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CN-122006996-A - Mixed wettability coating and preparation method and application thereof

CN122006996ACN 122006996 ACN122006996 ACN 122006996ACN-122006996-A

Abstract

The invention relates to a mixed wettability coating and a preparation method and application thereof, wherein the preparation method comprises the steps of (1) adding siloxane, nano silicon dioxide and nano aluminum oxide into a solvent, and uniformly mixing to obtain a premix; sequentially adding polytetrafluoroethylene powder and oily graphene dispersion liquid into the premix liquid for uniformly mixing to obtain a first coating, uniformly mixing a resin matrix containing active hydroxyl groups and carboxyl groups with deionized water, sequentially adding a dispersing agent, a filler, a cross-linking agent and a leveling agent for uniformly mixing to obtain a second coating, spraying the first coating on a substrate, baking to obtain a pretreated substrate containing a first coating, polishing a part of the area of the pretreated substrate, rolling the second coating on the part of the area to obtain an initial substrate containing a second coating, and sequentially drying and baking the initial substrate to obtain a substrate containing a mixed wettability coating. The mixed wettability coating improves the condensation efficiency and long-term stability of the corrugated curved substrate, and is suitable for industrial waste heat steam condensation scenes containing non-condensable gas.

Inventors

  • YU YANLING
  • HE WEI
  • SHANG HONGRU
  • YANG MIN
  • GUO LU

Assignees

  • 哈尔滨工业大学

Dates

Publication Date
20260512
Application Date
20260121

Claims (10)

  1. 1. A method of preparing a hybrid wettability coating comprising: (1) Adding siloxane, nano silicon dioxide and nano aluminum oxide into a solvent, and uniformly mixing to obtain a premix; sequentially adding polytetrafluoroethylene powder and oily graphene dispersion liquid into the premix liquid, and uniformly mixing to obtain a first coating; (2) Uniformly mixing a resin matrix containing active hydroxyl and carboxyl with deionized water, and sequentially adding a dispersing agent, a filler, a cross-linking agent and a leveling agent for uniformly mixing to obtain a second coating; (3) Spraying the first coating on a substrate, and baking to obtain a pretreated substrate containing a first coating; (4) Polishing a partial area of the pretreated substrate, and then rolling the second coating on the partial area to obtain an initial substrate with the second coating and the first coating alternately distributed; (5) And sequentially drying and baking the initial substrate to obtain the substrate containing the mixed wettability coating.
  2. 2. The method of claim 1, wherein in step (1): The siloxane is methyltrimethoxysilane or tetraethoxysilane; the particle size of the nano silicon dioxide is 10-50 nm; the particle size of the nano aluminum oxide is 20-100 nm; The solvent is ethanol water solution; preferably, the premix comprises, by mass, 30-50% of siloxane, 10-20% of nano silicon dioxide, 5-15% of nano aluminum oxide and 30-40% of solvent.
  3. 3. The method of claim 1, wherein in step (1): The grain diameter of the polytetrafluoroethylene powder is 1-10 mu m; the oily graphene dispersion liquid is prepared by filter pressing graphene, a wetting agent and a solvent, preferably, the solid content of the oily graphene dispersion liquid is 11-13 wt%, preferably, the wetting agent is a high molecular block copolymer or a silane coupling agent containing N element, and/or, The first coating comprises, by mass, 30-50% of premix, 8-15% of polytetrafluoroethylene powder, 8-15% of oily graphene dispersion and 20-50% of solvent.
  4. 4. The method of claim 1, wherein in step (2): The resin matrix comprises an aqueous acrylic resin emulsion; the dispersing agent is a polycarboxylate sodium salt dispersing agent, and preferably, the using amount of the dispersing agent is 0.5-1 wt% of the second coating; the filler is at least one of hydrophilic silica nanoparticles, graphene oxide, boron nitride or graphite, preferably the hydrophilic silica nanoparticles and the graphene oxide with the mass ratio of 1:3, and preferably the filler is 1-5 wt% of the resin matrix; The cross-linking agent is aziridine, preferably, the dosage of the cross-linking agent accounts for 2-3 wt% of the second coating; the leveling agent is polyether modified siloxane, and preferably, the consumption of the leveling agent accounts for 0.4-0.6 wt% of the second coating; More preferably, the solid content of the second coating is 20-40 wt%.
  5. 5. The method of claim 1, wherein in step (3): The spraying pressure is 0.25-0.3 MPa, the distance from the spray gun to the substrate is 15-25 cm, the moving speed of the spray gun is 0.3-0.5 m/s, and/or, The baking comprises the steps of heating to 100 ℃ at a heating rate of 5-10 ℃ per minute and preserving heat for 10 minutes, heating to 250-280 ℃ at a heating rate of 3-5 ℃ per minute and preserving heat for 15-25 minutes, and heating to 350-380 ℃ at a heating rate of 8-10 ℃ per minute and preserving heat for 20 minutes; Preferably, the thickness of the first coating is 80-100 μm.
  6. 6. The process according to claim 1, wherein in step (4), The roll coating speed is 0.5-1.5 m/min, and/or, The thickness of the second coating is 20-50 mu m.
  7. 7. The method according to any one of claims 1 to 6, wherein in step (5): The drying temperature is 20-30 ℃ and the drying time is 18-24 hours, and/or, The temperature of the baking treatment is 80-100 ℃ and the time is 1h.
  8. 8. The method according to any one of claims 1 to 7, wherein the substrate has a corrugated surface, preferably the partial region is a peak region of the substrate, more preferably the ratio of the width of the first coating to the width of the second coating in the mixed wettability coating is 1:1.
  9. 9. A hybrid wettability coating produced by the production method according to any one of claims 1 to 8.
  10. 10. Use of a hybrid wettability coating according to claim 9, wherein the hybrid wettability coating is applied on a heat exchange element with a corrugated surface, preferably in a condensation scene with non-condensable gases.

Description

Mixed wettability coating and preparation method and application thereof Technical Field The invention relates to the technical field of surface engineering, in particular to the technical field of heat energy recovery, and particularly relates to a mixed wettability coating, a preparation method and application thereof. Background In the aerobic composting processes of agricultural waste treatment, municipal sludge treatment, livestock and poultry cultivation and the like, a large amount of low-temperature saturated humid air at 50-80 ℃ can be continuously generated, the latent heat contained in the air accounts for more than 40% of the total energy consumption of the system, and the air conditioner has remarkable waste heat recovery value. However, non-condensable gases (NCGs) such as nitrogen, carbon dioxide and the like in the gas flow can form a diffusion resistance layer on the traditional smooth metal condensation surface, and the mass transfer process of water vapor condensation is seriously inhibited. Experiments show that even if the NCGs concentration is as low as 0.5%, the condensation heat transfer coefficient is reduced by more than 50%, so that a large amount of heat energy cannot be recovered and is directly discharged. Although mixed wettability surface technology can improve condensing efficiency, the technology still faces multiple bottlenecks when applied in industrial settings. The ultra-hydrophobic coating is easy to generate structural damage under the conditions of particle scouring, chemical corrosion and damp-heat circulation, so that the hydrophobic performance is quickly degraded, and meanwhile, although high-precision patterning processes such as photoetching, laser processing and the like can realize area wettability control, the requirements of large-area uniform coating of complex geometric structures such as corrugated pipes cannot be met due to high cost, complex procedures and difficulty in adapting to curved substrates. Moreover, the traditional research on optimizing the excessive focusing wettability neglects the cooperative improvement of the thermal conductivity, the mechanical strength and the long-term stability of the coating, so that the performance is obviously attenuated under the actual working condition. Especially for the core heat exchange elements such as corrugated pipes/plates with wave crest and wave trough alternate structures, the special geometric forms of the core heat exchange elements further increase the implementation difficulty. Accurate positioning of the functional coating is difficult to realize by the traditional mask method, improper wettability distribution is easy to cause liquid drop retention and channel blockage, and condensation efficiency is weakened instead. Thus, there is a need for a hybrid wettability coating and methods of making and using the same. Disclosure of Invention The invention provides a mixed wettability coating, a preparation method and application thereof, wherein the mixed wettability coating has long-term stability and excellent condensation efficiency, can be efficiently coated on a corrugated curved surface substrate, and improves the condensation efficiency in a scene containing non-condensable gas. The present invention provides in a first aspect a method of preparing a mixed wettability coating comprising: (1) Adding siloxane, nano silicon dioxide and nano aluminum oxide into a solvent, and uniformly mixing to obtain a premix; sequentially adding polytetrafluoroethylene powder and oily graphene dispersion liquid into the premix liquid, and uniformly mixing to obtain a first coating; (2) Uniformly mixing a resin matrix containing active hydroxyl and carboxyl with deionized water, and sequentially adding a dispersing agent, a filler, a cross-linking agent and a leveling agent for uniformly mixing to obtain a second coating; (3) Spraying the first coating on a substrate, and baking to obtain a pretreated substrate containing a first coating; (4) Polishing a partial area of the pretreated substrate, and then rolling the second coating on the partial area to obtain an initial substrate with the second coating and the first coating alternately distributed; (5) And sequentially drying and baking the initial substrate to obtain the substrate containing the mixed wettability coating. Preferably, in step (1): The siloxane is methyltrimethoxysilane or tetraethoxysilane; the particle size of the nano silicon dioxide is 10-50 nm; the particle size of the nano aluminum oxide is 20-100 nm; The solvent is ethanol water solution. More preferably, in the step (1), the mass fraction of each component in the premix is as follows, 30-50 wt% of siloxane, 10-20 wt% of nano silicon dioxide, 5-15 wt% of nano aluminum oxide and 30-40 wt% of solvent. Preferably, in step (1): The grain diameter of the polytetrafluoroethylene powder is 1-10 mu m; The oily graphene dispersion liquid is prepared from graphene, a wetting agent and a solvent