes of the present application, overlap sheer strength values
are as measured on untreated aluminum substrates (i.e., aluminum
substrates having no surface treatments or coatings other than
native oxide layers) according to the procedures of ASTM D1002-01,
"Standard Test Method for Apparent Shear Strength of
Single-Lap-Joint Adhesively Bonded Metal Specimens by Tension
Loading (Metal-to-Metal))."
[0065] In some embodiments, the cured compositions may have a
tensile strength ranging from 0.5-16 N/mm.sup.2, 1-10 N/mm.sup.2,
or 2-8 N/mm.sup.2, with the pulling rate between 0.8 and 1.5 mm/min
for fully cured systems (for purposes of the present application,
tensile strength values are as measured in accordance with ASTM
D638-14, "Standard Test Method for Tensile Properties of
Plastics.").
[0066] In some embodiments, the cured compositions may be
hydrolytically stable. In this regard, the cured composistions may
exhibit over 70% retention of overlap shear strength (measured as
described above) after humidity testing according to PR 308.2 Test
Method. Additionally, or alternatively, the cured composistions may
exhibit less than 30% reduction in tensile strength (measured as
described above) after humidity testing according to PR 308.2 Test
Method.
[0067] In some embodiments, the compositions may have desirable
cure rates. In this regard, the curable compositions of the present
disclosure may, at room temperature, exhibit gelation times (time
at which G' (storage modulus) is equal to G'' (loss modulus)) of no
more than 10 minutes, 30 minutes, 60 minutes, or 80 minutes, as
determined in using an oscillating shear rheometer measurement at
100 rad/s angular frequency at 1% strain on a Discovery HR-3
Rheometer (TA Instruments, Wood Dale, Ill., US) equipped with a
forced convection oven accessory.
[0068] In some embodiments, upon curing, the curable compositions
of the present disclosure may have a thermal conductivity ranging
from 1.0 to 5 W/(m*K), 1.0 to 2 W/(m*K), or 1.5 to 1.8 W/(m*k) (for
purposes of the present application, thermal conductivity values
are as determined by, first, measuring diffusivity according to
ASTM E1461-13, "Standard Test Method for Thermal Diffusivity by the
Flash Method" and, then, calculating thermal conductivity from the
measured thermal diffusivity, heat capacity, and density
measurements according the formula:
k=.alpha.cp.rho.,
where k is the thermal conductivity in W/(m K), .alpha. is the
thermal diffusivity in mm.sup.2/s, cp is the specific heat capacity
in J/K-g, and .rho. is the density in g/cm.sup.3. The sample
thermal diffusivity can be measured using a Netzsch LFA 467
"HYPERFLASH" directly and relative to standard, respectively,
according to ASTM E1461-13. Sample density can be measured using
geometric methods, while the specific heat capacity can measured
using Differential Scanning calorimetry.)
[0069] In some embodiments, within 10 minutes of mixing of the
first part and the second part, the viscosity of curable/partially
cured composition measured at room temperature may range from 100
to 50000 poise, and at 60.degree. C. may range from 100 to 50000
poise. Further regarding viscosity, the viscosity of the epoxy
composition (prior to mixing) measured at room temperature may
range from 100 to 100000 poise, and at 60.degree. C. may range from
10 to 10000 poise; and the viscosity of the thiol composition
(prior to mixing) measured at room temperature may range from 100
to 100000 poise, and at 60.degree. C. may range from 10 to 10000
poise (for purposes of the present application, viscosity values
are as measured using a 25 mm parallel-plate geometry at 1% strain
on a ARES Rheometer (TA Instruments, New Castle, Del., USA)
equipped with a forced convection oven accessory, at angular
frequencies ranging from 10-500 rad/s.)
[0070] The present disclosure is further directed to methods of
making the above-described curable compositions. In some
embodiments, the curable compositions of the present disclosure may
be prepared by, first, mixing the components of the first part
(including any additives) and, separately, mixing the components of
the second part (including any additives). The components of both
the first and second parts may be mixed using any conventional
mixing technique, including by use of a speed mixer. In embodiments
in which dispersants are employed, the dispersant may be pre-mixed
with the inorganic filler prior to incorporating into the
composition. Next, the first and second parts may be mixed together
using any conventional mixing technique to form the curable
composition.
[0071] In some embodiments, the curable compositions of the present
disclosure may be capable of curing without the use of catalyst or
other cure agents. Generally, the curable compositions may cure at
typical application conditions, e.g., at room temperature without
the need for elevated temperatures or actinic radiation (e.g.,
ultraviolet light). In some embodiments, the first curable
compositions cure at no greater than room temperature.
[0072] In some embodiments, the curable compositions of the present
disclosure may be provided as a two-part composition. Generally,
the two components of a two-part composition may be mixed prior to
being applied to the substrates to be bonded. After mixing, the
two-part composition may reach a desired handling strength, and
ultimately achieve a desired final strength. Applying the curable
composition can be carried out, for example, by dispensing the
curable composition from a dispenser comprising a first chamber, a
second chamber, and a mixing tip, wherein the first chamber
comprises the first part, wherein the second chamber comprises the
second part, and wherein the first and second chambers are coupled
to the mixing tip to allow the first part and the second part to
flow through the mixing tip.
[0073] The curable compositions of the present disclosure may be
useful for coatings, shaped articles, adhesives (including
structural and semi-structural adhesives), magnetic media, filled
or reinforced composites, caulking and sealing compounds, casting
and molding compounds, potting and encapsulating compounds,
impregnating and coating compounds, conductive adhesives for
electronics, protective coatings for electronics, as primers or
adhesion-promoting layers, and other applications that are known to
those skilled in the art. In some embodiments, the present
disclosure provides an article comprising a substrate, having a
cured coating of the curable composition thereon.
[0074] In some embodiments, the curable composition may function as
a structural adhesive, i.e. the curable composition is capable of
bonding a first substrate to a second substrate, after curing.
Generally, the bond strength (e.g. peel strength, overlap shear
strength, or impact strength) of a structural adhesive continues to
build well after the initial cure time. In some embodiments, the
present disclosure provides an article comprising a first
substrate, a second substrate and a cured composition disposed
between and adhering the first substrate to the second substrate,
wherein the cured composition is the reaction product of the
curable composition according to any one of the curable
compositions of the present disclosure. In some embodiments, the
first and/or second substrate may be at least one of a metal, a
ceramic and a polymer, e.g. a thermoplastic.
[0075] The curable compositions may be coated onto substrates at
useful thicknesses ranging from 5 microns to 10000 microns, 25
micrometers to 10000 micrometers, 100 micrometers to 5000
micrometers, or 250 micrometers to 1000 micrometers. Useful
substrates can be of any nature and composition, and can be
inorganic or organic. Representative examples of useful substrates
include ceramics, siliceous substrates including glass, metal
(e.g., aluminum or steel), natural and man-made stone, woven and
nonwoven articles, polymeric materials, including thermoplastic and
thermosets, (such as polymethyl (meth)acrylate, polycarbonate,
polystyrene, styrene copolymers, such as styrene acrylonitrile
copolymers, polyesters, polyethylene terephthalate), silicones,
paints (such as those based on acrylic resins), powder coatings
(such as polyurethane or hybrid powder coatings), and wood; and
composites of the foregoing materials.
[0076] In another aspect, the present disclosure provides a coated
article comprising a metal substrate comprising a coating of the
uncured, partially cured or fully cured curable composition on at
least one surface thereof. If the substrate has two major surfaces,
the coating can be coated on one or both major surfaces of the
metal substrate and can comprise additional layers, such as
bonding, tying, protective, and topcoat layers. The metal substrate
can be, for example, at least one of the inner and outer surfaces
of a pipe, vessel, conduit, rod, profile shaped article, sheet or
tube.
[0077] In some embodiments, the present disclosure is further
directed to a battery module that includes the uncured, partially
cured or fully cured curable compositions of the present
disclosure. Components of a representative battery module during
assembly are shown in FIG. 1, and an assembled battery module is
shown in FIG. 2. Battery module 50 may be formed by positioning a
plurality of battery cells 10 on first base plate 20. Generally,
any known battery cell may be used including, e.g., hard case
prismatic cells or pouch cells. The number, dimensions, and
positions of the cells associated with a particular battery module
may be adjusted to meet specific design and performance
requirements. The constructions and designs of the base plate are
well-known, and any base plate (typically metal base plates made of
aluminum or steel) suitable for the intended application may be
used.
[0078] Battery cells 10 may be connected to first base plate 20
through first layer 30 of a first curable composition according to
any of the embodiments of the present disclosure. First layer 30 of
the curable composition may provide first level thermal management
where the battery cells are assembled in a battery module. As a
voltage difference (e.g., a voltage difference of up to 2.3 Volts)
is possible between the battery cells and the first base plate,
breakthrough voltage may be an important safety feature for this
layer. Therefore, in some embodiments, electrically insulating
fillers like ceramics (typically alumina and boron nitride) may be
preferred for use in the curable compositions.
[0079] In some embodiments, layer 30 may comprise a discrete
pattern of the first curable composition applied to first surface
22 of first base plate 20, as shown in FIG. 1. For example, a
pattern of the material to the desired lay-out of the battery cells
may be applied, e.g., robotically applied, to the surface of the
base plate. In some embodiments, the first layer may be formed as a
coating of the first curable composition covering all or
substantially all of the first surface of the first base plate. In
alternative embodiments, the first layer may be formed by applying
the curable composition directly to the battery cells and then
mounting them to the first surface of the first base plate.
[0080] In some embodiments, the curable composition may need to
accommodate dimensional variations of up to 2 mm, up to 4 mm, or
even more. Therefore, in some embodiments, the first layer of the
first curable composition may be at least 0.05 mm thick, e.g., at
least 0.1 mm, or even at least 0.5 mm thick. Higher breakthrough
voltages may require thicker layers depending on the electrical
properties of the material, e.g., in some embodiments, at least 1,
at least 2, or even at least 3 mm thick. Generally, to maximize
heat conduction through the curable composition and to minimize
cost, the curable composition layer should be as thin as possible,
while still ensure good contact with the heat sink. Therefore, in
some embodiments, the first layer is no greater than 5 mm thick,
e.g., no greater than 4 mm thick, or even no greater than 2 mm
thick.
[0081] As the first curable composition cures, the battery cells
are held more firmly in-place. When curing is complete, the battery
cells are finally fixed in their desired position, as illustrated
in FIG. 2. Additional elements, such as bands 40 may be used to
secure the cells for transport and further handling.
[0082] Generally, it is desirable for the curable composition to
cure at typical application conditions, e.g., without the need for
elevated temperatures or actinic radiation (e.g., ultraviolet
light). In some embodiments, the first curable composition cures at
room temperature, or no greater than 30.degree. C., e.g., no
greater than 25.degree. C., or even no greater than 20.degree.
C.
[0083] In some embodiments, the time to cure is no greater than 60
minutes, e.g., no greater than 40 minutes, or even no greater than
20 minutes. Although very rapid cure (e.g., less than 5 minutes or
even less than 1 minute) may be suitable for some applications, in
some embodiments, an open time of at least 5 minutes, e.g., at
least 10 minutes, or even at least 15 minutes may be desirable to
allow time for positioning and repositioning of the battery cells.
Generally, it is desirable to achieve the desired cure times
without the use of expensive catalysts such as platinum.
[0084] As shown in FIG. 3, a plurality of battery modules 50, such
as those illustrated and described with respect to FIGS. 1 and 2,
are assembled to form battery subunit 100. The number, dimensions,
and positions of the modules associated with a particular battery
subunit may be adjusted to meet specific design and performance
requirements. The constructions and designs of the second base
plate are well-known, and any base plate (typically metal base
plates) suitable for the intended application may be used.
[0085] Individual battery modules 50 may be positioned on and
connected to second base plate 120 through second layer 130 of a
curable composition according to any of the embodiments of the
present disclosure.
[0086] Second layer 130 of a second curable composition may be
positioned between second surface 24 of first base plate 20 (see
FIGS. 1 and 2) and first surface 122 of second base plate 120. The
second curable composition may provide second level thermal
management where the battery modules are assembled into battery
subunits. At this level, breakthrough voltage may not be a
requirement. Therefore, in some embodiments, electrically
conductive fillers such as graphite and metallic fillers may be
used or alone or in combinations with electrically insulating
fillers like ceramics.
[0087] In some embodiments, the second layer 130 may be formed as
coating of the second curable composition covering all or
substantially all of first surface 122 of second base plate 120, as
shown in FIG. 3. In some embodiments, the second layer may comprise
a discrete pattern of the second curable composition applied to the
surface of the second base plate. For example, a pattern of the
material corresponding to the desired lay-out of the battery
modules may be applied, e.g., robotically applied, to the surface
of the second base plate. In alternative embodiments, the second
layer may be formed by applying the second curable composition
directly to second surface 24 of first base plate 20 (see FIGS. 1
and 2) and then mounting the modules to first surface 122 of second
base plate 120.
[0088] The assembled battery subunits may be combined to form
further structures. For example, as is known, battery modules may
be combined with other elements such as battery control units to
form a battery system, e.g., battery systems used in electric
vehicles. In some embodiments, additional layers of curable
compositions according to the present disclosure may be used in the
assembly of such battery systems. For example, in some embodiments,
thermally conductive gap filler according to the present disclosure
may be used to mount and help cool the battery control unit.
Listing of Embodiments
[0089] 1. A curable composition comprising:
[0090] a first part comprising an epoxy resin; and
[0091] a second part comprising a multifunctional, functional thiol
containing compound; and
[0092] an inorganic filler present in an amount of at least 20
weight %, based on the total weight of the curable composition
[0093] wherein the multifunctional, functional thiol containing
compound comprises an ether in the backbone thereof.
2. The curable composition of embodiment 1, wherein one or more of
the functional thiols are terminal thiols. 3. The curable
composition of embodiment 1, wherein the multifunctional,
functional thiol containing compound is represented by the
following formula:
##STR00008##
where R is an aliphatic hydrocarbon, n is 0 to 20, and m is 2 to 4.
4. The curable composition of embodiment 1, wherein the
multifunctional, functional thiol containing compound is
represented by one of the following formulas:
##STR00009##
where each of R1, R2 and R3 is, independently, an alkyl group
having 1 to 4 carbon atoms or hydrogen, and n is 0 to 20. 5. The
curable composition of any one of the previous embodiments, wherein
the epoxy resin comprises an internally flexible bisphenol epoxy
resin. 6. The curable composition of embodiment 5, wherein the
internally flexible bisphenol epoxy resin is represented by the
following formula:
##STR00010##
where Ar is bisphenol A, bisphenol F, bisphenol Z, or a mixture
thereof. 7. The curable composition of any one of the previous
embodiments, wherein the epoxy resin comprises a phosphonic acid
group in the backbone thereof. 8. The curable composition according
to any one of the previous embodiments, further comprising a silane
coupling agent. 9. The curable composition according to embodiment
8, wherein the silane coupling agent comprises an amine terminated
silane coupling agent. 10. The curable composition according to
embodiment 8, wherein the silane coupling agent comprises a
mercaptan terminated silane coupling agent. 11. The curable
composition according to embodiment 8, wherein the silane coupling
agent comprises an epoxy terminated silane coupling agent. 12. The
curable composition according to any one of the previous
embodiments, further comprising a catalyst. 13. The curable
composition according to embodiment 12, wherein the catalyst
comprises a basic catalyst. 14. The curable composition according
to embodiment 13, wherein the basic catalyst is represented by one
of the following formulas:
##STR00011##
15. The curable composition according to embodiment 12, wherein the
catalyst comprises a Lewis acid catalyst. 16. The curable
composition according to embodiment 15, wherein the Lewis acid
catalyst comprises calcium triflate, calcium nitrate, or a tin
catalyst. 17. The curable composition according to any one of the
previous embodiments, wherein epoxy resin is present in the curable
composition in an amount of at least 20 wt. %, based on the total
weight of the unfilled curable composition. 18. The curable
composition according to any one of the previous embodiments,
wherein multifunctional, functional thiol containing compounds are
present in the curable composition in an amount of at least 10 wt.
%, based on the total weight of the unfilled curable composition.
19. The curable composition according to any one of the previous
embodiments, wherein the curable composition has, upon curing, (i)
an elongation at break of greater than 5.5%, and (ii) an overlap
shear strength, on untreated aluminum, of 5-20 N/mm.sup.2. 20. The
curable composition according to any one of the previous
embodiments, wherein the curable composition has, upon curing, a
tensile strength of 1 to 16 N/mm2. 21. The curable composition
according to any one of the previous embodiments, wherein the
curable composition, upon curing, retains at least 70% of overlap
shear strength after humidity testing according to PR 308.2 Test
Method. 22. The curable composition according to any one of the
previous embodiments, wherein the curable composition, upon curing,
exhibits a less than 30% reduction in tensile strength after
humidity testing according to PR 308.2 Test Method. 23. The curable
composition according to any one of the previous embodiments,
wherein the curable composition exhibits a gelation time, at room
temperature, of no more than 60 minutes, as determined with an
oscillating shear rheometer measurement at 100 rad/s angular
frequency at 1% strain on a Discovery HR-3 Rheometer (TA
Instruments, Wood Dale, Ill., US) equipped with a forced convection
oven accessory. 24. The curable composition according to any one of
the previous embodiments, wherein the curable composition has, upon
curing, a thermal conductivity of at least 1.0 W/(m*K). 25. The
curable composition according to any one of the previous
embodiments, wherein the inorganic filler present in an amount of
at least 20 wt. %, based on the total weight of the curable
composition. 26. The curable composition according to any one of
the previous embodiments, wherein the inorganic filler present in
an amount of at least 50 wt. %, based on the total weight of the
curable composition. 27. The curable composition according to any
one of the previous embodiments, wherein the inorganic filler
comprises alumina. 28. The curable composition according to any one
of the previous embodiments, wherein the inorganic filler comprises
spherical alumina particles and semispherical alumina particles.
29. The curable composition according to any one of the previous
embodiments, wherein the inorganic filer comprises silane
surface-treated particles. 30. The curable composition according to
any one of the previous embodiments, wherein the inorganic filler
comprises ATH. 31. An article comprising a cured composition,
wherein the cured composition is the reaction product of the
curable composition according to any one of the previous
embodiments. 32. The article of embodiment 31, wherein the cured
composition has a thickness between from 5 microns to 10000
microns. 33. The article of any one of embodiments 31-32, further
comprising a substrate having a surface, wherein the cured
composition is disposed on the surface of the substrate. 34. The
article of embodiment 33, wherein the substrate is a metal
substrate. 35. An article comprising a first substrate, a second
substrate and a cured composition disposed between and adhering the
first substrate to the second substrate, wherein the cured
composition is the reaction product of the curable composition
according to any one of embodiments 1-30. 36. A battery module
comprising a plurality of battery cells connected to a first base
plate by a first layer of the reaction product of the curable
composition according to any one of embodiments 1-30. 37. A method
of making a battery module comprising: applying a first layer of a
curable composition according to any one of embodiments 1-30 to a
first surface of a first base plate, attaching a plurality of
battery cells to the first layer to connect the battery cells to
the first base plate, and curing the curable composition.
EXAMPLES
[0094] Objects and advantages of this disclosure are further
illustrated by the following comparative and illustrative examples.
Unless otherwise noted, all parts, percentages, ratios, etc. in the
examples and the rest of the specification are by weight, and all
reagents used in the examples were obtained, or are available, from
general chemical suppliers such as, for example, Sigma-Aldrich
Corp., Saint Louis, Mo., US unless otherwise specified.
Sample Preparation
[0095] Table 1 summarizes materials used in the examples.
TABLE-US-00001 TABLE 1 Materials List Product Name
Function/Description Source THIOCURE Trimethylolpropane Tri(3-
BRUNO BOCK, TMPMP mercaptopropionate) Ester Thiol Marschacht,
Germany GABEPRO Low Odor Multifunctional Ether Thiol GABRIEL
Chemicals, GPM-800 LO Akron, OH, US ARALDITE Bisphenol-A Type Epoxy
Resin Huntsman, The PY-4122 Woodlands, TX, US EPON 828 Difunctional
Bisphenol A/Epichlorohydrin Hexion, Columbus, OH, Epoxy Resin US
EP-49-10N Epoxy Resin ADEKA, Tokyo Japan MOLDX A110 Alumina
Trihydrate (ATH) Thermally HUBER Engineered Conductive Filler
Materials, Atlanta, GA, US BAK-70 Spherical Alumina Thermally
Conductive BESTRY Performance Filler: 70 .mu.m average particle
size Materials, Shanghai, China BAK-40 Spherical Alumina Thermally
Conductive BESTRY Performance Filler: 40 .mu.m average particle
size Materials, Shanghai, China MARTOXID Aluminum Oxide Thermally
Conductive HUBER Engineered TM-1250 Filler Materials, Atlanta, GA,
US MARTOXID Aluminum Oxide Thermally Conductive HUBER Engineered
TM-2250 Filler Materials, Atlanta, GA, US DBU
1,8-Diazabicyclo[5.4.0]undec-7-ene Alfa Aesar, Haverhill, Catalyst
MA, US K54 Tris-2,4,6-dimethylaminomethyl Phenol Sigma Aldrich
Sigma- Catalyst Aldrich Corp., Saint Louis, MO, US DABCO
1,4-diazabicyclo[2.2.2]octane Amine Sigma Aldrich Sigma- Catalyst
Aldrich Corp., Saint Louis, MO, US DBTDL Diburtyltindilaurate Sigma
Aldrich Sigma- Catalyst Aldrich Corp., Saint Louis, MO, US Calcium
triflate Catalyst GFS Chemicals, Columbus, OH PRIAMINE Dimer
Diamine CRODA, Chino Hills, 1074 CA, US XIAMETER Silane Coupling
Agent Additive DOW Chemical, OFS-6040 Midland, MI, US Silane
DYNASYLAN Silane Coupling Agent Additive EVONIK Industries, 1189
Essen, Germany SILQUEST A- Silane Coupling Agent Additive
Momentive, Columbus, 189 OH, US CAB-O-SIL Fumed Silica Thixotropic
Additive CABOT, Boston, MA, TS-720 US AEROSIL R202 Fumed Silica
Thixotropic Additive EVONIK Industries, Essen, Germany SOLPLUS
Dispersing Additive LUBRIZOL, Wickliffe, D510 OH, US DISPERBYK
Dispersing Additive BYK-Chemie, Wesel, 145 Germany
[0096] Detailed formulations for Comparative Example CE1 and
Examples 1 to 13 are listed in Tables 2 and 3.
[0097] To prepare the samples, Parts A and B were mixed
individually as follows. First, the organic components were
combined and mixed by hand. The thixotropic additive was then
added, followed by hand mixing. A speed mixer (SPEEDMIXER DAC 400,
FlackTek, Inc., Landrum, S.C., US) was then used at 1500 rpm for 2
min to thoroughly mix the materials. The remaining filler materials
were combined and added to the formulation in 2 portions. The
addition of each portion was followed by mixing in the DAC 400
mixer at 2000 RPM for 2 min. In a final step the materials were
mixed in the in DAC 400 mixer for 15 seconds at atmospheric
pressure at 1500 RPM, then for two minutes at 30 Torr and 2000 RPM,
and then a final 15 seconds at 1500 RPM as the pressure returned to
atmospheric pressure.
[0098] Part A and Part B were mixed based on the stoichiometric
ratios of the functional groups: moles of thiol groups in Part A
and combined moles of epoxide groups in Part B. A pneumatic
dispensing system with a static mixing nozzle was used to mix Part
A and Part B in the ratios listed in Tables 2 and 3.
TABLE-US-00002 TABLE 2 Composition of Examples CE-1 Ex. 1 Ex. 2 Ex.
3 Ex. 4 wt % wt % wt % wt % wt % Part A THIOCURE TMPMP 19.3 -- --
-- -- GABEPRO GPM-800 -- 16.5 25.7 21.3 21.3 LO DBU 1.9 -- -- -- --
K54 -- 1.7 2.6 2.1 2.1 MOLDX A110 77.2 -- -- -- -- BAK-70 -- -- --
-- -- BAK-40 -- 24.1 20.9 21.4 21.4 MARTOXID TM-1250 -- 56.2 48.8
50.0 -- MARTOXID TM-2250 -- -- -- -- 50.0 SOLPLUS D510 1.5 1.6 1.4
1.4 1.4 DISPERBYK 145 -- -- -- -- -- CAB-0-SIL TS-720 -- -- 0.70
0.71 0.71 Part B ARALDITE PY-4122 15.3 5.1 4.5 3.9 3.9 EPON 828 3.8
7.7 6.7 5.8 5.8 EP-49-10N -- -- -- -- -- XIAMETER OFS- 0.6 0.4 0.3
2.9 2.9 6040 MOLDX A110 78.7 -- -- -- -- BAK-70 -- -- -- -- --
BAK-40 -- 25.4 25.8 25.4 25.4 MARTOXID TM-1250 -- 59.3 60.2 59.4 --
MARTOXID TM-2250 -- -- -- -- 59.4 SOLPLUS D510 1.6 1.7 1.7 1.7 1.7
DISPERBYK 145 -- -- -- -- -- CAB-O-SIL TS-720 -- 0.42 0.86 0.85
0.85 AEROSIL R202 -- -- -- -- -- Part A: Part B 1:2.28 1:1 1:2 1:2
1:2 (vol:vol) Total filler (wt %) 78.30 82.06 82.10 81.6 81.6
TABLE-US-00003 TABLE 3 Composition of Examples Ex. 5 Ex. 6 Ex. 7
Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 Ex. 13 Part A wt % wt % wt % wt %
wt % wt % wt % wt % wt % GABEPRO 21.3 14.5 21.7 13.9 21.26 20.71
25.90 22.1 21.3 GPM-800 LO PRIAMINE -- -- -- 6.0 -- -- -- -- --
1074 SILQUEST 3.0 -- 3.0 3.0 2.93 2.85 2.80 -- -- A189 Dynasylan --
3.2 -- -- -- -- -- -- 3.0 1189 K54 2.1 1.5 2.2 2.4 -- -- -- -- 2.1
DABCO -- -- -- -- 2.50 5.0 2.60 2.2 -- DBTDL -- -- -- -- -- -- --
-- -- MOLDX -- -- -- -- -- -- -- -- -- A110 BAK-70 -- -- -- -- --
-- -- -- -- BAK-40 21.4 23.8 21.3 21.8 21.35 20.81 20.00 22.2 --
MARTOXID 50.0 55.4 49.7 50.8 49.82 48.55 46.70 51.7 71.4 TM-2250
SOLPLUS 1.4 -- 1.4 1.5 -- -- 1.30 -- -- D510 DISPERBYK -- 1.6 -- --
1.46 1.43 -- 1.5 1.43 145 CAB-O-SIL 0.7 -- 0.7 0.7 0.68 0.67 0.7
0.4 0.7 TS-720 Part B wt % wt % wt % wt % wt % wt % wt % wt % wt %
ARALDITE 3.9 2.9 3.5 3.9 3.9 3.9 3.7 6.5 3.9 PY-4122 EPON 828 5.9
11.4 5.3 5.9 5.9 5.9 5.5 9.7 5.9 EP-49-10N -- -- 0.88 0.97 -- --
1.97 3.46 -- XIAMETER 2.92 4.28 2.65 2.92 2.92 2.92 2.76 4.84 2.92
OFS-6040 MOLDX -- -- -- -- -- -- -- 73.4 -- A110 BAK-70 -- -- -- --
-- -- -- -- -- BAK-40 25.4 23.7 25.5 25.2 25.4 25.4 25.1 -- --
MARTOXID 59.4 55.4 59.6 58.7 59.4 59.4 58.5 -- 84.8 TM-2250 SOLPLUS
-- -- -- -- -- -- -- -- -- D510 DISPERBYK 1.70 1.58 1.70 1.68 1.70
1.70 1.67 1.47 1.70 145 CAB-O-SIL 0.85 0.79 0.85 0.84 0.85 0.85
0.84 0.73 0.85 TS-720 Part A: Part 1:2 1:1 1:2 1:2 1:2 1:2 1:2 1:1
1:2 B (vol:vol) Total filler 81.6 79.5 81.7 81.1 82.1 79.4 79.5
74.0 81.6 (wt %)
Test Procedures
Overlap Shear Adhesion (OLS)
[0099] Two 1 inch (2.54 centimeters (cm)) wide>4 inch (10 cm)
long.times.0.125 inch (0.32 cm) thick aluminum coupons were cleaned
using methyl ethyl ketone (MEK) and otherwise left untreated. At
the tip of one coupon, a 1 inch by 0.5 inch (2.54 cm.times.1.27 cm)
rectangle was covered by the mixed thiol/epoxy paste and then
laminated with another coupon in the opposite tip direction to give
about 10 to 30 mils (0.25 to 0.76 millimeters (mm)) of paste
between the aluminum coupons, which was clamped by a binder clip.
The laminated aluminum coupons were then cured at room temperature
for more than two days to give complete curing prior to overlap
shear testing.
[0100] OLS tests were conducted on an INSTRON Universal Testing
Machine model 1122 (INSTRON Corporation, Norwood, Mass., USA)
according to the procedures of ASTM D1002-01, "Standard Test Method
for Apparent Shear Strength of Single-Lap-Joint Adhesively Bonded
Metal Specimens by Tension Loading (Metal-to-Metal)." The crosshead
speed was 0.05 inch/minute (1.27 mm/minute).
Tensile Properties
[0101] For tensile strength tests, dog bone-shaped samples were
made in accordance with ASTM D1708-13, "Standard Test Method for
Tensile Properties of Plastics by Use of Microtensile Specimens" by
pressing the mixed paste into a dog bone-shaped silicone rubber
mold, which was then laminated with release liner on both sides.
The dog bone shape gives a sample with a length of about 0.6 inch
(1.5 cm) in the center straight area, a width of about 0.2 inch
(0.5 cm) in the narrowest area, and a thickness of about 0.06 to
about 0.1 inch (about 1.5 mm to about 2.5 cm). Samples were then
cured at room temperature for 24 hours, 100.degree. C. for 1 hour,
or 120.degree. C. for 1 hour to be fully cured prior to tensile
testing. The sample was then conditioned at room temperature for 30
minutes prior to tensile testing.
[0102] Tensile strength tests were conducted on an INSTRON
Universal Testing Machine model 1122 (INSTRON Corporation, Norwood,
Mass., US) according to ASTM D638-14, "Standard Test Method for
Tensile Properties of Plastics." The crosshead speed was 0.04
inch/minute (1 mm/minute). The modulus was calculated from the
slope of the linear portion of the stress-strain curve.
Thermal Conductivity
[0103] For thermal conductivity measurements, disk-shaped samples
were made by pressing the mixed paste into a disk-shaped silicone
rubber mold which was then laminated with release liner on both
sides. The disk shape gives samples with a diameter of 12.6 mm and
a thickness of 2.2 mm. The sample was then cured at room
temperature for 24 hours, room temperature for 15 hours, or
100.degree. C. for 1 hour to give complete curing.
[0104] Specific heat capacity, C.sub.p, was measured using a Q2000
Differential Scanning calorimeter (TA Instruments, Eden Prairie,
Minn., US) with sapphire as a method standard.
[0105] Sample density was determined using a geometric method. The
weight (m) of a disk-shaped sample was measured using a standard
laboratory balance, the diameter (d) of the disk was measured using
calipers, and the thickness (h) of the disk was measured using a
Mitatoyo micrometer. The density, .rho., was calculated by
.rho.=m/(.pi.h(d/2).sup.2).
[0106] Thermal diffusivity, .alpha.(T), was measured using an LFA
467 HYPERFLASH Light Flash Apparatus (Netzsch Instruments,
Burlington, Mass., US) according to ASTM E1461-13, "Standard Test
Method for Thermal Diffusivity by the Flash Method."
[0107] Thermal conductivity, k, was calculated from thermal
diffusivity, heat capacity, and density measurements according the
formula: k=.alpha.C.sub.p.rho. where k is the thermal conductivity
in W/(m K), .alpha. is the thermal diffusivity in mm.sup.2/s,
C.sub.p is the specific heat capacity in J/K-g, and .rho. is the
density in g/cm.sup.3.
Dielectric Breakdown Strength
[0108] Dielectric breakdown strength measurements were performed
according to ASTM D149-09(2013), "Standard Test Method for
Dielectric Breakdown Voltage and Dielectric Strength of Solid
Electrical Insulating Materials at Commercial Power Frequencies"
using a Model 6TC4100-10/50-2/D149 Automated Dielectric Breakdown
Test Set (Phenix Technologies, Accident, MD, US) that is
specifically designed for testing DC breakdown from 3-100 kV and AC
breakdown in the 1-50 kV, 60 Hz range. Each measurement was
performed while the sample was immersed in FLUORINERT FC-40 fluid
(3M Corporation, Saint Paul, Minn., US). The average breakdown
strength was based on an average of measurements up to 10 or more
samples. As is typical, a frequency of 60 Hz and a ramp rate of 500
volts per second was utilized for these tests.
Electrical Resistivity
[0109] Surface resistivity and volume resistivity were measured
with a Model 6517A Electrometer (Keithley Instruments, Cleveland,
Ohio, US) with 100 femtoAmp resolution and an applied voltage of
500 Volts, according to the procedures in to ASTM D257-14,
"Standard Test Methods for DC Resistance or Conductance of
Insulating Materials." A Keithley Model 8009 Resistivity test
fixture was used with compressible conductive rubber electrodes and
1 lb electrode force over approximately 2.5 inches of electrode and
sample. The samples were approximately 18 mils thick. The
corresponding detection threshold for surface resistivity is
approximately 1017 ohms. Each sample was measured once, and an
electrification time of 60 seconds was employed. A high resistance
sample PTFE, a low resistance sample (bulk loaded carbon in
Kapton), and a moderate resistance sample (paper) were used as
material reference standards.
Climate Aging Test
[0110] Climate aging and hydrolytic stability cycling was performed
according to the BMW SAE PR308.2, "Climatic Test for Bonded Joints"
standard. At least 5 test specimens were tested, which were
pre-cured for at least 24 hours at room temperature. A single test
cycle included 7 steps: Step 1: start at 23.degree. C. at 20%
relative humidity (RH); Step 2: ramp up to 90.degree. C. and 80% RH
in 1 hour; Step 3: Stay at 90.degree. C. and 80% RH for 4 hours;
Step 4: cool and dehumidify the system to 23.degree. C. and 20% RH;
Step 5: Cool the system to -30.degree. C. in 1 hour; Step 6: Stay
at -30.degree. C. for 4 hours; Step 7: Heat the system to
23.degree. C. and 20% RH in 1 hour. 20 cycles were required to
complete the aging test. Physical properties of the cured
compositions were measured before and after PR308.2 cycling.
Rheology
[0111] Storage modulus (G') and loss modulus (G'') were measured
using a 25 mm parallel-plate geometry at 1% strain on a Discovery
HR-3 Rheometer (TA Instruments, Wood Dale, Ill., US) equipped with
a forced convection oven accessory, using oscillating mode at
angular frequencies of 100 rad/s at 25.degree. C. for time study.
"Open time" of the compositions was defined as the time at which
G'=0.3 MPa, and the "gelation time" was defined as the time at
which G'=G''. Viscosity was measured using a 25 mm parallel-plate
geometry on an Discovery HR-3 Rheometer (TA Instruments, Wood Dale,
Ill., US) equipped with a forced convection oven accessory, using
steady flow mode with shear rate sweep from 0.001 1/s to 100 1/s at
25.degree. C.
Results
[0112] Table 4 summarizes the viscosity of Parts A and B of Example
5 (with 81.6 wt % filler) at 25.degree. C. and 35.degree. C., at
shear rates of 1 sec.sup.-1 and 4 sec.sup.-1. Thixotropic/shear
thinning behavior was observed for both Part A and Part B.
TABLE-US-00004 TABLE 4 Viscosity (cps) of Parts A and B of Example
5 25.degree. C. 35.degree. C. 1 sec.sup.-1 4 sec.sup.-1 1
sec.sup.-1 4 sec.sup.-1 Part A 384,357 142,063 304,211 101,607 Part
B 389,515 167,615 98,307 46,257
[0113] Table 5 summarizes the physical properties of compositions
fully cured at room temperature (RT), typically more than two days,
and then aged under high temperature and humidity for 20 cycles
using the PR308.2 standard conditions described above. CE1 showed
an increase in elongation at break and a decrease in tensile
strength after aging under PR308.2 test conditions; this is
attributed to bond dissociation after exposure to temperature and
humidity cycling. After temperature and humidity cycling, samples
that retain a high degree of their initial tensile strength and
OLS, and that exhibit little to no change in elongation at break
after aging are interpreted herein as having good hydrolytic
stability.
TABLE-US-00005 TABLE 5 Hydrolytic Stability after High Humidity
Thermal Cycling Conditions CE1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 12 OLS
on bare RT full cure 4.2 4.9 6.8 6.1 6.4 5.0 aluminum PR308.2 for
1.5 3.6 1.2 3.5 6.5 2.2 (MPa) 20 cycles Tensile RT full cure 3.6
4.5 5.7 6.9 6.9 4.6 Strength PR308.2 for 0.99 3.7 6.1 8.9 8.3 3.3
(MPa) 20 cycles Modulus RT full cure 31.6 51 71 101 101 24.5 (MPa)
PR308.2 for 22.3 30 42 126 126 24.9 20 cycles Elongation RT full
cure 14.9 16 13.6 11.2 11.2 20.6 at break (%) PR308.2 for 59.6 14
13 10.5 10 20.6 20 cycles
[0114] Tables 6 and 7 summarize the physical properties of
compositions fully cured at room temperature (RT), typically more
than two days, and then aged either under high temperature and
humidity for 20 cycles using the PR308.2 standard conditions
described above, or at 40.degree. C. and 95% relative humidity (RH)
for 10 days. Table 6 lists the measured data. Table 7 lists the
percentage of each property that was retained after aging, relative
to the value of the property directly after curing.
TABLE-US-00006 TABLE 6 Hydrolytic Stability Ex. Ex. Ex. Ex. Ex. Ex.
Ex. Conditions 5 6 7 8 9 11 13 OLS on RT curing 6.2 9.3 5.7 7.3 5.8
7.8 5.8 bare PR308.2 for 5.7 6.8 6.4 7.7 6.0 6.5 6.3 aluminum 20
cycles (MPa) 40.degree. C./95% 2.1 6.0 4.4 5.7 3.6 5.2 4.6 RH for
10 days Tensile RT curing 5.6 4 5.4 8.8 5.6 5.9 7.3 Strength
PR308.2 for 10.8 9.4 10.8 9.3 10.2 10.8 14.2 (MPa) 20 cycles
40.degree. C./95% 4.0 5.4 4.1 5.0 8.2 11.8 7.3 RH for 10 days
Modulus RT curing 97 102 75 174 143 97 95 (MPa) PR308.2 for 150 139
136 187 221 115 219 20 cycles 40.degree. C./95% 78 70 63 106 163
107 134 RH for 10 days Elongation RT curing 10.7 16.4 11.9 9.0 9.5
12.5 10.3 at break PR308.2 for 10.1 9.6 11.1 8.9 7.2 12.4 8.3 (%)
20 cycles 40.degree. C./95% 7.8 10.8 10.1 10.2 8.1 14.0 8.4 RH for
10 days
TABLE-US-00007 TABLE 7 Hydrolytic Stability Ex. Ex. Ex. Ex. Ex. Ex.
Ex. Conditions 5 6 7 8 9 11 13 OLS on PR308.2 91.9 73.1 112.3 105.5
103.4 83.3 108.6 bare for 20 aluminum cycles -% 40.degree. C./ 33.9
64.5 77.2 78.1 62.1 66.7 79.3 Retained 95% RH for 10 days Tensile
PR308.2 192.9 235.0 200.0 105.7 182.1 183.1 194.5 Strength for 20
-% cycles Retained 40.degree. C./ 71.4 135.0 75.9 56.8 146.4 200.0
100.0 95% RH for 10 days Modulus PR308.2 154.6 136.3 181.3 107.5
154.5 118.6 230.5 -% for 20 Retained cycles 40.degree. C./ 80.4
68.6 84.0 60.9 114.0 110.3 141.1 95% RH for 10 days Elongation
PR308.2 94.4 58.5 93.3 98.9 75.8 99.2 80.6 at break for 20 -%
cycles Retained 40.degree. C./ 72.9 65.9 84.9 113.3 85.3 112.0 81.6
95% RH for 10 days
[0115] Table 8 summarizes the open time and gelation time for
several illustrative compositions.
TABLE-US-00008 TABLE 8 Open Time and Gelation Time Open Time
Gelation (min) Time (min) Ex. 1 32.7 37.2 Ex. 2 19.6 23.9 Ex. 5
56.0 60.8 Ex. 7 49.6 55.0 Ex. 8 65.1 71.6 Ex. 9 8.2 8.9 Ex. 10 3.9
4.3 Ex. 11 7.8 8.4
[0116] Table 9 summarizes the thermal properties of several
illustrative compositions after full cure at room temperature for 2
days.
TABLE-US-00009 TABLE 9 Thermal Properties Thermal Heat Thermal
diffusivity Capacity Density Conductivity (mm.sup.2/s) (J/K/g)
(g/cm.sup.3) (W/mK) Ex. 1 0.67 0.97 2.82 1.83 Ex. 2 0.63 0.95 2.82
1.70 Ex. 5 0.70 0.95 2.67 1.77 Ex. 6 0.54 1.08 2.64 1.54 Ex. 7 0.70
0.96 2.67 1.78 Ex. 8 0.75 0.95 2.68 1.91 Ex. 9 0.69 1.03 2.67 1.92
Ex. 11 0.75 1.03 2.60 2.01
[0117] Table 10 summarizes the electrical properties of several
illustrative compositions after full cure at room temperature for 2
days.
TABLE-US-00010 TABLE 10 Dielectric Breakdown Strength and
Resistivity Breakdown Surface Volume Strength Resistivity
Resistivity (kV/mm) (Ohm-cm) (Ohm-cm) Ex. 1 19.4 1.3 .times.
10.sup.12 5.1 .times. 10.sup.9 Ex. 2 25.8 1.9 .times. 10.sup.13 6.3
.times. 10.sup.19 Ex. 5 17.0 6.8 .times. 10.sup.12 1.3 .times.
10.sup.11 Ex. 7 36.2 2.5 .times. 10.sup.14 6.3 .times. 10.sup.11
Ex. 8 32.9 9.6 .times. 10.sup.14 3.3 .times. 10.sup.12 Ex. 9 36.3
2.7 .times. 10.sup.14 4.7 .times. 10.sup.12 Ex. 13 19.0 3.1 .times.
10.sup.14 1.3 .times. 10.sup.12
[0118] Various modifications and alterations to this disclosure
will become apparent to those skilled in the art without departing
from the scope and spirit of this disclosure. It should be
understood that this disclosure is not intended to be unduly
limited by the illustrative embodiments and examples set forth
herein and that such examples and embodiments are presented by way
of example only with the scope of the disclosure intended to be
limited only by the claims set forth herein as follows. All
references cited in this disclosure are herein incorporated by
reference in their entirety.
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