Low-friction fluorinated coatings
Low-friction fluorinated coatings are disclosed herein. A preferred low-friction material contains a low-surface-energy fluoropolymer having a surface energy between about 5 mJ/m 2 to about 50 mJ/m 2 , and a hygroscopic material that is covalently connected to the fluoropolymer in a triblock copolymer, such as PEG-PFPE-PEG. The material forms a lubricating surface layer in the presence of humidity. An exemplary copolymer comprises fluoropolymers with average molecular weight from 500 g/mol to 20,000 g/mol, wherein the fluoropolymers are (α,ω)-hydroxyl-terminated and/or (α,ω)-amine-terminated, and wherein the fluoropolymers are present in the triblock structure T-(CH 2 —CH 2 —O)—CH 2 —CF 2 —O—(CF 2 —CF 2 —O) m (CF 2 —O) n —CF 2 —CH 2 —(O—CH 2 —CH 2 ) p -T where T is a hydroxyl or amine terminal group, p=1 to 50, m=1 to 100, and n=1 to 100. The copolymer also contains isocyanate species and polyol or polyamine chain extenders or crosslinkers possessing a functionality of preferably 3 or greater. These durable, solvent-resistant, and transparent coatings reduce insect debris following impact.
1. A material comprising:
a substantially continuous matrix containing a first component; and
a plurality of inclusions containing a second component, wherein said inclusions are uniformly and intimately dispersed within said matrix;
wherein one of said first component or said second component is a low-surface-energy fluoropolymer having a surface energy between about 5 mJ/m 2 to about 50 mJ/m 2 , and the other of said first component or said second component is a hygroscopic material that is covalently connected to said fluoropolymer in a triblock copolymer,
wherein said material forms a lubricating surface layer in the presence of humidity, and wherein said material is characterized by a coefficient of friction less than 0.2,
wherein said fluoropolymer is perfluoropolyether,
wherein said hygroscopic material is poly(ethylene glycol), and
wherein said triblock copolymer is
wherein:
X, Y═CH 2 —(O—CH 2 —CH 2 ) p -T, and X and Y are independently selected;
p=6 to 50;
T is a hydroxyl or amine terminal group;
m=1 to 100; and
n=1 to 100.
2. The material of claim 1 , wherein said continuous matrix further 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.
3. The material of claim 2 , wherein said isocyanate species are selected from the group consisting of 4,4′-methylenebis(cyclohexyl isocyanate), hexamethylene diisocyanate, cycloalkyl-based diisocyanates, tolylene-2,4-diisocyanate, 4,4′-methylenebis(phenyl isocyanate), isophorone diisocyanate, and combinations or derivatives thereof.
4. The material of claim 2 , wherein said polyol or polyamine chain extenders or crosslinkers are selected from the group consisting of 1,3-butanediol, 1,4-butanediol, 1,3-propanediol, 1,2-ethanediol, diethylene glycol, triethylene 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, triethanolamine, pentaerythritol, ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, diethyltoluenediamine, dimethylthiotoluenediamine, isophoronediamine, diaminocyclohexane, N,N,N′,N′-tetrakis(2-hydroxypropyl) ethylenediamine, and homologues, derivatives, or combinations thereof.
5. The material of claim 2 , wherein said one or more polyol or polyamine chain extenders or crosslinkers possess an average functionality of about 3 or greater.
6. The material of claim 1 , wherein said low-surface-energy polymer or said hygroscopic material is surface-treated.
7. The material of claim 1 , said material further comprising one or more additional components selected from the group consisting of a particulate filler, a pigment, a dye, a plasticizer, a flame retardant, a flattening agent, and a substrate adhesion promoter.
8. The material of claim 7 , wherein said particulate filler is selected from the group consisting of silica, alumina, silicates, talc, aluminosilicates, barium sulfate, mica, diatomite, calcium carbonate, calcium sulfate, carbon, wollastonite, and combinations thereof; and wherein said particulate filler is optionally surface-modified with a compound selected from the group consisting of fatty acids, silanes, alkylsilanes, fluoroalkylsilanes, silicones, alkyl phosphonates, alkyl phosphonic acids, alkyl carboxylates, alkyldisilazanes, and combinations thereof.
9. The material of claim 1 , wherein said material is characterized by a water absorption capacity of at least 10 wt % water based on total weight of said material.
10. The material of claim 1 , wherein said material is characterized by a surface contact angle of water of greater than 90°.
11. The material of claim 1 , wherein said material is optically transparent.