Compositions with carbon nanotubes for low hysteresis elastomers
The present application is directed to novel discrete carbon nanotubes with a surface modification that disperses well in elastomers and crosslinks elastomers to the surface of the discrete carbon nanotubes, or in the vicinity of the discrete carbon nanotube surface. Significant improvements in the performance of elastomeric formulations with a plurality of discrete carbon nanotubes with a surface modification and silica and/or carbon black result, for example, improved abrasion resistance while at the same time providing a reduced hysteresis effect on cyclic deformation. These improved properties are highly desired for fuel efficient and longer wear life tire formulations.
1 . A composition comprising a plurality of discrete carbon nanotubes wherein at least a portion of the plurality of discrete carbon nanotubes comprise a surface functionalization that is linked to molecules of an unsaturated elastomer;
wherein the composition further comprises silica in an amount of from about three to about fifty times the total amount of discrete carbon nanotubes by weight in the composition; and
wherein at least a portion of the surface functionalization is covalently attached to at least a portion of the plurality of discrete carbon nanotube using a silane;
wherein the weight ratio of silane to discrete carbon nanotubes is less than about 0.2.
2 . The composition of claim 1 , wherein the composition has a value weight loss of particles in a DIN abrasion test which is less than about 95% of a comparable composition that lacks the surface functionalization.
3 . The composition of claim 1 , wherein the unsaturated elastomer is selected from the group consisting of natural rubbers, polybutadiene, solution polymerized styrene-butadiene rubber, bromobutyl rubber, styrene butadiene rubber, acetonitrile butadiene, polyisoprene, styrene-isoprene rubbers, ethylene propylene diene rubbers, nitrile rubbers and any mixture thereof.
4 . The composition of claim 3 wherein the composition further comprises an additional elastomer selected from the group consisting of polyisobutylene, ethylene propylene, hydrogenated butadiene, styrene-hydrogenated butadiene, and any mixture thereof.
5 . The composition of claim 1 wherein the carbon nanotubes in the plurality of discrete carbon nanotubes are selected from single wall, double wall, multiwall carbon nanotubes, or any mixture thereof.
6 . The composition of claim 1 , wherein a majority of the plurality of discrete carbon nanotubes have a length of greater than about 0.2 micrometers.
7 . The composition of claim 1 , wherein the plurality of discrete carbon nanotubes comprises at least a bimodal distribution of length of the plurality of discrete carbon nanotubes.
8 . The composition of claim 1 , wherein the composition has an average size of particle lost in a DIN abrasion test which is more than about 1.05 times the average size of particles lost of a comparable composition that lacks the surface functionalization.
9 . The composition of claim 1 , wherein the surface functionalization is selected from the group of silane molecules that link unsaturated molecules comprising sulfur, disulfide, tetrasulfide, or any mixture thereof.
10 . The composition of claim 1 , wherein the surface functionalization is present at a concentration of at least 0.05 millimoles of surface functionalization per gram of discrete carbon nanotubes in the composition.
11 . The composition of claim 1 , wherein the unsaturated elastomer has a glass transition temperature of less than about 25° C.
12 . The composition of claim 1 , wherein the composition further comprises a filler.
13 . The composition of claim 12 , wherein the filler is selected from the group consisting of carbon black, oxidized carbon black, graphene, turbostratic graphene, carbon fiber, glass fiber, halloysite, clays, and any mixture thereof.
14 . The composition of claim 1 , wherein the surface functionalization is selected such that the discrete carbon nanotubes are substantially dispersed in an unsaturated elastomer.
15 . The composition of claim 1 in the form of a molded or fabricated article.
16 . The composition of claim 15 wherein the article is a tire, a hose, a belt, a seal or a track.
17 . The composition of claim 1 , wherein the discrete carbon nanotubes are primarily single wall and wherein at least a portion of the amount of discrete single wall carbon nanotubes present in the unsaturated elastomer is at least about 0.1 and up to about 3 percent by weight of the total weight of the unsaturated elastomer and discrete single wall carbon nanotubes.
18 . The composition of claim 1 , wherein the discrete carbon nanotubes are primarily multiwall and wherein the amount of discrete multiwall carbon nanotubes present in the unsaturated elastomer is at least about one and up to about 30 percent by weight of the total weight of the unsaturated elastomer and discrete multiwall carbon nanotubes.
19 . The composition of claim 1 , further comprising an additive selected from the group consisting of plasticizers, waxes, processing oils, epoxides, antiozonants, antioxidants, and any mixture thereof.
20 . The composition of claim 1 , wherein the linked composition has a hysteresis value of less than about 95% of a hysteresis value of a comparable composition that lacks the surface functionalization.