Cables with improved coverings and methods of forming thereof

Abstract

A cable including a conductor surrounded by a covering layer, the covering layer formed from a thermoplastic vulcanizate composition which includes a continuous phase and a dispersed phase. The continuous phase is formed of a thermoplastic polyolefin. The dispersed phase is formed of a cross-linked elastomeric polyolefin. The thermoplastic vulcanizate composition passes the Hot Creep Test at 150° C. in accordance with UL 2556 (2013) and has a dielectric loss of 3 or less. Methods of forming cables with coverings are also disclosed.

What is claimed is: 
     
         1 . A cable comprising:
 a conductor;   a covering layer surrounding the conductor, the covering layer formed from a thermoplastic vulcanizate composition, the thermoplastic vulcanizate composition comprising:
 about 20% to about 90% of a continuous phase, the continuous phase comprising a thermoplastic polyolefin; and 
 about 10% to about 80% of a dispersed phase, the dispersed phase comprising an at least partially cross-linked elastomeric polymer; and 
   wherein the thermoplastic vulcanizate composition passes a Hot Creep Test at 150° C. in accordance with UL 2556 (2013) and exhibits a dielectric loss of 3 or less when measured at 90° C., 60 Hz, and 80V/mil.   
     
     
         2 . The cable of  claim 1 , wherein the covering layer is one or more of an insulation layer or a jacket layer. 
     
     
         3 . The cable of  claim 1  has a breakdown strength of 400 V/mil or more in accordance with ICEA S-94-649 (2013) using a voltage rate increase of 1.0 kV/sec. 
     
     
         4 . The cable of  claim 1 , wherein the cross-linked elastomeric polymer has a glass transition temperature of −10° C. or less. 
     
     
         5 . The cable of  claim 1 , wherein the at least partially cross-linked elastomeric polymer is an olefin-based copolymer. 
     
     
         6 . The cable of  claim 1 , wherein the at least partially cross-linked elastomeric polymer comprises one or more of a polyolefin elastomer, an ethylene propylene rubber, an ethylene acrylic rubber, an ethylene propylene diene terpolymer, a silane grafted polyolefin, an ethylene copolymer, and a silicone copolymer. 
     
     
         7 . The cable of  claim 1 , wherein the thermoplastic polyolefin has a melting point temperature of about 110° C. or more. 
     
     
         8 . The cable of  claim 1 , wherein the thermoplastic polyolefin comprises one or more of polypropylene or a copolymer thereof, and wherein the polypropylene and the copolymers thereof each have a melting point temperature of about 150° C. or more. 
     
     
         9 . The cable of  claim 1 , wherein the dispersed phase comprises about 40% to about 70%, by weight, of the thermoplastic vulcanizate composition, and the continuous phase comprises about 30% to about 60%, by weight, of the thermoplastic vulcanizate composition. 
     
     
         10 . The cable of  claim 9 , wherein the thermoplastic polyolefin is polypropylene and the at least partially cross-linked elastomeric polymer is ethylene propylene diene monomer or silane grafted low density polyethylene. 
     
     
         11 . The cable of  claim 10 , wherein thermoplastic vulcanizate composition has a gel content, of about 5% to about 75% when measured in accordance to ASTM D2765 (2011). 
     
     
         12 . The cable of  claim 10 , wherein the thermoplastic vulcanizate composition further comprises about 3% to about 10% of an additive. 
     
     
         13 . The cable of  claim 12 , wherein the additive comprises one or more of a nucleating agent, an antioxidant, a UV stabilizer, a heat stabilizer, a metal deactivator, a processing aid, and a curing agent. 
     
     
         14 . The cable of  claim 13 , wherein the curing agent comprises a peroxide compound. 
     
     
         15 . The cable of  claim 1 , wherein the thermoplastic vulcanizate composition further comprises a filler, and wherein the filler comprises one or more of zinc oxide, magnesium oxide, boron nitride, aluminum nitride, talc, and calcined clay. 
     
     
         16 . The cable of  claim 1 , wherein the thermoplastic vulcanizate composition exhibits a thermal conductivity of about 0.20 W/mK or more. 
     
     
         17 . The cable of  claim 1 , wherein the dispersed phase has an average particle size of about 100 microns or less. 
     
     
         18 . The cable of  claim 1  configured to operate at voltages of about 1 kV or more. 
     
     
         19 . A method of forming a cable with a covering, the method comprising:
 providing a conductor;   extruding a covering layer around the conductor, the covering layer comprising a thermoplastic vulcanizate composition, the thermoplastic vulcanizate composition comprising:
 about 20% to about 90% of a continuous phase, the continuous phase comprising a thermoplastic polyolefin; and 
 about 10% to about 80% of a dispersed phase, the dispersed phase comprising an elastomeric polymer; and 
   curing the thermoplastic vulcanizate composition by dynamically cross-linking the elastomer polymer; and   wherein the cable passes the Hot Creep Test at 150° C. in accordance with UL 2556 (2013) and has a dielectric loss of 3 or less when measured at 90° C., 60 Hz, and 80V/mil.   
     
     
         20 . The method of  claim 19 , wherein the elastomeric polymer of the thermoplastic vulcanizate composition is partially cross-linked prior to extruding the covering layer.