Coatings, methods and coated articles

1. A coating layer, comprising

a composite of a fluoropolymer and a thermoplastic polyimide, the thermoplastic polyimide having 5 to 1000 units of the formula:

wherein

each V is the same or different, and is a substituted or unsubstituted tetravalent C 4-40 hydrocarbon group, and

each R is the same or different, and is a substituted or unsubstituted C 2-20 divalent organic group;

wherein the coating layer has a thickness of 2 to 50 μm;

wherein the thermoplastic polyimide has a particle size diameter of 1 to 25 μm; and

wherein the coating layer is in the form of a multilayer coating further comprising a second layer comprising a fluoropolymer disposed on at least a portion on of the layer comprising the composite of the fluoropolymer and the thermoplastic polyimide.

2. The coating layer of claim 1 , wherein the thermoplastic polyimide is a polyetherimide having units of the formula

wherein R is as defined in claim 1 ,

T is —O— or a group of the formula —O—Z—O— wherein the divalent bonds of the —O— or the —O—Z—O— group are in the 3,3′, 3,4′, 4,3′, or the 4,4′ positions, and

Z is an aromatic C 6-24 monocyclic or polycyclic moiety optionally substituted with 1 to 6 C 1-8 alkyl groups, 1 to 8 halogen atoms, or a combination comprising at least one of the foregoing, provided that the valence of Z is not exceeded.

3. The coating layer of claim 2 , wherein R is a group of the formula

wherein Q 1 is —O—, —S—, —C(O)—, —SO 2 —, —SO—, —C y H 2y — or a halogenated derivative thereof, wherein y is an integer from 1 to 5, or —(C 6 H 10 ) z —, wherein z is an integer from 1 to 4; and

Z is a group derived from a dihydroxy compound of the formula

wherein

Ra and Rb are each independently a halogen atom or a monovalent C 1-6 alkyl group;

p and q are each independently integers of 0 to 4;

c is 0 to 4; and

X a is a single bond, —O—, —S—, —S(O)—, —SO 2 —, —C(O)—, or a C 1-18 organic bridging group.

4. The coating layer of claim 3 , wherein each R is independently meta-phenylene or para-phenylene, and Z is 4,4′-diphenylene isopropylidene.

5. The coating layer of claim 1 , wherein the fluoropolymer is poly(tetrafluoroethylene), poly(tetrafluoroethylene-ethylene-propylene), poly(tetrafluoroethylene-hexafluoroethylene), a perfluoroalkoxy polymer, poly(ethylene-tetrafluoroethylene), or a combination comprising at least one of the foregoing.

6. The coating layer of claim 1 , wherein the thermoplastic polyimide comprises 10 to 80 wt % of the total weight of the coating layer.

7. The coating layer of claim 1 , further comprising a functional filler.

8. A method of coating a substrate, the method comprising

applying the coating layer of claim 1 to at least a portion of a surface of the substrate to form a first coating layer ( 30 ) having a first side ( 31 ) in contact with the substrate ( 20 ) and a second side ( 32 ) opposite the first side, and

applying a fluoropolymer layer over at least a portion of the second side ( 32 ) of the first coating layer to provide a second coating layer ( 40 );

optionally further comprising drying the first coating layer prior to applying the second coating layer, drying the second layer after application to the first coating layer; and

optionally curing the coating layers on the substrate.

9. A substrate, comprising the coating layer of claim 1 .

10. An article comprising the substrate of claim 9 .