CA2461110A1 - Shielding material and communications cable using same - Google Patents
Shielding material and communications cable using same Download PDFInfo
- Publication number
- CA2461110A1 CA2461110A1 CA002461110A CA2461110A CA2461110A1 CA 2461110 A1 CA2461110 A1 CA 2461110A1 CA 002461110 A CA002461110 A CA 002461110A CA 2461110 A CA2461110 A CA 2461110A CA 2461110 A1 CA2461110 A1 CA 2461110A1
- Authority
- CA
- Canada
- Prior art keywords
- particles
- additives
- emi
- nano
- shielding
- 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.)
- Abandoned
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
-
- 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
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/01—Use of inorganic substances as compounding ingredients characterized by their specific function
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B11/00—Communication cables or conductors
- H01B11/02—Cables with twisted pairs or quads
- H01B11/06—Cables with twisted pairs or quads with means for reducing effects of electromagnetic or electrostatic disturbances, e.g. screens
- H01B11/10—Screens specially adapted for reducing interference from external sources
- H01B11/1058—Screens specially adapted for reducing interference from external sources using a coating, e.g. a loaded polymer, ink or print
- H01B11/1066—Screens specially adapted for reducing interference from external sources using a coating, e.g. a loaded polymer, ink or print the coating containing conductive or semiconductive material
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02G—INSTALLATION OF ELECTRIC CABLES OR LINES, OR OF COMBINED OPTICAL AND ELECTRIC CABLES OR LINES
- H02G15/00—Cable fittings
- H02G15/02—Cable terminations
- H02G15/06—Cable terminating boxes, frames or other structures
- H02G15/064—Cable terminating boxes, frames or other structures with devices for relieving electrical stress
- H02G15/068—Cable terminating boxes, frames or other structures with devices for relieving electrical stress connected to the cable shield only
-
- 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
- C08K2201/00—Specific properties of additives
- C08K2201/011—Nanostructured additives
Description
TITLE OF THE INVENTION
SHIELDING MATERIAL AND COMMUNICATIONS CABLE USING SAME
BRIEF DESCRIPTION OF THE FIGURES
Figure 1 discloses percolation networks in accordance with an illustrative embodiment of the present invention;
Figure 2 provides a graph of conductivity as a function of loading, semi-spherical micro particles with aspect ratio greater than 1 in accordance with an illustrative embodiment of the present invention;
Figure 3 discloses an EMI shielding cable jacket in accordance with an illustrative embodiment of the present invention;
Figure 4 provides a graph of the conductivity of single-wall nanotube-filled polycarbonate compared to multi-wall nanotube-filled polycarbonate in accordance with an illustrative embodiment of the present invention; and Figure 5 provides a diagram of percolation networks of spherical micro particles and carbon nanotubes in accordance with an illustrative embodiment of the present invention.
DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS
The requirements for communication UTP (Unshielded Twisted Pair) cables in general and LAN UTP cables (covered by EIA/TIA 568 B) in particular, are being upgraded in view of the conversion from 100 Mbit/sec to 1 Gbit/sec and 10 Gbit/sec transmission speed protocols. At the same time, the standards for safety and long-term stability of these communication cables are also being upgraded.
SHIELDING MATERIAL AND COMMUNICATIONS CABLE USING SAME
BRIEF DESCRIPTION OF THE FIGURES
Figure 1 discloses percolation networks in accordance with an illustrative embodiment of the present invention;
Figure 2 provides a graph of conductivity as a function of loading, semi-spherical micro particles with aspect ratio greater than 1 in accordance with an illustrative embodiment of the present invention;
Figure 3 discloses an EMI shielding cable jacket in accordance with an illustrative embodiment of the present invention;
Figure 4 provides a graph of the conductivity of single-wall nanotube-filled polycarbonate compared to multi-wall nanotube-filled polycarbonate in accordance with an illustrative embodiment of the present invention; and Figure 5 provides a diagram of percolation networks of spherical micro particles and carbon nanotubes in accordance with an illustrative embodiment of the present invention.
DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS
The requirements for communication UTP (Unshielded Twisted Pair) cables in general and LAN UTP cables (covered by EIA/TIA 568 B) in particular, are being upgraded in view of the conversion from 100 Mbit/sec to 1 Gbit/sec and 10 Gbit/sec transmission speed protocols. At the same time, the standards for safety and long-term stability of these communication cables are also being upgraded.
Higher frequency transmission speeds leads to an increase in the interference (EMI) between adjacent cables, this interference generally referred to in the art as "Alien NEXT". This type of EMI cannot be cancelled by affordable active electronic filtering methods presently available. Additionally, FCC EMI limits may be also breached at the 10Gbit/sec levels.
One method of shielding cables to block EMI generated by high frequency transmission is, for example, by wrapping an aluminum-polyester tape around the cable core and placing a drain wire longitudinally along the cable to provide for continuity. An outer jacket is applied in a subsequent operation or in tandem with the tape.
Alternatively, the cable could be fabricated with two jackets and an aluminum-polyester tape applied between the two jackets for shielding purposes. One of the advantages of this structure is the reduction of the shield propensity to lower the impedance and increase the attenuation of the insulated conductors by removing the shield from the close proximity with the said insulated conductors. However, this improvement is compromised by the higher cost in materials as the outside jacket has to meet the minimum thickness requirements required by UL safety specs. Consequently, the dual jacketed cable has a higher overall diameter and requires greater installation space than single jacketed cables.
Additionally, metallic shielding of cables may require a completely shielded connectivity system with attendant increase in costs. Such a floating shield will otherwise become a powerful antenna that will either transmit or receive EMI radiation along the cable entire length if adequate grounding is not provided.
A different approach to obtain the shielding effect involves loading the jacketing material with conductive or paramagnetic particles, or both. The amount of conductive and/or paramagnetic particles is closely related with the capacity of the dispersed particles to form a continuous electromagnetic field.
Referring to Figure 1, the concentration of particles required for the achievement of such a field is called the percolation concentration. In the case of spherical or non-spherical particles, such as carbon black or ferromagnetic powders, the percolation concentration is anywhere between 30 to 60%
depending on the aspect ratio of the particles (the higher concentration being that of spheres, having an aspect ratio of 1, see Figures 1 and 2). The addition of such a high amount of particles to the material may compromise the mechanical properties of the jacket and should require an increase in the insulation thickness of the conductors due to the proximity of the modified jacket to the core.
New classes of conductive or paramagnetic nano-additives (smaller than one micron) have been developed that have fibrous (non-spherical) shapes.
These types of additives have much lower percolation concentrations due to their high aspect ratio. Two major classes of additives with non-spherical shapes are the nano-fibre and nano-flake or nano-platelet type additives. Use of such nano-particles is beneficial to the mechanical properties and surface quality of the resulting nanocomposite materials. Other benefits derived from the usage of these additives are improved flame and smoke retardant properties of the resulting nanocomposite materials and a better barrier to the diffusion of humidity and oils into the material containing nano-particles.
Thus, a smaller amount of conductive additives are required for percolation while at the same time the mechanical properties, flame and smoke resistance and surface quality of the resulting materials is improved. These features combine to yield a cable jacket that meets the UL physical and safety specifications. However, the cost of the nanocomposite additives is very high.
The shielding material of the present invention reduces the cost of using the new class of nanocomposite polymers while at the same time enabling, when applied to cabling constructions, the use of older shielding formulation technologies for an optimum coverage over a wide range of EMI frequencies.
In order to fabricate the cable in question, a jacketing co-extrusion process can be used. Referring to Figure 3, the first layer of the co-extruded jacket that envelops the inner cable core 14 consists of a polymer (for example the low smoke flame retardant PVC with designation L-1011 manufactured by Alpha Gary) that was found to meet UL safety requirements and transmission performance specifications such as the EIA/TIA 568 B2 up to and including enhanced Cat 6e electrical requirements.
Illustratively, the second layer 16 is co-extruded with the first layer 12 via a vertical extruder and through a co-extrusion jacketing head (both not shown).
The material matrix of the second layer 16 is typically the same material as the one used in the first layer 12 or another suitable material with enhanced adhesion between the two layers 12, 16 of the jacket. The achievement of good adhesion between the two layers 12, 16 improves the mechanical properties such that the UL safety specifications may be met. At the same time, the shielding material of the second layer 16 is doped (admixed) using with the nano-additives in combination with micro particles that will impart to the overall cable EMI shielding characteristics for sufficiently reducing Alien NEXT and EMI between adjacent cables in LAN installations and preventing electrostatic accumulation. Thus a number of objectives are attained in the proposed design, namely:
~ reduction in the cost of using the new class of nanocomposite polymers;
~ lowering in the size of the overall cable diameter by the co-extrusion of a single jacket structure that could meet the mechanical properties required by UL safety requirements at lower jacket thickness than the two jacket solution and/or the standard shielding solution; and ~ improving EMI and ESD compliance without compromising the other characteristics of the cable, such as impedance and insertion loss.
Doping the top co-extruded layer 16 with conductive nano-particles for EMI
One method of shielding cables to block EMI generated by high frequency transmission is, for example, by wrapping an aluminum-polyester tape around the cable core and placing a drain wire longitudinally along the cable to provide for continuity. An outer jacket is applied in a subsequent operation or in tandem with the tape.
Alternatively, the cable could be fabricated with two jackets and an aluminum-polyester tape applied between the two jackets for shielding purposes. One of the advantages of this structure is the reduction of the shield propensity to lower the impedance and increase the attenuation of the insulated conductors by removing the shield from the close proximity with the said insulated conductors. However, this improvement is compromised by the higher cost in materials as the outside jacket has to meet the minimum thickness requirements required by UL safety specs. Consequently, the dual jacketed cable has a higher overall diameter and requires greater installation space than single jacketed cables.
Additionally, metallic shielding of cables may require a completely shielded connectivity system with attendant increase in costs. Such a floating shield will otherwise become a powerful antenna that will either transmit or receive EMI radiation along the cable entire length if adequate grounding is not provided.
A different approach to obtain the shielding effect involves loading the jacketing material with conductive or paramagnetic particles, or both. The amount of conductive and/or paramagnetic particles is closely related with the capacity of the dispersed particles to form a continuous electromagnetic field.
Referring to Figure 1, the concentration of particles required for the achievement of such a field is called the percolation concentration. In the case of spherical or non-spherical particles, such as carbon black or ferromagnetic powders, the percolation concentration is anywhere between 30 to 60%
depending on the aspect ratio of the particles (the higher concentration being that of spheres, having an aspect ratio of 1, see Figures 1 and 2). The addition of such a high amount of particles to the material may compromise the mechanical properties of the jacket and should require an increase in the insulation thickness of the conductors due to the proximity of the modified jacket to the core.
New classes of conductive or paramagnetic nano-additives (smaller than one micron) have been developed that have fibrous (non-spherical) shapes.
These types of additives have much lower percolation concentrations due to their high aspect ratio. Two major classes of additives with non-spherical shapes are the nano-fibre and nano-flake or nano-platelet type additives. Use of such nano-particles is beneficial to the mechanical properties and surface quality of the resulting nanocomposite materials. Other benefits derived from the usage of these additives are improved flame and smoke retardant properties of the resulting nanocomposite materials and a better barrier to the diffusion of humidity and oils into the material containing nano-particles.
Thus, a smaller amount of conductive additives are required for percolation while at the same time the mechanical properties, flame and smoke resistance and surface quality of the resulting materials is improved. These features combine to yield a cable jacket that meets the UL physical and safety specifications. However, the cost of the nanocomposite additives is very high.
The shielding material of the present invention reduces the cost of using the new class of nanocomposite polymers while at the same time enabling, when applied to cabling constructions, the use of older shielding formulation technologies for an optimum coverage over a wide range of EMI frequencies.
In order to fabricate the cable in question, a jacketing co-extrusion process can be used. Referring to Figure 3, the first layer of the co-extruded jacket that envelops the inner cable core 14 consists of a polymer (for example the low smoke flame retardant PVC with designation L-1011 manufactured by Alpha Gary) that was found to meet UL safety requirements and transmission performance specifications such as the EIA/TIA 568 B2 up to and including enhanced Cat 6e electrical requirements.
Illustratively, the second layer 16 is co-extruded with the first layer 12 via a vertical extruder and through a co-extrusion jacketing head (both not shown).
The material matrix of the second layer 16 is typically the same material as the one used in the first layer 12 or another suitable material with enhanced adhesion between the two layers 12, 16 of the jacket. The achievement of good adhesion between the two layers 12, 16 improves the mechanical properties such that the UL safety specifications may be met. At the same time, the shielding material of the second layer 16 is doped (admixed) using with the nano-additives in combination with micro particles that will impart to the overall cable EMI shielding characteristics for sufficiently reducing Alien NEXT and EMI between adjacent cables in LAN installations and preventing electrostatic accumulation. Thus a number of objectives are attained in the proposed design, namely:
~ reduction in the cost of using the new class of nanocomposite polymers;
~ lowering in the size of the overall cable diameter by the co-extrusion of a single jacket structure that could meet the mechanical properties required by UL safety requirements at lower jacket thickness than the two jacket solution and/or the standard shielding solution; and ~ improving EMI and ESD compliance without compromising the other characteristics of the cable, such as impedance and insertion loss.
Doping the top co-extruded layer 16 with conductive nano-particles for EMI
5 shielding leads to other additional desirable characteristics, such as flame and smoke retardancy and smooth and low friction jacket surtace, which could be attained at a much lower cost.
In order to maximise the shielding effect at lower percolation concentrations, a multitude of nano-particles, in particular single wall carbon nanotubes (SWCNT) and multiple wall carbon nanotubes (MWCNT) provide improved results at much lower percolation concentrations than semi-spherical conductive particles. In particular, SWCNT nanotubes can be used to achieve a conductivity of 0.1 to 1 Siemens per centimetre at a concentration of 5%
(see Figure 4).
Referring to Figure 5, in an illustrative combination, (hollow or solid) glass spherical micro particles as in 18 (having an aspect ratio of 1 ) coated with metal and/or magnetic coatings are combined with carbon nanotube fibres as in 20. The combination of the carbon nanotubes 20 with the micro particles 18 increases the conductive pathways between the micro particles 18, thereby increasing EMI absorption. Additionally, increase of the EMI reflection due to the presence of metallic surfaces in the compound will also improve the overall EMI performance of the compound. The presence of micro particles 18 results in the reduction of the quantities of carbon nanotubes 20 that are required for high conductivity on the order of 0.1 to 1 Siemens per centimetre, making possible the use of SWCNT (aspect ratio 1000 to 10,000) in concentrations of less than about 5% with similar conductive results and at lower additive costs. Similarly, lower concentrations of multiple wall carbon nanotubes (MWCNT), less than about 10%, are sufficient for providing similar compounds having a conductivity of about 0.1 Siemens per centimetre.
In order to maximise the shielding effect at lower percolation concentrations, a multitude of nano-particles, in particular single wall carbon nanotubes (SWCNT) and multiple wall carbon nanotubes (MWCNT) provide improved results at much lower percolation concentrations than semi-spherical conductive particles. In particular, SWCNT nanotubes can be used to achieve a conductivity of 0.1 to 1 Siemens per centimetre at a concentration of 5%
(see Figure 4).
Referring to Figure 5, in an illustrative combination, (hollow or solid) glass spherical micro particles as in 18 (having an aspect ratio of 1 ) coated with metal and/or magnetic coatings are combined with carbon nanotube fibres as in 20. The combination of the carbon nanotubes 20 with the micro particles 18 increases the conductive pathways between the micro particles 18, thereby increasing EMI absorption. Additionally, increase of the EMI reflection due to the presence of metallic surfaces in the compound will also improve the overall EMI performance of the compound. The presence of micro particles 18 results in the reduction of the quantities of carbon nanotubes 20 that are required for high conductivity on the order of 0.1 to 1 Siemens per centimetre, making possible the use of SWCNT (aspect ratio 1000 to 10,000) in concentrations of less than about 5% with similar conductive results and at lower additive costs. Similarly, lower concentrations of multiple wall carbon nanotubes (MWCNT), less than about 10%, are sufficient for providing similar compounds having a conductivity of about 0.1 Siemens per centimetre.
In another illustrative combination, non spherical micro particles (such as flakes, ovals or other complex shapes) are combined with nano-additives (such as the SWCNT or MWCNT described hereinabove) with an aspect ratio much greater than that of the micro particles. Similarly, the micro particles can be coated with conductive (i.e. metallic) or magnetically active coatings to effect the same or improved EMI absorption and reflection capabilities as in the precedent claim and, due to the higher aspect ratio, result in even lower additive levels than in the combination with spherical micro particles.
By combining fibre type conductive pathways with micro particles coated with conductive or/and magnetically active materials, a shielding material is provided whereby the absorptive and reflective shielding mechanism is optimised for both high frequency and low frequency EMI.
Thus, enhanced EMI shielding can be achieved while maintaining or improving the absorptive characteristics of the shield, thereby reducing the ability of the shield to act as an emitting or transmitting antenna, given the length of installed cables and the absence of a ground (for example, in UTP
cabling systems without ground).
Doping of the composite shielding layer with conductive polymers is an additional preferred material combination that can also improve the overall EMI shielding capability without the formation of an antenna, in view of the enhanced absorptive characteristics of the shielding layer.
Although the present invention has been described hereinabove by way of an illustrative embodiment thereof, this embodiment can be modified at will without departing from the spirit and nature of the subject invention.
By combining fibre type conductive pathways with micro particles coated with conductive or/and magnetically active materials, a shielding material is provided whereby the absorptive and reflective shielding mechanism is optimised for both high frequency and low frequency EMI.
Thus, enhanced EMI shielding can be achieved while maintaining or improving the absorptive characteristics of the shield, thereby reducing the ability of the shield to act as an emitting or transmitting antenna, given the length of installed cables and the absence of a ground (for example, in UTP
cabling systems without ground).
Doping of the composite shielding layer with conductive polymers is an additional preferred material combination that can also improve the overall EMI shielding capability without the formation of an antenna, in view of the enhanced absorptive characteristics of the shielding layer.
Although the present invention has been described hereinabove by way of an illustrative embodiment thereof, this embodiment can be modified at will without departing from the spirit and nature of the subject invention.
Claims (3)
1. A shielding material comprising:
a polymer doped with nano-additives and micro-particles, wherein said nano-additives and micro-particles impart to the material EMI
shielding characteristics for reducing EMI and electrostatic accumulation.
a polymer doped with nano-additives and micro-particles, wherein said nano-additives and micro-particles impart to the material EMI
shielding characteristics for reducing EMI and electrostatic accumulation.
2. The shielding material of claim 1, wherein said polymer is doped with conductive fibrous nano-additives, micro-particles and/or conductive polymers and combinations thereof.
3. A telecommunications cable comprising:
a conductive inner cable core;
a first inner jacket layer encircling said core, said first layer comprised of a polymer that meets UL safety requirements and transmission performance specifications up 90 Gbit/sec; and a second outer jacket layer encircling said first layer, said second layer comprised of said polymer doped with nano-additives, micro-particles and/or conductive polymers and combinations thereof, wherein said additives impart to the overall cable EMI shielding characteristics for reducing EMI and electrostatic accumulation between adjacent cables.
a conductive inner cable core;
a first inner jacket layer encircling said core, said first layer comprised of a polymer that meets UL safety requirements and transmission performance specifications up 90 Gbit/sec; and a second outer jacket layer encircling said first layer, said second layer comprised of said polymer doped with nano-additives, micro-particles and/or conductive polymers and combinations thereof, wherein said additives impart to the overall cable EMI shielding characteristics for reducing EMI and electrostatic accumulation between adjacent cables.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002461110A CA2461110A1 (en) | 2004-03-15 | 2004-03-15 | Shielding material and communications cable using same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002461110A CA2461110A1 (en) | 2004-03-15 | 2004-03-15 | Shielding material and communications cable using same |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2461110A1 true CA2461110A1 (en) | 2005-09-15 |
Family
ID=35005557
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002461110A Abandoned CA2461110A1 (en) | 2004-03-15 | 2004-03-15 | Shielding material and communications cable using same |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2461110A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2983626A1 (en) * | 2011-12-02 | 2013-06-07 | Thales Sa | Wiring device, has connector comprising body forming shielding, and electric connection unit between body and shielding layer so as to ensure that continuity of shielding enters between cable and connector |
| DE102012203638A1 (en) * | 2012-03-08 | 2013-09-12 | Tyco Electronics Amp Gmbh | Cable with electrical shielding and seal |
-
2004
- 2004-03-15 CA CA002461110A patent/CA2461110A1/en not_active Abandoned
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2983626A1 (en) * | 2011-12-02 | 2013-06-07 | Thales Sa | Wiring device, has connector comprising body forming shielding, and electric connection unit between body and shielding layer so as to ensure that continuity of shielding enters between cable and connector |
| DE102012203638A1 (en) * | 2012-03-08 | 2013-09-12 | Tyco Electronics Amp Gmbh | Cable with electrical shielding and seal |
| US9613731B2 (en) | 2012-03-08 | 2017-04-04 | Te Connectivity Germany Gmbh | Cable having electrical shielding and seal |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |