U.S. patent application number 15/655073 was filed with the patent office on 2017-11-16 for functionally graded polymer articles and methods of making same.
The applicant listed for this patent is SABIC Global Technologies B.V.. Invention is credited to Sadasivam Gopalakrishnan, Poovanna Theethira Kushalappa, Sudhakar Ramamoorthy Marur, Hariharan Ramalingam.
Application Number | 20170326823 15/655073 |
Document ID | / |
Family ID | 50390140 |
Filed Date | 2017-11-16 |
United States Patent
Application |
20170326823 |
Kind Code |
A1 |
Kushalappa; Poovanna Theethira ;
et al. |
November 16, 2017 |
FUNCTIONALLY GRADED POLYMER ARTICLES AND METHODS OF MAKING SAME
Abstract
Disclosed herein are methods for manufacturing a functionally
graded polymer material. A method comprises preparing a melted
polymer mixture comprising a thermoplastic polymer and a magnetic
filler; molding the melted polymer mixture; and applying a magnetic
field to a portion of the melted polymer mixture to form the
functionally graded article, wherein as the melted polymer mixture
flows into the mold, the melted polymer mixture comes into contact
with the magnet field. Another method comprises molding the melted
polymer mixture; and applying a magnetic field from a first magnet
to a first portion of the melted polymer mixture and applying a
magnetic field from a second magnet to a second portion of the
melted polymer mixture to form the functionally graded article,
wherein the first magnet and the second magnet are positioned in a
manner such that the magnetic field produced by each are
nonoverlapping.
Inventors: |
Kushalappa; Poovanna Theethira;
(Bangalore, IN) ; Marur; Sudhakar Ramamoorthy;
(Bangalore, IN) ; Ramalingam; Hariharan;
(Bangalore, IN) ; Gopalakrishnan; Sadasivam;
(Tamil Nadu, IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SABIC Global Technologies B.V. |
Bergen op Zoom |
|
NL |
|
|
Family ID: |
50390140 |
Appl. No.: |
15/655073 |
Filed: |
July 20, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13827012 |
Mar 14, 2013 |
9731456 |
|
|
15655073 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B29C 70/62 20130101;
B29C 70/88 20130101; C08J 5/041 20130101; C08J 2323/06 20130101;
C08K 2003/2272 20130101; C08K 2003/0856 20130101; C23C 26/00
20130101; C08K 2003/2293 20130101; C08J 2325/06 20130101; C08J
2367/04 20130101; C08K 2201/01 20130101; C08J 2369/00 20130101;
C08K 9/04 20130101; C08K 2003/0862 20130101; C08J 5/00 20130101;
C08K 9/10 20130101; B29C 70/882 20130101; B29K 2995/0003 20130101;
C08K 2003/2275 20130101; C08J 2323/12 20130101; B29C 45/0013
20130101; C08J 2367/02 20130101; C08K 9/02 20130101; C08K 2003/0843
20130101 |
International
Class: |
B29C 70/62 20060101
B29C070/62; B29C 70/88 20060101 B29C070/88; B29C 45/00 20060101
B29C045/00; C08J 5/00 20060101 C08J005/00; C08K 9/10 20060101
C08K009/10; C23C 26/00 20060101 C23C026/00; C08K 9/02 20060101
C08K009/02; C08K 9/04 20060101 C08K009/04; C08J 5/04 20060101
C08J005/04; B29C 70/88 20060101 B29C070/88 |
Claims
1. A method of manufacturing a functionally graded article,
comprising: preparing a melted polymer mixture comprising a
thermoplastic polymer and a magnetic filler, wherein the magnetic
filler is dispersed in the thermoplastic polymer; molding the
melted polymer mixture; and applying a magnetic field to a portion
of the melted polymer mixture to form the functionally graded
article, wherein as the melted polymer mixture flows into the mold,
the melted polymer mixture comes into contact with the magnet
field.
2. The method of claim 1, wherein the magnet is an
electromagnet.
3. The method of claim 1, wherein the functionally graded article
has a magnetic filler gradient and wherein the filler gradient is
formed through a portion of a thickness of the functionally graded
article, wherein the portion of the thickness is less than the
entire thickness of the functionally graded article.
4. The method of claim 1, wherein the magnetic filler is modified
by coating, chemical modification, or a combination comprising at
least one of the foregoing.
5. The method of claim 1, wherein the magnetic field is applied
from a magnet incorporated into the mold.
6. The method of claim 1, wherein the magnetic filler comprises
magnetic particles, magnetic fibers, iron, nickel, cobalt,
ferrites, rare earth magnets, or a combination comprising at least
one of the foregoing.
7. The method of claim 6, wherein the magnetic fibers are metal
fibers, metal-coated fibers or a combination of metal fibers and
metal-coated fibers.
8. The method of claim 1, further comprising maintaining the melted
polymer in a melted state until the functionally graded article has
attained a desired functional gradation.
9. A method of manufacturing a functionally graded article,
comprising: preparing a melted polymer mixture comprising a
thermoplastic polymer and a magnetic filler, wherein the magnetic
filler is dispersed in the thermoplastic polymer; molding the
melted polymer mixture; and applying a magnetic field from a first
magnet to a first portion of the melted polymer mixture and
applying a magnetic field from a second magnet to a second portion
of the melted polymer mixture to form the functionally graded
article; wherein the first magnet and the second magnet are
positioned in a manner such that the magnetic field produced by
each are nonoverlapping.
10. The method of claim 9, wherein the first and second magnets are
electromagnets.
11. The method of claim 9, wherein the functionally graded article
has a magnetic filler gradient and wherein the filler gradient is
formed through a portion of a thickness of the functionally graded
article, wherein the portion of the thickness is less than the
entire thickness of the functionally graded article.
12. The method of claim 9, wherein the first and/or second magnet
is placed within the mold.
13. The method of claim 9, wherein the magnetic filler is further
modified by coating, chemical modification, or a combination
comprising at least one of the foregoing.
14. The method of claim 9, wherein the magnetic field from at least
one of the first magnet and the second magnet is applied as the
melted polymer mixture flows into the mold.
15. The method of claim 9, wherein the magnetic filler comprises
magnetic particles, magnetic fibers, iron, nickel, cobalt,
ferrites, rare earth magnets, or a combination comprising at least
one of the foregoing.
16. The method of claim 15, wherein the magnetic fibers are metal
fibers, metal-coated fibers or a combination of metal fibers and
metal-coated fibers.
17. The method of claim 9, further comprising maintaining the
melted polymer in a melted state until the functionally graded
article has attained a desired functional gradation.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 13/827,012, filed Mar. 14, 2013, which is incorporated herein
by reference in its entirety.
BACKGROUND
[0002] The present disclosure relates to functionally graded
polymer materials and to methods of making functionally graded
polymer articles.
[0003] Functionally graded materials are characterized by change in
the composition and structure of a material over volume.
Traditionally, processes of making functionally graded materials
have been limited to manufacturing techniques such as impregnation
of porous materials with functional nanoparticles, formation of
organic/inorganic nano-structured coatings by electrophoretic
disposition (EPD), electrodeposition of metal matrix composite
(MMC), chemical vapor deposition, and functionally graded thermal
barrier (TGM TBC) coatings, electric field assisted processing of
materials, and dispensing systems for thermosetting and
thermoplastic adhesives, to name a few. However, these methods are
typically slow and expensive.
[0004] It is therefore desirable to develop methods for making
functionally graded polymer articles which are both efficient and
cost-effective.
SUMMARY
[0005] Disclosed herein are methods of making functionally graded
polymer articles and articles made therefrom.
[0006] In one embodiment, a method of manufacturing a functionally
graded article, comprising, preparing a melted polymer mixture
comprising a thermoplastic polymer and a magnetic filler, wherein
the magnetic filler is dispersed in the thermoplastic polymer;
molding the melted polymer mixture; and applying a magnetic field
to a portion of the melted polymer mixture to form the functionally
graded article, wherein as the melted polymer mixture flows into
the mold, the melted polymer mixture comes into contact with the
magnet field.
[0007] In another embodiment, a method of manufacturing a
functionally graded article, comprising, preparing a melted polymer
mixture comprising a thermoplastic polymer and a magnetic filler,
wherein the magnetic filler is dispersed in the thermoplastic
polymer; molding the melted polymer mixture; and applying a
magnetic field from a first magnet to a first portion of the melted
polymer mixture and applying a magnetic field from a second magnet
to a second portion of the melted polymer mixture to form the
functionally graded article, wherein the first magnet and the
second magnet are positioned in a manner such that the magnetic
field produced by each are nonoverlapping.
[0008] These and other features and characteristics are more
particularly described below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The following is a brief description of the drawings wherein
like elements are numbered alike and which are presented for the
purposes of illustrating the exemplary embodiments disclosed herein
and not for the purposes of limiting the same.
[0010] FIG. 1 is an illustration of an exemplary electromagnet
induction mechanism and the gradation of magnetic fillers in the
polymer matrix.
[0011] FIG. 2 is an image showing the arrangement of migrated steel
particles in polyvinyl acetone (PVA) paste following the
application of a magnetic field.
[0012] FIG. 3 is an image showing a section of a molded polymer
cast in an aluminum mold.
[0013] FIG. 4 is an image showing an exemplary position of an
Alnico pot magnet in a molded polypropylene sample with a circular
band of magnetic filler surrounding the magnet.
[0014] FIG. 5 is an image showing an exemplary position of an
Alnico pot magnet in a molded polybutylene terephthalate sample
with a circular band of magnetic filler surrounding the magnet.
[0015] FIG. 6 is an image showing the position of polymer Samples 1
and 2 relative to the position of the magnet.
[0016] FIG. 7 is a an image of a molded polymer containing steel
filler indicating regions 1, 2, and 3 that were analyzed by optical
microscopy to determine the localized concentration of the steel
filler.
[0017] FIG. 8 is a graph showing the concentration of steel filler
present in each of regions 1, 2, and 3.
DETAILED DESCRIPTION
[0018] Disclosed herein, in various embodiments, are methods for
manufacturing functionally graded polymer materials.
[0019] As described herein, a functionally graded polymer refers to
materials having a polymer matrix and which exhibit spatial
variations in composition and/or microstructure through the volume
of the polymer matrix. The structure of the functionally graded
polymer results in continuously or discretely changing properties
(e.g., thermal, mechanical, chemical, functional, visual
properties, or a combination comprising at least one of the
foregoing). Functionally graded materials are ideal candidates for
applications involving extreme thermal gradients, ranging from
thermal structures in space shuttles to cutting tool inserts.
[0020] A method for manufacturing functionally graded polymer
materials can comprise a gradient of filler that is either magnetic
or which can be influenced by a magnetic field. The functionally
graded polymer materials can be formed by preparing a melted
polymer mixture comprising a thermoplastic polymer and a magnetic
filler dispersed in the polymer, molding the melted polymer
mixture, and subsequently applying a magnetic field to a portion of
the melted polymer mixture.
[0021] The magnetic field can be applied at strategic portions,
e.g. locations, of the melted polymer mixture to facilitate the
formation of a filler gradient at localized positions within the
polymer matrix. The magnetic field alters distribution of the
magnetic filler within the molten polymer to concentrate the
magnetic filler in a select region of the polymer matrix. The
location of the gradient in the functionally graded polymer mixture
can vary based upon the placement of the magnetic field. In this
manner, a functionally graded polymer material can be prepared from
a single, homogeneous polymer mixture.
[0022] The magnetic fields disclosed herein are in addition to
those produced by the earth's magnetic field. In general, a
magnetic field is the region in the area of a magnet, an electric
current, or a changing electric field, in which magnetic forces are
observed. Magnetic field strength, or magnetic field intensity,
corresponds to the density of magnetic field lines (e.g. lines of
magnetic force) surrounding the magnet. Magnetic flux refers to the
total number of magnetic field lines penetrating a given material,
while the magnetic flux density refers to the number of lines of
magnetic force that pass through a plane of a given area at a right
angle. The flux density is equal to the magnetic field strength
times the magnetic permeability in the region in which the field
exists.
[0023] The magnetic field can be applied to the melted polymer
mixture using a magnet. Various types of magnets can be used
including, for example, a permanent magnet, an electromagnet, a
superconductive electromagnet, or a combination comprising at least
one of the foregoing magnets. Permanent magnets are made from a
magnetized material that creates a persistent magnetic field. An
electromagnet is made from a coil of wire around a core of
ferromagnetic material. As an electric current passes through the
wire, a magnetic field is generated and is enhanced by the
ferromagnetic material. In an electromagnet, the magnetic field is
produced by the flow of electric current through the wire. A
superconducting magnet is an electromagnet made from coils of
superconducting wire. The superconducting wire is capable of
conducting larger electric currents as compared to wire materials
wrapped around ordinary electromagnets. As a result,
superconductive magnets are capable of generating intense magnetic
fields.
[0024] The magnet can be disposed adjacent to a portion of the
melted polymer mixture such that a magnetic field passes through
the mixture (e.g., through a desired region of the mixture or the
whole mixture) and alters distribution of the magnetic filler
within the molten polymer. To do so, the magnet can be positioned
in a manner that will enable contact between the melted polymer
mixture and the magnet field. For example, the magnet can be
strategically placed within the mold, and as the melted polymer
mixture flows into the mold, the mixture comes into contact with
the magnet field. Alternatively, the melted polymer mixture can be
allowed to fill the mold and the magnet can then be strategically
positioned adjacent to a portion of the melted polymer mixture. The
particles of magnetic filler, under the influence of the magnetic
field, are drawn through the molten polymer mixture along magnetic
field lines in the direction of the magnet e.g. the source of the
magnetic field. That is, the magnetic field alters distribution of
the magnetic filler within the molten polymer to concentrate the
magnetic filler in an area of the polymer. As a result a magnetic
filler gradient is formed. The position of the magnet with relation
to the polymer matrix during molding of the melted polymer mixture
therefore can determine the location at which the filler gradient
will be formed in the polymer matrix.
[0025] The specific magnetic intensity desired for a given
application can readily be determined based upon the type polymer
(e.g., the viscosity), the thickness of the area to be functionally
graded, and the type of polymer.
[0026] The filler gradient can be formed through a thickness of the
functionally graded polymer material. In this context, a filler
gradient refers to the rate at which the filler amount increases or
decreases across a thickness of the functionally graded polymer
material. The method can be used to form functionally graded
polymer materials having a gradient in filler particle size,
composition, and/or density. For example, the method can provide a
gradient in filler density from a first surface (e.g. an inner or
outer surface) to a second surface (e.g. outer or inner surface) of
the functionally graded polymer material such that the filler
density at the first surface of the polymeric material is the
greatest, and the filler density at the second surface (e.g.
opposite the first surface) is the lowest. Stated another way, the
filler can be concentrated at or near a surface of the functionally
graded polymer.
[0027] The filler gradient can be formed across the entire
thickness (e.g. 100%), or alternatively, across a portion (e.g.
region) of the thickness of the functionally graded polymer
material. For example, the filler gradient can be formed across 10%
to 25% of the thickness, more specifically across 25% to 33% of the
thickness, even more specifically 33% to 50% of the thickness, and
yet even more specifically 50 to 75% of the thickness of the
functionally graded polymer material.
[0028] The distribution and concentration of the magnetic filler in
the molten polymer can be controlled by varying parameters such as
the magnetic field strength, magnetic field pattern, magnetic field
direction, and a combination comprising at least one of the
foregoing parameters. Additional process parameters that can also
affect the distribution of the magnetic filler once the magnetic
field is applied to the melted polymer mixture include, but are not
limited to, melt temperature, mold surface temperature, rate of
cooling, the point of injection, the velocity at which the
polymeric material is injected into the mold (i.e. injection
speed), and the viscosity of the melted polymer mixture. The
specific parameters, which are dependent upon the specific polymer
and the specific magnetic filler, can readily be determined by an
artisan without undue experimentation.
[0029] The magnetic field can be applied prior to the curing or
hardening of the melted polymer mixture. Following the magnetic
orientation of the filler, the melted polymer material in the mold
can then be cured or hardened in order to fix the filler within the
polymer matrix and form the functionally graded polymer
material.
[0030] As described herein, methods of manufacturing a functionally
graded polymer material can include preparing a melted polymer
mixture comprising a polymer (e.g., thermoplastic polymer) and
magnetic filler dispersed therein. The polymer can be an oligomer,
a homopolymer, a copolymer, a block copolymer, an alternating block
copolymer, a random polymer, a random copolymer, a random block
copolymer, a graft copolymer, a star block copolymer, a dendrimer,
or the like, or a combination comprising at least one of the
foregoing. The polymer can also be a blend of polymers, copolymers,
terpolymers, or combinations comprising at least one of the
foregoing thermoplastic polymers.
[0031] Examples of the thermoplastic polymers are polyacetals,
polyolefins, polyacrylics, polycarbonates, polystyrenes,
polyesters, polyamides, polyamideimides, polyarylates,
polyarylsulfones, polyethersulfones, polyphenylene sulfides,
polyvinyl chlorides, polysulfones, polyimides, polyetherimides,
polytetrafluoroethylenes, polyetherketones, polyether etherketones,
polyether ketone ketones, polybenzoxazoles, 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, styrene acrylonitrile,
acrylonitrile-butadiene-styrene (ABS), polyethylene terephthalate,
polybutylene terephthalate, polyurethane, ethylene propylene diene
rubber (EPR), polytetrafluoroethylene, fluorinated ethylene
propylene, perfluoroalkoxyethylene, polychlorotrifluoroethylene,
polyvinylidene fluoride, or a combination comprising at least one
of the foregoing thermoplastic polymers.
[0032] Examples of blends of thermoplastic polymers include
acrylonitrile-butadiene-styrene/nylon,
polycarbonate/acrylonitrile-butadiene-styrene, acrylonitrile
butadiene styrene/polyvinyl chloride, polyphenylene
ether/polystyrene, polyphenylene ether/nylon,
polysulfone/acrylonitrile-butadiene-styrene,
polycarbonate/thermoplastic urethane, polycarbonate/polyethylene
terephthalate, polycarbonate/polybutylene terephthalate,
thermoplastic elastomer alloys, nylon/elastomers,
polyester/elastomers, polyethylene terephthalate/polybutylene
terephthalate, acetal/elastomer,
styrene-maleicanhydride/acrylonitrile-butadiene-styrene, polyether
etherketone/polyethersulfone, polyether etherketone/polyetherimide
polyethylene/nylon, polyethylene/polyacetal, or a combination
comprising at least one of the foregoing thermoplastic polymer
blends.
[0033] More particularly, the thermoplastic polymer used in the
core composition can include, but is not limited to, polycarbonate
resins (e.g., LEXAN.TM. resins, commercially available from SABIC's
Innovative Plastics business), polyphenylene ether-polystyrene
blends (e.g., NORYL.TM. resins, commercially available from SABIC's
Innovative Plastics business), polyetherimide resins (e.g.,
ULTEM.TM. resins, commercially available from SABIC's Innovative
Plastics business), polybutylene terephthalate-polycarbonate blends
(e.g., XENOY.TM. resins, commercially available from SABIC's
Innovative Plastics business), copolyestercarbonate resins (e.g.
LEXAN.TM. SLX resins, commercially available from SABIC's
Innovative Plastics business), acrylonitrile butadiene styrene
resins (e.g., CYCOLOY.TM. resins, commercially available from
SABIC's Innovative Plastics business) and combinations comprising
at least one of the foregoing resins.
[0034] The filler can be a magnetic filler, or alternatively, one
that can be influenced by a magnetic field. Fillers generally fall
into one of four different categories with regard to their
susceptibility to a magnetic field: ferromagnetic, paramagnetic,
diamagnetic, and non-magnetic. Ferromagnetic fillers have a strong
susceptibility and attraction to a magnetic field and can retain
magnetic properties once the field is removed. Paramagnetic fillers
are those that have a low susceptibility to and are weakly
influenced by a magnetic field. Diamagnetic fillers are negligibly
affected by magnetic fields, and can be slightly repelled by a
magnetic field, while non-magnetic fillers are those having
essentially no susceptibility to a magnetic field whatsoever. The
magnetic state (or phase) of a material can be affected by
variables such as, for example, temperature, applied pressure, the
applied magnetic field, and the like. The filler should be
influenced by a magnetic field to a degree that attains (for the
magnetic field being used) the desired gradation in the
article.
[0035] The magnetic fillers disclosed herein are responsive to
magnetic fields. Any metal that is magnetic or can be influenced by
a magnetic field can be used as the metal coating of the
metal-coated fiber. Examples of such magnetic fillers include iron,
nickel, cobalt, vanadium, molybdenum, combinations including at
least one of the foregoing, specifically, vanadium, and molybdenum.
Examples of alloys include Alnico (magnet alloy comprising
aluminum, iron, cobalt and nickel), steel, samarium cobalt (SmCo),
neodymium iron boron (NdFeB), ferrites, Fe.sub.2O.sub.3
(FeOFe.sub.2O.sub.3, NiOFe.sub.2O.sub.3, CuOFe.sub.2O.sub.3,
MgOFe.sub.2O.sub.3, etc.), MnBi, MnSb, Awaruite (Ni.sub.2Fe to
Ni.sub.3Fe), CoFe, CrO.sub.2, MnAs, and a combination comprising at
least one of the foregoing alloys. Alloys that include a
combination of magnetic materials and non-magnetic materials may
also be used. The non-magnetic portion present in the alloys may be
metals, ceramics, or polymers.
[0036] The magnetic fillers can have various physical forms and
chemical forms. Any of these various physical or chemical forms can
be used. For example, the magnetic filler can be in the form of
magnetic particles. The magnetic particles can be present in the
form of rods, tubes, whiskers, fibers, platelets, spheres, cubes,
or the like, or other geometrical forms, as well as combinations
comprising at least one of the foregoing. The magnetic filler can
be an unmodified filler. Alternatively, the magnetic filler can be
a modified magnetic filler. The magnetic fiber can comprise metal
filler, metal-coated filler, or a combination thereof. Examples of
core materials for the metal-coated fiber can include vitreous
mineral such as glass, silicates of aluminum, silicates of
magnesium, silicates of calcium, and the like; and inorganic carbon
materials such as graphite, carbon powders, carbon fibers, mica,
and the like; as well as combinations comprising at least one of
the foregoing. The metal coating (which can be an encapsulant) can
be any of the metals mentioned above as magnetic materials.
[0037] The magnetic filler can be at least partially coated or
encapsulated with various polymer materials. Coating of the
magnetic filler with a polymer material can, for example, improve
compatibility between the magnetic filler and the polymer matrix.
Alternatively, the coating or encapsulating polymer material can be
selected to minimize compatibility between the filler and the
thermoplastic polymer depending upon the desired outcome. Examples
of polymer materials that can be used to coat the magnetic filler
comprise siloxane based materials, organic materials (e.g.,
aliphatic or aromatic) with different functional moieties such as
--COOR, --CH.sub.3, --NH.sub.2, --CO--R--CO, or a combination
comprising at least one of the foregoing coating polymer materials.
R can be alkyl or aryl or halo groups.
[0038] Various types of additional materials can also be used to
encapsulate the magnetic filler. Materials that can be used to
encapsulate the magnetic filler comprise silicone rubbers,
polymeric materials (such as acrylonitrile-butadiene-styrene (ABS),
ethylene propylene diene monomer (EPDM), styrene-acrylonitrile
(SAN), and combinations comprising at least one of the foregoing.
Examples of such materials include fine filler particles such as
titanium dioxide (TiO.sub.2), talc, calcium carbonate, and a
combination comprising at least one of the foregoing encapsulating
or coating materials.
[0039] By chemically modifying (e.g. functionalizing) the magnetic
fillers with functionalizing elements, different types of
properties can be achieved across the filler gradient. The fillers
can be functionalized by chemically attaching materials directly to
the fillers. The functionalizing agent is selected to react with
functional groups on the surface of the filler. Examples of
functionalizing materials comprise diallyl based moieties, vinyl
functionalized based monomer or polymer, siloxane based materials
(e.g., with different functionalities such as COOR, COOCH.sub.3,
NH.sub.2 (e.g., CONH.sub.2), NHR.sub.2, R--CHO, R--CO--R, wherein R
may be an alkyl or aryl groups), or a combination comprising at
least one of the foregoing functionalizing materials.
[0040] Aggregates and agglomerates of the magnetic particles are
also envisioned. The particles can have average dimensions in the
nanometer range or in the micrometer range. The nanometer range
generally includes particle sizes of less than or equal to 100
nanometers, while the micrometer range generally includes particle
sizes of greater than 100 nanometers. The specific size is chosen
based upon the desired final properties.
[0041] The length of the magnetic fiber can be up to 30 millimeters
(mm) prior to molding (e.g., up to 15 mm for injection molding, and
up to 30 mm for extrusion). Specifically, the length of the
magnetic fiber can be at least 3 mm, more specifically at least 5
mm, and even more specifically, at least 10 mm prior to molding.
The length of the magnetic fiber can be up to 15 mm, or up to 20 mm
prior to molding. After molding, the length of the magnetic fiber
can be less than specified above. For example, after molding, the
length of the metal fiber can be 30 micrometers (.mu.m) to 3
mm.
[0042] The magnetic filler can be present in an amount of 0.01 to
15 wt %, specifically, 0.01 to 10 wt %, and more specifically 0.01
to 5 wt %, based on the total weight of the melted polymer
mixture.
[0043] One or more additives ordinarily incorporated into polymer
compositions of this type can also be employed, with the provision
that the additive(s) are selected so as to not significantly
adversely affect the desired properties of the material. Such
additives can be mixed at a suitable time during the mixing of the
components for forming the melted polymer mixture. Exemplary
additives include impact modifiers, fillers, reinforcing agents,
antioxidants, heat stabilizers, light stabilizers, ultraviolet (UV)
light stabilizers, plasticizers, lubricants, mold release agents,
antistatic agents, colorants (such as carbon black and organic
dyes), surface effect additives, radiation stabilizers (e.g.,
infrared absorbing), flame retardants, and anti-drip agents. A
combination of additives can be used, for example a combination of
a flame retardant heat stabilizer, mold release agent, and
ultraviolet light stabilizer. In general, the additives can be used
in the amounts generally known to be effective.
[0044] The polymer resin (e.g., matrix) along with the magnetic
filler and other additional additives can be compounded in any
commercially available production device such as, for example, an
extruder, roll mill, dough mixer, etc. The polymer can be initially
in the form of powder, strands or pellets, and can be
pre-compounded with the magnetic filler in a Henschel mixer or any
other type of mixer. The pre-compounded mixture can then be
extruded at a suitable temperature into a strand that is quenched
and pelletized. Alternately, the polymeric resin can be directly
added to the extruder with the magnetic filler added either
concurrently or sequentially into the extruder. Extruder
temperature is generally sufficient to cause the polymeric resin to
flow so that proper dispersion of the magnetic filler in the
thermoplastic polymer can be achieved.
[0045] Generally the functionally graded material can comprise
exposing a molten polymer comprising the magnetic filler, to a
magnetic force. The magnetic force creates motion of the magnetic
filler. The polymer is then allowed to cool to form the graded
article. For example, a powdered polymer resin (e.g., thermoplastic
polymer resin) is blended with magnetic filler (e.g., in a mixer
(such as a Henschel high speed mixer), in an extruder (e.g., a twin
screw extruder), or otherwise). The blend is then formed into
pellets for later use or can be formed into the desired shape
(injection molded to form an article, extruded to form a sheet,
etc.). If the pellets are first formed, they are later melted and
the article is formed accordingly. Once the article is formed, and
while the blend is still in the molten state, the magnetic field is
used to adjust the concentration of magnetic filler in various
areas of the article (e.g., to draw them toward the surface to
attain a particular protection on that side of the article. This
allows a lower amount of material to be employed while attaining
the same level of protection since the concentration of filler on a
side of the article (or in a particular area of the article) can be
much higher than the remainder of the article. In other words, it
is not necessary to increase the concentration throughout the
article in order to attain a certain concentration in a given
location.
[0046] The melted polymer mixture can be prepared by subjecting
pellets formed as a result of extrusion, or a conductive sheet
obtained from a roll mill, to a molding (e.g. forming) process. In
some instances the extruded mixture of thermoplastic polymer and
magnetic filler can be the melted polymer mixture.
[0047] Molding of the melted polymer mixture can include the
transfer of the melted polymer mixture into the mold. Examples of
molding processes include injection molding, blow molding, sheet
extrusion, profile extrusion, wire drawing, pultrusion, or a
combination comprising at least one of the foregoing processes.
[0048] The magnet is positioned in a manner that will enable
contact between the melted polymer blend and the magnetic field.
Following molding of the melted polymer blend, the magnet can be
disposed adjacent to a portion of the melted polymer blend such
that a magnetic field passes through the blend and alters
distribution of the magnetic filler within the blend.
Alternatively, the magnet can be placed within the mold at the
desired position for forming the filler gradient prior to molding
of the melted polymer mixture. As the melted polymer blend flows
into the mold, the blend comes into contact with the magnet field.
A combination of the afore-mentioned methods is also envisioned.
For example, a first magnet can be placed within the mold prior to
molding of the melted polymer blend, and an additional magnet(s)
can be placed adjacent to the melted polymer blend at a position
separate and apart from the first magnet. The first magnet and the
second magnet are positioned in a manner such that the magnetic
fields produced by each magnet are non-overlapping, and distinct
filler gradients are formed.
[0049] Alternatively, or in addition, relative motion can be
created between the melted polymer blend and the magnetic field
(e.g., the blend can be on a carrier and conveyed past the magnetic
field), e.g., in a sheet forming process.
[0050] In the present methods, the magnet applies a magnetic field
to the melted polymer blend. The particles of magnetic filler,
under the influence of the magnetic field, are drawn through the
molten polymer mixture along magnetic field lines in a direction
influence by the magnetic field. As a result, the magnetic filler
gradient is formed. The position of the magnet with respect to the
molten polymer blend therefore determines the location at which the
filler gradient will be formed.
[0051] The magnetic field can be applied prior to curing or
hardening of the melted polymer blend. Following the application of
the magnetic field and orientation of the magnetic filler, the
melted polymer mixture is cooled (e.g., solidified) and optionally
cured to form a molded article.
[0052] The present process can use a magnetic flux to induce
gradation of magnetic fillers in a polymer. The gradation can be
engineered by controlling magnetic flux and/or mold surface
temperature, and/or melted polymer temperature. The fillers can be
used, e.g., as functionalizing elements, to achieve a different
property at different locations (e.g., across a thickness and/or in
different areas) of an article. For example, an article can have
one side that is polymer rich, and another side that is filler
(e.g., carbon and/or metal (such as ferrous)) rich.
[0053] Finally, whether or not the filler aligns (e.g., fibers
align in a common direction), can be controlled depending upon
whether or not alignment is desired. The alignment can be
controlled by controlling the current, direction, and the strength
of the flux, thereby controlling the effect of the flux on the
filler.
[0054] Molded articles comprising functionally graded polymer
materials manufactured as described herein are also provided. This
process enables controlled property variation within an article,
thereby enabling the production of numerous product that could not
be produced as a single layer previously. The articles can be used,
for example, in aerospace applications, electronics, structural
products, optical devices, medical implants, protective layers, and
so forth, such as thermal gradients (e.g., thermal structures in
for example, space shuttles, cutting tool inserts, engine or
turbine films, and so forth). Examples of articles include a heat
sink (e.g., with directionally oriented magnetic fibers (i.e.,
greater than or equal to 80% of the fibers are oriented along the
same axis)); layer with an internal antenna; layer with an internal
trace (e.g., for a defroster, semiconductor, etc.). The
functionally graded polymer materials can also be used to form
articles for which an automotive Class A surface is desired.
[0055] Set forth below are some examples of the methods and
articles disclosed herein.
[0056] Embodiment 1: A method of manufacturing a functionally
graded article, comprising: preparing a melted polymer mixture
comprising a thermoplastic polymer and a magnetic filler, wherein
the magnetic filler is dispersed in the thermoplastic polymer;
molding the melted polymer mixture; and applying a magnetic field
to a portion of the melted polymer mixture to form the functionally
graded article, wherein the functionally graded article has a
magnetic filler gradient.
[0057] Embodiment 2: A method of manufacturing a functionally
graded article, comprising: modifying a magnetic filler; preparing
a melted polymer mixture comprising a thermoplastic polymer and the
modified magnetic filler, wherein the magnetic filler is dispersed
in the thermoplastic polymer; molding the melted polymer mixture;
and applying a magnetic field to a portion of the melted polymer
mixture to form the functionally graded article, wherein the
functionally graded article has a magnetic filler gradient.
[0058] Embodiment 3: The method of any of Embodiments 1-2, wherein
the magnetic field alters distribution of the magnetic filler
within the molten polymer to concentrate the magnetic filler in an
area of the polymer.
[0059] Embodiment 4: The method of any of Embodiments 1-3, wherein
the filler gradient is formed through a thickness of the
functionally graded article.
[0060] Embodiment 5: The method of any of Embodiments 1-4, wherein
the magnetic field draws the magnetic filler through the molten
polymer towards a magnetic field source.
[0061] Embodiment 6: The method of any of Embodiments 1-5, wherein
the molding comprises injection molding, blow molding, sheet
extrusion, profile extrusion, wire drawing, or a combination
comprising at least one of the foregoing processes.
[0062] Embodiment 7: The method of any of Embodiments 1-6, wherein
the magnetic field is applied using a permanent magnet, an
electromagnet, a superconductive electromagnet, or a combination
thereof.
[0063] Embodiment 8: The method of any of Embodiments 1-7, wherein
a temperature of the melted polymer mixture during the molding is
120 to 400.degree. C.
[0064] Embodiment 9: The method of any of Embodiments 1-8, wherein
the magnetic filler is modified by coating, encapsulation, chemical
modification, functionalization, or a combination comprising at
least one of the foregoing.
[0065] Embodiment 10: The method of Embodiment 8, wherein the
magnetic filler is modified with a material comprising
polyetherimide.
[0066] Embodiment 11: The method of any of Embodiments 1-10,
wherein the magnetic field is applied prior to curing or hardening
of the melted polymer mixture.
[0067] Embodiment 12: The method of any of Embodiments 1-11,
wherein the magnetic filler comprises iron, nickel, cobalt,
ferrites, rare earth magnets, or a combination comprising at least
one of the foregoing.
[0068] Embodiment 13: The method of any of Embodiments 1-12,
wherein the magnetic filler comprises magnetic particles, magnetic
fibers, or a combination comprising at least one of the
foregoing.
[0069] Embodiment 14: The method of any of Embodiments 1-13,
wherein the magnetic fibers are metal fibers, metal-coated fibers
or a combination of metal fibers and metal-coated fibers.
[0070] Embodiment 15: The method of any of Embodiments 1-14,
wherein the method further comprises modifying a surface of the
magnetic filler prior to preparing the melted polymer mixture.
[0071] Embodiment 16: The method of any of Embodiments 1-15,
further comprising controlling the temperature of the melted
polymer.
[0072] Embodiment 17: The method of Embodiment 16, wherein
controlling the temperature of the melted polymer comprises
maintaining the melted polymer in a melted state until the
functionally graded article has attained a desired functional
gradation.
[0073] Embodiment 18: The method of Embodiment 16, wherein
controlling the temperature of the melted polymer comprises heating
the mold to within 10.degree. C. of a melt temperature of the
thermoplastic polymer.
[0074] Embodiment 19: The method of Embodiment 16, wherein
controlling the temperature of the melted polymer comprises
maintaining the melted polymer at a temperature within 10.degree.
C. of its melt temperature.
[0075] Embodiment 20: The method of any of Embodiments 1-19,
wherein the melted polymer mixture comprises polycarbonate,
polyethylene, polypropylene, polystyrene, polybutylene
terephthalate, polylactic acid, and combinations comprising at
least one of the foregoing.
[0076] Embodiment 21: An article formed by the method of any of
Embodiments 1-20.
[0077] Embodiment 22: The article of Embodiment 21, wherein article
is used for electromagnetic interference (EMI) shielding.
[0078] Embodiment 23: The article of Embodiment 21, wherein the
magnetic filler gradient forms an antenna within the article.
[0079] Embodiment 24: The article of Embodiment 21, wherein the
article is a heat sink with directionally oriented magnetic
fibers.
[0080] Embodiment 25: The article of Embodiment 24, wherein the
filler is fibers and greater than or equal to 70%, or 80%, or 90%
of the fibers are oriented along one axis.
[0081] The methods of manufacturing a functionally graded polymer
composition are further illustrated by the following, non-limiting
examples.
EXAMPLES
Example 1
[0082] A small quantity (10 wt % based upon a total weight of the
paste) of steel powder (having a particle size of 180 micrometers)
dispersed in polyvinyl alcohol (PVA) paste was subjected to a
strong magnetic field using a AlNiCo Pot magnet in an aluminum
casting, having a 40 kilograms (kg) of holding force in 50 mm
diameter. The paste was exposed to the magnet for 35 to 40
seconds.
[0083] FIG. 2 shows the arrangement of the steel powder in the PVA
paste following exposure of the paste to the magnetic field. As
shown in FIG. 2, the steel powder migrated through the viscous PVA
paste to a position adjacent to where the magnet was placed. The
steel particles having a black color appear to be arranged as a
gradient in the PVA paste.
[0084] To evaluate whether migration of steel powder occurs in a
polymer melt, polybutylene terephthalate (PBT) was melted (weight
average molecular weight (Mw) of 55,000-60,000 grams per mole
(g/mole)), mixed with steel powder, and then cast into aluminum
cups. The cups were then subjected to a strong magnetic field using
neodymium magnets (30 square millimeter (mm.sup.2) with holding
force of 60 kg (kilograms)). Sections removed from the cups clearly
showed influence of magnetic flux on the casted part. FIG. 3 shows
the casted samples and a section of the PBT and steel powder.
Example 2
[0085] Experiments were conducted to confirm whether migration of
the magnetic filler, e.g. steel powder, occurs when a magnetic
field is applied under process conditions of high shear such as
injection molding.
[0086] PBT and 10 wt % steel powder were compounded together in a
ZSK extruder (Weiner & Pfleiderer) under the conditions shown
in Table 1 and formed into pellets.
TABLE-US-00001 TABLE 1 Barrel 1 2 3 4 5 6 7 8 9 10 Temp 200 230 240
250 250 250 250 250 255 260 (.degree. C.)
[0087] The PBT/steel pellets were fed into a heated barrel of an
injection molding machine (L/T/Demag 200T), mixed, and injected
into a mold having a steel cavity with an aluminum core, and an
AlNiCo pot magnet incorporated into the mold. The molding
conditions used are shown below and in Tables 2 and 3.
TABLE-US-00002 TABLE 2 Mold Zone Nozzle MH3 MH2 MH1 Feed
Temperature Temp 260 270 255 240 60 65 (.degree. C.)
TABLE-US-00003 TABLE 3 Injection pressure (bar) 95 Injection speed
(mm/sec) 5 Injection time (sec) 10 Back Pressure 1 (bar) 5 Back
Pressure 2 (bar) 5 Hold On Pressure (bar) 60 Screw speed (%) 20
Switch over pressure (bar) 60 Cooling (sec) 5 Hold On time (sec) 12
Cycle Time (sec) 35-40 Dosing (mm) 55 Melt cushion (mm) 3.8
[0088] Polypropylene (PP) and 10 wt % steel powder were compounded
together in a ZSK extruder under the conditions shown in Table 4
and formed into pellets.
TABLE-US-00004 TABLE 4 Barrel 1 2 3 4 5 6 7 8 9 10 Temp 100 180 180
180 190 190 200 200 200 210 (.degree. C.)
[0089] The PP/steel pellets were fed into a heated barrel of an
injection molding machine (L/T/Demag 200T), mixed, and injected
into a mold having a steel cavity with an aluminum core, and an
AlNiCo pot magnet incorporated into the mold. The molding
conditions used are shown below and in Tables 5 and 6.
TABLE-US-00005 TABLE 5 Mold Zone Nozzle MH3 MH2 MH1 Feed
Temperature Temp 200 210 195 185 60 60 (.degree. C.)
TABLE-US-00006 TABLE 6 Injection pressure (bar) 150 Injection speed
(mm/sec) 130 Injection time (sec) 0.7 Back Pressure 1 (bar) 5 Back
Pressure 2 (bar) 5 Hold On Pressure (bar) 45 Screw speed (%) 16
Switch over pressure (bar) 60 Cooling (sec) 10 Hold On time (sec)
12 Cycle Time (sec) 35-40 Dosing (mm) 55 Melt cushion (mm) 3.8
[0090] The molded PBT and PP samples were each subjected to X-ray
imaging to analyze the density of steel particles in the area
surrounding the position of the AlNiCo magnet. As shown in FIG. 4,
annular rings composed of steel filler were formed near and around
the position of the magnet within the mold, indicating the
influence of the magnetic force on the distribution of the steel
filler during the molding process.
[0091] Thermogravimetric analysis (TGA) was performed on two
different regions of the molded samples of PP. The first sample
(Sample 1) was taken from a region of the molded sample close to
the position of the magnet, while the second sample (Sample 2) was
taken from a region a further away from the magnet. (See FIG. 6)
The TGA showed that the concentration of steel powder (residue) in
Sample 1 was 13.80 wt %, while the concentration of steel powder in
Sample 2 was 9.846 wt %. The TGA analysis therefore indicates that
the amount of steel present at any given point in the molded
composition is dependent upon the proximity of that point to the
magnet, and demonstrates the influence of the applied magnetic flux
on the distribution of the steel filler.
[0092] Three different regions of the molded polymer sample were
analyzed using optical microscopy to determine the concentration of
steel filler present within each region. The first region (1) was
in a position directly adjacent to the pot magnet, with regions (2)
and (3) being at increasing distances from the magnet. As shown in
FIG. 7, the optical microscopy results on the molded sample clearly
shows the graded structure of the filler. As further presented in
FIG. 8, the amount of steel filler ranged from 5.3 wt %, to 3.9 wt
%, to 2.5 wt % for regions (1), (2) and (3) respectively. (The
amount of fillers was calculated in the optical microscope and
derived.) Thus the results show that the concentration of steel
filler in the molded polymer sample decreased with increasing
distance from the magnet resulting in a filler gradient in the
polymer.
Example 3
[0093] Experiments are conducted to confirm whether migration of
the magnetic filler occurs using polymer-coated magnetic
filler.
[0094] Steel powder (10 wt %) is combined with a solution of 10 wt
% polyetherimide (PEI) (Ultem.TM. resin commercially available from
SABIC's Innovative Plastics business) in dichloromethane (DCM) and
mixed in a shaker to coat the steel particles with the PEI. PBT
powder is added to the mixture and the mixture is dried. The dried
blend of PEI-coated steel and PBT is then subjected to injection
molding.
[0095] In addition to PBT, polymers such as poly(lactic) acid
(PLA), polycarbonate (PC), polyethylene (PE), polypropylene (PP),
and polystyrene (PS) are also tested as described above.
[0096] In general, the invention may alternately comprise (e.g.
include), consist of, or consist essentially of, any appropriate
components herein disclosed. The embodiments may additionally, or
alternatively, be formulated so as to be devoid, or substantially
free, of any components, materials, ingredients, adjuvants or
species used in the prior art compositions or that are otherwise
not necessary to the achievement of the function and/or objectives
of the present invention.
[0097] 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.
[0098] All ranges disclosed herein are inclusive of the endpoints,
and the endpoints are independently combinable with each other
(e.g., ranges of "up to 25 wt. %, or, more specifically, 5 wt. % to
20 wt. %", is inclusive of the endpoints and all intermediate
values of the ranges of "5 wt. % to 25 wt. %," etc.). "Combination"
is inclusive of blends, mixtures, alloys, reaction products, and
the like. Furthermore, the terms "first," "second," and the like,
herein do not denote any order, quantity, or importance, but rather
are used to denote one element from another. The terms "a" and "an"
and "the" herein do not denote a limitation of quantity, and are to
be construed to cover both the singular and the plural, unless
otherwise indicated herein or clearly contradicted by context. The
suffix "(s)" as used herein is intended to include both the
singular and the plural of the term that it modifies, thereby
including one or more of that term (e.g., the film(s) includes one
or more films). Reference throughout the specification to "one
embodiment", "another embodiment", "an embodiment", and so forth,
means that a particular element (e.g., feature, structure, and/or
characteristic) described in connection with the embodiment is
included in at least one embodiment described herein, and may or
may not be present in other embodiments. In addition, it is to be
understood that the described elements may be combined in any
suitable manner in the various embodiments.
[0099] While particular embodiments have been described,
alternatives, modifications, variations, improvements, and
substantial equivalents that are or may be presently unforeseen may
arise to applicants or others skilled in the art. Accordingly, the
appended claims as filed and as they may be amended are intended to
embrace all such alternatives, modifications variations,
improvements, and substantial equivalents.
* * * * *