U.S. patent application number 11/286097 was filed with the patent office on 2007-05-24 for nanoparticle enhanced thermoplastic dielectrics, methods of manufacture thereof, and articles comprising the same.
Invention is credited to Yang Cao, Patricia Chapman Irwin, Qi Tan.
Application Number | 20070116976 11/286097 |
Document ID | / |
Family ID | 38053916 |
Filed Date | 2007-05-24 |
United States Patent
Application |
20070116976 |
Kind Code |
A1 |
Tan; Qi ; et al. |
May 24, 2007 |
Nanoparticle enhanced thermoplastic dielectrics, methods of
manufacture thereof, and articles comprising the same
Abstract
Disclosed herein is a nanocomposite composition comprising a
polymeric composition; wherein the polymeric composition comprises
thermoplastic polymers; and nanoparticles, wherein the
nanoparticles have an average largest dimension of less than or
equal to about 500 nanometers; and wherein the nanocomposite
composition has a higher dielectric constant than the polymeric
composition without the nanoparticles. Disclosed herein too is a
method comprising blending a thermoplastic polymer with
nanoparticles to form a nanocomposite composition; wherein the
nanoparticles have an average largest dimension of less than or
equal to about 500 nanometers; and molding the nanocomposite
composition. Disclosed herein too is a method comprising method
comprising blending a thermoplastic polymer with nanoparticles to
form a nanocomposite composition; wherein the nanoparticles have an
average largest dimension of less than or equal to about 500
nanometers; and casting the nanocomposite composition on a
substrate.
Inventors: |
Tan; Qi; (Rexford, NY)
; Cao; Yang; (Niskayuna, NY) ; Irwin; Patricia
Chapman; (Altamont, NY) |
Correspondence
Address: |
GENERAL ELECTRIC COMPANY;GLOBAL RESEARCH
PATENT DOCKET RM. BLDG. K1-4A59
NISKAYUNA
NY
12309
US
|
Family ID: |
38053916 |
Appl. No.: |
11/286097 |
Filed: |
November 23, 2005 |
Current U.S.
Class: |
428/546 ;
977/700 |
Current CPC
Class: |
H01G 4/206 20130101;
C08K 2201/011 20130101; B82Y 30/00 20130101; Y10T 428/12014
20150115; C08K 3/22 20130101 |
Class at
Publication: |
428/546 ;
977/700 |
International
Class: |
B22F 5/00 20060101
B22F005/00 |
Claims
1. A nanocomposite composition comprising: a polymeric composition;
wherein the polymeric composition comprises a thermoplastic
polymer; and nanoparticles, wherein the nanoparticles have an
average largest dimension of less than or equal to about 500
nanometers; and wherein the nanocomposite composition has a higher
dielectric constant than the polymeric composition without the
nanoparticles.
2. The nanocomposite composition of claim 1 wherein the
nanocomposite composition has a dielectric constant that is about
50% greater than the polymeric composition without
nanoparticles.
3. The nanocomposite composition of claim 1 wherein the
nanocomposite composition has an energy density that is greater
than the polymeric composition without the nanoparticles.
4. The nanocomposite composition of claim 1 wherein the
nanocomposite composition has an energy density that is about 1
Joule/cubic centimeter to about 10 Joules/cubic centimeter.
5. The nanocomposite composition of claim 1, wherein the polymeric
composition further comprises a thermosetting polymer.
6. The nanocomposite composition of claim 1, wherein the
thermoplastic polymeric composition has a glass transition
temperature of greater than or equal to about 100.degree. C.
7. The nanocomposite composition of claim 1, wherein the polymeric
composition comprises thermoplastic polymers, and wherein the
thermoplastic polymers are polyurethanes, polyacrylics,
polycarbonates polystyrenes, polyesters, polyamides,
polyamideimides, polyarylates, polyarylsulfones, polyethersulfones,
polyphenylene sulfides, polysulfones, polyimides, polyetherimides,
polytetrafluoroethylenes, polyetherketones, polyether etherketones,
polyether ketone ketones, polybenzoxazoles, polyoxadiazoles,
polyacetals, polyvinyl ethers, polyvinyl thioethers, polyvinyl
alcohols, polyvinyl ketones, polyvinyl halides, polyvinyl nitriles,
polyvinyl esters, polysulfonates, polysulfides, polythioesters,
polysulfones, polysulfonamides, polyureas, polyphosphazenes,
polysilazanes, or a combination comprising at least one of the
foregoing thermoplastic polymers.
8. The nanocomposite composition of claim 1, wherein nanoparticles
having a particle size of greater than or equal to about 10
nanometers are treated with a silane coupling agent.
9. The nanocomposite composition of claim 1, having an energy
density of about 1 Joule per cubic centimeter to about 10 Joules
per cubic centimeters.
10. The nanocomposite composition of claim 1, wherein the
thermoplastic polymer is a polyetherimide.
11. The nanocomposite composition of claim 1, wherein the
nanoparticles comprise inorganic oxides, and wherein the inorganic
oxide comprises aluminum oxide, magnesium oxide, calcium oxide,
cerium oxide, copper oxide, silicon oxide, tantalum oxide, titanium
oxide, niobium oxide, yttrium oxide, zinc oxide, zirconium oxide,
perovskites and perovskite derivatives, barium titanate, barium
strontium titanate, strontium-doped lanthanum manganate, calcium
copper titanate, cadmium copper titanate, compounds having the
formula Ca.sub.1-xLa.sub.xMnO.sub.3, lithium, titanium doped nickel
oxide, or a combination comprising at least one of the foregoing
inorganic oxides.
12. The nanocomposite composition of claim 1, having a breakdown
strength of at least 300 V/micrometer, an energy density of about 1
Joule per cubic centimeter to about 10 Joules per cubic centimeter
and a corona resistance of about 1000 volts to 5000 volts applied
for about 200 hours to about 2000 hours.
13. The nanocomposite composition of claim 1, having an impact
strength of greater than or equal to about 10 kilojoules per square
meter, a Class A surface finish and a breakdown strength of at
least 300 V/micrometer.
14. The nanocomposite composition of claim 1, having an impact
strength of greater than or equal to about 10 kilojoules per square
meter, a Class A surface finish and a corona resistance of about
1000 volts to 5000 volts applied for about 200 hours to about 2000
hours.
15. A nanocomposite composition comprising: a polymeric
composition; wherein the polymeric composition comprises
polyetherimide, fluorenyl polyester (FPE), polyvinylidene fluoride,
polyvinylidine fluoride-trifluoroethylene,
polyvinylidene-tetrafluoroethylene copolymers, polyvinylidine
trifluoroethylene hexafluoropropylene copolymers, polyvinylidine
hexafluoropropylene copolymers, epoxy, polypropylene, polyester,
polyimide, polyarylate, polyphenylsulfone, polystyrene,
polyethersulfone, polyamideimide, polyurethane, polycarbonate,
polyetheretherketone, silicone; and nanoparticles of a size and an
amount effective to produce an impact strength of greater than or
equal to about 5 kilojoules per square meter, a Class A surface
finish and a breakdown strength of at least 300 V/micrometer.
16. The nanocomposite composition of claim 15, having an impact
strength of greater than or equal to about 10 kilojoules per square
meter and a corona resistance of about 1000 volts to 5000 volts
applied for about 200 hours to about 2000 hours
17. A method comprising: blending a thermoplastic polymer with
nanoparticles to form a nanocomposite composition; wherein the
nanoparticles have an average largest dimension of less than or
equal to about 500 nanometers; and molding the nanocomposite
composition.
18. The method of claim 17, wherein the blending comprises melt
blending, solution blending, or a combination comprising at least
one of the foregoing methods.
19. The method of claim 17, wherein the blending is conducted in a
twin screw extruder.
20. An article comprising the nanocomposite composition of claim
1.
21. The article of claim 20, wherein the article is a capacitor or
a component for a spark plug.
22. An article manufactured by the method of claim 17.
23. The article of claim 22, wherein the article is a capacitor or
a component for a spark plug.
24. A method comprising: blending a thermoplastic polymer with
nanoparticles to form a nanocomposite composition; wherein the
nanoparticles have an average largest dimension of less than or
equal to about 500 nanometers; and casting the nanocomposite
composition on a substrate.
25. The method of claim 24, wherein the casting comprises spin
casting, spray painting, electrostatic spray painting, dip coating,
or a combination comprising at least one of the foregoing methods
of casting.
26. An article manufactured by the method of claim 24.
Description
BACKGROUND
[0001] This disclosure relates to nanoparticle enhanced
thermoplastic dielectrics, methods of manufacture thereof, and
articles comprising the same.
[0002] It is desirable in commercial applications, such as spark
plug caps for automobiles, to have a high breakdown voltage and
corona resistance. Corona resistance is achieved by using large
volume fractions of fillers. This reduces mechanical properties
such as impact strength and ductility in the spark plug cap.
[0003] It is also desirable for energy storage devices, such as
DC-link capacitors, that are utilized in high energy density power
conversion applications to withstand the high voltage and high
temperature environments of electrical devices such as motors and
generators. It is therefore desirable for such storage devices to
display a high breakdown voltage and corona resistance.
[0004] In the electronics industry as well as in the automotive
industry, there is a need for new polymeric compositions with high
dielectric constants and high breakdown strength as well as good
mechanical strength. It is therefore desirable to have a
composition that combines improved impact strength with effective
corona resistance.
SUMMARY
[0005] Disclosed herein is a nanocomposite composition comprising a
polymeric composition; wherein the polymeric composition comprises
thermoplastic polymers; and nanoparticles, wherein the
nanoparticles have an average largest dimension of less than or
equal to about 500 nanometers; and wherein the nanocomposite
composition has a higher dielectric constant than the polymeric
composition without the nanoparticles.
[0006] Disclosed herein too is a nanocomposite composition
comprising a polymeric composition; wherein the polymeric
composition comprises polyetherimide, fluorenyl polyester (FPE),
polyvinylidene fluoride, polyvinylidine fluoride-trifluoroethylene,
polyvinylidene-tetrafluoroethylene copolymers, polyvinylidine
trifluoroethylene hexafluoropropylene copolymers, polyvinylidine
hexafluoropropylene copolymers, epoxy, polypropylene, polyester,
polyimide, polyarylate, polyphenylsulfone, polystyrene,
polyethersulfone, polyamideimide, polyurethane, polycarbonate,
polyetheretherketone, silicone, or a combination comprising at
least one of the foregoing; and nanoparticles of a size and an
amount effective to produce an impact strength of greater than or
equal to about 5 kilojoules per square meter, a Class A surface
finish and a breakdown strength of at least 300 V/micrometer.
[0007] Disclosed herein too is a method comprising blending a
thermoplastic polymer with nanoparticles to form a nanocomposite
composition; wherein the nanoparticles have an average largest
dimension of less than or equal to about 500 nanometers; and
molding the nanocomposite composition.
[0008] Disclosed herein too is a method comprising blending a
thermoplastic polymer with nanoparticles to form a nanocomposite
composition; wherein the nanoparticles have an average largest
dimension of less than or equal to about 500 nanometers; and
casting the nanocomposite composition on a substrate.
DESCRIPTION OF FIGURES
[0009] FIG. 1 represents a bar graph of the change in breakdown
strength of a nanocomposite composition when various silica
nanoparticles were incorporated into a polymeric composition;
[0010] FIG. 2 represents a bar graph of the change in breakdown
strength of a nanocomposite composition when various weight
percents of alumina nanoparticles were incorporated into a
polymeric composition;
[0011] FIG. 3 represents a graph of the increase in dielectric
constant when alumina nanoparticles were incorporated into a
polymeric composition; and
[0012] FIG. 4 is a scanning electron micrograph illustrating the
dispersion of alumina nanoparticles within a polymeric
composition.
DETAILED DESCRIPTION
[0013] It is to be noted that the terms "first," "second," and the
like as used herein do not denote any order, quantity, or
importance, but rather are used to distinguish one element from
another. The terms "a" and "an" do not denote a limitation of
quantity, but rather denote the presence of at least one of the
referenced item. The modifier "about" used in connection with a
quantity is inclusive of the stated value and has the meaning
dictated by the context (e.g., includes the degree of error
associated with measurement of the particular quantity). It is to
be noted that all ranges disclosed within this specification are
inclusive and are independently combinable.
[0014] Disclosed herein are nanocomposite compositions comprising a
polymeric composition and nanoparticles. In one embodiment, the
nanoparticles are inorganic oxides. The nanocomposite composition
has a dielectric constant, breakdown voltage, energy density,
corona resistance, and mechanical properties such as impact
strength, tensile strength and ductility that are superior to a
composition without the nanoparticles. The nanocomposite
composition also has impact strength that is superior to a
composition that comprises a polymeric composition and particles
whose sizes are in the micrometer range instead of in the nanometer
range. In one embodiment, the nanocomposite composition has a
dielectric constant that is greater than that of the polymeric
composition alone or greater than the composition that comprises a
polymeric composition and particles whose sizes are in the
micrometer range. The nanocomposite composition has a breakdown
voltage of greater than or equal to about 300 V/micrometer. The
nanocomposite composition advantageously has an energy density of
about 1 J/cm.sup.3 to about 10 J/cm.sup.3. The nanocomposite
composition has improved properties over the polymeric compositions
without the nanoparticles. These improved properties include a
higher dielectric constant, improved breakdown strength and corona
resistance, improved impact strength, tensile strength and
ductility, as well as improved ease of processing and a Class A
surface finish.
[0015] The polymeric composition comprises thermoplastic polymers.
In one embodiment, the polymeric composition comprises
thermoplastic polymers that have a high glass transition
temperature of greater than or equal to about 100.degree. C. In one
embodiment, the inorganic oxide nanoparticles comprise silica. In
another embodiment, the inorganic oxide nanoparticles comprise
metal oxides such as alumina, ceria, titanate, zirconia, niobium
pentoxide, tantalum pentoxide, or the like, or a combination
comprising at least one of the foregoing. In one embodiment, the
inorganic oxide nanoparticles have particle sizes of less than or
equal to about ten nanometers. In another embodiment, the inorganic
oxide nanoparticles have particle sizes of greater than or equal to
about ten nanometers. In another embodiment, the inorganic oxide
nanoparticles are surface treated to enhance dispersion within the
polymeric composition. For example, the surface treatment comprises
coating the inorganic oxide nanoparticles with an organic material
such as a silane. In one embodiment, the inorganic oxide
nanoparticles and the polymeric composition are combined with one
another by blending, such as solution blending, melt blending, or
the like, or a combination comprising at least one of the
foregoing.
[0016] The polymeric composition used in the nanocomposite
compositions may be selected from a wide variety of thermoplastic
polymers blends of thermoplastic polymers, or blends of
thermoplastic polymers with thermosetting polymers. The polymeric
composition can comprise a homopolymer, a copolymer such as a star
block copolymer, a graft copolymer, an alternating block copolymer
or a random copolymer, ionomer, dendrimer, or a combination
comprising at least one of the foregoing. The polymeric composition
may also be a blend of polymers, copolymers, terpolymers, or the
like, or a combination comprising at least one of the
foregoing.
[0017] Examples of thermoplastic polymers that can be used in the
polymeric composition include polyacetals, polyacrylics,
polycarbonates, polyalkyds, polystyrenes, polyolefins, polyesters,
polyamides, polyaramides, polyamideimides, polyarylates,
polyurethanes, epoxies, phenolics, silicones, polyarylsulfones,
polyethersulfones, polyphenylene sulfides, polysulfones,
polyimides, polyetherimides, polytetrafluoroethylenes,
polyetherketones, polyether etherketones, polyether ketone ketones,
polybenzoxazoles, polyoxadiazoles, polybenzothiazinophenothiazines,
polybenzothiazoles, polypyrazinoquinoxalines, polypyromellitimides,
polyquinoxalines, polybenzimidazoles, polyoxindoles,
polyoxoisoindolines, polydioxoisoindolines, polytriazines,
polypyridazines, polypiperazines, polypyridines, polypiperidines,
polytriazoles, polypyrazoles, polycarboranes,
polyoxabicyclononanes, polydibenzofurans, polyphthalides,
polyacetals, polyanhydrides, polyvinyl ethers, polyvinyl
thioethers, polyvinyl alcohols, polyvinyl ketones, polyvinyl
halides, polyvinyl nitriles, polyvinyl esters, polysulfonates,
polysulfides, polythioesters, polysulfones, polysulfonamides,
polyureas, polyphosphazenes, polysilazanes, polypropylenes,
polyethylenes, polyethylene terephthalates, polyvinylidene
fluorides, polysiloxanes, or the like, or a combination comprising
at least one of the foregoing thermoplastic polymers.
[0018] Exemplary thermoplastic polymers include polyetherimide,
fluorenyl polyester (FPE), polyvinylidene fluoride, polyvinylidine
fluoride-trifluoroethylene P(VDF-TrFE),
polyvinylidene-tetrafluoroethylene copolymers P(VDF-TFE),
polyvinylidine trifluoroethylene hexafluoropropylene copolymers
P(VDF-TFE-HFE) and polyvinylidine hexafluoropropylene copolymers
P(VDF-HFE), epoxy, polypropylene, polyester, polyimide,
polyarylate, polyphenylsulfone, polystyrene, polyethersulfone,
polyamideimide, polyurethane, polycarbonate, polyetheretherketone,
silicone, or the like, or a combination comprising at least one of
the foregoing. Exemplary polymers are ULTEM.RTM., a polyetherimide,
or SILTEM.RTM., a polyetherimide-polysiloxane copolymer, both
commercially available from General Electric Plastics (GE
Plastics).
[0019] Examples of blends of thermoplastic polymers include
acrylonitrile-butadiene-styrene/nylon,
polycarbonate/acrylonitrile-butadiene-styrene, polyphenylene
ether/polystyrene, polyphenylene ether/polyamide,
polycarbonate/polyester, polyphenylene ether/polyolefin, or the
like, or a combination comprising at least one of the
foregoing.
[0020] In another embodiment, thermosetting polymers can be blended
with the thermoplastic polymers for use in the nanocomposite
composition. Examples of thermosetting polymers are resins of
epoxy/amine, epoxy/anhydride, isocyanate/amine, isocyanate/alcohol,
unsaturated polyesters, vinyl esters, unsaturated polyester and
vinyl ester blends, unsaturated polyester/urethane hybrid resins,
polyurethane-ureas, reactive dicyclopentadiene (DCPD) resin,
reactive polyamides, or the like, or a combination comprising at
least one of the foregoing. An exemplary thermosetting polymer is
thermosetting NORYL.RTM. (TSN NORYL.RTM.), a polyphenylene ether,
commercially available from GE Plastics.
[0021] In one embodiment, suitable thermosetting polymers include
thermosetting polymers that can be made from an energy activatable
thermosetting pre-polymer composition. Examples include
polyurethanes such as urethane polyesters, silicone polymers,
phenolic polymers, amino polymers, epoxy polymers, bismaleimides,
polyimides, and furan polymers. The energy activatable
thermosetting pre-polymer component can comprise a polymer
precursor and a curing agent. The polymer precursor can be heat
activatable, eliminating the need for a catalyst. The curing agent
selected will not only determine the type of energy source needed
to form the thermosetting polymer, but may also influence the
resulting properties of the thermosetting polymer. Examples of
curing agents include aliphatic amines, aromatic amines, acid
anhydrides, or the like, or a combination comprising at least one
of the foregoing. The energy activatable thermosetting pre-polymer
composition may include a solvent or processing aid to lower the
viscosity of the composition for ease of extrusion including higher
throughputs and lower temperatures. The solvent could help retard
the crosslinking reaction and could partially or totally evaporate
during or after polymerization.
[0022] As noted above, it is desirable for the thermoplastic
polymers to have a glass transition temperature of greater than or
equal to about 150.degree. C. In one embodiment, it is desirable
for the thermoplastic polymers to have a glass transition
temperature of greater than or equal to about 175.degree. C. In
another embodiment, it is desirable for the thermoplastic polymers
to have a glass transition temperature of greater than or equal to
about 200.degree. C. In yet another embodiment, it is desirable for
the thermoplastic polymers to have a glass transition temperature
of greater than or equal to about 225.degree. C. In yet another
embodiment, it is desirable for the thermoplastic polymers to have
a glass transition temperature of greater than or equal to about
250.degree. C.
[0023] In one embodiment, the polymeric composition is used in an
amount of about 5 to about 99.999 wt % of the total weight of the
nanocomposite composition. In another embodiment, the polymeric
composition is used in an amount of about 10 wt % to about 99.99 wt
% of the total weight of the nanocomposite composition. In another
embodiment, the polymeric composition is used in an amount of about
30 wt % to about 99.5 wt % of the total weight of the nanocomposite
composition. In another embodiment, the polymeric composition is
used in an amount of about 50 wt % to about 99.3 wt % of the total
weight of the nanocomposite composition.
[0024] As noted above, the nanoparticles comprise inorganic oxides.
Examples of inorganic oxides include calcium oxide, silicon
dioxide, or the like, or a combination comprising at least one of
the foregoing. In one embodiment, the nanoparticles comprise metal
oxides such as metal oxides of alkali earth metals, alkaline earth
metals, transition metals, metalloids, poor metals, or the like, or
a combination comprising at least one of the foregoing. In another
embodiment, the nanosized metal oxides comprise perovskites and
perovskite derivatives such as barium titanate, barium strontium
titanate, and strontium-doped lanthanum manganate. In another
embodiment, the nanosized metal oxides comprise a composition with
a high dielectric constant such as calcium copper titanate
(CaCu.sub.3Ti.sub.4O.sub.12), cadmium copper titanate
(CdCu.sub.3Ti.sub.4O.sub.12), Ca.sub.1-xLa.sub.xMnO.sub.3, and (Li,
Ti) doped NiO, or the like, or a combination comprising at least
one of the foregoing. Suitable examples of metal oxides are, cerium
oxide, magnesium oxide, titanium oxide, zinc oxide, silicon oxide
(e.g., silica and/or fumed silica), copper oxide, aluminum oxide
(e.g., alumina and/or fumed alumina), or the like, or a combination
comprising at least one of the foregoing metal oxides.
[0025] Examples of nanoparticles comprising inorganic oxides
include aluminum oxide, calcium oxide, cerium oxide, copper oxide,
magnesium oxide, niobium oxide, silicon oxide, tantalum oxide,
titanium oxide, yttrium oxide, zinc oxide, and zirconium oxide.
[0026] Commercially available examples of nanosized inorganic
oxides are NANOACTIVE.TM. calcium oxide, NANOACTIVE.TM. calcium
oxide plus, NANOACTIVE.TM. cerium oxide, NANOACTIVE.TM. magnesium
oxide, NANOACTIVE.TM. magnesium oxide plus, NANOACTIVE.TM. titanium
oxide, NANOACTIVE.TM. zinc oxide, NANOACTIVE.TM. silicon oxide,
NANOACTIVE.TM. copper oxide, NANOACTIVE.TM. aluminum oxide,
NANOACTIVE.TM. aluminum oxide plus, all commercially available from
NanoScale Materials Incorporated.
[0027] As noted above, the nanoparticles are particles that have
one dimension in the nanometer range (10.sup.-9 meter range). In
one embodiment, the nanoparticles can have particle sizes of less
than or equal to about ten nanometers. In another embodiment, the
nanoparticles have particle sizes of greater than or equal to about
ten nanometers. In one embodiment, the nanoparticles can be surface
treated to facilitate bonding with the polymeric composition. In
another embodiment, the nanoparticles having particle sizes of less
than or equal to about ten nanometers are not surface treated. It
is generally desirable for the nanoparticles having particle sizes
greater than or equal to about ten nanometers to be surface
treated. In one embodiment, the surface treatment comprises coating
the nanoparticles with a silane- coupling agent. Examples of
suitable silane-coupling agents include tetramethylchlorosilane,
hexadimethylenedisilazane, gamma-aminopropoxysilane, or the like,
or a combination comprising at least one of the foregoing silane
coupling agents. The silane-coupling agents generally enhance
compatibility of the nanoparticles with the polymeric composition
and improve dispersion of the nanoparticles within the polymeric
composition.
[0028] In another embodiment, the nanoparticles can be surface
treated by coating with a polymer or a monomer such as, for
example, surface coating in-situ, spray drying a dispersion of
nanoparticle and polymer solution, co-polymerization on the
nanoparticle surface, and melt spinning followed by milling. In the
case of surface coating in-situ, the nanoparticles are suspended in
a solvent, such as, for example demineralized water and the
suspension's pH is measured. The pH can be adjusted and stabilized
with small addition of acid (e.g., acetic acid or dilute nitric
acid) or base (e.g., ammonium hydroxide or dilute sodium
hydroxide). The pH adjustment produces a charged state on the
surface of the nanoparticle. Once a desired pH has been achieved, a
coating material (for example, a polymer or other appropriate
precursor) with opposite charge is introduced into the solvent. The
coating material is coupled around the nanoparticle to provide a
coating layer around the nanoparticle. Once the coating layer has
formed, the nanoparticle is removed from the solvent by drying,
filtration, centrifugation, or another method appropriate for
solid-liquid separation. This technique of coating a nanoparticle
with another material using surface charge can be used for a
variety of nanocomposite compositions.
[0029] When a solvent is used to apply a coating, as in the in-situ
surface coating method described above, the polymeric composition
can also be dissolved in the solvent before or during coating, and
the final nanocomposite composition formed by removing the
solvent.
[0030] As noted above, the nanoparticles have at least one
dimension in the nanometer range. It is generally desirable for the
nanoparticles to have an average largest dimension that is less
than or equal to about 500 nm. The dimension may be a diameter,
edge of a face, length, or the like. The nanoparticles may have
shapes whose dimensionalities are defined by integers, e.g., the
nanoparticles are either 1, 2 or 3-dimensional in shape. They may
also have shapes whose dimensionalities are not defined by integers
(e.g., they may exist in the form of fractals). The nanoparticles
may exist in the form of spheres, flakes, fibers, whiskers, or the
like, or a combination comprising at least one of the foregoing
forms. These nanoparticles may have cross-sectional geometries that
may be circular, ellipsoidal, triangular, rectangular, polygonal,
or a combination comprising at least one of the foregoing
geometries. The nanoparticles, as commercially available, may exist
in the form of aggregates or agglomerates prior to incorporation
into the polymeric composition or even after incorporation into the
polymeric composition. An aggregate comprises more than one
nanoparticle in physical contact with one another, while an
agglomerate comprises more than one aggregate in physical contact
with one another.
[0031] Regardless of the exact size, shape and composition of the
nanoparticles, they may be dispersed into the polymeric composition
at loadings of about 0.0001 to about 50 wt % of the total weight of
the nanocomposite composition when desired. In one embodiment, the
nanoparticles are present in an amount of greater than or equal to
about 1 wt % of the total weight of the nanocomposite composition.
In another embodiment, the nanoparticles are present in an amount
of greater than or equal to about 1.5 wt % of the total weight of
the nanocomposite composition. In another embodiment, the
nanoparticles are present in an amount of greater than or equal to
about 2 wt % of the total weight of the nanocomposite composition.
In one embodiment, the nanoparticles are present in an amount of
less than or equal to 40 wt % of the total weight of the
nanocomposite composition. In another embodiment, the nanoparticles
are present in an amount of less than or equal to about 30 wt % of
the total weight of the nanocomposite composition. In another
embodiment, the nanoparticles are present in an amount of less than
or equal to about 25 wt % of the total weight of the nanocomposite
composition.
[0032] The polymeric composition together with the nanoparticles
and any other optionally desired fillers may generally be processed
in several different ways such as, but not limited to melt
blending, solution blending, or the like, or a combination
comprising at least one of the foregoing methods of blending. Melt
blending of the composition involves the use of shear force,
extensional force, compressive force, ultrasonic energy,
electromagnetic energy, thermal energy or a combination comprising
at least one of the foregoing forces or forms of energy and is
conducted in processing equipment wherein the aforementioned forces
are exerted by a single screw, multiple screws, intermeshing
co-rotating or counter rotating screws, non-intermeshing
co-rotating or counter rotating screws, reciprocating screws,
screws with pins, barrels with pins, rolls, rams, helical rotors,
or a combination comprising at least one of the foregoing.
[0033] Melt blending involving the aforementioned forces may be
conducted in machines such as, but not limited to, single or
multiple screw extruders, Buss kneader, Henschel, helicones, Ross
mixer, Banbury, roll mills, molding machines such as injection
molding machines, vacuum forming machines, blow molding machine, or
then like, or a combination comprising at least one of the
foregoing machines. It is generally desirable during melt or
solution blending of the composition to impart a specific energy of
about 0.01 to about 10 kilowatt-hour/kilogram (kwhr/kg) of the
composition. Within this range, a specific energy of greater than
or equal to about 0.05, preferably greater than or equal to about
0.08, and more preferably greater than or equal to about 0.09
kwhr/kg is generally desirable for blending the composition. Also
desirable is an amount of specific energy less than or equal to
about 9, preferably less than or equal to about 8, and more
preferably less than or equal to about 7 kwhr/kg for blending the
nanocomposite composition.
[0034] In one embodiment, the polymeric composition in powder form,
pellet form, sheet form, or the like, may be first dry blended with
the nanoparticles and other optional fillers if desired in a
Henschel or a roll mill, prior to being fed into a melt blending
device such as an extruder or Buss kneader. In another embodiment,
the nanoparticles are introduced into the melt blending device in
the form of a masterbatch. In such a process, the masterbatch may
be introduced into the melt blending device downstream of the
polymeric composition.
[0035] When a masterbatch is used, the nanoparticles may be present
in the masterbatch in an amount of about 1 to about 50 wt %, of the
total weight of the masterbatch. In one embodiment, the
nanoparticles are used in an amount of greater than or equal to
about 1.5 wt % of the total weight of the masterbatch. In another
embodiment, the nanoparticles are used in an amount of greater or
equal to about 2wt %, of the total weight of the masterbatch. In
another embodiment, the nanoparticles are used in an amount of
greater than or equal to about 2.5 wt %, of the total weight of the
masterbatch. In one embodiment, the nanoparticles are used in an
amount of less than or equal to about 30 wt %, of the total weight
of the masterbatch. In another embodiment, the nanoparticles are
used in an amount of less than or equal to about 10 wt %, of the
total weight of the masterbatch. In another embodiment, the
nanoparticles are used in an amount of less than or equal to about
5 wt %, of the total weight of the masterbatch. Examples of
polymeric compositions that may be used in masterbatches are
polypropylene, polyetherimides, polyamides, polyesters, or the
like, or a combination comprising at least on of the foregoing
polymeric compositions.
[0036] In another embodiment relating to the use of masterbatches
in polymeric blends, it is sometimes desirable to have the
masterbatch comprising a polymeric composition that is the same as
the polymeric composition that forms the continuous phase of the
nanocomposite composition. In yet another embodiment relating to
the use of masterbatches in polymeric blends, it may be desirable
to have the masterbatch comprising a polymeric composition that is
different in chemistry from other the polymers that are used in the
nanocomposite composition. In this case, the polymeric composition
of the masterbatch will form the continuous phase in the blend.
[0037] The nanocomposite composition comprising the polymeric
composition and the nanoparticles may be subject to multiple
blending and forming steps if desirable. For example, the
nanocomposite composition may first be extruded and formed into
pellets. The pellets may then be fed into a molding machine where
it may be formed into other desirable shapes. Alternatively, the
nanocomposite composition emanating from a single melt blender may
be formed into sheets or strands and subjected to post-extrusion
processes such as annealing, uniaxial or biaxial orientation.
[0038] Solution blending may also be used to manufacture the
nanocomposite composition. The solution blending may also use
additional energy such as shear, compression, ultrasonic vibration,
or the like to promote homogenization of the nanoparticles with the
polymeric composition. In one embodiment, a polymeric composition
suspended in a fluid may be introduced into an ultrasonic sonicator
along with the nanoparticles. The mixture may be solution blended
by sonication for a time period effective to disperse the
nanoparticles within the polymeric composition. The polymeric
composition along with the nanoparticles may then be dried,
extruded and molded if desired. It is generally desirable for the
fluid to swell the polymeric composition during the process of
sonication. Swelling the polymeric composition generally improves
the ability of the nanoparticles to impregnate the polymeric
composition during the solution blending process and consequently
improves dispersion.
[0039] In another embodiment related to solution blending, the
nanoparticles are sonicated together with polymeric composition
precursors. Polymeric composition precursors are generally
monomers, dimers, trimers, or the like, which can be reacted into
polymeric compositions. A fluid such as a solvent may optionally be
introduced into the sonicator with the nanoparticles and the
polymeric composition precursor. The time period for the sonication
is generally an amount effective to promote encapsulation of the
nanoparticles by the polymeric composition precursor. After the
encapsulation, the polymeric composition precursor is then
polymerized to form a polymeric composition within which is
dispersed the nanoparticles.
[0040] Suitable examples of monomers that may be used to facilitate
this method of encapsulation and dispersion are those used in the
synthesis of thermoplastic polymers such as, but not limited to
polyacetals, polyacrylics, polycarbonates, polystyrenes,
polyesters, polyamides, polyamideimides, polyarylates,
polyurethanes, polyarylsulfones, polyethersulfones, polyarylene
sulfides, polyvinyl chlorides, polysulfones, polyetherimides,
polytetrafluoroethylenes, polyetherketones, polyether etherketones,
or the like, or a combination comprising at least one of the
foregoing. In one embodiment, the mixture of polymeric composition,
polymeric composition precursor, fluid and/or the nanoparticles is
sonicated for a period of about 1 minute to about 24 hours. In
another embodiment, the mixture is sonicated for a period of
greater than or equal to about 5 minutes. In another embodiment,
the mixture is sonicated for a period of greater than or equal to
about 10 minutes. In another embodiment, the mixture is sonicated
for a period of greater than or equal to about 15 minutes. In one
embodiment, the mixture is sonicated for a period of less than or
equal to about 15 hours. In another embodiment, the mixture is
sonicated for a period of less than or equal to about 10 hours. In
another embodiment, the mixture is sonicated for a period of and
more preferably less than or equal to about 5 hours.
[0041] Solvents may optionally be used in the solution blending of
the nanocomposite composition. The solvent may be used as a
viscosity modifier, or to facilitate the dispersion and/or
suspension of nanoparticles. Liquid aprotic polar solvents such as
propylene carbonate, ethylene carbonate, butyrolactone,
acetonitrile, benzonitrile, nitromethane, nitrobenzene, sulfolane,
dimethylformamide, N-methylpyrrolidone, or the like, or a
combination comprising at least one of the foregoing solvents may
be used. Polar protic solvents such as water, methanol,
acetonitrile, nitromethane, ethanol, propanol, isopropanol,
butanol, or the like, or a combination comprising at least one of
the foregoing polar protic solvents may be used. Other non-polar
solvents such benzene, toluene, methylene chloride, carbon
tetrachloride, hexane, diethyl ether, tetrahydrofuran, or the like,
or a combination comprising at least one of the foregoing solvents
may also be used if desired. Co-solvents comprising at least one
aprotic polar solvent and at least one non-polar solvent may also
be used. In one embodiment, the solvent is xylene or
N-methylpyrrolidone.
[0042] If a solvent is used, it may be utilized in an amount of
about 1 to about 50 wt %, of the total weight of the nanocomposite
composition. In one embodiment, if a solvent is used, it may be
utilized in an amount of about 3 to about 30 wt %, of the total
weight of the nanocomposite composition. In yet another embodiment,
if a solvent is used, it may be utilized in an amount of about 5 to
about 20 wt %, of the total weight of the nanocomposite
composition. It is generally desirable to evaporate the solvent
before, during and/or after the blending of the nanocomposite
composition.
[0043] After solution blending, the solution comprising the desired
composition can be cast, spin cast, dip coated, spray painted,
brush painted and/or electrostatically spray painted onto a desired
substrate. The solution is then dried leaving behind the
composition on the surface. In another embodiment, the solution
comprising the desired composition may be spun, compression molded,
injection molded or blow molded to form an article comprising the
composition.
[0044] Blending can be assisted using various secondary species
such as dispersants, binders, modifiers, detergents, and additives.
Secondary species may also be added to enhance one to more of the
properties of the nanocomposite composition. Blending can also be
assisted by pre-coating the nanoparticles with a thin layer of the
polymeric composition or with a phase that is compatible with the
polymeric composition, such as, for example a silane layer.
[0045] A nanocomposite composition comprising a polymeric
composition and nanoparticles has advantages over the polymeric
composition alone or other commercially available compositions that
comprise a polymeric composition and particles having particle
sizes in the micrometer range. In one embodiment, the nanocomposite
composition has a dielectric constant that is at least 50% greater
than a composition comprising polymeric composition alone. In
another embodiment, the nanocomposite composition has a dielectric
constant that is at least 75% greater than the polymeric
composition alone. In another embodiment, the nanocomposite
composition has a dielectric constant that is at least 100% greater
than the polymeric composition alone.
[0046] The nanocomposite composition also has a breakdown voltage
that is advantageously greater than the polymeric composition alone
or other commercially available compositions that comprise a
polymeric composition and particles having particle sizes in the
micrometer range. In one embodiment, the nanocomposite composition
has a breakdown voltage that is at least 300 Volts/micrometer
(V/micrometer). The breakdown is generally determined in terms of
the thickness of the nanocomposite composition. In another
embodiment, the nanocomposite composition has a breakdown voltage
that is at least 400 V/micrometer. In another embodiment, the
nanocomposite composition has a breakdown voltage that is at least
500V/micrometer.
[0047] The nanocomposite composition also has a corona resistance
that is advantageously greater than the polymeric composition alone
or other commercially available compositions that comprise a
polymeric composition and particles having particle sizes in the
micrometer range. In one embodiment, the nanocomposite composition
has a corona resistance that is resistant to a current of about
1000 volts to 5000 volts applied for about 200 hours to about 2000
hours. In another embodiment, the nanocomposite composition has a
corona resistance that is resistant to a current of about 1000
volts to 5000 volts applied for about 250 hours to about 1000
hours. In yet another embodiment, the nanocomposite composition has
a corona resistance that is resistant to a current of about 1000
volts to 5000 volts applied for about 500 hours to about 900
hours.
[0048] In another embodiment, the nanocomposite composition also
has an impact strength of greater than or equal to about 5
kilojoules per square meter (kj/m.sup.2). In another embodiment,
the nanocomposite composition has an impact strength of greater
than or equal to about 10 kJ/m.sup.2. In another embodiment, the
nanocomposite composition has an impact strength of greater than or
equal to about 15 kJ/m.sup.2. In another embodiment, the
nanocomposite composition has an impact strength of greater than or
equal to about 20 kJ/m.sup.2.
[0049] In yet another embodiment, the nanocomposite composition
also has a Class A surface finish when molded. Molded articles can
be manufactured by injection molding, blow molding, compression
molding, or the like, or a combination comprising at least one of
the foregoing.
[0050] The nanocomposite composition can advantageously be used in
spark plug caps, capacitors, defibrillators, or other articles.
[0051] The following examples, which are meant to be exemplary, not
limiting, illustrate compositions and methods of manufacturing of
some of the various embodiments of the nanocomposite compositions
and the methods of manufacture described herein.
EXAMPLES
Example 1
[0052] Example 1 illustrates the effect on breakdown strength when
various silica nanoparticles are incorporated into a polymeric
composition. The polymeric composition is ULTEM.RTM. commercially
available from General Electric Advanced Materials. The silica
nanoparticles are AEROSIL.RTM. particles commercially available
from Degussa. The particles ranged in size from 7 nanometers to 40
nanometers. The silica nanoparticles tested were
hexamethyldisilazane (HDMZ) treated AEROSIL.RTM. R 812, untreated
AEROSIL.RTM. 380, densified AEROSIL.RTM. 200 W, untreated
AEROSIL.RTM. 200 Pharma, and untreated AEROSIL.RTM. EG 50.
[0053] The particle sizes are shown in the Table 1. TABLE-US-00001
TABLE 1 Particle Identification Particle size (nanometers)
hexamethyldisilazane (HDMZ) treated 7 AEROSIL .RTM. R 812 untreated
AEROSIL .RTM. 380 7.8 densified AEROSIL .RTM. 200 W 12 untreated
AEROSIL .RTM. 200 Pharma 12 untreated AEROSIL .RTM. EG 50 40
[0054] 25 grams of ULTEM.RTM. was first dissolved in 153 grams of
n-methyl pyrrolidone (NMP) solvent to form an ULTEM.RTM. solution.
The silica nanoparticles were added in an amount of about 5 wt %,
based on the total weigh of the ULTEM.RTM. as well as the
nanoparticles. The ULTEM.RTM. solution containing the nanoparticles
was then cast under a clean hood. The solution was dried until
films were formed. The nanocomposite composition films were
subjected to breakdown strength tests by applying an electric field
at a increasing rate of 500 volts per second. The results are shown
in the FIG. 1. From the FIG. I it may be seen that the smaller
particles having a particle size of less than or equal to about 10
nanometers were found to increase the breakdown strength. Surface
treated silica nanoparticles facilitate the development of a higher
breakdown strength. The coarser particles do not display a tendency
to increase the breakdown strength. From the FIG. 1, it may be seen
that the dielectric constant can increase by an amount of about 33%
by decreasing the size of the particles from micrometer sized
particles to nanoparticles.
Example 2
[0055] Example 2 illustrates the effect on breakdown strength when
various weight percents of alumina nanoparticles are incorporated
into a polymeric composition. The alumina nanoparticles were 40
nanometers in size and incorporated into ULTEM.RTM. at 2.5 wt % and
5 wt % as detailed in the Example 1. The results are shown as a bar
graph in FIG. 2. From the FIG. 2, it can be seen that the
incorporation of the nanoparticles increases the dielectric
strength by a factor of at least about 60%.
Example 3
[0056] Example 3 illustrates the increase in the dielectric
constant when alumina nanoparticles are incorporated into a
polymeric composition. The alumina nanoparticles were 40 nanometers
in size and incorporated into ULTEM.RTM. at 5 wt % in a manner
similar to that described in the Example 1. The results are shown
as a graph in FIG. 3. Dielectric constant as a function of
frequency of measurement was measured at room temperature using a
HP4285A LCR dielectric spectrometer manufactured by Hewlett
Packard. From the FIG. 3 it can be seen that the dielectric
constant for the nanocomposite is about 4, which is 25% increase as
compared to that of ULTEM.RTM., which has a dielectric constant (K)
of about 3.15.
[0057] FIG. 4 is a scanning electron micrograph of the dispersed
alumina nanoparticles at 5800.times. magnification.
[0058] From the above examples it may be seen that the breakdown
strength of the nanocomposite composition is increased by at least
50% over a polymeric composition that does not contain the
nanoparticles. In one embodiment, the breakdown strength of the
nanocomposite composition is increased by at least 100% over a
polymeric composition that does not contain the nanoparticles. In
another embodiment, the breakdown strength of the nanocomposite
composition is increased by at least 150% over a polymeric
composition that does not contain the nanoparticles.
[0059] In one exemplary embodiment, the nanocomposite composition
can have an impact strength of greater than or equal to about 10
kJ/m.sup.2, a Class A surface finish and a breakdown strength of at
least 300 V/micrometer.
[0060] In another exemplary embodiment, the nanocomposite
composition can have an impact strength of greater than or equal to
about 10 kJ/m.sup.2, a Class A surface finish and a corona
resistance of about 1000 volts to 5000 volts applied for about 200
hours to about 2000 hours.
[0061] While the invention has been described with reference to
exemplary embodiments, it will be understood by those skilled in
the art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment disclosed as the best mode contemplated for
carrying out this invention, but that the invention will include
all embodiments falling within the scope of the appended
claims.
* * * * *