U.S. patent application number 11/278863 was filed with the patent office on 2006-12-14 for thermoplastic long fiber composites, methods of manufacture thereof and articles derived thererom.
Invention is credited to Paul M. Atkinson.
Application Number | 20060280938 11/278863 |
Document ID | / |
Family ID | 36889275 |
Filed Date | 2006-12-14 |
United States Patent
Application |
20060280938 |
Kind Code |
A1 |
Atkinson; Paul M. |
December 14, 2006 |
THERMOPLASTIC LONG FIBER COMPOSITES, METHODS OF MANUFACTURE THEREOF
AND ARTICLES DERIVED THEREROM
Abstract
An electrically conducting long fiber composite that offers
improved surface resistivity and/or impact strength when used in a
molded product. The composite includes a thermoplastic resin;
carbon long fibers; and glass long fibers; wherein the carbon long
fibers and the glass long fibers have a length of greater then or
equal to about 2 millimeters and wherein the electrically
conducting long fiber composite upon being molded into an article
displays a surface resistivity of less than or equal to about
10.sup.8 ohm per square centimeter and a notched Izod impact
strength of greater than or equal to about 10 kilojoules per square
meter.
Inventors: |
Atkinson; Paul M.;
(Columbus, IN) |
Correspondence
Address: |
GEAM - LNP-CE 08CE;IP LEGAL
ONE PLASTICS AVENUE
PITTSFIELD
MA
01201-3697
US
|
Family ID: |
36889275 |
Appl. No.: |
11/278863 |
Filed: |
April 6, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60689475 |
Jun 10, 2005 |
|
|
|
Current U.S.
Class: |
428/364 |
Current CPC
Class: |
Y10T 428/2913 20150115;
C08K 7/14 20130101; C08K 2201/004 20130101; C08K 7/06 20130101;
H01B 1/24 20130101 |
Class at
Publication: |
428/364 |
International
Class: |
D02G 3/00 20060101
D02G003/00 |
Claims
1. An electrically conducting long fiber composite comprising: a
thermoplastic resin; carbon long fibers; and glass long fibers;
wherein the carbon long fibers and the glass long fibers have a
length of greater then or equal to about 2 millimeters and wherein
the electrically conducting long fiber composite upon being molded
into an article displays a surface resistivity of less than or
equal to about 10.sup.8 ohm per square centimeter and a notched
Izod impact strength of greater than or equal to about 10
kilojoules per square meter.
2. The composite of claim 1, wherein the article has a surface
resistivity of less than or equal to about 10.sup.4 ohm per square
centimeter and a notched Izod impact strength of greater than or
equal to about 15 kilojoules per square meter.
3. The composite of claim 1, wherein the article has a specific
volume resistivity of less than or equal to about 10.sup.4 ohm per
square centimeter and a notched Izod impact strength of greater
than or equal to about 20 kilojoules per square meter.
4. The composite of claim 1, wherein the electrically conducting
long fiber composite has a Class A surface finish.
5. The composite of claim 1, wherein the carbon long fibers are
produced by the pyrolysis of organic precursors in fibrous
form.
6. The composite of claim 1, wherein the carbon long fibers are
derived from pitch, phenolics or polyacrylonitrile.
7. The composite of claim 1, comprising carbon long fibers in an
amount of up to about 50 weight percent, based on the weight of the
electrically conducting long fiber composite.
8. The composite of claim 1, wherein the glass long fibers are
E-glass, A-glass, C-glass, D-glass, R-glass, S-glass or a
combination comprising at least one of the foregoing glass
fibers.
9. The composite of claim 1, comprising glass long fibers in an
amount of up to about 75 weight percent, based on the weight of the
electrically conducting long fiber composite.
10. The composite of claim 1, wherein the thermoplastic polymer is
a polyarylene sulfide, a polyalkyd, a polystyrene, a polyester, a
polyamide, a polyaramide, a polyamideimide, a polyarylate, a
polyarylsulfone, a polyethersulfone, a polyimide, a polyetherimide,
a polytetrafluoroethylene, a polyetherketone, a polyether
etherketone, a polyether ketone ketone, a polybenzoxazole, a
polyoxadiazole, a polybenzothiazinophenothiazine, a
polybenzothiazole, a polypyrazinoquinoxaline, a
polypyromellitimide, a polyquinoxaline, a polybenzimidazole, a
polyoxindole, a polyoxoisoindoline, a polydioxoisoindoline, a
polytriazine, a polypyridazine, a polypiperazine, a polypyridine, a
polypiperidine, a polytriazole, a polypyrazole, a polycarborane, a
polyoxabicyclononane, a polydibenzofuran, a polyphthalide, a
polyacetal, a polyanhydride, a polyvinyl ether, a polyvinyl
thioether, a polyvinyl alcohol, a polyvinyl ketone, a polyvinyl
halide, a polyvinyl nitrile, a polyvinyl ester, a polysulfonate, a
polysulfide, a polysulfonamide, a polyurea, a polyphosphazene, a
polysilazane, a polysiloxane, a polyolefin, or a combination
comprising at least one of the foregoing thermoplastic
polymers.
11. The composite of claim 1, further comprising at least one
electrically conducting filler.
12. The composite of claim 1, wherein the at least one electrically
conducting filler is selected from short carbon fibers having a
length of less than 2 millimeters, carbon black, carbon nanotubes,
single wall carbon nanotubes, multiwall carbon nanotubes, vapor
grown carbon fibers, metallic fillers, electrically conducting
non-metallic fillers, or a combination comprising at least one of
the foregoing electrically conductive fillers.
13. An article derived from the composite of claim 1.
14. The article of claim 13, wherein the article is used in an
automobile.
15. A method of manufacturing an electrically conducting long fiber
composite comprising: blending a carbon long fiber composite with a
glass long fiber composite to produce an electrically conducting
long fiber composite; wherein the carbon long fiber composite
comprises carbon long fibers having a length of greater than or
equal to about 2 millimeters disposed in a first thermoplastic
resin; and wherein the glass long fiber composite comprises glass
long fibers having a length of greater than or equal to about 2
millimeters disposed in a second thermoplastic resin.
16. The method of claim 15, wherein the first thermoplastic resin
is different from the second thermoplastic resin.
17. The method of claim 15, wherein the first thermoplastic resin
is the same as the second thermoplastic resin.
18. The method of claim 15, wherein the electrically conducting
long fiber composite has a surface resistivity of less than or
equal to about 10.sup.8 ohms per square centimeter and a notched
Izod impact strength of greater than or equal to about 15
kilojoules per square meter.
19. A method of manufacturing an electrically conducting long fiber
comprising: pultruding a first roving comprising carbon fibers
through a first impregnation bath comprising a first molten
thermoplastic polymer; impregnating the carbon fibers with the
first molten thermoplastic polymer to produce a carbon long fiber
composite; pultruding a second roving comprising glass fibers
through a second impregnation bath comprising a second molten
thermoplastic polymer; impregnating the glass fibers with the
second molten thermoplastic polymer to produce a glass long fiber
composite; and molding the carbon long fiber composite and the
glass long fiber composite to form an electrically conducting long
fiber composite.
20. The method of claim 19, wherein the first roving is the same as
the second roving and wherein the first impregnation bath is the
same as the second impregnation bath, and wherein the carbon long
fiber composite and the glass long fiber composite are combined to
form the electrically conducting long fiber composite in the
impregnation bath.
21. The method of claim 19, wherein the first roving is different
from the second roving.
22. The method of claim 19, wherein the first thermoplastic polymer
is the same as the second thermoplastic polymer.
23. The method of claim 19, wherein the first thermoplastic polymer
is different from the second thermoplastic polymer.
24. The method of claim 19, wherein the first impregnation bath is
the same as the second impregnation bath.
25. The method of claim 19, wherein the first impregnation bath is
different from the second impregnation bath.
26. The method of claim 19, further comprising pelletizing the
carbon long fiber composite and the glass long fiber composite
prior to molding.
27. The method of claim 19, wherein the carbon long fiber composite
and the glass long fiber composite have fiber lengths of greater
than or equal to about 2 millimeter.
28. The method of claim 19, wherein the electrically conducting
long fiber composite has a surface resistivity of less than or
equal to about 10.sup.8 ohm per square centimeter and a notched
Izod impact strength of greater than or equal to about 10
kilojoules per square meter.
29. A method of manufacturing an electrically conducting composite
comprising: pultruding a roving comprising carbon fibers and glass
fibers through an impregnation bath comprising a molten
thermoplastic polymer; impregnating the carbon fibers and the glass
fibers with the molten thermoplastic polymer to produce an
electrically conducting long fiber composite; and molding the
electrically conducting long fiber composite to form an article,
wherein the article has a surface resistivity of less than or equal
to about 10.sup.8 ohm per square centimeter and a notched Izod
impact strength of greater than or equal to about 15 kilojoules per
square meter.
30. The method of claim 29, further comprising pelletizing the
electrically conducting long fiber composite.
31. The method of claim 29, wherein the carbon fibers and the glass
fibers in the electrically conducting long fiber composite have a
length of greater than or equal to about 2 millimeter.
32. The method of claim 29, wherein the article is used in an
automobile.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional
Application No. 60/689,475, which was filed Jun. 10, 2005, which
application is hereby incorporated by reference in its
entirety.
FIELD OF THE INVENTION
[0002] The present invention is directed to thermoplastic long
fiber composites, methods of manufacture thereof and articles
derived therefrom.
BACKGROUND OF THE INVENTION
[0003] Long fiber composites differ from other composites in that
the fiber reinforcement has a substantially larger aspect ratio
than the fiber reinforcement used in the other composites. The
aspect ratio is defined as the ratio of the length to the diameter
of the fiber. Long fiber composites generally employ glass long
fibers disposed in a thermoplastic polymer. Long fiber composites
can be manufactured in several ways, one of which is known as
pultrusion. Pultruded long fiber composites are used to manufacture
a variety of articles for automobiles, electronics, computers, or
the like.
[0004] Thermoplastic materials and glass fibers are generally
electrically insulating in nature and hence are not useful in
applications where electrostatic dissipation or electromagnetic
shielding is required. Pultruded long fiber composites that use
glass fibers therefore cannot be used in applications where
electrical conductivity is desired. It is therefore desirable to
manufacture long fiber composites that are electrically conducting
and can be used in applications where electrostatic dissipation is
desirable.
SUMMARY OF THE INVENTION
[0005] Disclosed herein is an electrically conducting long fiber
composite including a thermoplastic resin; carbon long fibers; and
glass long fibers; wherein the carbon long fibers and the glass
long fibers have a length of greater then or equal to about 2
millimeters and wherein the electrically conducting long fiber
composite upon being molded into an article displays a surface
resistivity of less than or equal to about 10.sup.8 ohm per square
centimeter and a notched Izod impact strength of greater than or
equal to about 10 kilojoules per square meter.
[0006] Also disclosed herein is a method of manufacturing an
electrically conducting long fiber composite including the step of
blending a carbon long fiber composite with a glass long fiber
composite to produce an electrically conducting long fiber
composite; wherein the carbon long fiber composite includes carbon
long fibers having a length of greater than or equal to about 2
millimeters disposed in a first thermoplastic resin; and wherein
the glass long fiber composite includes glass long fibers having a
length of greater than or equal to about 2 millimeters disposed in
a second thermoplastic resin.
[0007] Disclosed herein as well is a method of manufacturing an
electrically conducting long fiber including the steps of
pultruding a first roving having carbon fibers through a first
impregnation bath having a first molten thermoplastic polymer;
impregnating the carbon fibers with the first molten thermoplastic
polymer to produce a carbon long fiber composite; pultruding a
second roving having glass fibers through a second impregnation
bath having a second molten thermoplastic polymer; impregnating the
glass fibers with the second molten thermoplastic polymer to
produce a glass long fiber composite; and molding the carbon long
fiber composite and the glass long fiber composite to form an
electrically conducting long fiber composite.
[0008] Lastly, disclosed herein is a method of manufacturing an
electrically conducting composite including the steps of pultruding
a roving having carbon fibers and glass fibers through an
impregnation bath having a molten thermoplastic polymer;
impregnating the carbon fibers and the glass fibers with the molten
thermoplastic polymer to produce an electrically conducting long
fiber composite; and molding the electrically conducting long fiber
composite to form an article, wherein the article has a surface
resistivity of less than or equal to about 10.sup.8 ohm per square
centimeter and a notched Izod impact strength of greater than or
equal to about 15 kilojoules per square meter.
DETAILED DESCRIPTION OF THE INVENTION
[0009] The present invention is more particularly described in the
following description and examples that are intended to be
illustrative only since numerous modifications and variations
therein will be apparent to those skilled in the art. As used in
the specification and in the claims, the singular form "a," "an,"
and "the" may include plural referents unless the context clearly
dictates otherwise. Also, as used in the specification and in the
claims, the term "comprising" may include the embodiments
"consisting of" and "consisting essentially of." Furthermore, all
ranges disclosed herein are inclusive of the endpoints and are
independently combinable.
[0010] As used herein, approximating language may be applied to
modify any quantitative representation that may vary without
resulting in a change in the basic function to which it is related.
Accordingly, a value modified by a term or terms, such as "about"
and "substantially," may not to be limited to the precise value
specified, in some cases. In at least some instances, the
approximating language may correspond to the precision of an
instrument for measuring the value.
[0011] Disclosed herein are electrically conducting long fiber
composites that may be used in applications where electrostatic
dissipation and/or electromagnetic shielding are desirable. The
electrically conducting long fiber composites include a
thermoplastic polymer, glass fibers and carbon fibers. Both the
glass fibers and the carbon fibers in the composite are long
fibers, i.e., they have a length of about 2 to about 50
millimeters. A process involving pultrusion is generally used to
manufacture the electrically conducting long fiber composites. The
ability to electrostatically dissipate an electronic charge permits
articles manufactured from these composites to be electrostatically
painted.
[0012] The thermoplastic polymer used in the long fiber composites
is electrically insulating. The thermoplastic polymer may be any
electrically insulating material including, but not limited to, an
oligomer, a polymer, a copolymer, a block copolymer, a random
copolymer, an alternating copolymer, an alternating block
copolymer, a graft copolymer, a star block copolymer, an ionomer, a
dendrimer, or the like, or a combination including at least one of
the foregoing. Examples of suitable thermoplastic polymers are
polyarylene sulfides, polyalkyds, polystyrenes, polyesters,
polyamides, polyaramides, polyamideimides, polyarylates,
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,
polyolefins, polysiloxanes, polybutadienes, polyisoprenes, or the
like, or a combination including at least one of the foregoing
thermoplastic polymers.
[0013] In one exemplary embodiment, the thermoplastic polymer is a
polyamide. Exemplary polyamides are nylon 6, and nylon 6,6. In
another exemplary embodiment, the thermoplastic polymer is a blend
of a polyamide with a polyarylene ether. An exemplary polyarylene
ether is polyphenylene ether manufactured by General Electric
Advanced Materials. In yet another exemplary embodiment, the
thermoplastic polymer is a compatibilized blend of a polyamide with
a polyarylene ether.
[0014] It is beneficial for the thermoplastic polymers employed in
the process to have a melt viscosity of about 1 to about 50
Newton-seconds/square meter (Ns/m.sup.2). In one embodiment, the
melt viscosity of the thermoplastic polymer is less than or equal
to about 30 Ns/m.sup.2. In another embodiment, the melt viscosity
of the thermoplastic polymer is less than or equal to about 10
Ns/m.sup.2. The melt viscosity of the thermoplastic polymer is
dictated by the molecular weight of the polymer.
[0015] The thermoplastic polymer may be used in the long fiber
composite in an amount of about 20 to about 90 weight percent (wt
%), based on the weight of the electrically conducting long fiber
composite. In one embodiment, the thermoplastic polymer may be used
in the long fiber composite in an amount of about 30 to about 70
weight percent (wt %), based on the weight of the electrically
conducting long fiber composite. In another embodiment, the
thermoplastic polymer may be used in the long fiber composite in an
amount of about 35 to about 65 weight percent (wt %), based on the
weight of the electrically conducting long fiber composite. In yet
another embodiment, the thermoplastic polymer may be used in the
long fiber composite in an amount of about 40 to about 60 weight
percent (wt %), based on the weight of the electrically conducting
long fiber composite.
[0016] The electrically conducting long fiber composite includes,
in one embodiment, glass fibers and carbon fibers. The glass fibers
may be continuous fibers. The glass fibers may also be referred to
as a plurality of continuous filaments. By, the term "continuous
fibers" or "plurality of continuous filaments" is meant a fibrous
product in which the fibers are sufficiently long to give a roving
or tow of sufficient strength, under the processing conditions
used, to be hauled through the molten polymer without the frequency
of breakage which would render the process unworkable. Examples of
suitable fibers are glass fiber, carbon fiber, jute and high
modulus synthetic polymer fibers.
[0017] In order to have sufficient strength to be hauled through
the molten polymer of the impregnation system without breakage, the
majority of the continuous fibers of the fibrous product should lie
in one direction so that the fibrous product can be drawn through
molten polymer with the majority of the continuous fibers aligned.
Fibrous products such as mats made up of randomly disposed
continuous fibrous are suitable for the process if at least 40% by
volume of the fibers are aligned in the direction of draw.
[0018] The continuous fibers may be in any form having sufficient
mechanical integrity to be pulled through the molten thermoplastic
polymer. The continuous fibers generally include bundles of
individual fibers or filaments, hereinafter termed "rovings" in
which substantially all the fibers are aligned along the length of
the bundles. Any number of such rovings may be employed. In the
case of commercially available glass rovings each roving may
include up to 8000 or more continuous glass filaments. Carbon fiber
tapes containing up to 6000 or more carbon fibers may be used.
Cloths woven from rovings are also suitable for use in the
electrically conducting long fiber composites. The continuous
fibers may be provided with a surface sizing. Surface sizings are
generally designed to maximize bonding between the fiber and the
matrix polymer. Exemplary sizings are
.gamma.-aminopropyltriethoxysilane, aminosilane and/or
epoxysilane.
[0019] It is generally desirable to wet as much of the surface of
the fiber as possible with the molten polymer. Thus where a fiber
includes a plurality of filaments, the surfaces of the individual
filaments making up the fiber are beneficially wetted for optimum
effect. Where the filament is treated with a sizing or anchoring
agent, the polymer will not be in direct contact with the surface
of the fiber or filament because the sizing is interposed between
the fiber and the polymer. However, providing that good adhesion
between the fiber and the sizing and between the sizing and the
polymer are achieved, the product will have a high flexural modulus
and the sizing will enhance the properties obtained.
[0020] Useful glass fibers can be formed from any type of
fiberizable glass composition and include those prepared from
fiberizable glass compositions commonly known as "E-glass,"
"A-glass," "C-glass," "D-glass," "R-glass," "S-glass," as well as
E-glass derivatives that are fluorine-free and/or boron-free. Most
reinforcement mats have glass fibers formed from E-glass and are
included in the conductive compositions of this invention. Such
compositions and methods of making glass filaments therefrom are
well known to those skilled in the art. Commercially produced glass
fibers generally having nominal filament diameters of about 4 to
about 35 micrometers may be used in the electrically conducting
long fiber composites. In one embodiment, glass fibers generally
having nominal filament diameters of about 9 to about 35
micrometers may be used in the electrically conducting long fiber
composites.
[0021] In one embodiment, the glass fibers include glass strands
that have been coated with a sizing agent. In another embodiment,
the glass fibers are not coated with a sizing agent. The amount of
sizing employed is generally the amount that is sufficient to bind
the glass filaments into a continuous strand. When the fibers are
coated with a sizing agent, it is generally beneficial for the
glass fibers to have a sizing of about 0. 1 to about 5 wt %, based
on the combined weight of the glass fibers and the sizing.
[0022] The glass fibers are, in one embodiment, present in the
electrically conducting long fiber composite in an amount of up to
about 75 wt %, based on the total weight of the electrically
conducting long fiber composite. In one embodiment, the glass
fibers are present in the electrically conducting long fiber
composite in an amount of about 5 about 60 wt %, based on the total
weight of the electrically conducting long fiber composite. In
another embodiment, the glass fibers are present in the
electrically conducting long fiber composite in an amount of about
10 about 40 wt %, based on the total weight of the electrically
conducting long fiber composite.
[0023] Various types of electrically conductive carbon fibers may
also be used in the electrically conducting long fiber composite.
Carbon fibers are generally classified according to their diameter,
morphology, and degree of graphitization (morphology and degree of
graphitization being interrelated). These characteristics are
presently determined by the method used to synthesize the carbon
fiber. For example, carbon fibers having diameters down to about 5
micrometers, and graphene ribbons parallel to the fiber axis (in
radial, planar, or circumferential arrangements) are produced
commercially by pyrolysis of organic precursors in fibrous form,
including phenolics, polyacrylonitrile (PAN), or pitch. The carbon
fibers may optionally be coated with a sizing agent if desired.
[0024] The carbon fibers generally have a diameter of greater than
or equal to about 1,000 nanometers (1 micrometer) to about 30
micrometers. In one embodiment, the fibers can have a diameter of
about 2 to about 10 micrometers. In another embodiment, the fibers
can have a diameter of about 3 to about 8 micrometers.
[0025] Carbon fibers are, in one embodiment, used in amounts of up
to about 60 wt % of the total weight of the electrically conducting
long fiber composite. In one embodiment, carbon fibers are used in
amounts of about 1 wt % to about 50 wt %, based on the weight of
the electrically conducting long fiber composite. In another
embodiment, carbon fibers are used in amounts of about 2 wt % to
about 30 wt %, based on the weight of the electrically conducting
long fiber composite. In yet another embodiment, carbon fibers are
used in amounts of about 3 wt % to about 25 wt %, based on the
weight of the electrically conducting long fiber composite.
[0026] The glass and the carbon fibers in the long fiber composite
can both have long fiber lengths. For purposes of this disclosure,
a long fiber length is about 2 millimeters to about 50 millimeters.
In one embodiment, a glass long fiber can be mixed with a short
carbon fiber. A short fiber length is one that is less than or
equal to about 2 millimeters. The use of short carbon fibers in
combination with carbon long fibers will permit electrical
conductivity to be developed in the long fiber composite at a
loading of the carbon fiber that is different from the loading than
when a carbon long fiber is employed. By using various combinations
of carbon long fibers with short carbon fibers in the electrically
conducting long fiber composite, a variety of physical properties
can be achieved. In an exemplary embodiment, the carbon fiber is a
long fiber.
[0027] Other electrically conductive fillers may be added to the
long fiber composite to enhance electrical conductivity in the
composite. Examples of such electrically conductive fillers are
carbon black, carbon nanotubes, single wall carbon nanotubes,
multiwall carbon nanotubes, vapor grown carbon fibers, metallic
fillers, electrically conducting non-metallic fillers, or the like,
or a combination including at least one of the foregoing
electrically conductive fillers.
[0028] The electrically conductive fillers may be used in loadings
of about 0.01 to about 50 wt %, based on the weight of the
electrically conducting long fiber composite. In one embodiment,
the electrically conductive fillers may be used in amounts of about
0.25 wt % to about 30 wt %, based on the weight of the electrically
conducting long fiber composite. In another embodiment, the
electrically conductive fillers may be used in amounts of about 0.5
wt % to about 20 wt %, based on the weight of the electrically
conducting long fiber composite. In yet another embodiment, the
electrically conductive fillers may be used in amounts of about 1
wt % to about 10 wt %, based on the weight of the electrically
conducting long fiber composite.
[0029] In one embodiment, in one method of manufacturing the
electrically conducting long fiber composite, a roving including
glass and carbon fibers can be jointly and simultaneously pultruded
using a thermoplastic resin as the binder. The thermoplastic resin
may be in the form of a melt or in the form of a powder suspension.
Thus a single pellet manufactured in the pultrusion process will
contain both glass long fibers and carbon long fibers.
Alternatively, separate rovings including the glass fibers and the
carbon fibers can be pultruded in separate steps. The composite
formed after impregnation can be pelletized in a pelletizer.
[0030] The respective pellets contain fibers of a length equal to
the length of the pellet. The pellets generally have a length of
about 2 mm to about 50 mm. An exemplary pellet length is 25 mm. The
pellets containing either glass long fibers or carbon long fibers
can then be combined in a molding machine to produce an article
including the electrically conducting long fiber composite.
[0031] In this embodiment, first roving including carbon fibers is
pultruded through a first impregnation bath including a first
molten thermoplastic polymer. The carbon fibers are impregnated
with the first molten thermoplastic polymer to produce a carbon
long fiber composite. The carbon long fiber composite is pulled
through a first die and then pelletized. Additionally, a second
roving including glass fibers is pultruded through a second
impregnation bath including a second molten thermoplastic polymer.
The glass fibers are impregnated with the second molten
thermoplastic polymer to produce a glass long fiber composite. The
carbon long fiber composite is pulled through a second die and then
pelletized. The glass long fiber composite and the carbon long
fiber composite are then molded into an electrically long fiber
composite in a molding machine. An exemplary molding machine is an
injection-molding machine.
[0032] In one embodiment, the first roving and the second roving
can be the same or different. When the first roving and the second
roving are the same, the carbon fibers and the glass fibers are
contained in the same roving. Similarly, the first impregnation
bath and the second impregnation bath can be the same or different.
In other words, strands of carbon fiber and glass fiber can be
impregnated jointly and simultaneously in the same bath. After
pelletization, the pellets may be molded in an injection-molding
machine to form the electrically conducting long fiber
composite.
[0033] When the first roving is not the same as the second roving,
the first roving and the second roving can be impregnated in
separate baths. The carbon long fiber composite and the glass long
fiber composite are then pelletized and molded together in a
injection-molding machine to form the electrically conducting long
fiber composite.
[0034] In yet another embodiment, in another method of
manufacturing the electrically conducting long fiber composite, the
glass fiber can be pultruded separately in a single step to form
glass long fiber composite pellets. Similarly, the carbon fiber can
be pultruded separately in a single step to form the carbon long
fiber composite pellets. However, the molten thermoplastic resin
that impregnates the glass long fiber composite and the carbon long
fiber composite may contain an electrically conducting filler. Thus
the electrically conducting long fiber composite includes
additional electrically conducting filler in addition to the carbon
long fibers.
[0035] The electrically conducting long fiber composite may be
molded to have a smooth surface finish. In one embodiment, the
electrically conducting long fiber composite may have a Class A
surface finish after molding. Articles molded from the electrically
conducting long fiber composite may have an electrical specific
volume resistivity (SVR) of less than of equal to about 10.sup.12
ohm-cm. In one embodiment, the molded articles may have an
electrical volume resistivity of less than of equal to about
10.sup.8 ohm-cm. In another embodiment, the molded articles may
have an electrical volume resistivity of less than of equal to
about 10.sup.5 ohm-cm. The molded articles may also have a surface
resistivity of less than or equal to about 10.sup.12 ohm per square
centimeter (ohms/square). In one embodiment, the molded articles
may also have a surface resistivity of less than or equal to about
10.sup.8 ohm per square centimeter. In another embodiment, the
molded articles may also have a surface resistivity of less than or
equal to about 10.sup.4 ohm per square centimeter. In yet another
embodiment, the molded articles may also have a surface resistivity
of less than or equal to about 10.sup.2 ohm per square
centimeter.
[0036] The electrically conducting long fiber composites also
display mechanical properties that are favorable for a large number
of high temperature, high strength applications. In one embodiment,
the electrically conducting long fiber composite has a notched Izod
impact strength of greater than or equal to about 10 kilojoules per
square meter (kJ/m.sup.2). In another embodiment, the electrically
conducting long fiber composites also advantageously have a notched
Izod impact strength of greater than or equal to about 15
kJ/m.sup.2. In yet another embodiment, the electrically conducting
long fiber composites also advantageously have a notched Izod
impact strength of greater than or equal to about 20 kJ/m.sup.2. In
still another embodiment, the electrically conducting long fiber
composites also advantageously have a notched Izod impact strength
of greater than or equal to about 30 kJ/m.sup.2.
[0037] The electrically conducting long fiber composites
advantageously display a flexural modulus of greater than or equal
to about 8 gigapascals (GPa). In one embodiment, the electrically
conducting long fiber composites display a flexural modulus of
greater than or equal to about 10 GPa.
[0038] As noted above, the thermoplastic composition described
herein can be advantageously used in the manufacture of a variety
of commercial articles. In one embodiment, an exemplary article is
a chip tray. They can also be used in other applications where
dimensional stability and/or electrical conductivity are beneficial
such as automobiles interiors, aircraft, lampshades, or the like.
In another embodiment, an exemplary article is an automotive
exterior body panel that is to be electrostatically painted.
[0039] The following examples, which are meant to be exemplary, not
limiting, illustrate compositions and methods for manufacturing the
electrically conducting long fiber composite described herein.
EXAMPLES
Example 1
[0040] This example was conducted to demonstrate the manufacture of
a pultruded electrically conducting long fiber composite that
contains both glass long fibers and carbon long fibers. Carbon long
fibers and glass long fibers that were first pultruded through
nylon 6,6 to create a pultruded composite. The pultruded composite
contained 25 wt % carbon long fiber and 30 wt % glass long fiber.
The pultruded composite was either blended with VERTON RF-7007 EM
HS BK9001.RTM., a nylon 6,6 containing only glass long fiber
manufactured by General Electric Advanced Materials, or with
STAT-KON R-1 HI.RTM., a nylon 6,6 containing carbon black also
manufactured by General Electric Advanced Materials to create the
long fiber composite. The long fiber composites were in the form of
rectangular molded plaques having dimensions of 10
centimeters.times.12.5 centimeters. The samples were molded on a
220 Ton Milacron injection molding machine. Table 1 shows the
molded compositions and the specific volume resistivity for these
samples.
[0041] Sample #s 1 through 7 from Table 1 are molded compositions
that were derived by molding the pultruded composite with the
VERTON RF-7007 EM HS BK9001.RTM., while the Sample #s 8 through 15
in Table 1 were obtained by blending the pultruded composite with
STAT-KON R-1HI.RTM.. Samples #s 1 through 15 contain from 3.5 to 11
wt % carbon fiber, based on the total weight of the electrically
conducting long fiber composite.
[0042] Table 1 shows the surface resistivity of the samples.
Surface resistivity measurements were made by using a Keithley
resistivity meter. The Table 1 below illustrates that a
surprisingly low weight fraction of conductive additive can be used
and still retain sufficient conductivity. TABLE-US-00001 TABLE 1
Carbon Carbon Surface Fiber Black Glass Resistivity Sample# (wt %)
(wt %) (wt %) (Ohm/square) 1 3.5 0 34.2 3.10E+04 2 4.4 0 34
1.55E+04 3 5.3 0 33.8 7.76E+03 4 5.7 0 33.7 2.00E+03 5 7 0 33.4
2.90E+03 6 8.8 0 33 4.40E+02 7 11 0 32.5 2.50E+02 8 2.2 1.8 31
4.80E+05 9 2.75 2.25 30 2.80E+04 10 2.2 2.7 29.25 2.30E+04 11 3.3
2.7 29 5.50E+03 12 4.4 2.7 28.75 8.10E+02 13 3.3 3.6 27.25 4.40E+03
14 4.4 3.6 27 4.10E+02 15 5.5 4.5 25 4.40E+02
[0043] The results from Table 1 show that the Samples #'s 1 to 7
that contain only the carbon long fiber and the glass long fiber
have a surface resistivity that is generally equal to or better
than Samples # 8-15 that contain carbon black in addition to the
carbon long fiber and the glass long fiber.
Example 2
[0044] This example was undertaken to compare the properties of
electrically conductive composites that contain carbon long fibers
versus those that contain carbon short fibers. As noted above,
carbon long fibers have lengths of greater than or equal to about 2
millimeters, while carbon short fibers have lengths of less than 2
millimeters. The plaques for testing were manufactured by injection
molding a blend of a glass long fiber composite with either a
carbon long fiber composite or a carbon short fiber composite. The
air burnout indicates how much glass fiber is present; the nitrogen
burnout indicates how much total fiber is present. Details of the
test are shown in Table 2 below. TABLE-US-00002 TABLE 2 Properties
Sample # 16 Sample # 17 Carbon fiber form Long Short Air burnout, %
31.74 31.6 Nitrogen burnout, % 44.37 43.1 Specific gravity 1.45
1.46 Tensile strength, MPa 246.1 266 Tensile elongation, % 1.47
2.02 Tensile modulus, GPa 20 21.5 Flexural strength, MPa 381.1 372
Flexural modulus, GPa 17.64 16.6 Notch Izod, kJ/m.sup.2 35.3
28.4
[0045] From the Table 2 it may be seen that the comparative sample
(Sample #17) having carbon long fibers displays improved impact and
flexural properties over the sample that has carbon short fibers.
Thus an electrically conducting long fiber composite including
glass long fibers and carbon long fibers produces superior
properties over a composite that includes glass long fibers and
carbon short fibers.
Example 3
[0046] This example was undertaken to demonstrate that electrically
conducting long fiber composites can be manufactured with a variety
of different resins. Table 4 shows two compositions, Sample #18
that includes nylon 6,6 and Sample #19 that includes a
compatibilized blend of nylon 6,6 with polyphenylene ether. The
compositions and the properties for the respective electrically
conducting long fiber composites are shown in the Table 3 below.
TABLE-US-00003 TABLE 3 Sample # 18 Sample # 19 Composition (wt %)
(wt %) Nylon 6,6 65 32.5 Polyphenylene ether 32.5 Carbon long
fibers 10 10 Glass long fibers 25 25 Properties Specific gravity
(g/cc) 1.35 1.32 Tensile strength, MPa 197.2 183.5 Tens elongation,
% 1.52 1.41 Tens modulus, GPa 17.5 14.8 Notch Izod, kJ/m.sup.2
21.95 21.9 Surface resistivity, ohm/sq 2.50E+03 6.20E+02
[0047] From the Table 3, it may be seen that electrically
conducting long fiber composites can be advantageously manufactured
with a variety of thermoplastic resins.
Example 4
[0048] This example demonstrates that the electrically conducting
long fiber composites can be manufactured with a wide range of
carbon long fiber loadings. The amount of the carbon long fiber is
varied from about 3.5 to about 10.5 wt %, based on the total weight
of the electrically conducting long fiber composite. The amount of
glass long fiber was varied from about 19 to about 48 wt %, based
on the total weight of the electrically conducting long fiber
composite. These examples also show that the invention is not
limited to a narrow range of overall fiber loading. These examples
are shown in Table 4. TABLE-US-00004 TABLE 4 Sample Sample Sample
Sample Sample Sample Sample Sample Sample #20 #21 #22 #23 #24 #25
#26 #27 #28 Composition Nylon 6,6 wt % 70.1 70.2 70.15 58.6 61.8
59.6 50.05 49.2 50 Long Glass Fiber, wt % 19.34 26.28 22.81 34.36
34.68 29.84 42.91 47.28 39.44 Long Carbon Fiber, wt % 10.56 3.52
7.04 7.04 3.52 10.56 7.04 3.52 10.56 Total Long Fiber, wt % 29.9
29.8 29.85 41.4 38.2 40.4 49.95 50.8 50 Properties Nitrogen TGA
burnout, % 30.4 30.8 32.3 44.2 41.7 40.2 52.8 52.4 52.3 Specific
gravity 1.311 1.359 1.367 1.461 1.448 1.427 1.569 1.594 1.537
Tensile strength, MPa 196.57 185.13 180.11 233.75 225.87 233.34
231.56 261 226.57 Tensile elongation, % 1.14 1.56 1.38 1.46 1.7 1.3
1.18 1.46 0.96 Tensile modulus, GPa 20.4 12.9 14 17.9 15.1 20.6
22.5 21.8 27.7 Flexural strength, MPa 297.73 288.82 286.39 355.01
324.77 348.14 367.1 378.59 375.64 Flexural Modulus, GPa 12.8 11.6
11.4 15 12.7 15.9 18.5 16.4 19.4 Izod notched impact, kJ/m.sup.2
16.55 15.65 19.44 33.92 32 25.63 34.39 36.55 38.99 Surface
Resistivity (ohm/sq) 0.9 1.1 1.7 0.7 4.6 1.1 1.1 5.1 0.9
[0049] The results shown in the Table 5 demonstrate that the carbon
long fibers produce advantageous mechanical and electrical
properties in the electrically conducting long fiber composites.
These synergistic properties cannot generally be achieved in other
long fiber composites that contain only short carbon fibers, carbon
powders such as carbon black, carbon nanotubes or the like. The
electrically conducting long fiber composites can be advantageously
used in automotive applications such as exterior body panels that
are electrostatically painted. They may also be used in integrated
circuit trays or the like.
[0050] 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.
* * * * *