EP3478786A2 - Low-adhesion coatings with solid-state lubricants - Google Patents
Low-adhesion coatings with solid-state lubricantsInfo
- Publication number
- EP3478786A2 EP3478786A2 EP17821312.0A EP17821312A EP3478786A2 EP 3478786 A2 EP3478786 A2 EP 3478786A2 EP 17821312 A EP17821312 A EP 17821312A EP 3478786 A2 EP3478786 A2 EP 3478786A2
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- Prior art keywords
- low
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- adhesion
- coating
- poly
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G65/00—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule
- C08G65/002—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from unsaturated compounds
- C08G65/005—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from unsaturated compounds containing halogens
- C08G65/007—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from unsaturated compounds containing halogens containing fluorine
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J11/00—Features of adhesives not provided for in group C09J9/00, e.g. additives
- C09J11/08—Macromolecular additives
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/08—Processes
- C08G18/10—Prepolymer processes involving reaction of isocyanates or isothiocyanates with compounds having active hydrogen in a first reaction step
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/08—Processes
- C08G18/16—Catalysts
- C08G18/22—Catalysts containing metal compounds
- C08G18/24—Catalysts containing metal compounds of tin
- C08G18/244—Catalysts containing metal compounds of tin tin salts of carboxylic acids
- C08G18/246—Catalysts containing metal compounds of tin tin salts of carboxylic acids containing also tin-carbon bonds
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
- C08G18/30—Low-molecular-weight compounds
- C08G18/32—Polyhydroxy compounds; Polyamines; Hydroxyamines
- C08G18/3203—Polyhydroxy compounds
- C08G18/3206—Polyhydroxy compounds aliphatic
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
- C08G18/40—High-molecular-weight compounds
- C08G18/48—Polyethers
- C08G18/50—Polyethers having heteroatoms other than oxygen
- C08G18/5003—Polyethers having heteroatoms other than oxygen having halogens
- C08G18/5015—Polyethers having heteroatoms other than oxygen having halogens having fluorine atoms
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
- C08G18/65—Low-molecular-weight compounds having active hydrogen with high-molecular-weight compounds having active hydrogen
- C08G18/66—Compounds of groups C08G18/42, C08G18/48, or C08G18/52
- C08G18/6666—Compounds of group C08G18/48 or C08G18/52
- C08G18/667—Compounds of group C08G18/48 or C08G18/52 with compounds of group C08G18/32 or polyamines of C08G18/38
- C08G18/6674—Compounds of group C08G18/48 or C08G18/52 with compounds of group C08G18/32 or polyamines of C08G18/38 with compounds of group C08G18/3203
- C08G18/6677—Compounds of group C08G18/48 or C08G18/52 with compounds of group C08G18/32 or polyamines of C08G18/38 with compounds of group C08G18/3203 having at least three hydroxy groups
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/70—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the isocyanates or isothiocyanates used
- C08G18/72—Polyisocyanates or polyisothiocyanates
- C08G18/74—Polyisocyanates or polyisothiocyanates cyclic
- C08G18/75—Polyisocyanates or polyisothiocyanates cyclic cycloaliphatic
- C08G18/758—Polyisocyanates or polyisothiocyanates cyclic cycloaliphatic containing two or more cycloaliphatic rings
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- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D171/00—Coating compositions based on polyethers obtained by reactions forming an ether link in the main chain; Coating compositions based on derivatives of such polymers
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D171/00—Coating compositions based on polyethers obtained by reactions forming an ether link in the main chain; Coating compositions based on derivatives of such polymers
- C09D171/02—Polyalkylene oxides
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D175/00—Coating compositions based on polyureas or polyurethanes; Coating compositions based on derivatives of such polymers
- C09D175/04—Polyurethanes
- C09D175/08—Polyurethanes from polyethers
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J11/00—Features of adhesives not provided for in group C09J9/00, e.g. additives
- C09J11/02—Non-macromolecular additives
- C09J11/04—Non-macromolecular additives inorganic
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J11/00—Features of adhesives not provided for in group C09J9/00, e.g. additives
- C09J11/02—Non-macromolecular additives
- C09J11/06—Non-macromolecular additives organic
Definitions
- Patent App. No. 62/356,867 filed on June 30, 2016, and to U.S. Patent App. No. 15/638,340, filed on June 29, 2017, each of which is hereby incorporated by reference herein.
- the present invention generally relates to low-adhesion materials, coatings, and systems.
- Coatings and materials can become soiled from debris (particles, insects, oils, etc.) impacting the surface.
- the debris affects airflow over the surface as well as aesthetics and normally is removed by washing.
- Insect impact residue affects vehicle fuel economy, aesthetics, and operator vision.
- insect residue interferes with airflow over a surface, increasing drag and thus fuel consumption.
- the light dispersion of headlights, operator vision through the windshield, and aesthetic appeal are degraded from insect remains.
- Enzyme-filled coatings leech out enzymes that dissolve debris on the surface. However, enzymes are quickly depleted and cannot be refilled, rendering this approach impractical.
- Fluoropolymer sheets or treated surfaces have low surface energies and thus low adhesion force between foreign matter and the surface. However, friction between impacting debris and the surface results in the sticking of contaminants.
- Fluorofluid-filled surfaces have low adhesion between impacting debris and the surface. However, if any of the fluid is lost, the surface cannot be refilled/renewed once applied on the vehicle, and thus loses its properties (see Wong et al., "Bioinspired self-repairing slippery surfaces with pressure-stable
- Coatings and materials can also become contaminated from ice forming on the surface.
- the debris and ice both affect airflow over the surface, for example.
- Passive, durable anti-icing coatings have been identified as a need in the aerospace field for many decades. However, previous solutions lacked a required level of performance in ice adhesion reduction, adequate long-term durability, or both of these. Some of the most-effective coatings for reducing ice adhesion are dependent on sacrificial oils or greases that have limited useful lifetimes and require regular reapplication.
- durable coatings for exposed areas on fixed wing and rotorcraft include thermoplastic elastomers bonded to the vehicle surface using a film adhesive or an activated adhesive backing incorporated into the coating itself.
- thermoplastic elastomers bonded to the vehicle surface using a film adhesive or an activated adhesive backing incorporated into the coating itself.
- compositions do not provide any benefit in lowering ice adhesion.
- coatings on aircraft exteriors in order to passively suppress the growth of ice, in addition to removing debris, near strategic points on the vehicle—such as the rotorblade edge, wing leading edge, or engine inlet.
- high- performance coating materials fabricated in a way that preserves coating function during actual use of aerospace structures.
- Low-adhesion coatings are useful in both bugphobic and icephobic applications. Low-adhesion coatings are certainly not limited to aerospace-relevant surfaces. Other potential applications include wind turbine blades, automobiles, trucks, trains, ocean-going vessels, electrical power transmission lines, buildings, windows, antennas, filters, instruments, sensors, cameras, satellites, weapon systems, and chemical plant infrastructure (e.g., distillation columns and heat exchangers).
- Some variations of the invention provide a low-adhesion composition comprising:
- X, Y CH 2 -(0-CH 2 -CH 2 ) p -T, and X and Y are independently selected;
- T is a hydroxyl or amine terminal group
- n 1 to 100;
- the solid-state lubricants are selected from the group consisting of graphite, graphene, molybdenum disulfide, tungsten disulfide, hexagonal boron nitride, poly(tetrafluoroethylene), fluoropolymers, and combinations thereof.
- the solid-state lubricants are particles having outer surfaces containing (e.g., coated with) a metal selected from the group consisting of cadmium, lead, tin, zinc, copper, nickel, and combinations or alloys thereof.
- the solid-state lubricants may have an average particle size from about
- 0.1 ⁇ to about 500 ⁇ such as from about 1 ⁇ to about 100 ⁇ .
- the state lubricants are distributed uniformly throughout the composition.
- the fluoropolymers may have an average molecular weight from about
- the fluoropolymers have an average molecular weight from about 1,000 g/mol to about 10,000 g/mol, and/or p is selected from 6 to 50 for each of X and Y, in the molecular triblock structure.
- the fluoropolymers are preferably (a,Q)-hydroxyl-terminated and/or (a,co)-amine- terminated.
- the isocyanate species may be selected from the group consisting of
- the polyol or polyamine chain extenders or crosslinkers may be selected from the group consisting of 1,3-butanediol, 1,4-butanediol, 1,3 -propanediol, 1,2-ethanediol, di ethylene glycol, tri ethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, neopentyl glycol, 1,6-hexanediol, 1,4- cyclohexanedimethanol, ethanol amine, diethanol amine, methyldiethanolamine, phenyldiethanolamine, glycerol, trimethylolpropane, 1,2,6-hexanetriol,
- isophoronediamine diaminocyclohexane, N,N,N',N'-tetrakis(2-hydroxypropyl) ethylenediamine, and homologues, derivatives, or combinations thereof.
- the composition contains, in a hard segment, the reacted form of the one or more isocyanate species, combined with the reacted form of the one or more polyol or polyamine chain extenders or crosslinkers.
- Some variations of the invention provide a low-adhesion coating comprising:
- one of the first component or the second component is a low-surface- energy polymer having a surface energy between about 5 mJ/m 2 to about 50 mJ/m 2
- the other of the first component or the second component is a hygroscopic material
- the solid-state lubricant is distributed within the matrix but not within the inclusions. In other embodiments, the solid-state lubricant is distributed within the inclusions but not within the matrix. In preferred embodiments, but without limitation, the solid-state lubricant is distributed throughout the coating.
- the solid-state lubricant may be selected from the group consisting of graphite, graphene, molybdenum disulfide, tungsten disulfide, hexagonal boron nitride, poly(tetrafluoroethylene), fluoropolymers, and combinations thereof.
- the solid-state lubricant is a plurality of particles having outer surfaces containing a metal selected from the group consisting of cadmium, lead, tin, zinc, copper, nickel, and combinations or alloys thereof.
- the solid-state lubricant is characterized by an average particle size from about 0.1 ⁇ to about 500 ⁇ .
- the polymer is a fluoropolymer, such as a fluoropolymer selected from the group consisting of polyfluoroethers,
- perfluoropolyethers polyfluoroacrylates, polyfluorosiloxanes, and combinations thereof.
- the fluoropolymer is N-(2-aminoethyl)-2-aminoethyl-N-(2-aminoethyl)-2-aminoethyl-N-(2-aminoethyl)-2-aminoethyl-N-(2-aminoethyl)-2-aminoethyl-N-(2-aminoethyl)-2-aminoe
- perfluoropolyether and the hygroscopic material is poly(ethylene glycol).
- the hygroscopic material may be covalently connected to the fluoropolymer in a triblock copolymer, such as:
- X, Y CH 2 -(0-CH 2 -CH 2 ) p -T, and X and Y are independently selected;
- T is a hydroxyl or amine terminal group
- n 1 to 100.
- the hygroscopic material is selected from the group consisting of poly(acrylic acid), poly(ethylene glycol), poly(2-hydroxyethyl methacrylate), poly(vinyl imidazole), poly(2-methyl-2-oxazoline), poly(2-ethyl-2- oxazoline), poly(vinylpyrolidone), cellulose, modified cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, hydrogels, PEG diacryalate, monoacrylate, and combinations thereof.
- the continuous matrix contains (i) one or more isocyanate species possessing an average isocyanate functionality of about 2 or greater, or a reacted form thereof; and (ii) one or more polyol or polyamine chain extenders or crosslinkers possessing an average functionality of about 2 or greater, or a reacted form thereof.
- the isocyanate species may be selected from the group consisting of
- the polyol or polyamine chain extenders or crosslinkers may be selected from the group consisting of 1,3-butanediol, 1,4-butanediol, 1,3 -propanediol, 1,2-ethanediol, di ethylene glycol, tri ethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, neopentyl glycol, 1,6-hexanediol, 1,4- cyclohexanedimethanol, ethanol amine, diethanol amine, methyldiethanolamine, phenyldiethanolamine, glycerol, trimethylolpropane, 1,2,6-hexanetriol,
- isophoronediamine diaminocyclohexane, N,N,N',N'-tetrakis(2-hydroxypropyl) ethylenediamine, and homologues, derivatives, or combinations thereof.
- the coating optionally also includes one or more additional components selected from the group consisting of a pigment, a dye, a plasticizer, a flame retardant, a flattening agent, and a substrate adhesion promoter, for example.
- the low-adhesion coating may be characterized by a coefficient of friction less than 0.5 measured at 50% humidity. In these or other embodiments, the low-adhesion coating is characterized by a coefficient of friction less than 0.3 measured at 90% humidity.
- FIG. 1 depicts a structural cross-section of a coating or surface with lubricating properties, in some embodiments of the invention, in which solid-state lubricants are dispersed throughout the material.
- FIG. 2 depicts a structural cross-section of a coating or surface with lubricating properties, in some embodiments of the invention, in which solid-state lubricants are dispersed throughout a continuous matrix but not within inclusions.
- FIG. 3 depicts a structural cross-section of a coating or surface with lubricating properties, in some embodiments of the invention, in which solid-state lubricants are dispersed within inclusions but not the continuous matrix.
- FIG. 4 depicts a structural cross-section of a coating or surface with lubricating properties, in some embodiments of the invention, in which solid-state lubricants are dispersed throughout the material, including a high surface
- FIG. 5 is a table of experimental data of coating coefficients of friction at different humidity levels, for Example 5 herein.
- solid-state lubricant means a material that is a solid at a temperature of 25°C and 1 atm pressure, and that reduces friction of an object or particle that is sliding along the surface of a coating containing the material.
- the solid-state lubricant aids the sliding of debris (e.g., bug fragments, dirt, ice, etc.) across the surface.
- a solid-state lubricant is capable of providing a low overall (coating) coefficient of friction, i.e. improved coating lubricity, while also maintaining or increasing durability.
- lubrication may be developed via moisture in the atmosphere being drawn into hygroscopic components of the coating. In some embodiments of the present disclosure, this moisture-derived lubrication is still present, in addition to the solid-state lubricants that are incorporated into the coating. In fact, there are synergies.
- the lubricating water can be aided by the solid-state lubricant incorporated into the coating.
- Certain solid-state lubricants (notably, graphite) work better with moisture present, and thus (without being limited by speculation) may be more effective for lubricity when hygroscopic inclusions are also present in the coating.
- Some variations of the invention provide a low-adhesion composition comprising:
- fluoropolymers having an average molecular weight from about 500 g/mol to about 20,000 g/mol, wherein the fluoropolymers are (a,Q)-hydroxyl-terminated and/or (a,Q)-amine-terminated, and wherein the fluoropolymers are present in the triblock structure:
- X, Y CH 2 -(0-CH 2 -CH 2 ) p -T, and X and Y are independently selected;
- T is a hydroxyl or amine terminal group
- n 1 to 100;
- the solid-state lubricants may be organic, inorganic, or a mixture of organic and inorganic materials.
- the solid-state lubricants are selected from the group consisting of graphite, graphene (single layer or multilayer graphene), molybdenum disulfide, tungsten disulfide, hexagonal boron nitride,
- PTFE poly(tetrafluoroethylene)
- fluoropolymers fluoropolymers
- Other known solid lubricants include, but are not limited to, talc, calcium fluoride, and cerium fluoride.
- Certain embodiments employ solid-state lubricants that do not include poly(tetrafluoroethylene) or other fluoropolymers.
- the solid-state lubricants are particles having outer surfaces containing a metal selected from the group consisting of cadmium, lead, tin, zinc, copper, nickel, and combinations or alloys thereof. Alloys include bronze, brass, and many other possibilities.
- particles are coated with one or more metals.
- the particles that are coated with metal(s) may be made from one of the materials listed above, such as poly(tetrafluoroethylene), or another material, such as silica or alumina.
- metallic particles are used, in which the solid-state lubricant particles are made from the selected metal, optionally with other materials present. Hollow metal spheres may also be employed.
- one or more materials selected from graphite, graphene, molybdenum disulfide, tungsten disulfide, hexagonal boron nitride, poly(tetrafluoroethylene), fluoropolymers, or combinations thereof are employed as a surface coating on base particles, which (when surface-coated) form the solid-state lubricant particles.
- base particles which (when surface-coated) form the solid-state lubricant particles.
- graphene may be coated onto silica, or a base particle may be surface-functionalized to incorporate fluoropolymers.
- the base particles are actually the inclusions provided within the overall composition. In this case, the inclusions are only partially coated with the lubricating material so that the inclusions can still function as hygroscopic domains or as low- surface-energy domains.
- the solid-state lubricants may be characterized by a coefficient of friction from about 0.01 to about 1.0, preferably less than 0.5, more preferably less than 0.3, and most preferably less than 0.2. This is the coefficient of friction of the solid-state lubricant material itself, not the friction coefficient of the overall coating (which is discussed later).
- An example is graphite, which has a coefficient of friction of about 0.1 (Lide, CRC Handbook of Chemistry and Physics, Boca Raton, Florida, CRC Press, 1994, 15-40).
- the solid-state lubricants are generally particulates, such as powders.
- the solid-state lubricants may have an average particle size from about 0.1 ⁇ to about 500 ⁇ , such as from about 1 ⁇ to about 100 ⁇ . In various embodiments, the solid-state lubricants have an average particle size of about, or less than about, 0.1, 0.5, 1, 2, 3, 4, 5, 10, 20, 30, 40, 50, 75, 100, 200, 300, 400, or 500 ⁇ , including all intervening ranges.
- the solid-state lubricants are distributed uniformly throughout the composition.
- the concentration of solid-state lubricants may vary widely.
- the solid-state lubricants may be present at a concentration from about 0.1 wt% to about 50 wt%, such as from about 1 wt% to about 20 wt% (based on total weight of coating).
- the solid- state lubricants are present at a concentration of about 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, or 50 wt% (based on total weight of coating).
- the solid-state lubricants may be present at a concentration from about 0.1 wt% to about 50 wt%, such as from about 1 wt% to about 20 wt% (based on total weight of the phase). In various embodiments, the solid-state lubricants are present at a
- concentration of about 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, or 50 wt% (based on total weight of the phase).
- the fluoropolymers have an average molecular weight from about 500 g/mol to about 20,000 g/mol, and/or p is selected from 1 to 50 for each of X and Y, in the molecular triblock structure.
- p is selected from 1 to 50 for each of X and Y, in the molecular triblock structure.
- fluoropolymers may have an average molecular weight of about 1,000 g/mol, 5,000 g/mol, 10,000 g/mol, or 15,000 g/mol, or an intervening range.
- the value of p may be selected from 6 to 50, such as from 10 to 20, for each of X and Y.
- fluoropolymers are preferably (a,Q)-hydroxyl-terminated and/or (a,co)-amine- terminated.
- the isocyanate species may be selected from the group consisting of
- the polyol or polyamine chain extenders or crosslinkers may be selected from the group consisting of 1,3-butanediol, 1,4-butanediol, 1,3 -propanediol, 1,2-ethanediol, di ethylene glycol, tri ethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, neopentyl glycol, 1,6-hexanediol, 1,4- cyclohexanedimethanol, ethanol amine, diethanol amine, methyldiethanolamine, phenyldiethanolamine, glycerol, trimethylolpropane, 1,2,6-hexanetriol,
- the composition contains, in a hard segment, the reacted form of the one or more isocyanate species, combined with the reacted form of the one or more polyol or polyamine chain extenders or crosslinkers.
- Some variations of the invention provide a low-adhesion coating comprising:
- one of the first component or the second component is a low-surface- energy polymer having a surface energy between about 5 mJ/m 2 to about 50 mJ/m 2
- the other of the first component or the second component is a hygroscopic material
- the solid-state lubricant is distributed within the matrix but not within the inclusions. In other embodiments, the solid-state lubricant is distributed within the inclusions but not within the matrix. In preferred embodiments, but without limitation, the solid-state lubricant is distributed throughout the coating.
- the solid-state lubricant may be selected from the group consisting of graphite, graphene, molybdenum disulfide, tungsten disulfide, hexagonal boron nitride, poly(tetrafluoroethylene), fluoropolymers, and combinations thereof.
- the solid-state lubricant is a plurality of particles having outer surfaces containing a metal selected from the group consisting of cadmium, lead, tin, zinc, copper, nickel, and combinations or alloys (e.g., bronze) thereof.
- the solid-state lubricant may be characterized by an average particle size from about 10 nm to about 500 ⁇ .
- the surface energy of the low-surface-energy polymer is between about 10 mJ/m 2 to about 40 mJ/m 2 , such as about 10, 15, 20, 25, 30, 35, or 40, mJ/m 2 .
- the polymer is a fluoropolymer, such as a fluoropolymer selected from the group consisting of polyfluoroethers, perfluoropolyethers, polyfluoroacrylates, polyfluorosiloxanes, and combinations thereof.
- the fluoropolymer is a fluoropolymer selected from the group consisting of polyfluoroethers, perfluoropolyethers, polyfluoroacrylates, polyfluorosiloxanes, and combinations thereof.
- perfluoropolyether and the hygroscopic material is poly(ethylene glycol).
- the hygroscopic material may be covalently connected to the fluoropolymer in a triblock copolymer, such as:
- X, Y CH 2 -(0-CH 2 -CH 2 ) p -T, and X and Y are independently selected;
- T is a hydroxyl or amine terminal group
- n 1 to 100.
- the hygroscopic material is selected from the group consisting of poly(acrylic acid), poly(ethylene glycol), poly(2-hydroxyethyl methacrylate), poly(vinyl imidazole), poly(2-methyl-2-oxazoline), poly(2-ethyl-2- oxazoline), poly(vinylpyrolidone), cellulose, modified cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, hydrogels, PEG diacryalate, monoacrylate, and combinations thereof.
- the hygroscopic material is also classified as a hydrophilic material.
- a hygroscopic substance will actively attract and absorb water.
- a hydrophilic substance is one where water will preferentially wet the surface, demonstrated by contact angles ⁇ 90°.
- the continuous matrix contains (i) one or more isocyanate species possessing an average isocyanate functionality of about 2 or greater, or a reacted form thereof; and (ii) one or more polyol or polyamine chain extenders or crosslinkers possessing an average functionality of about 2 or greater, or a reacted form thereof.
- the isocyanate species may be selected from the group consisting of
- the polyol or polyamine chain extenders or crosslinkers may be selected from the group consisting of 1,3-butanediol, 1,4-butanediol, 1,3 -propanediol, 1,2-ethanediol, di ethylene glycol, tri ethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, neopentyl glycol, 1,6-hexanediol, 1,4- cyclohexanedimethanol, ethanol amine, diethanol amine, methyldiethanolamine, phenyldiethanolamine, glycerol, trimethylolpropane, 1,2,6-hexanetriol,
- isophoronediamine diaminocyclohexane, N,N,N',N'-tetrakis(2-hydroxypropyl) ethylenediamine, and homologues, derivatives, or combinations thereof.
- the coating optionally also includes one or more additional components selected from the group consisting of a pigment, a dye, a plasticizer, a flame retardant, a flattening agent, and a substrate adhesion promoter, for example.
- the low-adhesion coating may be characterized by a coefficient of friction less than 0.5, such as from about 0.1 to about 0.4, measured at 50% humidity. In various embodiments, the low-adhesion coating is characterized by a coefficient of friction less than less than 0.30, less than 0.25, or less than 0.20, measured at 50% humidity.
- the low-adhesion coating may be characterized by a coefficient of friction less than 0.3, such as from about 0.05 to about 0.25, measured at 90% humidity. In various embodiments, the low-adhesion coating is characterized by a coefficient of friction less than less than 0.25, less than 0.20, or less than 0.15, measured at 90% humidity.
- the coefficient of friction of the low-adhesion coating may be measured using, for example, ASTM D1894 ("Standard Test Method for Static and Kinetic Coefficients of Friction of Plastic Film and Sheeting").
- ASTM D1894 Standard Test Method for Static and Kinetic Coefficients of Friction of Plastic Film and Sheeting.
- the above-recited coefficients of friction may be static friction coefficients, dynamic friction
- FIGS. 1 to 4. These drawings are not to scale. The top of each figure is presumed to be the surface of the coating, i.e. the surface exposed to environmental conditions.
- FIG. 1 depicts a structural cross-section of a coating or surface with lubricating properties, in some embodiments.
- the structure 100 of FIG. 1 includes a continuous matrix 110.
- a "continuous matrix” (or equivalently, “substantially continuous matrix”) means that the matrix material is present in a form that includes chemical bonds among molecules of the matrix material. An example of such chemical bonds is crosslinking bonds between polymer chains.
- the structure 100 further includes a plurality of inclusions 120 (depicted as two-dimensional circles for illustration purposes only), intimately dispersed within the matrix 110, each of the inclusions 120 being or comprising a hygroscopic material.
- the inclusions 120 are covalently bonded with the matrix 110 in a copolymer, such as the fluoropolymer copolymerized with poly(ethylene glycol).
- the structure 100 also includes a plurality of solid-state lubricants 130 (depicted as two-dimensional stars for illustration purposes only). In FIG. 1, the solid-state lubricants 130 are distributed uniformly throughout the coating, both within the matrix 110 and within, and/or on the surface of, inclusions 120. The distribution of the solid-state lubricants 130 may be random or ordered.
- a random distribution means with respect to FIG. 1, that the number of solid-state lubricants 130 in any given volume of coating 100 is a random number.
- An ordered distribution means with respect to FIG. 1, that the solid-state lubricants 130 in coating 100 are present in a pattern, such as a layered configuration (parallel with surface) of solid-state lubricants 130 within the matrix 110, columns of solid- state lubricants 130 (perpendicular to surface) within the matrix 110, and so on. Also, the distribution of the solid-state lubricants 130 may be uniform or non-uniform.
- FIG. 2 depicts a structural cross-section of a coating or surface with lubricating properties, in some embodiments.
- the structure 200 of FIG. 2 includes a continuous matrix 210.
- the structure 200 further includes a plurality of inclusions 220 (depicted as two-dimensional circles for illustration purposes only), intimately dispersed within the matrix 210, each of the inclusions 220 being or comprising a hygroscopic material.
- the structure 200 also includes a plurality of solid-state lubricants 230 (depicted as two-dimensional stars for illustration purposes only). In FIG. 2, the solid-state lubricants are distributed throughout the matrix 210, but not within or on the surface of the inclusions 220. The distribution of the solid-state lubricants 230 may be random or ordered within the matrix 210.
- a random distribution means with respect to FIG. 2, that the number of solid-state lubricants 230 in any given volume of coating 200 is a random number.
- An ordered distribution means with respect to FIG. 2, that the solid-state lubricants 230 in coating 200 are present in a pattern, such as a layered configuration (parallel with surface) of solid-state lubricants 230 within the matrix 210 but not within or on the surface of the inclusions 220, columns of solid-state lubricants 230 (perpendicular to surface) within the matrix 210 but not within or on the surface of the inclusions 220, and so on.
- the number of solid-state lubricants 230 in any given region of matrix 210 may be a random number.
- the distribution of the solid-state lubricants 230 may be uniform or non-uniform.
- FIG. 3 depicts a structural cross-section of a coating or surface with lubricating properties, in some embodiments.
- the structure 300 of FIG. 3 includes a continuous matrix 310.
- the structure 300 further includes a plurality of inclusions 320 (depicted as two-dimensional circles for illustration purposes only), intimately dispersed within the matrix 310, each of the inclusions 320 being or comprising a hygroscopic material.
- the structure 300 also includes a plurality of solid-state lubricants 330 (depicted as two-dimensional stars for illustration purposes only). In FIG. 3, the solid-state lubricants 330 are contained within the inclusions 320, but not within the matrix 310. The distribution of the solid-state lubricants 330 may be random or ordered within each of the inclusions 320.
- a random distribution means with respect to FIG. 3, that the number of solid-state lubricants 330 in any given volume of coating 300 is a random number.
- An ordered distribution means with respect to FIG. 3, that the solid-state lubricants 330 in coating 300 are present in a pattern, such as a layered configuration (parallel with surface) of solid-state lubricants 330 within the inclusions 320 but not within the matrix 310, and so on.
- the number of solid-state lubricants 330 in any given inclusion 320 may be a random number.
- the distribution of the solid-state lubricants 330 may be uniform or non-uniform, with respect to the overall coating 300 and/or with respect to an individual inclusion 320.
- each inclusion 320 contains from 1 to 3 solid-state lubricants 330.
- the inclusions 320 may each contain at least 1, 5, 10, 50, 100, 500, or more individual particles of solid-state lubricants 330, for example.
- FIG. 4 depicts a structural cross-section of a non-uniform coating or surface with lubricating properties, in some embodiments.
- the structure 400 of FIG. 4 includes a continuous matrix 410.
- the structure 400 further includes a plurality of inclusions 420 (depicted as two-dimensional circles for illustration purposes only), intimately dispersed within the matrix 410, each of the inclusions 420 being or comprising a hygroscopic material.
- the structure 400 also includes a plurality of solid-state lubricants 430 (depicted as two-dimensional stars for illustration purposes only).
- the solid-state lubricants 430 are distributed throughout the coating, both within the matrix 410 and within, and/or on the surface of, inclusions 420.
- a relatively high concentration of solid-state lubricants 430 is contained at the surface (top of drawing) of the coating 400.
- the distribution of the solid-state lubricants 430 may otherwise be random or ordered, as described above.
- the functions of the continuous matrix 110, 210, 310, and 410 and discrete inclusions 120, 220, 320, and 420 may be reversed. That is, in some variations, the continuous matrix 110, 210, 310, or 410 may be hygroscopic, while the inclusions 120, 220, 320, or 420 may include a low- surface-energy polymer.
- the continuous matrix 110, 210, 310, and 410 and/or the inclusions 120, 220, 320, and 420 may further comprise one or more additives selected from the group consisting of fillers, colorants, UV absorbers, defoamers, plasticizers, viscosity modifiers, density modifiers, catalysts, and free-radical scavengers.
- Some variations of this invention incorporate a material that possesses both low surface energy (for low adhesion) and the ability to absorb water.
- a structured material or coating passively absorbs water from the atmosphere to create a lubrication/self-cleaning layer and to reduce the friction and adhesion of the impacting body (such as an insect) on the surface.
- the material may be used as a coating or as a surface.
- Some embodiments provide combinations of fluorinated and hygroscopic precursors that demonstrate the ability to microphase-separate into discrete islands of fluoropolymer or hygroscopic-rich domains. These systems produce excellent performance in freezing-delay reduction as well as reduced coefficient of friction, especially when coupled with a solid-state lubricant.
- the disclosed material in some embodiments, can absorb water from the atmosphere and use this water as a co-lubricant (along with the solid-state lubricant) to wash and remove debris from the surface.
- the surface contains domains of a low-surface-energy polymer (such as, but not limited to, a fluoropolymer) providing low adhesion, and microphase-separated domains of a hygroscopic material. Atmospheric water is thus captured as a co-lubricant and is a continually available, renewable resource.
- Debris may be organic or inorganic and may include insects, dirt, dust, soot, ash, pollutants, particulates, ice, seeds, plant or animal fragments, plant or animal waste products, combinations or derivatives of any of the foregoing, and so on.
- the coating in some embodiments may be characterized as "bugphobic," which is intended to mean the coating has relatively low adhesion with an impacting bug.
- Some variations provide a low-adhesion material that creates a lubricated absorbed water layer on a low-surface-energy coating.
- This material is formed by coupling hygroscopic and fluorinated materials, which typically repel each other, into a polymer network.
- these antagonistic chemistries high/low contact angle and low/high water absorption
- the desired low wetting and adhesion of one material (fluorinated component) is coupled with the desired water absorption of the other (hygroscopic material).
- This system differs from previous work that relied on purely hydrophilic films to create a liquid water layer on a surface.
- the hydrophobicity of the coatings provided herein is important for reducing adhesion and wetting of insect debris.
- this system is different from previous work that relied on trapping non-aqueous fluids on surfaces to lower adhesion.
- slippery liquid- infused porous surfaces provide low adhesion from a fluorinated fluid trapped in a porous surface layer, such surfaces cannot extract more fluid from the environment, to counteract fluid loss.
- the hygroscopic component extracts fluid from the environment during (without implying a limitation) rain or frosting, to counteract fluid loss.
- the hygroscopic material can absorb at least some water.
- materials provided herein contain large variations in wetting across the surface at ⁇ 100 ⁇ length scales— arising from low-surface-energy domains closely juxtaposed with high-surface-energy domains. These small length scales are similar to the air-versus-solid variation on known superhydrophobic surfaces exhibiting low insect-impact debris accumulation. In this respect, without being limited by theory, it is noted that although there is no surface roughness, variations in wetting at 1-100 ⁇ length scales (or less) can reduce insect debris adhesion, in some embodiments.
- low-adhesion structures are created by a heterogeneous microstructure comprising a low-surface-energy polymer that is interspersed with hygroscopic domains (lubricating inclusions). Debris impacting the surface has low adhesion energy with the surface. Due to the presence of the low- surface-energy polymer as well as the solid-state lubricant, the debris will not remain on the surface.
- Preferred embodiments employ fluoropolymers, without limitation of the invention, as described in more detail below.
- One technique to compatibilize fluoropolymers and hygroscopic materials is the use of segmented polyurethane or urea systems. These species demonstrate strong hydrogen bonding potential between them and as a result can create strong associative forces between the chains.
- regions of highly flexible and weakly interacting chains soft segments
- strongly associating elements hard segments
- Such synthesis results in chains that possess alternating hard and soft segments composed of regions of high urethane bond density and the chosen soft segment component (e.g., fluoropolymer and/or hygroscopic element), respectively.
- This covalent linkage of dissimilar hard and soft blocks drives the systems to microphase separation and creates regions of flexible soft blocks surrounding regions of hard blocks.
- the associative forces among the hard segments prevent flow under stress and can produce elastomeric materials capable of displaying high elongation and tensile strength.
- a copolymer composition comprises one or more ⁇ , ⁇ (alpha, omega)-amine-terminated or ⁇ , ⁇ (alpha, omega)-hydroxyl- terminated polyfluoropolymer soft segments having an average molecular weight of between about 500 grams per mole to about 20,000 grams per mole.
- the exemplary composition optionally further comprises one or more polyethylene glycol second soft segments having an average molecular weight of between about 500 grams per mole to about 10,000 grams per mole.
- a total content of the soft segments is present in an amount of from about 40% by weight to about 90% by weight, based on a total weight percent of the composition.
- the composition further comprises one or more hard segments present in an amount of from about 15% by weight to about 50% by weight, based on the total weight percent of the composition, for example.
- the one or more hard segments comprise a combination of one or more isocyanate species and one or more low-molecular-weight polyol or polyamine chain extenders or crosslinkers.
- fluoropolymers having an average molecular weight from about 500 g/mol to about 20,000 g/mol, wherein the fluoropolymers are (a,Q)-hydroxyl-terminated and/or (a,Q)-amine-terminated, and wherein the fluoropolymers are present in the triblock structure:
- X, Y CH 2 -(0-CH 2 -CH 2 ) p -T, and X and Y are independently selected;
- p 1 to 50, such as 6 to 50;
- T is a hydroxyl or amine terminal group
- n 1 to 100;
- the X and Y terminal PEG chains may be the same or different.
- X and Y are different.
- X and Y differ in the terminal group T.
- X may be terminated with a hydroxyl group and Y may be terminated with an amine group.
- X and Y may be terminated with different types of amine groups.
- the p value (chain length) may be the same or different between X and Y.
- the p value of one of X or Y may be selected from 0 to 50, while the p value of the other of X or Y (on the other end of the fluoropolymer) is selected from 6 to 50.
- Certain variations of the invention utilize a fluoropolymer having an average molecular weight from about 500 g/mol to about 20,000 g/mol, wherein the fluoropolymer is present in the triblock structure:
- X and Y are independently selected and pi and p2 are independently selected;
- T is a hydroxyl or amine terminal group
- n 1 to 100.
- (a,co)-terminated polymers are terminated at each end of the polymer.
- the a-termination may be the same or different than the co- termination.
- “(a,Q)-termination” includes branching at the ends, so that the number of terminations may be greater than 2 per polymer molecule.
- the polymers herein may be linear or branched, and there may be various terminations and functional groups within the polymer chain, besides the end ( ⁇ , ⁇ ) terminations.
- T is a hydroxyl or amine terminal group
- p 6 to 50
- m 1 to 100
- n 1 to 100.
- the soft-segment phase containing the fluoropolymers, or an additional soft-segment phase contains one or more second soft segments selected from polyesters or poly ethers, wherein the polyesters or poly ethers are ( ⁇ , ⁇ )- hydroxyl-terminated and/or (a,Q)-amine-terminated.
- the molar ratio of second soft segments to first soft segments (fluoropolymers) may be less than 2.0, such as about 0.1 to about 1.5.
- the molar ratio of the second soft segments to the first soft segments is about 0, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2.0.
- Polyurethanes are generally produced by reacting an isocyanate containing two or more isocyanate groups per molecule with one or more polyols containing on average two or more hydroxyl groups per molecule, in the presence of a catalyst.
- Polyols are polymers in their own right and have on average two or more hydroxyl groups per molecule.
- ⁇ , ⁇ -hydroxyl-terminated perfluoropoly ether is a type of polyol.
- Polyfluoroether refers to a class of polymers that contain an ether group— an oxygen atom connected to two alkyl or aryl groups, where at least one hydrogen atom is replaced by a fluorine atom in an alkyl or aryl group.
- PFPE Perfluoropoly ether
- Polyureas are generally produced by reacting an isocyanate containing two or more isocyanate groups per molecule with one or more multifunctional amines (e.g., diamines) containing on average two or more amine groups per molecule, in the presence of a catalyst.
- a "chain extender or crosslinker” is a compound (or mixture of compounds) that links long molecules together and thereby completes a polymer reaction.
- Chain extenders or crosslinkers are also known as curing agents, curatives, or hardeners.
- a curative is typically comprised of hydroxyl-terminated or amine-terminated compounds which react with isocyanate groups present in the mixture. Diols as curatives form urethane linkages, while diamines as curatives form urea linkages.
- the choice of chain extender or crosslinker may be determined by end groups present on a given prepolymer.
- chain extenders or crosslinkers may have an average functionality greater than 2 (such as 3 or greater), i.e. beyond diols or diamines.
- the chain extenders or crosslinkers possess an average functionality of about 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, or more.
- a functionality of 3 or more is beneficial for vulcanized (highly crosslinked) materials.
- the one or more chain extenders or crosslinkers may be present in a concentration, in the copolymer composition, from about 0.01 wt% to about 10 wt%, such as about 0.05 wt% to about 1 wt%.
- a "low-surface-energy polymer” means a polymer, or a polymer-containing material, with a surface energy of no greater than 50 mJ/m 2 .
- the principles of the invention may be applied to low-surface-energy materials with a surface energy of no greater than 50 mJ/m 2 , in general (i.e., not necessarily limited to polymers).
- the low-surface-energy polymer includes a fluoropolymer, such as (but not limited to) a fluoropolymer selected from the group consisting of polyfluoroethers, perfluoropolyethers, fluoroacrylates, fluorosilicones, and combinations thereof.
- a fluoropolymer such as (but not limited to) a fluoropolymer selected from the group consisting of polyfluoroethers, perfluoropolyethers, fluoroacrylates, fluorosilicones, and combinations thereof.
- the low-surface-energy polymer includes a siloxane.
- a siloxane contains at least one Si-O-Si linkage.
- the low-surface-energy polymer may consist of polymerized siloxanes or polysiloxanes (also known as silicones). One example is polydimethylsiloxane.
- the fluoropolymers are selected from the group consisting of perfluoropolyethers, polyfluoroacrylates, polyfluorosiloxanes, and combinations thereof.
- the fluoropolymers include a fluoropolymer copolymer with poly(ethylene glycol) having the structure:
- X, Y CH 2 -(0-CH 2 -CH 2 ) p -T, and X and Y are independently selected;
- T is a hydroxyl or amine terminal group
- n 1 to 100;
- one or more F atoms may be replaced by H atoms or other atoms or groups.
- some of the F atoms that are present in square brackets i.e., the chains with extents of polymerization m or n
- the polyesters or polyethers may be selected from the group consisting of
- the copolymer composition contains, in a hard segment, a reacted form of the one or more isocyanate species, combined with a reacted form of the one or more polyol or polyamine chain extenders or crosslinkers.
- the hard segment is present in an amount from about 5 wt% to about 60 wt%, based on total weight of the composition.
- the functions of the matrix and inclusions may be reversed, such that the matrix provides hygroscopic properties while the inclusions provide low surface energy.
- the PEG phase may be regarded as the matrix and the fluoropolymer phase may be regarded as the inclusions, depending on the magnitude of m, n, and p values in the copolymer. Large p and small m and n values would tend to make the PEG phase the matrix, while small p values and large m and n values would tend to make the fluoropolymer phase the matrix.
- the length scales of inclusions and space between adjacent inclusions are similar, the geometries are arbitrary, and the phases are distinct, it does not really matter which phase is called the matrix.
- the inclusions are three-dimensional domains, which may be of any shape, geometry, or aspect ratio.
- the inclusions may be geometrically symmetric or asymmetric.
- the inclusions are anisotropic.
- anisotropic inclusions have at least one chemical or physical property that is directionally dependent. When measured along different axes, an anisotropic inclusion will have some variation in a measurable property.
- the property may be physical (e.g., geometrical) or chemical in nature, or both.
- the inclusions may be characterized as templates, domains, or regions.
- the inclusions are phase-separated as discrete, non-continuous regions dispersed in the continuous matrix. In other embodiments, the inclusions are either not phase-separated or are phase-separated at a very small length scale, such as about 20, 10, 5, 4, 3, 2, 1 ⁇ or less (including below the wavelength of light).
- the low-surface-energy polymer and the hygroscopic material are covalently connected in a block copolymer, in which the inclusions and the continuous matrix are distinct phases of the block copolymer.
- the hygroscopic inclusions may be dispersed uniformly within the continuous matrix.
- the continuous matrix may form a continuous framework in the coating, in certain embodiments.
- a "block copolymer” means a copolymer containing a linear arrangement of blocks, where each block is defined as a portion of a polymer molecule in which the monomeric units have at least one constitutional or configurational feature absent from the adjacent portions.
- block copolymers include AB block copolymers, ABA block copolymers, ABC block copolymers, segmented block copolymers, and random copolymers.
- the continuous matrix may be from about 5 wt% to about 95 wt%, such as from about 10 wt% to about 50 wt% of the material.
- the inclusions may be from about 1 wt% to about 90 wt%, such as from about 10 wt% to about 50 wt% of the coating.
- the solid-state lubricants may be from about 0.1 wt% to about 50 wt% of the coating.
- the low-surface-energy polymer may be from about 50 wt% to 100 wt%, such as about 60, 70, 80, 90, 95, or 100 wt%.
- the hygroscopic material may be from about 50 wt% to 100 wt%, such as about 60, 70, 80, 90, 95, or 100 wt%.
- the low-surface-energy polymer and/or the hygroscopic material may be surface-treated, such as to adjust hydrophobicity.
- the low-adhesion material optionally further contains one or more additional components selected from the group consisting of a filler, a pigment, a dye, a plasticizer, a flame retardant, a flattening agent, and a substrate adhesion promoter.
- a filler may be selected from the group consisting of silica, alumina, silicates, talc, aluminosilicates, barium sulfate, mica, diatomite, calcium carbonate, calcium sulfate, carbon, wollastonite, and combinations thereof.
- the particulate fillers generally are in the size range of about 5 nm to about 10 ⁇ , such as about 20 nm to 2 ⁇ . The filler itself is not the same thing as the solid-state lubricant.
- the fillers may be surface-modified with a compound selected from the group consisting of fatty acids, silanes, silicones, alkyl phosphonates, alkyl phosphonic acids, alkyl carboxylates, and combinations thereof.
- the fillers may be surface- modified with a hydrophobic material, such as (but not limited to) an alkylsilane, a fluoroalkylsilane, and/or an alkyldisilazane (e.g., hexamethyldisilazane).
- the low-adhesion material further includes voids.
- a "void" is a discrete region of empty space, or space filled with air or another gas, that is enclosed within the continuous matrix.
- the voids may be open (e.g., interconnected voids) or closed (isolated within the continuous matrix), or a combination thereof.
- the voids may partially surround inclusions.
- the low-adhesion material may be characterized by a water absorption capacity of at least 10 wt% water based on total weight of the low-adhesion material.
- the material is characterized, according to some embodiments, by a water absorption capacity of at least 1, 2, 3, 4, 5, 6, 7, 8, or 9 wt% water, preferably at least 10, 1 1, 12, 13, 14, 15, 16, 17, 18, 19, or 20 wt% water, based on total weight of the material.
- the low-adhesion material may be characterized by a surface contact angle of water of greater than 90° (hydrophobic).
- the material may also be hydrophilic, i.e. characterized by an effective contact angle of water that is less than 90°.
- the material is characterized by an effective contact angle of water of about 70°, 75°, 80°, 85°, 90°, 95°, 100°, or higher.
- the low-adhesion material may also be lipophobic or partially lipophobic in some embodiments.
- the low-adhesion material is characterized by an effective contact angle of hexadecane (as a measure of lipophobicity) of about 50°, 55°, 60°, 65°, 70°, 75°, 80°, 85°, 90°, or higher.
- the low-adhesion material may simultaneously have hydrophobic and lipophobic properties.
- the material is characterized by an effective contact angle of water of at least 90° (such as about 95-100°) and
- the low-adhesion material is characterized by an effective contact angle of water of at least 80° (such as about 80-85°) and
- an effective contact angle of hexadecane of at least 70° (such as about 75-80°).
- the low-adhesion material is characterized by a coefficient of friction, measured at 40-55% (e.g. 50%) relative humidity and room temperature, less than 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, or 0.2. In these or other embodiments, the low-adhesion material is characterized by a coefficient of friction, measured at 85-90% relative humidity and room temperature, less than 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, or 0.1.
- the coefficient of friction is relatively low due to the presence of the solid-state lubricants as well as a lubricating surface layer in the presence of humidity.
- the specific level of humidity is not regarded as critical, but in general may range from about 1% to 100%, typically about 30% to about 70% relative humidity.
- Relative humidity is the ratio of the water vapor density (mass per unit volume) to the saturation water vapor density. Relative humidity is approximately the ratio of the actual partial pressure of water vapor to the saturation (maximum) vapor pressure of water in the atmosphere.
- the coating substrate is thus lubricated both by a solid (the solid-state lubricant) as well as by a liquid (water). While the liquid substance that lubricates the substrate is primarily water, it should be noted that other components from the environment may be present in the lubricating surface layer, including oils, metals, dust, dissolved gases, dissolved aqueous components, suspended non-aqueous components, fragments of debris, fragments of polymers, and so on.
- the low-adhesion material is a coating and/or is present at a surface of an object or region.
- the low-adhesion material could be present within a bulk region of an object or part, or could contain a temporary, protective laminating film for storage or transport, which is later removed, for example.
- Variations of the invention also provide a hardenable precursor material for a low-adhesion material, the precursor material comprising a material capable of forming (i) a substantially continuous matrix containing a first component and (ii) a plurality of phase-separated inclusions containing a second component, wherein one of the first component or the second component is a low-surface-energy polymer having a surface energy between about 5 mJ/m 2 to about 50 mJ/m 2 , and the other of the first component or the second component is a hygroscopic material.
- a precursor material comprises a material capable of forming a substantially continuous matrix, and the precursor material further comprises inclusions, i.e. inclusions that are already formed and dispersed within the precursor material prior to hardening the matrix.
- the low-adhesion material in some embodiments, is formed from a precursor material (or combination of materials) that may be provided, obtained, or fabricated from starting components.
- the precursor material is capable of hardening or curing in some fashion, to form a substantially continuous matrix along with a plurality of inclusions, dispersed within the matrix.
- the precursor material may be a liquid; a multiphase liquid; a multiphase slurry, emulsion, or suspension; a gel; or a dissolved solid (in water and/or organic solvent), for example.
- the coatings may be waterborne coatings, solventborne coatings, or coatings derived from a precursor dissolved in a solvent that contains both water as well as an organic solvent.
- the low-surface-energy polymer and the hygroscopic material may initially be in the same phase or in different phases.
- the low- surface-energy polymer is in liquid or dissolved form while the hygroscopic material is in dissolved-solid or suspended solid form.
- the low-surface- energy polymer is dissolved-solid or suspended-solid form while the hygroscopic material is in liquid or dissolved form.
- the low-surface-energy polymer and the hygroscopic material are both in liquid form.
- the low-surface-energy polymer and the hygroscopic material are both in dissolved (solvent) form.
- a material or coating precursor is applied to a substrate and allowed to react, cure, or harden to form a final coating, wherein the material, coating precursor, or final coating contains a copolymer composition comprising:
- fluoropolymers having an average molecular weight from about 500 g/mol to about 20,000 g/mol, wherein the fluoropolymers are (a,Q)-hydroxyl-terminated and/or (a,Q)-amine-terminated, and wherein the fluoropolymers are present in the triblock structure:
- X, Y CH 2 -(0-CH 2 -CH 2 ) p -T, and X and Y are independently selected;
- T is a hydroxyl or amine terminal group
- n 1 to 100;
- the hygroscopic material is also hardenable, either alone or in combination with the low-surface-energy polymer.
- a low-surface-energy polymer and a hygroscopic polymer may form a high-molecular- weight block copolymer and thus harden.
- the hygroscopic material assists in the curability (hardenability) of the low-surface-energy polymer.
- a precursor material is prepared and then dispensed (deposited) over an area of interest. Any known methods to deposit precursor materials may be employed.
- a fluid precursor material allows for convenient dispensing using spray coating or casting techniques over a large area, such as the scale of a vehicle or aircraft.
- the fluid precursor material may be applied to a surface using any coating technique, such as (but not limited to) spray coating, dip coating, doctor-blade coating, spin coating, air knife coating, curtain coating, single and multilayer slide coating, gap coating, knife-over-roll coating, metering rod (Meyer bar) coating, reverse roll coating, rotary screen coating, extrusion coating, casting, or printing. Because relatively simple coating processes may be employed, rather than lithography or vacuum-based techniques, the fluid precursor material may be rapidly sprayed or cast in thin layers over large areas (such as multiple square meters).
- any coating technique such as (but not limited to) spray coating, dip coating, doctor-blade coating, spin coating, air knife coating, curtain coating, single and multilayer slide coating, gap coating, knife-over-roll coating, metering rod (Meyer bar) coating, reverse roll coating, rotary screen coating, extrusion coating, casting, or printing. Because relatively simple coating processes may be employed, rather than lithography or vacuum-based techniques, the fluid precursor material may be rapidly sprayed or cast
- the solvent or carrier fluid may include one or more compounds selected from the group consisting of water, alcohols (such as methanol, ethanol, isopropanol, or tert-butanol), ketones (such as acetone, methyl ethyl ketone, or methyl isobutyl ketone), hydrocarbons (e.g., toluene), acetates (such as tert-butyl acetate), acids (such as organic acids), bases (such as organic bases), and any mixtures thereof.
- inorganic non-aqueous solvents such as sulfuryl chloride fluoride
- a solvent or carrier fluid may be in a concentration of from about 10 wt% to about 99 wt% or higher, for example.
- the precursor material may be converted to an intermediate material or the final material using any one or more of curing or other chemical reactions, or separations such as removal of solvent or carrier fluid, monomer, water, or vapor.
- Curing refers to toughening or hardening of a polymeric material by cross-linking of polymer chains, assisted by electromagnetic waves, electron beams, heat, and/or chemical additives. Chemical removal may be accomplished by heating/flashing, vacuum extraction, solvent extraction, centrifugation, etc. Physical transformations may also be involved to transfer precursor material into a mold, for example.
- Additives may be introduced during the hardening process, if desired, to adjust pH, stability, density, viscosity, color, or other properties, for functional, ornamental, safety, or other reasons.
- the overall thickness of the final material or coating may be from about 1 ⁇ to about 1 cm or more, such as about 10 ⁇ , 20 ⁇ , 25 ⁇ , 30 ⁇ , 40 ⁇ , 50 ⁇ , 75 ⁇ , 100 ⁇ , 500 ⁇ , 1 mm, 1 cm, or 10 cm.
- Relatively thick coatings offer good durability and mechanical properties, such as impact resistance, while preferably being relatively lightweight. Domains of low-adhesion material exist throughout the material, in both planar and depth dimensions. The low-adhesion function is retained even after abrasion of the top layer of the material. This creates an environmentally durable coating.
- Example 1 Baseline Polymer Without Solid-State Lubricant.
- HMDI 4,4'-Methylenebis (cyclohexyl isocyanate)
- TMP 1, 1,1- tris(hydroxymethyl) propane
- DBTDL dibutyltin dilaurate
- Example 2 Low-Adhesion Polymer With 15.7 vol% MoS 2 .
- HMDI 4,4'-Methylenebis (cyclohexyl isocyanate)
- TMP 1, 1,1- tris(hydroxymethyl) propane
- DBTDL dibutyltin dilaurate
- IV molybdenum
- PFPE-ethoxylated diol is purchased from Solvay Specialty Polymers.
- Example 3 Low-Adhesion Polymer With 15.7 vol% Graphite.
- HMDI 4,4'-Methylenebis (cyclohexyl isocyanate)
- TMP 1, 1,1- tris(hydroxymethyl) propane
- DBTDL dibutyltin dilaurate
- 5147X PFPE-ethoxylated diol is purchased from Solvay Specialty Polymers.
- CPREME G8 graphite is purchased from ConocoPhillips.
- Example 4 Low-Adhesion Polymer With 30 vol% Graphite.
- HMDI 4,4'-Methylenebis (cyclohexyl isocyanate)
- TMP 1, 1,1- tris(hydroxymethyl) propane
- DBTDL dibutyltin dilaurate
- 5147X PFPE-ethoxylated diol is purchased from Solvay Specialty Polymers.
- CPREME G8 graphite is purchased from ConocoPhillips.
- Example 5 Friction Testing of Example 1-4 Coatings.
- Example 1 The friction changes as well as contact angles are shown in the table of FIG. 5.
- Example 1 The friction of the Example 1 material increases with humidity, but when lubricants are added (Examples 2-4), the friction increase is much less or the friction even decreases. At high humidity, the friction coefficients for all samples containing solid-state lubricants are lower than the friction coefficient of the Example 1 baseline sample (no solid-state lubricant).
- Example 6 Ice Formation Testing of Example 1-4 Coatings.
- the kinetic delay of freezing is measured by placing three 50 ⁇ _, drops of deionized water on a surface held at -10°C with a thermoelectric cooler. The time for ice to initially form in the droplets is measured. While this does not relate directly to friction, understanding how these materials affect ice formation will expand or limit their uses.
- Example 2-4 coatings may be useful in conditions where ice formation is likely.
- Practical applications for the present invention include, but are not limited to, aerospace vehicles, windows, optical lenses, filters, instruments, sensors, eyeglasses, cameras, satellites, and weapon systems.
- automotive applications can utilize these coatings to prevent the formation of debris on back-up camera lenses or back-up sensors.
- the principles taught herein may also be applied to self-cleaning materials, anti-adhesive coatings, corrosion-free coatings, etc.
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Health & Medical Sciences (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Wood Science & Technology (AREA)
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Abstract
Description
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US201662356867P | 2016-06-30 | 2016-06-30 | |
US15/638,340 US10836974B2 (en) | 2014-03-14 | 2017-06-29 | Low-adhesion coatings with solid-state lubricants |
PCT/US2017/040153 WO2018005896A2 (en) | 2016-06-30 | 2017-06-30 | Low-adhesion coatings with solid-state lubricants |
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EP3478786A4 EP3478786A4 (en) | 2020-03-18 |
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IT1252660B (en) * | 1991-12-23 | 1995-06-20 | Ausimont Spa | POLYURETHANE AND POLYURETHANE-UREE FLUORINATED AND PROCESSES FOR THEIR PREPARATION |
IT1318558B1 (en) * | 2000-06-08 | 2003-08-27 | Ausimont Spa | LOW FRICTION COEFFICIENT POLYURETHANE. |
JP2003064463A (en) * | 2001-06-15 | 2003-03-05 | Nippon Piston Ring Co Ltd | Wear-resistant sprayed coating film on sliding member |
ITMI20021228A1 (en) * | 2002-06-06 | 2003-12-09 | Ausimont Spa | COMPOSITIONS OF CROSS-LINKABLE POLYURETHANE |
DE10331484A1 (en) * | 2003-07-11 | 2005-03-03 | Construction Research & Technology Gmbh | Polyurethane-polymer hybrid dispersion with improved surface properties, process for their preparation and their use |
ITMI20040106A1 (en) * | 2004-01-27 | 2004-04-27 | Solvay Solexis Spa | POLIURETANI |
BR112015019146B1 (en) * | 2013-02-26 | 2022-01-04 | Akzo Nobel Coatings International B.V. | ANTI-FOULING COMPOSITION COMPRISING A CURABLE POLYMER AND A POLYMER OR OLIGOMER CONTAINING FLUORIDED OXYALKYLENE, AND METHOD OF INHIBITING FOLLOWING OF A SUBSTRATE IN AQUATIC ENVIRONMENT BY APPLYING THE ANTI-FOULING COMPOSITION |
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