Abstract:
A communication cable can comprise twisted pairs of electrical conductors for transmitting electrical signals, such as for digital communication or data transmission. The pairs can be twisted to different tightness in connection with managing interference among the pairs. Within the cable, a separator having an economical polymeric composition can maintain the pairs in a desired orientation. The pairs can be insulated with polymeric materials that compensate for relaxed electrical characteristics of the economical polymeric composition of the separator. One or more pairs having relatively tight twist can be insulated with a premium polymeric material that provides a relatively high level of electrical performance. One or more pairs twisted less tightly can be insulated with another polymeric material providing somewhat lesser but still sufficient electrical performance.

Description:
FIELD OF THE TECHNOLOGY 
     The present invention relates to communication cables comprising multiple twisted pairs of electrical conductors for transmitting communication signals, and more specifically to cables in which pairs are twisted at different rates and insulated with different polymers. 
     BACKGROUND 
     The escalating desire for enhanced communication bandwidth presses transmission media to convey information at higher speeds while maintaining signal fidelity and avoiding crosstalk. Additionally, the market expects cost reduction to accompany such advances in performance. 
     A single communication cable may be called upon to transmit multiple communication signals over respective electrical conductors concurrently. Such a communication cable may have two or more twisted pairs of insulated electrical conductors (“twisted pairs”). A flexible member extending internally within the cable may help maintain these twisted pairs in a desirable orientation. Each pair may be twisted to a different twist length or “lay length” in order to control interference associated with signal energy coupling between or among the pairs, including through the flexible member. The materials of the flexible member and the insulation of the twisted pairs affect this interference. Materials offering improved electrical performance typically have higher costs. Meanwhile, the flexible member and the pair insulation materials account for a substantial portion of cost of a cable. 
     Accordingly, need exists for technology to impart a cable with enhanced signal performance economically. A capability addressing such need or some other related deficiency in the art would support cost effective communications and elevate bandwidth that a communication cable can carry cost effectively. 
     SUMMARY 
     In one aspect of the present invention, a communication cable can comprise multiple electrical conductors for transmitting multiple communication signals concurrently. The communication signals can comprise digital or discrete signal levels supporting digital communication, for example. The communication cable can comprise twisted pairs of insulated electrical conductors that extend lengthwise along the cable. A flexible member running lengthwise within the cable can maintain the twisted pairs in a desirable orientation. The pairs can be twisted to different lengths towards controlling or avoiding interference among the twisted pairs. Pairs having tighter twist can be insulated with premium materials offering high electrical performance. With such elevated electrical performance of the tightly twisted pairs, the flexible member can be made from economical material that could otherwise compromise cable performance. Pairs twisted less tightly, and thus less susceptible to the economical material of the flexible member, can be insulated with materials having relaxed electrical performance relative to the premium insulation. 
     The foregoing discussion of materials and configurations for twisted pair cables is for illustrative purposes only. Various aspects of the present invention may be more clearly understood and appreciated from a review of the following detailed description of the disclosed embodiments and by reference to the drawings and the claims that follow. Moreover, other aspects, systems, methods, features, advantages, and objects of the present invention will become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such aspects, systems, methods, features, advantages, and objects are to be included within this description, are to be within the scope of the present invention, and are to be protected by the accompanying claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross sectional view of an exemplary communication cable that comprises four twisted pairs of electrical conductors having different insulation and different twist lengths in accordance with certain embodiments of the present invention. 
         FIG. 2  is an illustration of an exemplary twisted pair of a communication cable in accordance with certain embodiments of the present invention. 
         FIG. 3  is an illustration depicting exemplary twists of a communication cable in accordance with certain embodiments of the present invention. 
         FIG. 4  is an illustration depicting exemplary insulation covering an electrical conductor of a twisted pair in accordance with certain embodiments of the present invention. 
     
    
    
     Many aspects of the invention can be better understood with reference to the above drawings. The elements and features shown in the drawings are not to scale, emphasis instead being placed upon clearly illustrating the principles of exemplary embodiments of the present invention. Moreover, certain dimensions may be exaggerated to help visually convey such principles. In the drawings, reference numerals designate like or corresponding, but not necessarily identical, elements throughout the several views. 
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Technology for cost effective management of electrical performance of twisted pairs of a communication cable will now be described more fully with reference to  FIGS. 1-4 , which illustrate representative embodiments of the present invention.  FIGS. 1 ,  2 ,  3 , and  4  describe exemplary features of a communication cable comprising twisted pairs having different twist lengths and different insulation materials. 
     The invention can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those having ordinary skill in the art. Furthermore, all “examples” or “exemplary embodiments” given herein are intended to be non-limiting and among others supported by representations of the present invention. 
     Turning now to  FIG. 1 , this figure illustrates a cross sectional view of a communication cable  100  that comprises four twisted pairs  105  ( 1051 ,  1052 ,  1053 ,  1054 ) of electrical conductors having different insulation  101  ( 1011 ,  1012 ,  1013 ,  1014 ) and different twist lengths according to certain exemplary embodiments of the present invention. 
     A jacket  120  typically having a polymer-based composition seals the communication cable  100  from the environment and provides strength and structural support. In one exemplary embodiment, the jacket  120  has an outer diameter of about 0.205 inches and a wall thickness of about 0.016 inches. In various embodiments, the jacket  120  comprises polymeric material, polyvinyl chloride (“PVC”), polyurethane, one or more polymers, a fluoropolymer, polyethylene, neoprene, cholorosulphonated polyethylene, fluorinated ethylene propylene (“FEP”), flame retardant PVC, low temperature oil resistant PVC, polyolefin, flame retardant polyurethane, flexible PVC, or some other appropriate material known in the art, or a combination thereof, for example. In certain exemplary embodiments, the jacket  120  can comprise flame retardant and/or smoke suppressant materials. Outfitted with such materials or other materials having suitable fire properties, the illustrated communication cable  100  can be deployed in plenum applications and/or designated as a plenum cable. 
     The jacket  120 , which extends lengthwise along the communication cable  100 , can be single layer or have multiple layers. In certain exemplary embodiments, a tube or tape (not illustrated) can be disposed between the jacket  120  and the twisted pairs  105 . Such a tube or tape can be made of polymeric or dielectric material, for example. In various embodiments, the jacket  120  can be characterized as an outer jacket, an outer sheath, a casing, a circumferential cover, or a shell. 
     The communication cable  100  can comprise shielding or may be unshielded, as  FIG. 1  illustrates. In certain exemplary embodiments, a metallic foil or other electrically conductive material can cover the twisted pairs  105  and/or the cable core  125  to provide shielding. In certain exemplary embodiments, the communication cable  100  can be shielded with a system of electrically isolated patches of shielding material, for example as described in U.S. patent application Ser. No. 12/313,914, entitled “Communication Cable Comprising Electrically Isolated Patches of Shielding Material.” The entire contents of U.S. patent application Ser. No. 12/313,914, entitled “Communication Cable Comprising Electrically Isolated Patches of Shielding Material” are hereby incorporated herein by reference. 
     A metallic material, whether continuous or comprising electrically conductive patches, can be disposed on a substrate, such as a tape placed between the twisted pairs  105  and the jacket  120 , or adhered to the jacket  120 . For example, shielding, whether continuous or electrically isolated, can be disposed or sandwiched between the jacket  120  and a tube or tape that is disposed between the jacket  120  and the twisted pairs  105 . In certain embodiments, the jacket  120  comprises conductive material and may be or function as a shield. In certain embodiments, the jacket  120  comprises armor, or the communication cable  100  comprises a separate, outer armor for providing mechanical protection. 
     In the illustrated embodiment, the cable core  125  of the communication cable  100  contains four twisted pairs  105 , four being an exemplary, rather than limiting, number. Other exemplary embodiments may have fewer or more twisted pairs  105 . The twisted pairs  105  extend along the longitudinal axis  135  of the communication cable  100  within the cable core  125 . 
     Each twisted pair  1051 ,  1052 ,  1053 ,  1054  can carry data or some other form of information, for example in a range of about one to ten Giga bits per second (“Gbps”) or at another appropriate speed, whether faster or slower. In certain exemplary embodiments, each twisted pair  1051 ,  1052 ,  1053 ,  1054  supports data transmission of about two and one-half (2.5) Gbps (e.g. nominally two and one-half Gbps), with the communication cable  100  supporting about ten Gbps (e.g. nominally ten Gbps). In certain exemplary embodiments, each twisted pair  1051 ,  1052 ,  1053 ,  1054  supports data transmission of about ten Gbps (e.g. nominally ten Gbps), with the communication cable  100  supporting about forty Gbps (e.g. nominally forty Gbps). In certain exemplary embodiments, the communication cable  100  carries about twelve and one-half Gbps. 
     The illustrated communication cable  100  can convey four distinct channels of information simultaneously, one channel per twisted pair  1051 ,  1052 ,  1053 ,  1054 . In certain exemplary embodiments, the metallic conductor diameter of each twisted pair  1051 ,  1052 ,  1053 ,  1054  can be in a range of about 0.0223 inches to about 0.0227 inches. In certain exemplary embodiments, the outer, insulation diameter covering each metallic conductor can be in a range of about 0.0385 inches to about 0.0395 inches, for example. As will be discussed in further detail below, the insulation  101  ( 1011 ,  1012 ,  1013 ,  1014 ) covering the electrical conductors of the twisted pairs  105  can comprise materials selected according to pair twist length. 
     As will be discussed in further detail below, at least two of the twisted pairs  1051 ,  1052 ,  1053 ,  1054  have different twist rates (twists-per-meter or twists-per-foot). That is, at least two of the twisted pairs  1051 ,  1052 ,  1053 ,  1054  have different twist lengths or twist lays, which can be characterized in units of centimeters-per-twist, inches-per-twist, or inches-per-lay. In certain exemplary embodiments, each of the twisted pairs  1051 ,  1052 ,  1053 ,  1054  has a different twist length. 
     In the illustrated view, each twisted pair  1051 ,  1052 ,  1053 ,  1054  sweeps out a respective twist path  115  as it twists/rotates, with the twist paths  115  generally circular when viewed end-on as illustrated. (The twist paths  115  are illustrated in approximation.) 
     In certain exemplary embodiments, the differences between twist rates of twisted pairs  105  that are circumferentially adjacent one another (for example the twisted pair  1051  and the twisted pair  1052 ) are greater than the differences between twist rates of twisted pairs  105  that are diagonal from one another (for example the twisted pair  1051  and the twisted pair  1053 ). As a result of having similar twist rates, the twisted pairs  105  that are diagonally disposed can be more susceptible to crosstalk issues than the twisted pairs  105  that are circumferentially adjacent. The different twist lengths can help reduce crosstalk among the twisted pairs  105 . Additionally, electrical performance demands, including interference issues, can be associated with tighter pair twisting. 
     The cable core  125  can be filled with a gas such as air (as illustrated) or alternatively a gelatinous, solid, powder, moisture absorbing material, water-swellable substance, dry filling compound, or foam material, for example in interstitial space between the twisted pairs  105 . Other elements can be added to the cable core  125 , for example one or more optical fibers, additional electrical conductors, additional twisted pairs, or strength members, depending upon application goals. 
     In the illustrated embodiment, the communication cable  100  comprises a flexible member  150  that maintains a desired orientation of the twisted pairs  105  to provide beneficial signal performance. In an exemplary embodiment, the flexible member  150  can be a pair separator. The illustrated embodiment of the flexible member  150  has a cross sectional geometry resembling a plus sign. Various embodiments may be shaped like an “X,” a “T,” a “Y,” a “J,” a “K”, an “L” an “I,” or have a form of a flat strip, or a circular cross section, or comprise two or three or more fins, for example. In certain exemplary embodiments, the communication cable  100  may not include a flexible member for maintaining geometric orientation of the twisted pairs  105 . 
     In various exemplary embodiments, the flexible member  150  can comprise polyvinyl chloride (PVC) (typically but not necessarily low-smoke PVC), polypropylene, polyethylene, FEP, ethylene chlorotrifluoroethlyene (“ECTFE”), or some other suitable polymeric or dielectric material, for example. In various exemplary embodiments, the flexible member  150  can consist of, or substantially consist of, PVC, polypropylene, polyethylene, FEP, ECTFE, or some other suitable polymeric or dielectric material, for example. The flexible member  150  can be filled, unfilled, foamed, un-foamed, homogeneous, or inhomogeneous and may or may not comprise additives. The flexible member  150  can comprise flame retardant and/or smoke suppressant materials. In certain exemplary embodiments, the strip  155  is crosslinked. The flexible member  150  can be extruded, pultruded, or formed in another appropriate process known in the art. 
     The flexible member  150  can have a substantially uniform composition, can be made of a wide range of materials, and/or can be fabricated in a single manufacturing pass. Further, the flexible member  150  can be a composite and can include one or more strength members, fibers, optical fibers, metallic conductors, cavities, threads, or yarns. Additionally, the flexible member  150  can be hollow to provide a cavity that may be filled with air or some other gas, gel, fluid, moisture absorbent, water-swellable substance, dry filling compound, powder, an optical fiber, a metallic conductor, shielding, or some other appropriate material or element. 
     In certain exemplary embodiments, the flexible member  150  can comprise electrically conductive patches that are electrically isolated from one another to provide one or more shields. Such patches can adhere to a surface of the flexible member  150 , for example. 
     In certain exemplary embodiments, the flexible member  150  has a polymeric composition having a propensity or a capability to diminish or degrade electrical performance of at least one of the twisted pairs  1051 ,  1052 ,  1053 ,  1054  at an operating frequency or data rate of the communication cable  100 . In such embodiments, at least one of the twisted pairs  1051 ,  1052 ,  1053 ,  1054  can be insulated with a material that addresses, mitigates, or overcomes such electrical performance degradation. In certain embodiments, one or more of the twisted pairs  1051 ,  1052 ,  1053 ,  1054  are configured such that they are particularly susceptible to diminished electrical performance associated with interaction with the flexible member  150 . The insulation  101  ( 1011 ,  1012 ,  1013 ,  1014 ) of the specific twisted pair or pairs  1051 ,  1052 ,  1053 ,  1054  with such susceptibility can have a premium composition that overcomes the susceptibility. 
     In certain exemplary embodiments, the twisted pairs  1051  and  1053  are twisted more tightly and thus have shorter twist lengths than the twisted pairs  1052  and  1054 . With such twisting, the twisted pairs  1051  and  1053  can be more sensitive than the twisted pairs  1052  and  1054  to a composition of the flexible member  150  that includes a substantial level of PVC or another economical polymeric material. To overcome this sensitivity, the insulation  1011  and  1013  of the twisted pairs  1051  and  1053  can have improved electrical properties relative to the insulation  1012  and  1014  of the twisted pairs  1052  and  1054 . In certain exemplary embodiments, the insulations  1011 ,  1012 ,  1013 ,  1014  all comprise FEP, with the insulations  1011  and  1013  having a composition or grade of FEP that electrically outperforms the insulations  1012  and  1014 . Accordingly, the insulations  1011 ,  1012 ,  1013 ,  1014  can have fluoropolymers providing two (or more) performance levels. 
     For example, the flexible member  150  can comprise PVC, be based on PVC, or have a composition that is at least 70 percent, 80 percent, 90 percent, 95 percent, 99 percent PVC or in a range between any two of these values. (In certain embodiments, such percentages are on a volume basis. In certain embodiments, such percentages are on a weight basis.) In certain exemplary embodiments, the flexible member  150  is formed from a material available from Teknor Apex of Pawtucket, R.I. under the product identifier “910A-34-NL” and the registered mark “FIREGUARD.” Table 1 below provides exemplary properties for this material, as provided by the supplier. 
     
       
         
               
             
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Exemplary Properties for the Flexible Member 
               
             
          
           
               
                   
                 U.S.  
                   
               
               
                 Properties 
                 Units/Metric 
                 Test Method 
               
               
                   
               
               
                 Hardness (Shore ‘C’ Duro +/−3) 
                 82/82 
                 ASTM D-2240 
               
               
                 10 Second Reading 
                   
                   
               
               
                 Specific Gravity +/−0.02 
                 1.66/1.66 
                 ASTM D-792 
               
               
                 Tensile Strength, psi (MPa) 
                 2276/15.7 
                 ASTM D-638 
               
               
                 Elongation, % 
                 235/235 
                 ASTM D-638 
               
               
                 Brittle Point, ° C. 
                 −8 
                 ASTM D-746 
               
               
                 Dielectric Constant @ 1 kHz. @ 1 MHz. 
                 4.67/3.67 
                 ASTM D-150 
               
               
                 Dissipation Factor @ 1 kHz. @ 1 MHz. 
                 0.068/0.032 
                 ASTM D-150 
               
               
                 Oxygen Index (%) 
                 52.5 
                 ASTM D-2863 
               
               
                 Dynamic Heat Stability @ 205 2 ° C., 
                 56 
                   
               
               
                 100 RPM, 72 gr. #5 Bowl 
                   
                 ASTM D-2538 
               
               
                 (Mins. to Decomposition) 
                   
                   
               
               
                 Kayeness ACR @ 350 ° F., 1000 sec−1 
                 362 
                 ASTM D-3835 
               
               
                 (Pa-sec) 
                   
                   
               
               
                 Cone Calorimeter @ 75 kW/m2) 
                   
                   
               
               
                 Peak Heat Release Rate (kW/m2) 
                 110.8 
                   
               
               
                 Avg. Heat Release Rate (kW/m2) 
                 57.1 
                   
               
               
                 Total Heat Released (MJ/m 2 ) 
                 66 
                 ISO-5660 
               
               
                 Avg. Heat of Combustion (MJ/kg) 
                 10.5 
                   
               
               
                 Avg. Specific Extinction Area (m 2 /kg) 
                 142 
                   
               
               
                 Peak Smoke (1/m) 
                 1.29 
                   
               
               
                 Maximum Operating Temperature, ° C. 
                 75 
                   
               
               
                 Suggested Melt Temperature, ° F. 
                 385 
               
               
                   
               
             
          
         
       
     
     In certain embodiments, the flexible member  150  and the jacket  120  can comprise common polymeric materials, for example both being based on PVC. Accordingly, the flexible member  150  can have a substantial content of PVC or another economical polymeric material that may negatively impact data transmission fidelity or quality, such as associated with interplay between tightly twisted pairs and the flexible member  150 . To mitigate or alleviate such negative impact, one or more tightly twisted pairs can be insulated with polymeric insulation material that is premium relative to loosely twisted pairs. 
     Turning now to  FIG. 2 , this figure illustrates a twisted pair  105  ( 1051 ,  1052 ,  1053 ,  1054 ) of the communication cable  100  according to certain exemplary embodiments of the present invention. The twisted illustrated twisted pair  105  has a twist length  200  (which may also be characterized as twist lay). For example, if the insulated electrical conductors  201  and  202  of the illustrated pair  105  ( 1051 ,  1052 ,  1053 ,  1054 ) are twisted together so as to revolve around one another two times-per-inch, the twist rate would be two twists-per-inch, and the twist length or lay length would be one-half inch. In certain exemplary embodiments, each of the twisted pairs  1051 ,  1052 ,  1053 ,  1054  of the communication cable  100  has a different twist length  200 . In certain exemplary embodiments, the twist lengths  200  of the twisted pairs  105  ( 1051 ,  1052 ,  1053 ,  1054 ) can be in a range of about 0.250 to 0.800 inches, 0.280 to 0.420 inches, or 0.350 to 0.475 inches, for example. 
     In various exemplary embodiments, the twisted pairs  105  can have a common twist direction that is clockwise or counterclockwise. In certain embodiments, at least one of the twisted pairs  1051 ,  1052 ,  1053 ,  1054  can be twisted in a clockwise direction, while other ones are twisted counterclockwise. Accordingly, the twisted pairs  105  may have a “left hand lay” or a “right hand lay” or a combination thereof. 
     As discussed above, material compositions and electrical performances of the insulation  101  ( 1011 ,  1012 ,  1013 ,  1014 ) of the twisted pairs  105  ( 1051 ,  1052 ,  1053 ,  1054 ) can be selected according to twist length  200 . In this manner, economical insulation and premium insulation can be incorporated where appropriate. 
     Turning now to  FIG. 3 , this figure illustrates twists of the communication cable  100  according to certain exemplary embodiments of the present invention. In the illustrated embodiment of  FIG. 3 , the core  125  has a twist  365  in a direction that is common to the pair twist. Thus, the core  125  and the twisted pairs  1051 ,  1052 ,  1053 ,  1054  can each have left hand lay or twist in counterclockwise direction as illustrated. Alternatively, the core  125  and the twisted pairs  1051 ,  1052 ,  1053 ,  1054  can each have right hand lay or twist in clockwise direction. Accordingly, the four twisted pairs  1051 ,  1052 ,  1053 ,  1054  can be collectively twisted about a longitudinal axis  135  (see  FIG. 1 ) of the communication cable  100  in a common direction. 
     Turning now to  FIG. 4 , this figure illustrates insulation  101  ( 1011 ,  1012 ,  1013 ,  1014 ) covering an electrical conductor  415  of a twisted pair  105  ( 1051 ,  1052 ,  1053 ,  1054 ) according to in certain exemplary embodiments of the present invention. In certain exemplary embodiments, the insulation  101  ( 1011 ,  1012 ,  1013 ,  1014 ) comprises a skin  405  covering a foamed region. 
     In certain exemplary embodiments, the electrical conductors  415  of the communication cable  100  can have consistent or common diameters (twice the illustrated radius  425  that extends from the center axis  435  radially outward), for example being manufactured to a common specification. Alternatively, in certain exemplary embodiments, the electrical conductors  415  of different twisted pairs  105  can have different diameters. In certain exemplary embodiments, the electrical conductors  415  can be 22, 23, or 24 AWG (American Wire Gauge). In certain exemplary embodiments, the electrical conductors  415  can have a diameter in a range of about 0.0201 to 0.0253 inches, for example. 
     In certain exemplary embodiments, the insulated electrical conductors  400  of each twisted pair  1051 ,  1052 ,  1053 ,  1054  within the communication cable  100  can have an outer diameter (twice the illustrated radius  420 ) that is consistent or common. Alternatively, in certain exemplary embodiments, the insulated electrical conductors  400  of the communication cable  100  can have different insulation thicknesses. In certain exemplary embodiments, the thickness of the insulation  101  ( 1011 ,  1012 ,  1013 ,  1014 ) can be in a range of about 0.007 to 0.015 inches, for example. 
     As discussed above, the compositions of the insulation  101  ( 1011 ,  1012 ,  1013 ,  1014 ) of the twisted pairs  105  ( 1051 ,  1052 ,  1053 ,  1054 ) typically differs in accordance with twist length  200 . In one exemplary embodiment of the communication cable  100 , the insulation  101  and  103  of the twisted pairs  1051  and  1053  comprises an FEP-based material providing a relatively high electrical performance and those twisted pairs  1051  and  1053  have a substantially tighter twist than the twisted pairs  1052  and  1054 . Such a material is available from Daikin America Inc. of Decatur, Ala. under the product identifier “NP-1105.” Table 2 below provides exemplary properties for this material, as provided by the supplier. Meanwhile, the insulation  1012  and  1014  of the twisted pairs  1052  and  1054  comprises an FEP-based material offering lower electrical performance, but lower cost, and those twisted pairs  1052  and  1054  have a substantially looser twist than the twisted pairs  1051  and  1053 . Such a material is available from Daikin America Inc. under the product identifier “NP-102.” Table 3 below provides exemplary properties for this material, as provided by the supplier. The flexible member  125  for this embodiment of the communication cable  100  can have the properties and composition reflected in Table 1, as discussed above. As shown in exemplary Tables 2 and 3, the insulation  1011  and  1013  exhibits a substantially reduced dissipation factor at 2.5 GHz as compared to the insulation  1012  and  1014 . Thus, the twisted pairs  1051  and  1053  can be twisted more tightly and operated in proximity of the flexible member  125  without sacrificing electrical performance. Accordingly, the communication cable  100  can achieve tight cost constraints by utilizing economical polymeric materials where feasible and incorporating premium polymeric materials strategically to offset performance issues otherwise associated with economical materials utilization. 
     
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Exemplary Properties for Premium Insulation 
               
             
          
           
               
                 Properties 
                 Test Method  
                 Values 
                 Units 
               
               
                   
               
               
                 Specific gravity 
                 ASTM 2116 
                 2.14-2.17 
                 N/A 
               
               
                 Melt Flow Rate 
                 ASTM 2116 
                 19-26 
                 g/10 min. 
               
               
                 Melting Point 
                 ASTM 2116 
                 250-60 
                 ° C. 
               
               
                 Tensile Strength 
                 ASTM 2116 
                 20 (2900) 
                 MPa 
               
               
                 Minimum 
                   
                   
                 ( Psi) 
               
               
                 Elongation Percent 
                 ASTM 2116 
                 280 minimum 
                 % 
               
               
                 Thermal Conductivity 
                 C117 
                 6 × 10-4 
                 (cal/sec/cm 2 , 
               
               
                   
                   
                   
                 ° C./cm) 
               
               
                 Maximum Continuous 
                   
                 200 
                 ° C. 
               
               
                 Temperature Use 
                   
                   
                   
               
               
                 Dielectric Constant 
                 D150/10 3   
                 2.1 
                   
               
               
                   
                 D150/10 6   
                 2.1 
                   
               
               
                 Dissipation Factor 
                 @ 2.4 GHz 
                 4 E-4 
                   
               
               
                 Chemical resistance 
                   
                 Excellent 
                   
               
               
                 Weatherability 
                   
                 Excellent 
                   
               
               
                 Combustibility 
                 D2863/Oxygen 
                 &gt;95 
                 % 
               
               
                   
                 Concentration 
                   
                   
               
               
                   
                 Index 
                   
                   
               
               
                 Contact Angle 
                 Angle to level 
                 114 
                 Degrees 
               
               
                 Flex Life 
                 MIT 
                 5000 
                 Cycles 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
               
                 Exemplary Properties for Premium Insulation 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Specific gravity 
                 ASTM 2116 
                 2.12-2.17 
                 N/A 
               
               
                 Melt Flow Rate 
                 ASTM 2116 
                 23.0-30.0 
                 g/10 min. 
               
               
                 Melting Point 
                 ASTM 2116 
                 250-265 
                 ° C. 
               
               
                 Tensile Strength Min. 
                 ASTM 2116 
                 20 (2900) 
                 MPa (Psi) 
               
               
                 Elongation Percent 
                 ASTM 2116 
                 275-400 
                 % 
               
               
                 Thermal Conductivity 
                 C117 
                 6 × 10-4 
                 (cal/sec/cm2, 
               
               
                   
                   
                   
                 ° C./cm) 
               
               
                 Melt Viscosity 
                   
                 4 × 10 4    ~ 10 5  (300 ~ 330°) 
                 Poise 
               
               
                 Coef. of Linear Expansion 
                 D696/23°  ~ 60° 
                 8.3  ~ 10.5 × 10-5 
                 (1/° C.) 
               
               
                 Max. Cont. Temp. Use 
                   
                 200 
                 ° C. 
               
               
                 Compression Strength 
                 D695/1% Def., 25° C. 
                 5 ~ 6 
                 MPa 
               
               
                 Flexural Modulus 
                 D790/23° C. 
                 539 ~ 637 
                 MPa 
               
               
                 Hardness 
                 Durometer 
                 D55 
                 (Shore) 
               
               
                 Deformation Under Load 
                 D621/100° C., 6.8 MPa, 24 h 
                 5.0 
                 % % 
               
               
                   
                 D621/25° C., 13.7 MPa, 24 h 
                 3.0 
                   
               
               
                 Impact Strength 
                 D256/23° C., Izod 
                 No break 
                 (ft-lb/in) 
               
               
                 Static Friction Coef. 
                 Coated Steel Surface 
                 0.05 
                 N/A 
               
               
                 Dielectric Constant 
                 D150/10 3  D150/10 6   
                 2.1 2.1 
                   
               
               
                 Dissipation Factor 
                 @ 2.4 GHz 
                 9 E-4 
                   
               
               
                 Diel. Breakdown Strength 
                 D149 short time ⅛ in 
                 500 ~ 600 
                 V/mil 
               
               
                 Volume Resistivity 
                 D257 
                 &lt;10 18   
                 Ohm-cm 
               
               
                 Chemical resistance 
                   
                 Excellent 
                   
               
               
                 Weatherability 
                   
                 Excellent 
                   
               
               
                 Combustibility 
                 D2863/Oxygen Conc. 
                 &gt;95 
                 % 
               
               
                   
                 Index 
                   
                   
               
               
                 Contact Angle 
                 Angle to level 
                 114 
                 Degrees 
               
               
                 Flex Life 
                 MIT 
                 5000 
                 Cycles 
               
               
                 Critical Shear Rate 
                 (360 ~ 400° C.) 
                 60 ~ 130 
                 Sec−1 
               
               
                   
               
             
          
         
       
     
     From the foregoing, it will be appreciated that an embodiment of the present invention overcomes the limitations of the prior art. Those skilled in the art will appreciate that the present invention is not limited to any specifically discussed application and that the embodiments described herein are illustrative and not restrictive. From the description of the exemplary embodiments, equivalents of the elements shown herein will suggest themselves to those skilled in the art, and ways of constructing other embodiments of the present invention will suggest themselves to practitioners of the art. Therefore, the scope of the present invention is to be limited only by the claims that follow.