U.S. patent application number 11/615316 was filed with the patent office on 2010-06-03 for compositions of carbon nanotubes.
Invention is credited to Nan-Xing Hu, Carolyn Patricia Moorlag.
Application Number | 20100137499 11/615316 |
Document ID | / |
Family ID | 39415367 |
Filed Date | 2010-06-03 |
United States Patent
Application |
20100137499 |
Kind Code |
A1 |
Moorlag; Carolyn Patricia ;
et al. |
June 3, 2010 |
COMPOSITIONS OF CARBON NANOTUBES
Abstract
A coating composition may include a fluoropolymer; a plurality
of carbon nanotubes, in the carbon nanotubes are substantially
non-agglomerated and substantially uniformly dispersed in the
fluoropolymer; and a coupling agent. The coupling agent may include
a first functional group, a second functional group, and a linking
group. The first functional group may be bonded to the carbon
nanotubes. The second functional group may be bonded to the
fluoropolymer. The linking group may bond the first functional
group to the second functional group.
Inventors: |
Moorlag; Carolyn Patricia;
(Mississauga, CA) ; Hu; Nan-Xing; (Oakville,
CA) |
Correspondence
Address: |
PEPPER HAMILTON LLP
500 GRANT STREET, ONE MELLON CENTER, 50TH FLOOR
PITTSBURGH
PA
15219
US
|
Family ID: |
39415367 |
Appl. No.: |
11/615316 |
Filed: |
December 22, 2006 |
Current U.S.
Class: |
524/496 ;
977/742; 977/750; 977/752 |
Current CPC
Class: |
Y10T 428/139 20150115;
B82Y 30/00 20130101; G03G 15/2057 20130101; C01B 2202/28 20130101;
Y10T 428/31544 20150401; B82Y 40/00 20130101; C01B 2202/06
20130101; C08K 3/041 20170501; C09D 127/12 20130101; C01B 2202/36
20130101; Y10T 428/3154 20150401; C09D 127/12 20130101; C01B 32/174
20170801; C09D 127/12 20130101; C08K 3/046 20170501; C08K 3/041
20170501; C01B 2202/02 20130101; C08K 3/041 20170501; C08K 5/0025
20130101 |
Class at
Publication: |
524/496 ;
977/750; 977/752; 977/742 |
International
Class: |
C08K 3/04 20060101
C08K003/04 |
Claims
1. A coating composition, comprising: a fluoropolymer a plurality
of carbon nanotubes, wherein the carbon nanotubes are substantially
non-agglomerated and substantially uniformly dispersed in the
fluoropolymer; and a covalent coupling agent comprising a first
functional group, a second functional group, and a linking group
joining the first functional group and second functional group;
wherein the first functional group covalently bonds to the carbon
nanotubes and is selected from the group consisting of aziridine,
oxazolidinone, and mixtures thereof; wherein the second functional
group covalently bonds to the fluoropolymer; and wherein the
linking group covalently bonds the first functional group to the
second functional group.
2. (canceled)
3. The coating composition of claim 1, wherein: the fluoropolymer
comprises a monomeric repeat unit that is selected from the group
consisting of vinylidene fluoride, hexafluoropropylene,
tetrafluoroethylene, perfluoro(methyl vinyl ether), and mixtures
thereof.
4. The coating composition of claim 1, wherein the carbon nanotubes
are selected from the group consisting of single wall carbon
nanotubes, multi-wall carbon nanotubes, carbon nanofibers, and
mixtures thereof.
5. The coating composition of claim 1, wherein the carbon nanotubes
have a diameter less than 100 nanometers.
6. The coating composition of claim 1, wherein the carbon nanotubes
are present in an amount of from about 0.5 to about 20 percent by
weight of coating composition.
7. (canceled)
8. (canceled)
9. The coating composition of claim 1, wherein the linking, group
is selected from the group consisting of a linear aromatic
hydrocarbon group having from about 6 to about 60 carbons, a
branched aromatic hydrocarbon group having from about 6 to about 60
carbons, a linear aliphatic hydrocarbon group having from about 1
to about 30 carbons, a branched aliphatic hydrocarbon group having
from about 1 to about 30 carbons, a heteroatom, and mixtures
thereof.
10. The coating composition of claim 1 further comprising an
effective fluoropolymer cross-linking agent.
11. A coated fusing member, comprising: a fusing member substrate;
and a fluoropolymer coating as an outermost coating, layer on the
substrate, wherein the fluoropolymer coating comprises: a plurality
of carbon nanotubes, wherein the carbon nanotubes are substantially
non-agglomerated and substantially uniformly dispersed in the
fluoropolymer; and a covalent coupling agent comprising a first
functional group, a second functional group, and a linking group
joining the first functional group and second functional group;
wherein the first functional group covalently bonds to the carbon
nanotubes and is selected from the group consisting of aziridine,
oxazolidinone, and mixtures thereof; wherein the second functional
group covalently bonds to the fluoropolymer; and wherein the
linking group covalently bonds the first functional group to the
second functional group.
12. The coated fusing member of claim 11, wherein the fluoropolymer
comprises a monomeric repeat unit that is selected from the group
consisting of vinylidene fluoride, hexafluoropropylene,
tetrafluoroethylene, perfluoro(methyl vinyl ether), and mixtures
thereof.
13. The coated fusing member of claim 11, wherein the fluoropolymer
comprises a copolymer of vinylidene fluoride with another monomer
selected from the group consisting with another monomer selected
from the group consisting of hexafluoropropylene,
tetrafluoromethylene, and mixtures thereof.
14. The coated fusing member of claim 11, wherein the fluoropolymer
comprises more than 60% of fluorine content.
15. The coated fusing member of claim 11, wherein the carbon
nanotubes are selected from the group consisting of single wall
carbon nanotubes, multi-wall carbon nanotubes, carbon nanofibers,
and mixtures thereof.
16. The coated fusing member of claim 11, wherein the carbon
nanotubes have a diameter less than 100 nanometers.
17. The coated fusing, member of claim 11, wherein the carbon
nanotubes are present in an amount of from about 0.5 to about 20
percent by weight of coating composition.
18. The coated fusing member of claim 11, wherein the carbon
nanotubes are present in an amount of from about 1 to about 10
percent by weight of coating composition.
19. (canceled)
20. (canceled)
21. The coated fusing member of claim 11, wherein the linking group
is selected from the group consisting, of a linear hydrocarbon
group having, from about 6 to about 60 carbons, a branched aromatic
hydrocarbon group haying from about 6 to about 60 carbons, a linear
aliphatic hydrocarbon group having from about 1 to about 30
carbons, a branched aliphatic hydrocarbon group having from about 1
to about 30 carbons, a heteroatom, and mixtures thereof.
22. The coated fusing member of claim 11, wherein the linking group
is selected from siloxane, phosphazene and combinations
thereof.
23. The coated fusing member of claim 11 further comprising an
effective fluoropolymer cross-linking agent.
24. The coated fusing member of claim 11, wherein the fluoropolymer
coating is crosslinked.
25. A coating composition, comprising: a fluoropolymer; a plurality
of carbon nanotubes, wherein the carbon nanotubes are substantially
non-agglomerated and substantially uniformly dispersed in the
fluoropolymer; and a covalent coupling agent comprising a first
functional group, a second functional group, and a linking group
joining the first functional group and second functional group;
wherein the first functional group covalently bonds to the carbon
nanotubes, wherein the second functional group covalently bonds to
the fluoropolymer and is selected from the group consisting of
phenol, amine, and mixtures thereof; and wherein the linking group
covalently bonds the first functional group to the second
functional group and is selected from siloxane, phosphazene and
mixtures thereof.
26. The coating composition of claim 1, wherein the second
functional group is selected from the group consisting of phenol,
amine, olefin, and mixtures thereof.
27. The coating composition of claim 1, wherein the fluoropolymer
comprises a monomeric repeat unit that is selected from the group
consisting of vinylidene fluoride, hexafluoropropylene,
tetrafluoroethylene, and perfluoro(methyl vinyl ether).
28. The coating composition of claim 1, wherein the covalent bond
coupling the first functional group to the carbon nanotubes
comprises a pyrrolidine-type ring bond.
29. The coated fusing member of claim 11, wherein the second
functional group is selected from the group consisting of phenol,
amine, olefin, and mixtures thereof.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Not applicable
STATEMENT REGARDING FEDERAL SPONSORED RESEARCH
[0002] Not applicable.
NAMES OF PARTIES TO A JOINT RESEARCH AGREEMENT
[0003] Not applicable.
SEQUENCE LISTING
[0004] Not applicable.
BACKGROUND
[0005] 1. Technical Field
[0006] The disclosed embodiments generally relate to the field of
coatings. In particular, this disclosure relates to coatings as
those that may be useful for applying a top layer coating onto a
fuser roll used in printing and copying operations. The top layer
coating includes a carbon nanotube reinforced fluoropolymer
composite of substantially uniform dispersion, where the carbon
nanotubes are chemically bonded with the fluoropolymer.
[0007] 2. Description of the Related Art
[0008] In a typical electrostatographic printing apparatus, a light
image of an original to be copied is recorded in the form of an
electrostatic latent image upon a photosensitive member and the
latent image is subsequently rendered visible by the application of
electroscopic thermoplastic resin particles which are commonly
referred to as toner. The visible toner image is then in a loose
powdered form and can be easily disturbed or destroyed. The toner
image is usually fixed or fused upon a support which may be a
photosensitive member itself or other support sheet such as plain
paper.
[0009] The use of thermal energy for fixing toner images onto a
support member is well known. In order to fuse electroscopic toner
material onto a support surface permanently by heat, it is
necessary to elevate the temperature of the toner material to a
point at which the constituents of the toner material coalesce and
become tacky. This heating causes the toner to flow to some extent
into the fibers or pores of the support member. Thereafter, as the
toner material cools, solidification of the toner material causes
the toner material to be firmly bonded to the support.
[0010] Typically, thermoplastic resin particles are fused to the
substrate by heating to a temperature of between about 90.degree.
C. to about 160.degree. C. or higher depending upon the softening
range of the particular resin used in the toner. It is not
desirable, however, to raise the temperature of the substrate
substantially higher than about 200.degree. C. because of the
tendency of the substrate to discolor at such elevated
temperatures, particularly when the substrate is paper.
[0011] Several approaches to thermal fusing of electroscopic toner
images have been described in the prior art. These methods include
providing the application of heat and pressure substantially
concurrently by various means: a roll pair maintained in pressure
contact; a belt member in pressure contact with a roll; and the
like. Heat may be applied by heating one or both of the rolls,
plate members or belt members. The fusing of the toner particles
takes place when the proper combination of heat, pressure and
contact time is provided. The balancing of these parameters to
bring about the fusing of the toner particles is well known in the
art, and they can be adjusted to suit particular machines or
process conditions.
[0012] During operation of a fusing system in which heat is applied
to cause thermal fusing of the toner particles onto a support, both
the toner image and the support are passed through a nip formed
between the roll pair, or plate or belt members. The concurrent
transfer of heat and the application of pressure in the nip affect
the fusing of the toner image onto the support. It is important in
the fusing process that no offset of the toner particles from the
support to the fuser member take place during normal operations.
Toner particles that offset onto the fuser member may subsequently
transfer to other parts of the machine or onto the support in
subsequent copying cycles, thus increasing the background or
interfering with the material being copied there. The referred to
"hot offset" occurs when the temperature of the toner is increased
to a point where the toner particles liquefy and a splitting of the
molten toner takes place during the fusing operation with a portion
remaining on the fuser member. The hot offset temperature or
degradation to the hot offset temperature is a measure of the
release property of the fuser roll, and accordingly it is desired
to provide a fusing surface, which has a low surfaced energy to
provide the necessary release. To ensure and maintain good release
properties of the fuser roll, it has become customary to apply
release agents to the fuser roll during the fusing operation.
Typically, these materials are applied as thin films of for
example, silicone oils to prevent toner offset.
[0013] Fuser and fixing rolls may be prepared by applying one or
more layers to a suitable substrate. Cylindrical fuser and fixer
rolls, for example, may be prepared by applying an elastomer or
fluoroelastomer to an aluminum cylinder. The coated roll is heated
to cure the elastomer. Such processing is disclosed, for example,
in U.S. Pat. Nos. 5,501,881; 5,512,409; and 5,729,813; the
disclosure of each of which is incorporated by reference herein in
their entirety.
[0014] Fusing systems using fluoroelastomers as surfaces for fuser
members are described in U.S. Pat. Nos. 4,264,181; 4,257,699;
4,272.179; and 5,061,965; the disclosure of each of which is
incorporated by reference herein in their entirety.
[0015] U.S. Pat. No. 5,017,432, which is incorporated by reference
herein in its entirety, describes a fusing surface layer obtained
from a specific fluoroelastomer,
poly(vinylidenefluoride-hexafluoropropylene-tetrafluoroethylene)
where the vinylidenefluoride is present in an amount of less than
40 weight percent. This patent further discloses curing the
fluoroelastomer with Viton.RTM. Curative No. 50 (VC-50) available
from E. I. du Pont de Nemours, Inc., which is soluble in a solvent
solution of the polymer at low base levels and is readily available
at the reactive sites for cross-linking. This patent also discloses
use of a metal oxide (such as cupric oxide) in addition to VC-50
for curing.
[0016] U.S. Pat. No. 7,127,205, which is incorporated in its
entirety herein, provides a process for providing an elastomer
surface on a fusing system member. Generally, the process includes
forming a solvent solution/dispersion by mixing a fluoroelastomer
dissolved in a solvent such as methyl ethyl ketone and methyl
isobutyl ketone, a dehydrofluorinating agent such as a base, for
example the basic metal oxides, MgO and/or Ca(OH).sub.2, and a
nucleophilic curing agent such as VC-50 which incorporates an
accelerator and a cross-linking agent, and coating the solvent
solution/dispersion onto the substrate. The surface is then
stepwise heat cured. Prior to the stepwise heat curing, ball
milling is usually performed, for from 2 to 24 hours.
[0017] Cross-linked fluoropolymers fo elastomers, or
fluoroelastomers, are chemically stable and exhibit good release
properties. They also relatively soft and display elastic
properties. Fillers are often used as in polymer formulations as
reinforcing particles to improve the polymer formulation hardness
and wear resistance. Thermal conductivity of the fuser system is
also important because the fuser or fixer must adequately conduct
heat to soften the toner particles for fusing. In order to increase
the thermal conductivity of the fuser or fixer member, thermally
conductive particles, such as metal oxide particles have been used
as fillers. In order to provide high thermal conductivity, the
loading of the filler must be high. Loading of a filler that is too
high, however, leads to coatings that are too hard, brittle, and
more prone to wear. The addition of fillers of conventional metal
oxides, such as aluminum, iron, copper, tin and zinc oxides are
disclosed in U.S. Pat. Nos. 6,395,444; 6,159,588; 6,114,041;
6,090,491; 6,007,657; 5,998,033; 5,935,712; 5,679,463; and
5,729,813; each of which is incorporated by reference herein in
their entirety. Metal oxide fillers, at loadings of up to about 60
wt %, provide thermal conductivities from about 0.2 to about 1.0
Wm.sup.-1'K.sup.1-. However, the increased loading adversely
affects the wear and lifetime of the fuser.
[0018] A more mechanically robust coating is required for new
generation fusing systems in order to improve lifetime and diminish
the occurrence of roll failure due to edge wear. Higher thermal
conductivity of the top layer would improve heat retention at the
surface during fusing, and electrical conductivity would dissipate
any static charge buildup.
[0019] The disclosure contained herein describes attempts to
address one or more of the problems described above.
SUMMARY
[0020] A coating or coating composition may include a
fluoropolymer; a plurality of carbon nanotubes, wherein the carbon
nanotubes are substantially non-agglomerated and substantially
uniformly dispersed in the fluoropolymer; and a coupling agent. The
coupling agent may include a first functional group, a second
functional group, and a linking group. The first functional group
may be bonded to the carbon nanotubes. The second functional group
may be bonded to the fluoropolymer. The linking group may bond the
first functional group to the second functional group.
[0021] In other embodiments, the first functional group may be
chemically bonded to the carbon nanotubes; the second functional
group may be chemically bonded to the fluoropolymer; and the
linking group may chemically bond the first functional group to the
second functional group.
[0022] In some embodiments, the fluoropolymer may include a
monomeric repeat unit that is selected from the group consisting of
vinylidene fluoride, hexafluoropropylene, tetrafluoroethylene,
perfluoro(methyl vinyl ether), and mixtures thereof.
[0023] In further embodiments, the carbon nanotubes may be selected
from the group consisting of single wall carbon nanotubes,
multi-wall carbon nanotubes, carbon nanofibers, and mixtures
thereof. In still further embodiments, the carbon nanotubes may
have a diameter less than 100 nanometers. Exemplary embodiment
include those where the carbon nanotubes may be present in an
amount of from about 0.5 to about 20 percent by weight of coating
composition.
[0024] In some embodiment of a coating or coating composition, the
first functional group may be selected from the group consisting of
carbene, free radical, nitrene, aziridine, azomethine glide, aryl
diazonium cation, oxazolidinone, and mixtures thereof.
[0025] In further embodiments, the second functional group may be
selected from the group consisting of phenol, amine, olefin, and
mixtures thereof.
[0026] Yet in further embodiments, the linking group may be
selected from the group consisting of a linear aromatic hydrocarbon
group having from about 6 to about 60 carbons, a branched aromatic
hydrocarbon group having from about 6 to about 60 carbons, a linear
aliphatic hydrocarbon group having from about 1 to about 30
carbons, a branched aliphatic hydrocarbon group having from about 1
to about 30 carbons, a heteroatom, and mixtures thereof.
[0027] Still in further embodiments, a coating composition may
include an effective fluoropolymer cross-linking agent.
[0028] Embodiments herein include a coated fusing member or fuser.
A coated fusing member may include a fusing member substrate, and a
fluoropolymer or fluoroelastomer coating as an outermost coating
layer on the substrate. A fluoropolymer coating may include a
plurality of carbon nanotubes, wherein the carbon nanotubes are
substantially non-agglomerated and substantially uniformly
dispersed in the fluoropolymer, and a coupling agent. A coupling
agent of a coated fusing member may include a first functional
group, a second functional group, and a linking group. The first
functional group of a coated fuser may be chemically bonded to the
carbon nanotubes. The second functional group may be chemically
bonded to the fluoropolymer. In embodiments, the linking group may
chemically bond the first functional group to the second functional
group.
[0029] In some embodiments of a coated fusing member, the
fluoroelastomer may include a monomeric repeat unit that is
selected from the group consisting of vinylidene fluoride,
hexafluoropropylene, tetrafluoroethylene, perfluoro(methyl vinyl
ether), and mixtures thereof. In still other embodiments, the
coated fusing member may have a fluoropolymer that may include a
copolymer of vinylidene fluoride with another monomer selected from
the group consisting with another monomer selected from the group
consisting of hexafluoropropylene, tetrafluoroethyelene, and
mixtures thereof. In some embodiments of a coated fusing member,
the fluoropolymer may have more than 60% of fluorine content.
[0030] In exemplary embodiments, a coated fusing may include carbon
nanotubes that are selected from the group consisting of single
wall carbon nanotubes, multi-wall carbon nanotubes, carbon
nanofibers, and mixtures thereof. In some embodiments of a coated
fusing member, the carbon nanotubes may have a diameter less than
100 nanometers. In further embodiments of a coated fusing member
the carbon nanotubes may be present in an amount of from about 0.5
to about 20 percent by weight of coating composition. In still
other embodiments, a coated fusing member may include carbon
nanotubes present in an amount of from about 1 to about 10 percent
by weight of coating composition.
[0031] Exemplary embodiments of a fusing member include those where
the first functional group may be selected from the group
consisting of carbene, free radical, nitrene, aziridine, azomethine
glide, aryl diazonium cation, oxazolidinone, and mixtures
thereof.
[0032] In further exemplary embodiments of a fusing member, the
second functional group may be selected from the group consisting
of phenol, amine, olefin, and mixtures thereof.
[0033] In still further exemplary embodiments of a fusing member, a
linking group may selected from the group consisting of a linear
aromatic hydrocarbon group having from about 6 to about 60 carbons,
a branched aromatic hydrocarbon group having from about 6 to about
60 carbons, a linear aliphatic hydrocarbon group having from about
1 to about 30 carbons, a branched aliphatic hydrocarbon group
having from about 1 to about 30 carbons, a heteroatom, and mixtures
thereof. In still other embodiments, a coated fusing member may
include a linking group that is a hydrocarbon group containing a
siloxane group.
[0034] In embodiments, a coated fusing member may include an
effective fluoropolymer cross-linking went, and in embodiments, the
fluoropolymer coating may be a cross-linked fluoroelastomer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] FIG. 1 is a transmission electron micrograph of a
fluoropolymer coating containing substantially non-agglomerated and
substantial uniformly dispersed carbon nanotubes with a coupling
agent bonding the fluoropolymers and nanotubes.
[0036] FIG. 2 is a chemical structure of an embodiment of a
coupling agent or linker herein.
[0037] FIG. 3 are chemical structures of illustrative first
functional groups of embodiments of coupling agents herein.
[0038] FIG. 4 are chemical structures of illustrative second
functional groups of embodiments of coupling agents herein.
[0039] FIG. 5 depicts reactants in an exemplary carbon
nanotube/coupling agent/fluoropolymer system.
[0040] FIG. 6 depicts reaction products in an exemplary carbon
nanotube/coupling agent/fluoropolymer system.
[0041] FIG. 7 depicts an exemplary chemical synthesis route to
prepare an exemplary coupling agent of embodiments herein.
DETAILED DESCRIPTION
[0042] Before the present methods, systems and materials are
described, it is to be understood that this disclosure is not
limited to the particular methodologies, systems and materials
described, as these may vary. It is also to be understood that the
terminology used in the description is for the purpose of
describing the particular versions or embodiments only, and is not
intended to limit the scope. For example, as used herein and in the
appended claims, the singular forms "a," "an," and "the" include
plural references unless the context clearly dictates otherwise. In
addition, the word "comprising" as used herein is intended to mean
"including but not limited to." Unless defined otherwise, all
technical and scientific terms used herein have the same meanings
as commonly understood by one of ordinary skill in the art.
[0043] Embodiments herein disclose and claim a composite
composition of fluoropolymers displaying good chemical and thermal
stability and low surface energy. Cross-linked fluoropolymers form
elastomers that are relatively soft and display elastic properties.
The fluoropolymer used for coating fuser rolls may be Viton-GF.RTM.
(E. I. du Pont de Nemours, Inc), comprised of tetrafluoroethylene
(TEE), hexafluoropropylene (HFP), vinylidene fluoride (VF2), and a
brominated peroxide cure site.
[0044] Fillers are often used in polymer formulations as
reinforcing particles to improve the hardness and wear resistance.
Examples of fillers include spherical particles such as metal
oxides or carbon black, carbon fibers, and carbon nanotubes. Carbon
nanotubes (CNTs) are nanoscale in size and have a high aspect
ratio, so that loading may be lowered to obtain significantly
improved mechanical properties versus incorporating larger
spherical particles, such as carbon black. Carbon nanotubes are
also electrically and thermally conductive, and can impart these
properties into a composite material.
[0045] U.S. patent application Ser. No. 11/167,158, which is
incorporated by reference herein in its entirety, was filed for the
incorporation of carbon nanotubes into elastomers for improvements
of coatings for fusing applications, including a fluoropolymer/CNT
composite material wherein interactions between the fluoropolymer
and the CNTs would be via incidental surface interactions.
Embodiments herein, disclose and claim a composite coating
composition including: 1) any fluoropolymer, 2) single- or
multi-walled carbon nanotubes or carbon nanofibers, and 3) a
suitable multifunctional linker group or coupling agent that bonds
directly to the both the fluoropolymer chains and to carbon
nanotubes.
[0046] Referring to FIG. 1, a transmission electron micrograph of a
coating composition embodiment of a coating on a substrate 10 is
presented. In an embodiment, a coating on a substrate 10 comprises
a fluoropolymer matrix 20. The coating may further comprise a
plurality of carbon nanotubes (CNTs) 30. The carbon nanotubes 30
are substantially non-agglomerated and substantially uniformly
dispersed in the fluoropolymer. In exemplary embodiments the
coating 10 further comprises a coupling agent (not shown in FIG.
1). The coupling agent may comprise a first functional group, a
second functional group, and a linking group; wherein the first
functional group is bonded to the carbon nanotubes 30; wherein the
second functional group is bonded to the fluoropolymer 20; and
wherein the linking group bonds the first functional group to the
second functional group.
[0047] In another embodiment of a coating 10, the first functional
group may be chemically bonded to the carbon nanotubes, the second
functional group may be chemically bonded to the fluoropolymer, and
the linking group may chemically bond the first functional group to
the second functional group. Details of the coupling agents and
functional groups are presented infra.
[0048] in an embodiment, the coating 10 may comprise a
fluoropolymer which has a monomeric repeat unit that is selected
from the group consisting of vinylidene fluoride,
hexafluoropropylene, tetrafluoroethylene, perfluoro(methyl vinyl
ether), and mixtures thereof. In another embodiment, the
fluoropolymer is comprised of a poly(vinylidene fluoride), or a
copolymer of vinylidene fluoride with another monomer. For example,
the fluoropolymer is a copolymer of vinylidene fluoride with
another monomer selected from the group consisting of
hexafluoropropylene, tetrafluoroethyelene, and a mixture
thereof.
[0049] Embodiments of fluoropolymers herein may include the
Viton.RTM. fluoropolymers from E. I. du Pont de Nemours, Inc.
Viton.RTM. fluoropolymers include for example: Viton.RTM.-A,
copolymers of hexafluoropropylene (HFP) and vinylidene fluoride
(VDF or VF2), Viton.RTM.-B, terpolymers of tetrafluoroethylene
(TFE), vinylidene fluoride (VDF) and hexafluoropropylene (HFP); and
Viton.RTM.-GF, tetrapolymers composed of TFE, VF2, HFP, and small
amounts of a cure site monomer.
[0050] The CNTs dispersed in the fluoropolymer are an example of a
solid-solid dispersion. A dispersion is a two-phase system where
one phase consists of finely divided particles, often in the
colloidal size range, distributed throughout a bulk substance, the
particles being the dispersed or internal phase, and the bulk
substance the continuous phase. (Hawley's Condensed Chemical
Dictionary, 14.sup.th Ed, Rev. by R. J. Lewis, Sr., John Wiley
& Sons, Inc., New York (2001) p. 415).
[0051] In embodiments, the composite coating may contain about 0.1%
to about 40% (w/w) of CNT in a fluoropolymer. Other embodiments use
about 0.5% to about 20% (w/w) of CNT in fluoropolymer. Preferred
embodiments use about 1% to about 10% (w/w).
[0052] Carbon nanotubes (CNTs) are an allotrope of carbon. They
take the form of cylindrical carbon molecules and have novel
properties that make them useful in a wide variety of applications
in nanotechnology, electronics, optics and other fields of
materials science. They exhibit extraordinary strength and unique
electrical properties, and are efficient conductors of heat. Carbon
nanofibers are similar to carbon nanotubes in dimension and they
are cylindric structures, but they are not perfect cylinders, as
are CNTs. Carbon nanofibers are within the scope of embodiments
herein.
[0053] Nanotubes are members of the fullerene structural family,
which also includes buckyballs. Whereas buckyballs are spherical in
shape, a nanotube is cylindrical. The diameter of a nanotube is on
the order of a few nanometers, while they can be up to several
millimeters in length. There are two main types of nanotubes:
single-walled nanotubes (SWNTs) and multi-walled nanotubes (MWNTs)
both of which are encompassed in embodiments herein. In embodiments
of the coating, the carbon nanotubes may be selected from
single-walled nanotubes (SWNTs), multi walled nanotubes (MWNTs),
carbon nanofibers, and mixtures thereof. In embodiments, the carbon
nanotubes may have a diameter less than 100 nanometers. In
embodiments, the carbon nanotubes may be present in an amount of
from about 0.5 to about 20 percent by weight of coating
composition
[0054] Coupling agents of embodiments herein may be multifunctional
coupling agents, wherein the functional groups on the coupling
agent bond with the CNTs and the fluoropolymer matrix. Exemplary
embodiments of coupling agents may encompass chemical coupling
agents, where functional groups on the chemical coupling agent fowl
chemical bonds with the CNTs and the fluoropolymer matrix.
[0055] A non-limiting example of a coupling agent of embodiments
herein is presented in FIG. 2. The coupling agent 50 of FIG. 2 may
comprise a first functional group 60, wherein the first functional
group is selected to interact or bond with CNT surfaces. The
coupling agent may further comprise a second functional group 70,
wherein the second functional group may be selected to interact or
bond with the fluoropolymer chains in a fashion analogous to the
reactions of fluoropolymer cross-linking agents with certain
fluoropolymer chains. The coupling agents of embodiments herein
further may include a linking group 80. The linking group 80
connects first functional group 60 with the second functional group
70 of the coupling agent 50.
[0056] The exemplary coupling agent 50 of FIG. 2 may be considered
a multifunctional chemical coupling agent. The first functional
group 60 of the coupling agent 50 in FIG. 2 is an example of an
azomethine ylide, which is capable of chemically reacting with the
rings on the outside graphene surfaces of carbon nanotubes. The
second functional group 70 depicted in FIG. 2 comprises a bisphenol
group, which is capable of chemically reacting with unsaturated
monomers present on certain fluoropolymers. The linking group 80,
represented by the letter "R" comprises stable chemical bonds that
chemically link the first functional group 60 to the second
functional group 70. Examples and more details of embodiments of
each of these groups of a chemical coupling agent 50 are presented
infra.
[0057] In general strong chemical bonding is associated with the
sharing or transfer of electrons between participating atoms.
Generally covalent and ionic bonds are described as strong, whereas
hydrogen bonds and van der Walls are considered weaker. It should
be noted, however that while chemical bond formation between the
coupling agent, the CNTs and the fluoropolymer are exemplary, the
embodiments herein are not to be limited to covalent and ionic bond
formation. Other stable bonding mechanisms that are effective in
bonding or linking the CNTs, the coupling agent, and the
fluoropolymer together, such as but not limited to, hydrogen
bonding and dispersion forces are within the scope of embodiments
herein.
[0058] Referring now to FIGS. 2 and 3, other embodiments of a
coating may comprise first functional groups 60 of aziridine rims
62, ylides 64, and diazonium compounds 66. In another embodiment
the first functional group 60 may be selected from the group
consisting of carbine, free radical, nitrene, aziridine, azomethine
ylide, aryl diazonium cation, oxazolidinone, and mixtures
thereof.
[0059] Referring now to FIGS. 2 and 4, in still other embodiments
of a coating, a second functional group 70 may be selected from the
group consisting of phenol 72 and amine 74. In yet another
embodiment a second functional group may be selected from the group
comprising phenol, amine, olefin, and mixtures thereof.
[0060] In still further embodiments, the linking group 80 may be
may be an organic chain of any chain length that is effective for
maintaining the CNTs in a substantially non-agglomerated and
substantially uniformly dispersed condition in the fluoropolymer
matrix. Altering the chain length of the linking group 80 may be an
effective method of modifying mechanical and electrical properties
of the coating 10 for particular uses.
[0061] The linking group may consist of aromatic groups, saturated
and unsaturated groups, linear groups, branched groups, heteroatom
groups, and mixtures thereof. Heteroatom groups are sections of the
linking group 80 that may contain atoms other than carbon, such as
for example oxygen, nitrogen, silicon, halogens, or others, and
mixtures thereof. In embodiments, the linking group may be selected
from the group consisting of a linear aromatic hydrocarbon group
having from about 6 to about 60 carbons, a branched aromatic
hydrocarbon group having from about 6 to about 60 carbons, a linear
aliphatic hydrocarbon group haying from about 1 to about 30
carbons, a branched aliphatic hydrocarbon group having from about 1
to about 30 carbons, a heteroatom, and mixtures thereof. The
linking group for embodiments herein is not limited to organic
groups. For example, and not to be limiting, the linking group may
comprise inorganic chains such as siloxane and phosphazene.
[0062] Embodiments of a coating may further comprise an effective
fluoropolymer cross-linking agent, bonding agent, curing agent, or
cross-linker. Exemplary cross-linkers are bisphenol compounds. An
exemplary bisphenol cross-linker may comprise Viton.RTM. Curative
No. 50 (VC-50) available from E. I. du Pont de Nemours, Inc. VC-50
is soluble in a solvent suspension of the CNT and fluoropolymer and
is readily available at the reactive sites for cross-linking.
Curative VC-50 contains Bisphenol-AF as a cross-linker and
diphenylbenzylphosphonium chloride as an accelerator. Bisphenol-AF
is also known as 4,4-(hexafluoroisopropylidene)diphenol. Effective
fluoropolymer cross-linking agents include any compound that is
capable of reacting with and cross-linking fluoropolymers.
[0063] While not desiring to be bound to specific reaction
mechanisms or theories, a schematic representation of an embodiment
of a coupling agent reaction for coatings herein s presented in
FIGS. 5 and 6 for illustrative purposes. In FIG. 5, the reactive
components 100 in a fluoropolymer CNT/coupling agent system are
presented. An embodiment of a coating herein includes a plurality
of carbon nanotubes 110. Carbon nanotubes 110 are usually thought
of as one atom thick layers of graphite, called graphene sheets,
rolled up into nanometer-sized cylinders or tubes. Perfect
graphenes consist exclusively of hexagonal cells 120; pentagonal
and heptagonal cells constitute defects. Hexagonal, pentagonal, and
heptagonal cells of graphene and carbon nanotubes are all potential
reactive sites for embodiments herein.
[0064] An exemplary coupling agent 50 is also depicted in FIG. 5,
which for example contains an azomethine ylide 64 first functional
group 60. In this embodiment, a phenol 72 second functional group
70 is shown for example, and specifically in this non-limiting
embodiment, a bisphenol second functional group 70 is depicted.
[0065] FIG. 5 also present representations of fluoropolymer chains
130. In an embodiment, dehydrofluorinating agents or acid acceptors
140, in this exemplary instance the basic salts MgO and
Ca(OH).sub.2, are also depicted. These agents or basic salts may
aid in the reaction of the bisphenol second functional group 70
with the fluoropolymer chains 130.
[0066] The reaction product 150 of an embodiment of a coupling went
chemically coupling a CNT and fluoropolymer chains is depicted in
FIG. 6. Referring now to both FIGS. 5 and 6, in an embodiment, an
azomethine ylide 64 first functional group 60 may react with a
portion of a hexagonal ring 120 of a CNT 110 to form CNT/coupling
agent bond 160. In the embodiment of FIG. 6 the reaction product of
the first functional group 60 may result in a pyrrolidine-type ring
bond 160 that chemically couples the CNT 110 to the coupling agent
50.
[0067] In the embodiment of FIGS. 5 and 6, the phenolic portions 72
of a second functional group 70 may react with fluoropolymer chains
130. The basic salts 140 may abstract a hydrogen atom from a VF2
monomer, leading to an unsaturated site to which a phenolic 72
portion of a second functional group 70 may add to form a coupling
agent/fluoropolymer bond 170, and specifically in the embodiment of
FIG. 6, an alkoxybenzene-type linkage 170 that chemically couples
the coupling agent 50 to the fluoropolymer chains 130.
[0068] In a fashion detailed through the use of the depictions of
FIGS. 5 and 6, embodiments of chemically coupling or linking CNT
with a fluoropolymer matrix are disclosed. It is emphasized that
the reactions shown in FIGS. 5 and 6 are examples of embodiments
herein, and are in no fashion to be interpreted as limiting. Any
coupling agents or linkers 50 that effectively bond, couple, or
link CNTs and fluoropolymers, which are known now or hereinafter to
one of ordinary skill in the within scope of embodiments
herein.
[0069] A chemical synthesis route 200 for an exemplary coupling
agent or linker of an embodiment is presented in FIG. 7.
Bis(hydroxyphenyl)valeric acid 210 may be reacted with an amine in
the presence of LiAlH.sub.4 220 to form an amide (not shown) that
may be reduced to an amine 230. The amine 230 may be reacted with
ethyl 2,3-dibromopropionate 240 to yield a carboethoxy aziridine
functionality 250 that binds carbon nanotubes. This resulting
coupling agent 260 would also have the ability to cross-link
fluoropolymer chains through the phenolic groups 270 during the
curing process, while further strengthening the elastomeric
material via bonding to CNTs.
[0070] Embodiments of the coating may be employed when the
substrate comprises a fuser member, such as but not limited to
belts, plates, and cylindrical drums. Fuser members or fixer
members may comprise aluminum cylinders or aluminum fuser rolls.
Fuser members, as used herein, may comprise any material and
configuration that is known now or hereinafter by one of ordinary
skill in the art to serve effectively in a fusing capacity.
[0071] In embodiments of methods herein, a combination comprising a
plurality of carbon nanotubes, at least one fluoropolymer, and a
chemical coupling agent is dispersed into an effective solvent to
form a stable suspension. During dispersing, reactions between the
CNTs, the coupling agent, and the fluoropolymer chains occur, as
disclosed and illustrated supra. Effective solvents include, but
are not limited to, acetone, methyl isobutyl ketone (MIBK), methyl
ethyl ketone (MEK), and mixtures thereof. Other solvents that form
stable suspensions, as described herein, are within the scope of
the embodiments herein and include those solvents known now or
hereafter by one of ordinary skill in the art.
[0072] The suspension comprises solubilized polymer that is reacted
with a coupling agent, which is in turn reacted with CNTs,
resulting in a substantially uniformly dispersed suspension of
substantially non-agglomerated CNTs. The suspension has been found
to be relatively stable in a substantially uniformly dispersed
state for a period of greater than a day.
[0073] A suspension is a system in which very small particles
(solid, semisolid, or liquid) are more or less uniformly dispersed
in a liquid or gaseous medium. If the particles are small enough to
pass through filter membranes the system is a colloidal suspension.
The term colloids refer to matter when one or more of its
dimensions lie in the range between 1 millimicron (nanometer) and 1
micron. (micrometer). (Hawley's Condensed Chemical Dictionary,
14.sup.th Ed, Rev. by R. J. Lewis, Sr., John Wiley & Sons,
Inc., New York (2001) pp. 286, 1062).
[0074] In embodiments herein, when the CNT/chemical coupling
agent/fluoropolymer combination is dispersed into an effective
solvent, a suspension is formed. Embodiments of the suspension
herein could be considered a colloidal suspension, since they are
able to pass through filter membranes. In addition, a solid in
liquid colloidal suspension can interchangeably be referred to as a
colloidal dispersion (or loosely called a solution). (Hawley's
Condensed Chemical Dictionary, 14.sup.th Ed, Rev. by R. J. Lewis,
Sr., John Wiley & Sons, Inc., New York (2001) pp. 415,
1062).
[0075] The stability of suspensions of embodiments herein is
increased compared with other methods of forming CNT/fluoropolymer
suspensions. The stability of a suspension is the tendency for the
particles to remain suspended in the solvent and not settle out to
the bottom of the container. A major obstacle for use of CNT in
prior art coatings has been their tendency for agglomeration. As
previously indicated, carbon nanotubes are usually thought of as
one atom thick layers of graphite, called graphene sheets rolled up
into nanometer-sized cylinders or tubes. CNTs tend to pack into
bundles or ropes, at least partially due to strong dispersion
interactions between graphene sheets of respective nanotubes. The
CNT bundles are not easily dispersed into individual CNTs when
mixed into a solvent. The CNT bundles in a solvent settle faster
than individually dispersed CNTs. Further, when a suspension of
bundled CNTs with fluoropolymers is used for coating a substrate, a
non-homogeneous coating is produced on the surface. The
non-homogeneous coating with bundled CNTs results in a reduction of
mechanical strength of the coating and a reduction in the thermal
and electrical conductivity of the coating, as compared with a
coating where the CNTs are substantially non-agglomerated and
substantially uniformly dispersed.
[0076] The suspensions resulting from dispersing a combination of
carbon nanotubes, a coupling agent or linker, and at least one
fluoropolymer are relatively stable. The reaction of the coupling
agents with the CNTs' surfaces may inhibit the CNTs from
agglomerating.
[0077] In an alternative embodiment, the coupling agent may be
reacted with the carbon nanotubes to form grafted carbon nanotubes
prior to dispersing the combination of CNTs, coupling agent, and
fluoropolymer into an effective solvent.
[0078] In still another embodiment, a coupling agent may be reacted
with a fluoropolymer to form grafted fluoropolymer prior dispersing
the combination into an effective solvent.
[0079] In still another embodiment, the combination may be extruded
to form a composite prior to dispersing into the effective solvent.
The method may include extruding a mixture of carbon nanotubes
(CNTs), coupling agent, and a fluoropolymer to form a composite. In
an embodiment, the extrusion may be accomplished with a twin screw
extruder. An exemplary process may involve the use of a
commercially prepared masterbatch of CNT/fluoropolymer material,
followed by lowering the concentration of CNT by a letdown
extrusion process, where the master batch is co-extruded with a
neat fluoropolymer and possibly a coupling agent, so that the CNTs
are reacted with the coupling agent, which in turn is reacted with
the fluoropolymer, resulting in an extruded composite in which the
CNTs are substantially non-agglomerated and substantially uniformly
dispersed in a fluoropolymer matrix.
[0080] The phrase "non-agglomerated" as used herein is a condition
in which the nanotubes or nanoparticles are substantially singly
dispersed within the matrix, that is, there are substantially no
nanotubes or nanoparticles bundled with other nanotubes or
nanoparticles. The phrase "substantially uniformly dispersed" as
used herein, is a condition in which the concentration of nanotubes
or nanoparticles is substantially the same throughout the
matrix.
[0081] In an embodiment, grafted carbon nanotubes, that is, CNTs
reacted with a coupling agent may be extruded with fluoropolymer
prior to dispersing the combination into an effective solvent.
[0082] In an embodiment, grafted fluoropolymer, that is,
fluoropolymer reacted with a coupling agent may be extruded with
CNTs prior to dispersing the combination into an effective
solvent.
[0083] In a method embodiment, the fluoropolymer may comprises a
monomeric repeat unit that is selected from the group consisting of
vinylidene fluoride, hexafluoropropylene, tetrafluoroethylene,
perfluoro(methyl vinyl ether), and mixtures thereof. In another
embodiment, the fluoropolymer is comprised of a poly(vinylidene
fluoride), or a copolymer of vinylidene fluoride with another
monomer. For example, the fluoropolymer is a copolymer of
vinylidene fluoride with another monomer selected from the group
consisting of hexafluoropropylene, tetrafluoroethyelene, and
mixtures thereof.
[0084] In still another method embodiment, the carbon nanotubes may
be selected from the group consisting of single wall carbon
nanotubes, multi-wall carbon nanotubes, carbon nanofibers, and
mixtures thereof.
[0085] In some embodiments, the chemical coupling agent may
comprise at least two effective functional groups selected from the
group consisting of carbene, free radical, nitrene, aziridine,
azomethine glide, aryl diazonium cation, oxazolidinone, phenol,
amine, olefin, and mixtures thereof; and a linking group for
chemically linking the effective functional groups. Effective
functional groups on a coupling agent are those that couple, bond,
or link the CNTs with the fluoropolymer.
[0086] In embodiments, the suspension may be coated onto a
substrate or onto a fusing member substrate to form a coating. Gap
coating can be used to coat a flat substrate, such as a belt or
plate, whereas flow coating can be used to coat a cylindrical
substrate, such as a drum or fuser roll or fuser member substrate.
Various means of coating substrates are familiar to those skilled
in the art and need not be elaborated upon herein.
[0087] The fusing member of an embodiment may include a metallic
substrate, and may further include substrates of aluminum, anodized
aluminum, steel, nickel, copper, and mixtures thereof. Other
substrate fusing member materials known now or hereafter to one of
ordinary skill in the art are within the scope of the embodiments
herein. The fusing member substrate may comprise a hollow cylinder,
a belt, or a sheet.
[0088] After coating, the solvent may be at least partially
evaporated. In an exemplary embodiment, the solvent was allowed to
evaporate for about two hours or more at room temperature. Other
evaporation times and temperatures are within the scope of
embodiments herein.
[0089] Following evaporation the coating may be cured. An exemplary
curing process is a step-wise cure. For example, the coated
substrate may be placed in a convection oven at about 149.degree.
C. for about 2 hours; the temperature may be increased to about
177.degree. C. and further curing may take place for about 2 hours;
the temperature may be increased to about 204.degree. C. and the
coating is further cured at that temperature for about 2 hours;
lastly, the oven temperature may be increased to about 232.degree.
C. and the coating may be cured for another 6 hours. Other curing
schedules are possible. Curing schedules known now or hereinafter
to those skilled in the art are within the scope of embodiments
herein.
[0090] In embodiments, a cross-linking agent may be added together
with the combination prior to coating or casting. The suspension
containing the cross-linker may be mixed briefly, as the
cross-linking in solution occurs rapidly. In an embodiment
employing cross-linking the suspension, a basic oxide, such as, but
not limited to, MgO and Ca(OH).sub.2 may be added to the suspension
along with a cross-linking agent.
[0091] The thickness of the composite coating after curing may
range from about 5 .mu.m to about 100 .mu.m. In other embodiments,
a composite coating thickness of about 20 .mu.m to about 50 .mu.m
is produced.
[0092] Embodiments herein also include a coated fusing member. The
coated fusing member of an embodiment may include a metallic
substrate, and may further include substrates of aluminum, anodized
aluminum, steel, nickel, copper, and mixtures thereof. Other
substrate fusing member materials known now or hereafter to one of
ordinary skill in the art are within the scope of the embodiments
herein. The fusing member substrate may comprise a hollow cylinder,
a belt, or a sheet.
[0093] A fusing member may also include a fluoropolymer coating as
an outermost coating layer on the fusing member substrate. The
fluoropolymer may include a monomeric repeat unit that is selected
from the group consisting of vinylidene fluoride,
hexafluoropropylene, tetrafluoroethylene, perfluoro(methyl vinyl
ether), and mixtures thereof. In other embodiments, the
fluoropolymer may include a copolymer of vinylidene fluoride with
another monomer selected from the group consisting with another
monomer selected from the group consisting of hexafluoropropylene,
tetrafluoroethyelene, and mixtures thereof. The coated fusing
member may include a fluoropolymer that contains more than 60% by
weight of fluorine content.
[0094] The fluoropolymer coating may comprise a plurality of carbon
nanotubes. The carbon nanotubes may be substantially
non-agglomerated and substantially uniformly dispersed in the
fluoropolymer. In embodiments of a coated fusing member the carbon
nanotubes may be selected from the group consisting of single wall
carbon nanotubes, carbon nanotubes, carbon nanofibers, and mixtures
thereof. In some embodiments of a coated fusing member the carbon
nanotubes may have a diameter less than 100 nanometers. In some
embodiments the carbon nanotubes are present in an amount of from
about 0.5 to about 20 percent by weight of coating composition. In
other embodiments of a coated fusing member, the carbon nanotubes
are present in an amount of from about 1 to about 10 percent by
weight of coating composition.
[0095] A coupling agent comprising a first functional group, a
second functional group, and a linking group may be present in an
exemplary embodiment of a fusing member. The first functional group
of the coupling agent may be chemically bonded to the carbon
nanotubes; wherein the second functional group may be chemically
bonded to the fluoropolymer; and wherein the linking group may
chemically bond the first functional group to the second functional
group. In embodiments of a coated fuser the first functional group
may be selected from the group consisting of carbene, free radical,
nitrene, aziridine, azomethine ylide, aryl diazonium cation,
oxazolidinone, and mixtures thereof. In some embodiments of a
coated fuser, the second functional group may be selected from the
group consisting of phenol, amine, olefin, and mixtures thereof.
Exemplary embodiments of a coated fusing member may include those
where the linking group may be selected from the group consisting
of a linear aromatic hydrocarbon group having from about 6 to about
60 carbons, a branched aromatic hydrocarbon group having from about
6 to about 60 carbons, a linear aliphatic hydrocarbon group having
from about 1 to about 30 carbons, a branched aliphatic hydrocarbon
group having from about 1 to about 30 carbons, a heteroatom, and
mixtures thereof. Embodiments of a coated fusing member may include
a linking group that is a hydrocarbon group containing a siloxane
group.
[0096] In embodiments, a coated fusing member may include an
effective fluoropolymer cross-linking agent, and in some
embodiments, the fluoropolymer coating may be crosslinked.
EXAMPLES
[0097] A fluoropolymer composite was prepared as follow: 28.83
grams of CNT masterbatch (containing 12 weight % of multi-walled
CNT in Viton A, commercially purchased from Hyperion Catalysis
International) and 29.17 grams of Viton GF (available from E. I. du
Pont de Nemours, Inc.) were heated to about 170.degree. C. and
extruded using a twin screw extruder at a rotor speed of 20
revolutions per minute (rpm) for 20 minutes to form about 50 grams
of polymer composite containing 5 weight percent of carbon
nanotubes.
[0098] To form a fuser coating, 41 g of the polymer composite was
mixed with 200 g of methyl isobutyl ketone for 18 hours. The
resulted tare was sonicated for 15 minutes to form a suspension
solution. 0.12 gram of 3-(diethoxymethylsilyl)-propylamine and 0.16
gram, of N-(3-diethoxymethyl silyl)propyl 2-carboethoxy aziridine
were added into the suspension. Prior to coating, a designated
amount (for example, ranging from about 0.5 to about pph) of a
curing agent mixture comprised of magnesium oxide, calcium
hydroxide, and VC-50 (Viton.RTM. Curative No. 50 available from E.
I. du Pont de Nemours, Inc.) pre-mixed in methyl isobutyl ketone
was added to the coating solution. The resulted dispersion was then
coated onto a suitable fuser roll substrate by flow coating
technique. The coating was allowed to evaporate most of the
solvent, followed by curing at about 170.degree. C. for 2 hours and
additional 6 hours at about 200.degree. C. The thickness of the
composite coating was about 25 microns after curing. It was
speculated that a coupling agent was formed in situ from the
hydrolytic condensation of 3-(diethoxymethylsilyl)-propylamine and
N-(3-diethoxymethyl silyl)propyl 2-carboethoxy aziridine, resulting
in a siloxane derivative having a amine group capable of reacting
with the fluoropolymer, and a carboethoxy aziridine group capable
of reacting with the carbon nanotubes. The dispersion quality of
the composite coating was confirmed by TEM image as shown in FIG.
1.
[0099] It will be appreciated that various of the above-disclosed
and other features and functions, or alternatives thereof, may be
desirably combined into many other different systems or
applications. Also that various presently unforeseen or
unanticipated alternatives, modifications, variations or
improvements therein may be subsequently made by those skilled in
the art which are also intended to be encompassed by the following
claims.
* * * * *