Elastomeric coatings

Abstract

A polymer nanocomposite coating of an elastomeric film containing at least 30 wt % conductive nanoparticles based on combined weight of elastomer and conductive nanoparticles is provided. The conductive nanoparticles have an average particle size along each dimension of less than 500 nm for nanoparticles having an aspect ratio of less than 20:1 or have an average particle size along each dimension of less than 2000 nm for nanoparticles having an aspect ratio of 20:1 or greater. The conductive nanoparticles are formed into hierarchical micro- and nano-sized aggregates having re-entrant morphology. The coating is both superoleophobic and conductive and retains these properties even when stretched under strain to over 100%. The coatings may be produced with simple spray technology.

1 . A polymer nanocomposite coating comprising an elastomeric film containing at least 30 wt % conductive nanoparticles based on the combined weight of the elastomer and the conductive nanoparticles, wherein:
 for nanooarticies having an aspect ratio of less than 20:1, the conductive nanoparticles have an average particle size along each dimension of less than 500 nm.   for nanoparticles having an aspect ratio of 20:1 or greater, the conductive nanoparticles have an average particle size along each dimension of less than 2000 nm, and   the conductive nanoparticles form micro- and nano-sized aggregates having re-entrant morphology,   
     
     
         2 . The coating according to  claim 1 , wherein the nanoparticles have an average particle size of 10-50 nm and/or an aspect ratio of less than 40:1. 
     
     
         3 . The coating according to  claim 1 , wherein the nanoparticles form nano-sized aggregates 100-200 nm in size and micro-sized aggregates 50-500 μm in size embedded in the elastomer. 
     
     
         4 . The coating according to  claim 1 , wherein the nanoparticies comprise carbon black, carbon nanotubes, or mixtures thereof. 
     
     
         5 . The coating according to  claim 1 , wherein the elastomer comprises polyolefin-based elastomers, polydimethylsiloxanes, or mixtures thereof. 
     
     
         6 . The coating according to  claim 1 , wherein the elastomer is cross-linked. 
     
     
         7 . The coating according to  claim 1 , further comprising a fluorinated compound. 
     
     
         8 . The coating according to  claim 1 , comprising an electrical resistivity of less than about 0.015 Ohm·m and a contact angle of greater than about 150° with hexadecane when the coating is uniaxially stretched with strain up to about 100%. 
     
     
         9 . A substrate comprising the coating as defined in  claim 1  coated thereon. 
     
     
         10 . A process for producing a polymer nanocomposite coating, the process comprising spraying a blend of an elastomer and conductive nanopanicies onto a substrate to form a film on the substrate, wherein:
 the blend comprises at least 40 wt % of the conductive nanoparticles based on the combined weight of the elastomer and the conductive nanoparticles,   for nanoparticles having an aspect ratio of less than 20:1, the conductive nanoparticles have an average particle size along each dimension of less than 500 nm,   for nanoparticles having an aspect ratio of 20:1 or greater, the conductive nanoparticles have an average particle size along each dimension of less than 2000 nm, and   the conductive nanoparticles form micro- and nano-sized aggregates on the substrate, the aggregates having re-entrant morphology, and   
       optionally curing or cross-linking the film. 
     
     
         11 . The process according to  claim 10 , wherein the blend comprises a dispersion of the elastomer and nanoparticles in a solvent, with the elastomer and nanoparticles present in the dispersion at a combined solids concentration of 4-50 mg/ml. 
     
     
         12 . The process according to  claim 10 , further comprising including fluorinated moieties on the surface of the film, in particular applying perfluorosilanes to the film. 
     
     
         13 . The process according to  claim 10 , wherein the elastomer comprises polyisoprene, poly(isobutene-co-isoprene), polyisobutene-co-isoprene) functionalized with one or more of an anhydride group, a carboxyl group, a hydroxyl group, an epoxy group, a polyethylene oxide group or a halo group, or mixtures thereof. 
     
     
         14 . The process according to  claim 10 , wherein the nanoparticles comprise carbon black of carbon nanotubes having an average particle size of 10-50 nm and an aspect ratio of less than 40:1. 
     
     
         15 . The process according to  claim 10 , wherein the blend comprises at least 50 wt % nanoparticles based on the combined weight of elastomer and the nanoparticles. 
     
     
         16 . The process according to  claim 10 , wherein the blend comprises 55-75 wt % nanoparticles based on the combined weight of the elastomer and the nanoparticles. 
     
     
         17 . The coating according to  claim 1 , wherein:
 the coating comprises at least 50 wt % nanoparticles;   for nanoparticles having an aspect ratio of less than 20:1, the conductive nanoparticles have an average particle size along each dimension of less than 300 nm, and   for nanoparticles having an aspect ratio of 20:1 or greater, the conductive nanoparticles have an average particle size along each dimension of 1000 to 2000 nm, and   the nanoparticles have an average particle diameter of about 1-75 nm.   
     
     
         18 . The coating according to  claim 1 , wherein:
 the nanoparticles have an average particle diameter of about 10-50 nm; and   the aspect ratio of the nanoparticles is less than about 30:1.   
     
     
         19 . The coating according to  claim 1 , wherein:
 the nanoparticles have an average particle diameter of about 10-30 nm or about 40-60 nm; and   the aspect ratio of the nanoparticles is less than about 20:1.   
     
     
         20 . The coating according to  claim 1 , wherein:
 the nanoparticles comprise conductive carbon black;   the nanoparticles have a longest dimension with an average size of less than about 90 nm;   the nanoparticles form nano-sized aggregates 100-200 nm in size and micro-sized aggregates 50-500 μm in size embedded in the elastomer;   the elastomer comprises polyisobutene, polyisoprene, poly(isobutene-co-isoorene), ethylene-propylene monomer (EPM), ethylene-propylene diene monomer (EPDM), hydrogenated nitrile butadiene, functionalized derivatives thereof, or mixtures thereof; and   the coating further comprises a perfluorosilane on the surface of the coating.