CA1218231A - Fiber-reinforced composite materials - Google Patents
Fiber-reinforced composite materialsInfo
- Publication number
- CA1218231A CA1218231A CA000432893A CA432893A CA1218231A CA 1218231 A CA1218231 A CA 1218231A CA 000432893 A CA000432893 A CA 000432893A CA 432893 A CA432893 A CA 432893A CA 1218231 A CA1218231 A CA 1218231A
- Authority
- CA
- Canada
- Prior art keywords
- elongated
- fiber
- resin
- granule
- fibers
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K7/00—Use of ingredients characterised by shape
- C08K7/02—Fibres or whiskers
- C08K7/04—Fibres or whiskers inorganic
- C08K7/06—Elements
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
- H01B1/20—Conductive material dispersed in non-conductive organic material
- H01B1/22—Conductive material dispersed in non-conductive organic material the conductive material comprising metals or alloys
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C2045/0091—Pellets or granules, e.g. their structure, composition, length, height, width
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S428/00—Stock material or miscellaneous articles
- Y10S428/902—High modulus filament or fiber
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/249921—Web or sheet containing structurally defined element or component
- Y10T428/249924—Noninterengaged fiber-containing paper-free web or sheet which is not of specified porosity
- Y10T428/24994—Fiber embedded in or on the surface of a polymeric matrix
- Y10T428/249942—Fibers are aligned substantially parallel
- Y10T428/249944—Fiber is precoated
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
- Y10T428/2913—Rod, strand, filament or fiber
- Y10T428/2933—Coated or with bond, impregnation or core
- Y10T428/294—Coated or with bond, impregnation or core including metal or compound thereof [excluding glass, ceramic and asbestos]
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/31504—Composite [nonstructural laminate]
- Y10T428/31507—Of polycarbonate
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/31504—Composite [nonstructural laminate]
- Y10T428/31678—Of metal
Abstract
FIBER-REINFORCED COMPOSITE MATERIALS
ABSTRACT
A composite plastic material having improved shielding against electromagnetic interference is provided by injection molding a molding compound comprising elongated granules obtained by incorporating into a thermoplastic resin matrix stainless steel fibers in the form of continuous strands.
ABSTRACT
A composite plastic material having improved shielding against electromagnetic interference is provided by injection molding a molding compound comprising elongated granules obtained by incorporating into a thermoplastic resin matrix stainless steel fibers in the form of continuous strands.
Description
¦I RC--155'',`"03%~1 li l l ~Z18i~3~
FORCED COMPOS ITE ~lATERIALS
FIBE;R--REIN
ABS'rRACT
A composite plastic material having improved shielding against electromagne!tic interference is provided by injection molding a molding compound cc,mprising elongated granules obtained by incorporating into a ther~loplastic resin matrix stainless steel fibers in the form of continuous strands.
BACKGROUND OF THE INVENTION
The use of plastic housings for electronic equipment and components is widely accepted in the automotive and electronic equipment fields today. However, the presently available plastic materials suffer from the disadvantage of being transparent or permeable to electromagnetic interference commonly known as, and referred to, as EMI. This drawback in available plastic materials is a matter of considerable concern in view of the susceptibility of electL~onic equipment to the adverse effects of EMI emission by the growing number of consumer products which produce such EMI
signals and to the increasing regulatory controls exercised over such electromagnetic pollution.
Currently, the major approach to solving plastic material jshielding problems is through the application of metallic surface coatings to the molded plastic. Among such approaches are the use of vacuum deposition, metal foil linings, metal-filled spray coat-ings, zinc flame-spray and electric arc discharge. Each of these procedures is accompanied by one or more drawbacks with respect to cost, adhesion, scratch resistance, environmental resistance, the length of time reauired for application and the difficulties in ~adequately protecting many of the diverse geometrical forms in !which the molded plastic must be provided.
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More recently, attempts have been made to resolve the problem of EMI by formulation of composite plastic materials based upon the use of various fillers in thermoplastic matrices~ Among the conductive fillers which have been employed for this purpose are carbon black, carbon fibers, silver coated glass beads and metallized glass fibers. However, these materials are subject to the disadvantages of ~eing brittle to the extent that they break up into shorter lengths in processing. The shorter length fibers and particles require higher loadings or filler concentrations leading to embrittlement of the plastic matrix and higher costs which render them commercially unacceptable. Hence, none of the composite plastic products developed heretofore have proven com-pletely satisfactory.
SU~ARY OF THE INVENTION
It has been found in accordance with the present inven- ¦
tion that a composite product providing outstanding shielding against electromagnetic interferences is obtained by molding the reinforced thermoplastic resin composition obtained by incorpor-ating into a thermoplastic resin matrix stainless steel fibers ¦employed in the form of continuous strands.
¦ The combination of this material with a thermoplastic Iresin enables the realization of a composite product with excellent ¦electromagnetic interference shielding effectiveness. The compos-¦ite products of the present invention are eminently suita~le for use for shielding purposes in a wide variety of end use products such as radios, transmitters, computers and the like.
The composite comprising the therm~plastic resin and stainless steel fibers can be prepared according to procedures ¦known to those skilled in the art. However, it has been found ¦that the most advantageous properties are realized when ~uch com- ¦
Iposites are prepared by the process of U.S. Pat. No. 2,877,501, i In the composite the fibers are commingled in the r~sin matrix and the resulting composition molded according t~ methods i ~ 3~ ~
well known in the resin molding field. Preferably, however, the end products are prepared by in3ection molding and it is advan~
tageous to employ this method of preparation for the achievement of optimum results.
DETAILED DESCRIP'rION OF THE INVENTION
The fiber reinforced components can be advantageously prepared by what is known in the art as the "long ~lass" process, the resulting products being characterized in the art as "long fiber" products. The length of the majority of the fibers in these "long fiber" products will generally range well above the majority fiber length of the fibers in so-called "short fiber"
products, which are normally in the range of about 0.01 inch to about 0.03 inch, and will generally extend the full length of the pieces themselves. The fiber form can be continuous roving of from 60 to 20,000 filaments or a staple yarn which may nominally contain 2,000 filaments. The staple yarn is comprised of a con-tinuous strand which is made up of discreet lengths of fiber the range of which may be 3" to 10" long for each single fiber length.
These discreet fiber lengths are often referred to as "slivers".
This process generally involves the use of continuous lengths of filaments which are passed through a bath containing molten resin whereby such filaments become impre~nated with the desired quantit~
of resin. Once the continuous filaments are impregnated they are continuously withdrawn from the bath, commingled, either before or after passage through a heat source, and cooled to solidify the molten resin around the stainless steel fibers followed by a sub-stantially transverse se~ering operation to form the short pieces.
These pieces are similar to the pieces of the above described "short fiber" products in that the fibers extend substantially parallel to each other and substantially parallel to the axis ¦defined by the direction in which the materials are withdrawn from ~the bath. However, contrary to the "short fiber" products, the ~¦fibers of eh "long fiber" products extend s~bstantially the entir _ 3 _ ~ 23~9L
distance from one severed side of the piece to the other severed side. Again, the l'long fiber" product pieces may range from about 1/16 inch to about 1-1/2 inches, preferably 1/8 inch to 1 inch. A
process of this type is described in U.S. Pat. No. 3,042,S70.
It is understood that rather than using a bath of molten resin in the above process the filaments may be impregnated with a resin suspension or emulsion and s~bse~uently subjected to suf-ficient heat to dry and fuse the resin around the commingled fila-ments. Such a process is described in U.S. Pat. No. 2,877,501.
In both products, that is, the "short fiber" products and "long fiber" products, the cross-sectional dimPnsion~ may vary considerably depending on several factors. With the "short fiber"
products, which are formed by extruding strands, the cross- I
sectional dimension will depend upon the size of the extrusion orifice. With the "long fiber" products, which are formed by impregnating continuous lengths of filaments, the cross-sectional dimension will depend upon the total number of filaments being impregnated and gathered together and the amount of resin. There are, of course, certain practical limits on the cross-sectional dimensions of the pieces due to processing limitations. In gen-eral, it has been found most convenient to orm pieces having ¦nominal cross sectional dimensions in the range of about ~/16 inch Ito about 1/4 inch.
¦ Elongated granules containing the stainless steel fibers lin the thermoplastic resin matrix are prepared using one of the procedures described earlier in this application. After prepara-tion of the elongated granules of stainless steel fibers in ther-moplastic resin, illustratively, in polycarbonate resin, the resulting composite is then molded in accordance with known pro-cedures. Homogenization will be effected in the molding step.
The proportions by weight of the components in the final ¦blend can be varied over a range of total fiber reinforcement to ¦resin of from about 0.5% to about 60%, with a preferred r~nge of !from about 1~ to about 8% by weight. Within this range, selection ~ 4 _ of the optimum proportion will be dependent on the end application or the particular objective sought. For optimum results, in some circumstances it has been found that a proportion of fiber to resin of from 1% to 5~ by weight is most advantageous for electrostatic dissipation and from 1% to 19~ by weight for EMI/RFI shielding applications.
It is, of course, possible to include conventional glass fiber, such as "E" glass fiberr in the composition as an extender.
Similarly, other conventional fillers, pigments and the like may also be included.
The reinforcing fibers employed according to the present in~ention are stain~ess steel fibers. These fibers are availa~le in roving form and in chopped form. In the practice of the presen~
inven~ion, it has been found necessary to utilize the stainle~s steel fibers in the form of staple yarn, rovings or continuous strands.
Our investigations have shown that when the stainless steel fiber is employed in chopped form, no appreciable EMI/RFI
shielding or electrical conductivity is realized without the use of excessive loading levels, of the order of about 25%. It is only when the stainless steel fibers are used in the ~orm of con-tinuous tow or staple yarn that the desired EMI/RFI shielding and elec~rical conductivity are obtained at substantially lower load-ings than possible with the short fiber pxoduct. The lower load-¦ings provide for greater impact, ductility and lower cost as com-¦pared to the short fiber products.
¦ Thermoplastic resins in general may be employed in pro-!ducing the reinfsrced resin component. Included among these ¦resins are polyolefins, particularly polypropylene and copolymers ¦of ethylene and propylene; polystyrene, styrene-acrylonitrile ¦polymers, ABS polymers (polymers based on acrylonitrile-polybuta- ¦
diene-styrene); nylons, particularly Nylon 6,6; polyphenylene ~oxides; polyphenylene oxide-polystyrene blends; polyphenylene Isulfides; polyacetals; polysulfones; polycarbonates; polyurethanes;¦
Icellulose ~sters; polyesters such as polyethylene terephthalate;
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¦polymonochlorostyrene; acrylic polymers; polyvinyl chlorides;
polyvinylidene chlorides; copolymers of vinyl-chloride and vinyli-dene chloride, various thermoplastic elastomers such as those based on styrene and butadiene or ethylene or propylene; and blends of any of the foregoing resins.
In processing the composite material of this invention, the mixture is fed in the normal manner to a feed hopper of the injection molding equipment. Thereafter, the mixture is processed through the equipment in the usual manner at temperature conditions which render the resin molten and flowable.
The following examples illustrate the present invention but are not to be construed as limiting the scope thereof.
A composition of elongated pellets containing 5% stain-less steel fiber product produced by blending a 30% stainless steel filled long fiber polycarbonate granule with unfilled poly- j carbonate at the ratio of 1 to 5 is fed to a screw type injection molding machine. The composition is processed in the machine at temperatures in the range of 500 to 580F, providing a molded product having desirable uniformity of appearance and good physical properties.
For purposes of comparison, elongated pellets containing 15% of stainless steel chopped fiber of 8 micron diameter in poly-carbonate resin is processed under identical conditions and the molded product obtained is tested against the product containing the continuous strand stainless steel fibers for EMI shielding effectiveness. The results of this comparative testing are set forth in Table I below.
TABLE I
I Chopped Fiber Continuous Strand IShielding Effectiveness at ¦1000 MHz flat panel dB 1 40 ~ 8;;~3~ I
¦ EXAMPLE 2 Compositions containing the amounts and the forms of stainless steel fiber shown in Table II were prepared and molded by the procedure set forth in Example 1. The resulting products were tested and the results of the tests are set forth in Table II.
TABLE II
Flat Panel Shielding-Effectiveness _ at 1000 MHz, dB
Polycarbonate Containing 5% 10% 15%
3mm 8 microna Chopped 0 0 Stainless Steel Fiber 8 micron continuousb 38.5 40.5 Stainless Steel Fiber Controls 8% Fiberglass in 0 dB
Polycarbonate Polycarbonate - ~ickel55 Paint a Pellet length 1/8"
Pellet length 3/8" - 1/2"
Compositions containing the amounts and the forms of stainless steel fiber shown in Table III were prepared and molded ~s in Examples 1 and 2. The resulting products were tested for conductivity and EMI shielding and the results thereof are set forth in Table III.
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TABLE III
CONDUCTIVITY AND EMI SHIELDING
OF LONG FIBER AND SHORT FIBER
. _ ~
STAINLESS STEEL FIBER MOLDING COMPOUND
A B C
Bulk Resistivity of 3" x 6" x .125" ~ 400 30 plaque, ohms EMI Shielding Effectiveness of 10 20 35 6" x 6" x ~125" plaque dB at 1000 ~z Explanation:
A - Polycarbonate containing 5 weight percent 4 micron 6 mm chopped stainless steel fiber randomly dispersed in 1/4"
long pellets.
B - Polycarbonate containin~ 5 weight percent 8 micron continuous stainless steel fiber impregnated in 1/4" long pellets.
C - Polycarbonate containing 5 weight percent 8 micron continuous stainless steel fiber impregnated in 3/8" long pellets.
- Infinity indicates open circuit, i.e. no conductivity.
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FORCED COMPOS ITE ~lATERIALS
FIBE;R--REIN
ABS'rRACT
A composite plastic material having improved shielding against electromagne!tic interference is provided by injection molding a molding compound cc,mprising elongated granules obtained by incorporating into a ther~loplastic resin matrix stainless steel fibers in the form of continuous strands.
BACKGROUND OF THE INVENTION
The use of plastic housings for electronic equipment and components is widely accepted in the automotive and electronic equipment fields today. However, the presently available plastic materials suffer from the disadvantage of being transparent or permeable to electromagnetic interference commonly known as, and referred to, as EMI. This drawback in available plastic materials is a matter of considerable concern in view of the susceptibility of electL~onic equipment to the adverse effects of EMI emission by the growing number of consumer products which produce such EMI
signals and to the increasing regulatory controls exercised over such electromagnetic pollution.
Currently, the major approach to solving plastic material jshielding problems is through the application of metallic surface coatings to the molded plastic. Among such approaches are the use of vacuum deposition, metal foil linings, metal-filled spray coat-ings, zinc flame-spray and electric arc discharge. Each of these procedures is accompanied by one or more drawbacks with respect to cost, adhesion, scratch resistance, environmental resistance, the length of time reauired for application and the difficulties in ~adequately protecting many of the diverse geometrical forms in !which the molded plastic must be provided.
;
~ ` ''' ~
I ~L2~823~
More recently, attempts have been made to resolve the problem of EMI by formulation of composite plastic materials based upon the use of various fillers in thermoplastic matrices~ Among the conductive fillers which have been employed for this purpose are carbon black, carbon fibers, silver coated glass beads and metallized glass fibers. However, these materials are subject to the disadvantages of ~eing brittle to the extent that they break up into shorter lengths in processing. The shorter length fibers and particles require higher loadings or filler concentrations leading to embrittlement of the plastic matrix and higher costs which render them commercially unacceptable. Hence, none of the composite plastic products developed heretofore have proven com-pletely satisfactory.
SU~ARY OF THE INVENTION
It has been found in accordance with the present inven- ¦
tion that a composite product providing outstanding shielding against electromagnetic interferences is obtained by molding the reinforced thermoplastic resin composition obtained by incorpor-ating into a thermoplastic resin matrix stainless steel fibers ¦employed in the form of continuous strands.
¦ The combination of this material with a thermoplastic Iresin enables the realization of a composite product with excellent ¦electromagnetic interference shielding effectiveness. The compos-¦ite products of the present invention are eminently suita~le for use for shielding purposes in a wide variety of end use products such as radios, transmitters, computers and the like.
The composite comprising the therm~plastic resin and stainless steel fibers can be prepared according to procedures ¦known to those skilled in the art. However, it has been found ¦that the most advantageous properties are realized when ~uch com- ¦
Iposites are prepared by the process of U.S. Pat. No. 2,877,501, i In the composite the fibers are commingled in the r~sin matrix and the resulting composition molded according t~ methods i ~ 3~ ~
well known in the resin molding field. Preferably, however, the end products are prepared by in3ection molding and it is advan~
tageous to employ this method of preparation for the achievement of optimum results.
DETAILED DESCRIP'rION OF THE INVENTION
The fiber reinforced components can be advantageously prepared by what is known in the art as the "long ~lass" process, the resulting products being characterized in the art as "long fiber" products. The length of the majority of the fibers in these "long fiber" products will generally range well above the majority fiber length of the fibers in so-called "short fiber"
products, which are normally in the range of about 0.01 inch to about 0.03 inch, and will generally extend the full length of the pieces themselves. The fiber form can be continuous roving of from 60 to 20,000 filaments or a staple yarn which may nominally contain 2,000 filaments. The staple yarn is comprised of a con-tinuous strand which is made up of discreet lengths of fiber the range of which may be 3" to 10" long for each single fiber length.
These discreet fiber lengths are often referred to as "slivers".
This process generally involves the use of continuous lengths of filaments which are passed through a bath containing molten resin whereby such filaments become impre~nated with the desired quantit~
of resin. Once the continuous filaments are impregnated they are continuously withdrawn from the bath, commingled, either before or after passage through a heat source, and cooled to solidify the molten resin around the stainless steel fibers followed by a sub-stantially transverse se~ering operation to form the short pieces.
These pieces are similar to the pieces of the above described "short fiber" products in that the fibers extend substantially parallel to each other and substantially parallel to the axis ¦defined by the direction in which the materials are withdrawn from ~the bath. However, contrary to the "short fiber" products, the ~¦fibers of eh "long fiber" products extend s~bstantially the entir _ 3 _ ~ 23~9L
distance from one severed side of the piece to the other severed side. Again, the l'long fiber" product pieces may range from about 1/16 inch to about 1-1/2 inches, preferably 1/8 inch to 1 inch. A
process of this type is described in U.S. Pat. No. 3,042,S70.
It is understood that rather than using a bath of molten resin in the above process the filaments may be impregnated with a resin suspension or emulsion and s~bse~uently subjected to suf-ficient heat to dry and fuse the resin around the commingled fila-ments. Such a process is described in U.S. Pat. No. 2,877,501.
In both products, that is, the "short fiber" products and "long fiber" products, the cross-sectional dimPnsion~ may vary considerably depending on several factors. With the "short fiber"
products, which are formed by extruding strands, the cross- I
sectional dimension will depend upon the size of the extrusion orifice. With the "long fiber" products, which are formed by impregnating continuous lengths of filaments, the cross-sectional dimension will depend upon the total number of filaments being impregnated and gathered together and the amount of resin. There are, of course, certain practical limits on the cross-sectional dimensions of the pieces due to processing limitations. In gen-eral, it has been found most convenient to orm pieces having ¦nominal cross sectional dimensions in the range of about ~/16 inch Ito about 1/4 inch.
¦ Elongated granules containing the stainless steel fibers lin the thermoplastic resin matrix are prepared using one of the procedures described earlier in this application. After prepara-tion of the elongated granules of stainless steel fibers in ther-moplastic resin, illustratively, in polycarbonate resin, the resulting composite is then molded in accordance with known pro-cedures. Homogenization will be effected in the molding step.
The proportions by weight of the components in the final ¦blend can be varied over a range of total fiber reinforcement to ¦resin of from about 0.5% to about 60%, with a preferred r~nge of !from about 1~ to about 8% by weight. Within this range, selection ~ 4 _ of the optimum proportion will be dependent on the end application or the particular objective sought. For optimum results, in some circumstances it has been found that a proportion of fiber to resin of from 1% to 5~ by weight is most advantageous for electrostatic dissipation and from 1% to 19~ by weight for EMI/RFI shielding applications.
It is, of course, possible to include conventional glass fiber, such as "E" glass fiberr in the composition as an extender.
Similarly, other conventional fillers, pigments and the like may also be included.
The reinforcing fibers employed according to the present in~ention are stain~ess steel fibers. These fibers are availa~le in roving form and in chopped form. In the practice of the presen~
inven~ion, it has been found necessary to utilize the stainle~s steel fibers in the form of staple yarn, rovings or continuous strands.
Our investigations have shown that when the stainless steel fiber is employed in chopped form, no appreciable EMI/RFI
shielding or electrical conductivity is realized without the use of excessive loading levels, of the order of about 25%. It is only when the stainless steel fibers are used in the ~orm of con-tinuous tow or staple yarn that the desired EMI/RFI shielding and elec~rical conductivity are obtained at substantially lower load-ings than possible with the short fiber pxoduct. The lower load-¦ings provide for greater impact, ductility and lower cost as com-¦pared to the short fiber products.
¦ Thermoplastic resins in general may be employed in pro-!ducing the reinfsrced resin component. Included among these ¦resins are polyolefins, particularly polypropylene and copolymers ¦of ethylene and propylene; polystyrene, styrene-acrylonitrile ¦polymers, ABS polymers (polymers based on acrylonitrile-polybuta- ¦
diene-styrene); nylons, particularly Nylon 6,6; polyphenylene ~oxides; polyphenylene oxide-polystyrene blends; polyphenylene Isulfides; polyacetals; polysulfones; polycarbonates; polyurethanes;¦
Icellulose ~sters; polyesters such as polyethylene terephthalate;
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¦polymonochlorostyrene; acrylic polymers; polyvinyl chlorides;
polyvinylidene chlorides; copolymers of vinyl-chloride and vinyli-dene chloride, various thermoplastic elastomers such as those based on styrene and butadiene or ethylene or propylene; and blends of any of the foregoing resins.
In processing the composite material of this invention, the mixture is fed in the normal manner to a feed hopper of the injection molding equipment. Thereafter, the mixture is processed through the equipment in the usual manner at temperature conditions which render the resin molten and flowable.
The following examples illustrate the present invention but are not to be construed as limiting the scope thereof.
A composition of elongated pellets containing 5% stain-less steel fiber product produced by blending a 30% stainless steel filled long fiber polycarbonate granule with unfilled poly- j carbonate at the ratio of 1 to 5 is fed to a screw type injection molding machine. The composition is processed in the machine at temperatures in the range of 500 to 580F, providing a molded product having desirable uniformity of appearance and good physical properties.
For purposes of comparison, elongated pellets containing 15% of stainless steel chopped fiber of 8 micron diameter in poly-carbonate resin is processed under identical conditions and the molded product obtained is tested against the product containing the continuous strand stainless steel fibers for EMI shielding effectiveness. The results of this comparative testing are set forth in Table I below.
TABLE I
I Chopped Fiber Continuous Strand IShielding Effectiveness at ¦1000 MHz flat panel dB 1 40 ~ 8;;~3~ I
¦ EXAMPLE 2 Compositions containing the amounts and the forms of stainless steel fiber shown in Table II were prepared and molded by the procedure set forth in Example 1. The resulting products were tested and the results of the tests are set forth in Table II.
TABLE II
Flat Panel Shielding-Effectiveness _ at 1000 MHz, dB
Polycarbonate Containing 5% 10% 15%
3mm 8 microna Chopped 0 0 Stainless Steel Fiber 8 micron continuousb 38.5 40.5 Stainless Steel Fiber Controls 8% Fiberglass in 0 dB
Polycarbonate Polycarbonate - ~ickel55 Paint a Pellet length 1/8"
Pellet length 3/8" - 1/2"
Compositions containing the amounts and the forms of stainless steel fiber shown in Table III were prepared and molded ~s in Examples 1 and 2. The resulting products were tested for conductivity and EMI shielding and the results thereof are set forth in Table III.
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TABLE III
CONDUCTIVITY AND EMI SHIELDING
OF LONG FIBER AND SHORT FIBER
. _ ~
STAINLESS STEEL FIBER MOLDING COMPOUND
A B C
Bulk Resistivity of 3" x 6" x .125" ~ 400 30 plaque, ohms EMI Shielding Effectiveness of 10 20 35 6" x 6" x ~125" plaque dB at 1000 ~z Explanation:
A - Polycarbonate containing 5 weight percent 4 micron 6 mm chopped stainless steel fiber randomly dispersed in 1/4"
long pellets.
B - Polycarbonate containin~ 5 weight percent 8 micron continuous stainless steel fiber impregnated in 1/4" long pellets.
C - Polycarbonate containing 5 weight percent 8 micron continuous stainless steel fiber impregnated in 3/8" long pellets.
- Infinity indicates open circuit, i.e. no conductivity.
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Claims (11)
1. A thermoplastic resin elongated granule providing improved electromagnetic interference shielding properties comprising a thermoplastic resin elongated granule having incorporated therein a fiber constituent comprised of continuous strands of stainless steel fibers, said fibers extending substantially parallel to each other and substantially parallel to a length of the elongated granule.
2. An elongated granule according to claim 1 wherein the fiber component and the resin component are present by over a range of fiber to resin of from about 0.5% to about 60% by weight.
3. An elongated granule according to claim 1 wherein the range of fiber to resin is from about 1.0% to about 8.0% by weight.
4. An elongated granule according to claim 1 wherein the thermoplastic resin is a member selected from the group consisting of polyolefins, polystyrene, styreneacrylonitrile polymers, acrylonitrile-polybutadiene-styrene, nylon, polyphenylene sulfides, polyacetals, polysulfones, polycarbonates, polyurethanes, cellulose esters, polyester, acrylic polymers, polyvinyl chlorides, poly-vinylidene chlorides, copolymers of vinyl chloride and vinylidene chloride, polyphenylene oxides, polyphenylene oxide-polystyrene blends of any of the foregoing resins.
5. An elongated granule according to claim 4 wherein the composition resin is a polycarbonate resin.
6. Molded products characterized by superior electromagnetic interference shielding properties derived from elongated granules as claimed in claim 1.
7. Molded products as claimed in claim 6 when formed by an injection molding process.
8. A molded article characterized by superior electromagnetic interference shielding properties comprising a polymeric matrix and continuous strands of stainless steel fibers, wherein said article is derived from the elongated granules of claim 1 having incorporated therein said fibers which extend substantially entirely over said length of said elongated granule.
9. An elongated granule of claim 1 wherein said steel fibers comprise from about 60 to about 20,000 filaments.
10. An elongated granule of claim 1 wherein said granule has a length of from about 1/16 to about 1? inches and a nominal cross-section of about 1/16 to about ? inch.
11. An elongated granule of claim 10 wherein each of said fibers has a diameter of about 8 microns.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US400,779 | 1982-07-22 | ||
| US06/400,779 US4500595A (en) | 1982-07-22 | 1982-07-22 | Stainless steel fiber-thermosplastic granules and molded articles therefrom |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1218231A true CA1218231A (en) | 1987-02-24 |
Family
ID=23584971
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000432893A Expired CA1218231A (en) | 1982-07-22 | 1983-07-21 | Fiber-reinforced composite materials |
Country Status (14)
| Country | Link |
|---|---|
| US (1) | US4500595A (en) |
| JP (1) | JPS5941246A (en) |
| AU (1) | AU571448B2 (en) |
| BE (1) | BE897277A (en) |
| CA (1) | CA1218231A (en) |
| DE (1) | DE3325954A1 (en) |
| ES (1) | ES8504545A1 (en) |
| FR (1) | FR2531968B1 (en) |
| GB (1) | GB2123838B (en) |
| IT (1) | IT1167658B (en) |
| NL (1) | NL8302573A (en) |
| NZ (1) | NZ204907A (en) |
| SE (1) | SE460851B (en) |
| ZA (1) | ZA835187B (en) |
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| CN101840745A (en) * | 2010-04-07 | 2010-09-22 | 湖南惠同新材料股份有限公司 | Preparation method of conductive plastics master batch containing stainless steel fibers |
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-
1982
- 1982-07-22 US US06/400,779 patent/US4500595A/en not_active Expired - Fee Related
-
1983
- 1983-07-13 BE BE0/211167A patent/BE897277A/en not_active IP Right Cessation
- 1983-07-14 AU AU16830/83A patent/AU571448B2/en not_active Ceased
- 1983-07-15 NZ NZ204907A patent/NZ204907A/en unknown
- 1983-07-15 ZA ZA835187A patent/ZA835187B/en unknown
- 1983-07-19 GB GB08319449A patent/GB2123838B/en not_active Expired
- 1983-07-19 DE DE19833325954 patent/DE3325954A1/en not_active Withdrawn
- 1983-07-19 NL NL8302573A patent/NL8302573A/en not_active Application Discontinuation
- 1983-07-20 IT IT2215983A patent/IT1167658B/en active
- 1983-07-21 SE SE8304085A patent/SE460851B/en not_active IP Right Cessation
- 1983-07-21 CA CA000432893A patent/CA1218231A/en not_active Expired
- 1983-07-21 JP JP58132040A patent/JPS5941246A/en active Pending
- 1983-07-22 FR FR8312207A patent/FR2531968B1/en not_active Expired
- 1983-07-22 ES ES524387A patent/ES8504545A1/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101840745A (en) * | 2010-04-07 | 2010-09-22 | 湖南惠同新材料股份有限公司 | Preparation method of conductive plastics master batch containing stainless steel fibers |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2123838B (en) | 1986-01-22 |
| GB2123838A (en) | 1984-02-08 |
| US4500595A (en) | 1985-02-19 |
| DE3325954A1 (en) | 1984-01-26 |
| ES524387A0 (en) | 1985-04-16 |
| NZ204907A (en) | 1987-02-20 |
| AU571448B2 (en) | 1988-04-21 |
| FR2531968A1 (en) | 1984-02-24 |
| IT1167658B (en) | 1987-05-13 |
| FR2531968B1 (en) | 1986-12-26 |
| BE897277A (en) | 1983-11-03 |
| ZA835187B (en) | 1984-03-28 |
| ES8504545A1 (en) | 1985-04-16 |
| SE8304085D0 (en) | 1983-07-21 |
| IT8322159A0 (en) | 1983-07-20 |
| NL8302573A (en) | 1984-02-16 |
| SE460851B (en) | 1989-11-27 |
| IT8322159A1 (en) | 1985-01-20 |
| GB8319449D0 (en) | 1983-08-17 |
| JPS5941246A (en) | 1984-03-07 |
| SE8304085L (en) | 1984-01-23 |
| AU1683083A (en) | 1984-01-26 |
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