Electrically conductive, mesophase-separated olefin multiblock copolymer compositions
Free radically crosslinked, electrically conductive compositions exhibiting a highly stable volume resistivity comprise an olefin multiblock copolymer (OBC) having a high, e.g., greater than 20 mole percent comonomer content, e.g., butylene or octene, and carbon black. These compositions exhibit a highly stable volume resistivity relative to a composition similar in essentially all aspects save that the high comonomer OBC is replaced with a low comonomer OBC of similar density and melt index.
1. A composition comprising in weight percent based on the weight of the composition:
(A) from 70 to 93% of a mesophase separated ethylene-α-olefin multiblock copolymer having an Mw/Mn from 1.4 to 2.8 and comprising hard segments and soft segments and consisting of (1) a majority mole fraction ethylene), and (2) at least 20 mole percent of a C 3 -C 12 α-olefin comonomer, the comonomer located primarily in the soft segment of the copolymer with (i) a difference in mole percent comonomer between the hard segment and the soft segment (Δ comonomer) of 22 to 45 mole percent, and (ii) the hard segments and the soft segments are mesophase separated to form locally segregated ordered domains having a size from greater than 40 nm to 300 nm as measured in the smallest dimension,
(B) from at least 20% to less than 36% conductive filler, in which the conductive filler is at least one of a conductive carbon black, conductive carbon and metal filler,
(C) Optionally an elastomer other than the ethylene-α-olefin high comonomer, mesophase-separated olefin multiblock copolymer,
(D) Optionally a plasticizer,
(E) Optionally a cure agent,
(F) Optionally one or more additives, and
the composition has a volume resistivity less than 500 ohm-cm.
2. The composition of claim 1 in which the conductive filler as at least one of carbon black, graphene and carbon nanotubes.
3. The composition of claim 1 in which the metal filler comprises at least one of aluminum, zinc, iron, nickel, tin, lead, and silver.
4. The composition of claim 1 in which the optional elastomer is at least one of a polyolefin homopolymer, polyolefin interpolymer and a non-phase separated olefin multiblock copolymer, and is present in an amount of 1 to 35 wt % based on the weight of the composition.
5. The composition of claim 1 in which the optional elastomer is a non-olefin elastomer comprising at least one of silicone elastomer, urethane elastomer, styrene-butadiene rubber (SBR), nitrile rubber, chloroprene, fluorelastomer, perfluoroelastomer, polyether block amide and chlorosulfonated polyethylene, and is present in an amount of 1 to 35 wt % based on the weight of the composition.
6. The composition of claim 5 in which the plasticizer is present in an amount of 1 to 20 wt % based on the weight of the composition.
7. The composition of claim 4 in which the elastomer is present and at least one of the mesophase-separated olefin multiblock copolymer and elastomer comprises silane functionality.
8. The composition of claim 6 in which the cure agent is present and is at least one of an organic base, carboxylic acid, sulfonic acid, and an organometallic compound.
9. The composition of claim 1 free of halogen.
10. A wire or cable article comprising the composition of claim 1 .
11. The composition of claim 1 wherein the comonomer is octene.
12. The composition of claim 1 wherein the domains have a size from 60 nm to 200 nm.
13. The composition of claim 1 wherein the composition has a volume resistivity of less than 20 ohm-cm after 25 days aging.
14. The composition of claim 1 wherein the mesophase separated ethylene-α-olefin multiblock copolymer has a melt index of 0.1 to 30 g/10 min as measured by ASTM D1238 (190° C./2.16 kg).
15. The composition of claim 14 wherein the mesophase separated ethylene-α-olefin multiblock copolymer has a density less than 0.90 g/cc.
16. A composition comprising in weight percent based on the weight of the composition:
(A) a high comonomer olefin block copolymer (HC-OBC) having an Mw/Mn from 1.4 to 2.8 and having hard segments and soft segments, the HC-OBC consisting of (1) a majority mole fraction ethylene and (2) at least 20 mol % of a C 3 -C 12 α-olefin comonomer, wherein the comonomer is located primarily in the soft segment of the HC-OBC with (i) a difference in mole percent comonomer between the hard segment and the soft segment (Δ comonomer) of 22 to 45 mole percent, and (ii) the hard segments and the soft segments are mesophase separated to form locally segregated ordered domains having a size from greater than 40 nm to 300 nm as measured in the smallest dimension;
(B) from at least 20% to less than 36% conductive filler, in which the conductive filler is at least one of a conductive carbon black, conductive carbon and metal filler;
(C) optionally an elastomer other than the ethylene-α-olefin high comonomer; mesophase-separated olefin multiblock copolymer,
(D) optionally a plasticizer,
(E) optionally a cure agent,
(F) optionally one or more additives, and
the composition has a volume resistivity less than 250 ohm-cm.
17. The composition of claim 16 comprising from 70% to 93% of the high comonomer OBC.
18. The composition of claim 1 wherein the conductive filler is carbon black.
19. The composition of claim 16 wherein the conductive filler is carbon black.