SEGMENT COPOLYMER FOR MAKING ICEPHOBIC COATINGS

Abstract

This invention relates to segment copolymer comprising rigid and soft segments wherein the soft segments are doped with a wax. A model polymer of this new type can be synthesized by the free radical copolymerization of methyl methacrylate (MMA) (39 wt %), lauryl, methacrylate (LMA) (10 wt %) and an adduct monomer of glycidyl methacrylate (GMA) and 1-dodecylamine (DDA). Doping with paraffin wax is one suitable approach to obtain the inventive material. The invention further relates to a simple and low-cost process to make these polymers and coatings comprising the polymers. Using the polymer material a coating with a highly icephobic surface can be obtained comprising soft hydrophobic micro domains segregated and stabilized by rigid copolymer on its surface. The icephobic behaviour may find new application in aerospace applications.

Claims

1. A segment copolymer comprising rigid and soft segments wherein the soft segments are doped with a wax.

2. The segment copolymer of claim 1 wherein the rigid segments comprise polymer chains comprising: monomer units selected from methacrylate, styrene, acrylonitrile butadiene styrene, 4-hydroxylbenzoic acid, vinyl chloride, or monomers made from bisphenol A (BPA) pre-monomers and the soft segments comprise polymer chains comprising monomer units bearing long aliphatic side chains.

3. The segment copolymer of claim 1 wherein the rigid segment comprises a polymer chain comprising: monomer units selected from methacrylate, styrene, or 4-hydroxylbenzoic acid and the soft segments comprise a polymer chain comprising: monomer units bearing a side chain selected from linear or branched C10 (decyl) to C18 (octadecyl) alkyl groups which are optionally substituted and wherein methylene (CH2-) groups may be optionally replaced by NH, CO, C(O), C(O)NH or O groups.

4. The segment copolymer of claim 1 wherein the polymer chain of the soft segment additionally comprises: monomers with organic functional groups that can be crosslinked via a crosslinker.

5. The segment copolymer of claim 4 wherein the functional groups are located on side chains close to the main polymer chain of the copolymer.

6. The segment copolymer of claim 4 wherein the functional groups are NH, OH, SH, NH2, N3, C3 to C7 alkynyl, or COOH groups.

7. The segment copolymer of claim 1 wherein the monomers of the segment copolymer comprise methyl methacrylate (MMA), lauryl methacrylate (LMA) and an adduct monomer of glycidyl methacrylate (GMA) and 1-dodecylamine (DDA).

8. The segment copolymer of claim 1 wherein the rigid segments substantially consist of polymer chains of methyl methacrylate (MMA) and the rigid segments surround the segregated soft segments which substantially consist of a copolymer of a lauryl methacrylate (LMA) monomer and an adduct monomer of glycidyl methacrylate (GMA) and 1-dodecylamine (DDA).

9. The segment copolymer copolymer of claim 7 wherein the molar ratio of the monomer units LMA:(GMA/DDA) is 1:1 to 1:10 and PMMA:(LMA and (GMA/DDA) is 5:1 to 1:2.

10. The segment copolymer of claim 7 wherein the molar ratio of wax to the combined molar ratios the monomer units of the polymer chains in the soft segments is about 0.6-2.5 mol %.

11. The segment copolymer of claim 1 wherein the wax is selected from linear alkanes, branched alkanes, aromatic or naphthenic substituted alkanes, or glycerides.

12. The segment copolymer of claim 1 wherein the weight ratio of wax to the combined weight ratios the monomer units of the segmented polymer is 0.1 to 10 wt. %.

13. The segment copolymer of claim 1 wherein the overall amount of wax used for the doping is between 4 to 20 mg per g of the copolymer.

14. The segment copolymer of claim 1 which is additionally doped with a polyethylene, polypropylene, perfluoroacrylate, silicone or polyamide oligomer as wax additive wherein the weight ratio of polyethylene oligomer to the wax is about 25 to 55%.

15. A process for making a segment copolymer comprising rigid and soft segments wherein the soft segments are doped with a wax, and wherein the method comprises: synthesizing the segmented copolymer by reacting the monomers of the soft segment and the rigid segment; adding wax to the segment copolymer.

16. The process of claim 15 wherein the wax is added during the synthesis of the copolymer.

17. The process of claim 15 wherein in operation (i) the monomers of the rigid and soft segment are polymerized together in a free-radical polymerization and segmentation is achieved by a stronger self-polymerization of the monomers of the rigid segment compared with the copolymerization with the monomers of the soft segment.

18. The process of claim 15 wherein in operation (ii) a polyethylene oligomer is added together with the wax and wherein the weight ratio of polyethylene oligomer to the wax is about 25 to 50%.

19. The process of claim 15 wherein the molar ratio of wax to the combined molar ratios the monomers forming the soft segment is about 0.6 to 2.5 mol %.

20. A polymer coating with hydrophobic microdomains surrounded by rigid segments obtained by curing a coating solution comprising a segment copolymer comprising rigid and soft segments, wherein the soft segments are doped with a wax.

Description

DESCRIPTION OF DRAWINGS

[0092] The accompanying drawings illustrate a disclosed embodiment or reaction scheme and serve to explain the principles of the disclosed embodiments. It is to be understood, however, that the drawings are designed for purposes of illustration of examples only, and not as a limitation of the invention.

[0093] FIG. 1 shows a scheme for the synthesis of adduct monomer, followed by solution polymerization with MMA and LMA to form comb like copolymer.

[0094] FIG. 2 shows a graphic illustration of the formation of a soft hydrophobic microdomain.

[0095] FIG. 3 shows DSC profiles for polymer coating under different paraffin wax loading S1 (0%), S1B (12.8 mol %), S2 (3.2 mol %) and S3 (0.8 mol %).

[0096] FIG. 4 shows an AFM surface topology characterization phase images of Sample S2 (d) and of Sample S5 with soft domain/rigid boundary microstructure (e).

[0097] FIG. 5 shows FESEM images of (a) Pristine PU topcoat, (b) PU cast with comb-like copolymer, Sample S1, (c) Coating further modified with 3.2 wt. % paraffin wax, Sample S2, (d) Sample S3, 0.8 wt. % paraffin wax, (e) Sample S4, 1.7 mw. % PE, and (f) Sample S5, 1.7 wt. % PE and 3.2 wt. % paraffin wax.

[0098] FIG. 6 shows an electron micrograph of sample S2 described in Table 1.

[0099] FIG. 7 shows a configuration of a Peltier icing device, the pertinent cooling profile over 30 minutes and visualization of icing over the 4 selected samples at two cooling time points.

[0100] FIG. 8 shows: Top: Microscopic frost formation monitoring on PU topcoat, Scale bar: 500 m, magnification 50, and field-of-view dimension of 1.82.5 mm, (a-b) visualizing the progress of water condensation at t=2 min (T9 C.) and t=5 min (T1 C.), respectively, (c) onset of frost formation at t=8 min (T5.1 C.), (d) spreading of frosting wave front over the entire field-of-view at t=8.5 min (T5.6 C.), and (e-f) subsequent build-up of ice crystals from t=10 to 15 min (T6.3 to 8.9 C.); Bottom: Microscopic frost formation monitoring on IpC S3, Scale bar: 500 m, magnification 50, and field-of-view dimension of 1.82.5 mm, (a-b) visualizing the progress of water condensation at t=2 min (T9 C.) and t=5 min (T1 C.), respectively, (c) onset of frost formation at t=21.7 min (T10.3 C.), (d) spreading of frosting wave front over the entire field-of-view at t=23 min (T10.4 C.), and (e-f) subsequent build-up of ice crystals from t=25 to 30 min (T10.8 to 11.4 C.).

[0101] FIG. 9 shows an experimental setup for the determination of the critical shear stress between ice and coating surface, left: Instron 5569 Table Universal testing machine coupled with icing device, right: dissection of icing device metal chamber.

[0102] FIG. 10 shows a graphic illustration for the two ice-coating interaction profiles due to different ice adhesions to the surfaces in question.

INDUSTRIAL APPLICABILITY

[0103] The inventive segment copolymer can be used in coating solutions to prepare coatings with icephobic capabilities as described above. The coatings can be cured on various substrates, especially metal or other polymer coatings. They can find use in many applications where a coating is desired to render a coated substrate icephobic.

[0104] As shown in the examples a special use of the inventive segment copolymer is the use in coatings for aerospace applications. Ice adhesion on critical aircraft surfaces affects aerodynamic control and is a serious hazard. The coatings obtainable are compatible to standard commercial paint systems of aerospace applications. An effective approach to implement ice repellence to a commercial topcoat of aerospace polyurethane (PU, PPG) through covering the PU topcoat with a thin film, which is formed of a segment copolymer, a di-isocyanate curing agent and an appropriately small amount of paraffin wax has already been shown. The achieved reduction is ice adhesion strength may open up numerous new applications. This is especially given as the coatings according to the invention can be prepared according a relatively simple low-cost process. The coatings obtained are colourless and transparent. It can expected that they can be easily adopted in the aerospace industry. The coatings further provide good weatherability (>800 hr in weathering chamber).

[0105] It will be apparent that various other modifications and adaptations of the invention are available to the person skilled in the art after reading the foregoing disclosure without departing from the spirit and scope of the invention and it is intended that all such modifications and adaptations come within the scope of the appended claims.