Polyamide 3D printed part super-hydrophobic integrated treatment method

Abstract

The invention relates to the technical field of additive manufacturing aftertreatment, and discloses a polyamide 3D printed part super-hydrophobic integrated treatment method which comprises the following steps that a composite solvent system containing long-chain fluorinated silane is configured, and the composite solvent system is used for achieving part surface swelling, micropore filling and hydrophobic function precursor loading; the method comprises the following steps: putting a polyamide 3D printed part into a reaction chamber subjected to steam treatment, and controlling the steam temperature and time, so that solvent steam fully acts on the surface and internal micropores of the part; carrying out gradient heating drying on the workpiece subjected to steam treatment, and removing a volatile solvent in a system; the dried workpiece is subjected to thermocuring treatment, so that the long-chain fluorinated silane forms a stable hydrophobic film layer on the surface of the workpiece and the inner walls of micropores, integrated construction of surface smoothness, micropore sealing and a super-hydrophobic function is completed, the treated workpiece shows excellent waterproofness, self-cleaning capacity and antifouling and anti-adhesion characteristics, the technical effect is remarkable, and the method is suitable for industrial production. And the method has high industrial application value.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing post-processing technology, specifically to an integrated superhydrophobic processing method for polyamide 3D printed parts. Background Technology

[0002] Polyamide parts formed by 3D printing technologies such as selective laser sintering (SLS) have the following technical defects due to their inherent porosity and surface roughness:

[0003] (a) Core performance defects:

[0004] 1. Hydrophilicity and permeability: The rough and porous microstructure easily adsorbs and permeates liquids such as water and oil through capillary action, which leads to the expansion of the part size, the decrease of mechanical properties, and provides a continuously moist environment for the growth of microorganisms.

[0005] SLS parts have a porosity of 10% to 30% (pore size is mostly 1-50μm), and the surface roughness Ra is usually 10-17μm. The capillary action of the rough surface and the internal porous structure form "permeation channels", which easily adsorb liquids such as water, oil, and medicine, resulting in the expansion of the part size (the size change rate of PA6 after water absorption can reach 2% to 3%), the decline of mechanical properties (tensile strength decreases by 15% to 20%), and the growth of bacteria and mold in humid environments.

[0006] 2. Easily contaminated and difficult to clean: After liquids and dirt seep into the micropores, conventional wiping and rinsing cannot completely remove them, and long-term use can easily lead to "internal contamination"; for example, rainwater seeps into the casing of outdoor electronic devices and media residues in fluid transport components, which not only affect the appearance but also shorten the service life of the parts.

[0007] (ii) Existing technological bottlenecks: limited functionality and insufficient stability

[0008] Current post-processing technologies for polyamide 3D printed parts have significant limitations and cannot simultaneously solve the above-mentioned problems:

[0009] 1. Traditional steam smoothing technology (such as using ethanol or ethyl acetate vapor): can only reduce surface roughness (Ra can be reduced to 2-5μm) through solvent swelling, but cannot seal deep micropores, and the surface after treatment is still hydrophilic (static water contact angle < 90°), and there is no improvement in weather resistance;

[0010] 2. Surface coating technology (such as spraying hydrophobic coatings): Although it can achieve superhydrophobicity, the coating has weak adhesion to the substrate and is easy to fall off after long-term friction or chemical erosion. In addition, the coating cannot fill the internal micropores, and the permeability problem has not been solved.

[0011] 3. Physical sealing technologies (such as hot pressing and impregnation): can only block surface micropores, cannot reduce roughness, and have no hydrophobic function. Additional modification steps are still required afterward, making the process complex and costly.

[0012] In summary, traditional vapor smoothing techniques primarily focus on reducing surface roughness, but conventional solvent systems can only provide limited improvement in water resistance after treatment and cannot actively construct a stable superhydrophobic surface. Simple physical seals are prone to failure under long-term mechanical friction or chemical corrosion and lack self-cleaning capabilities. Therefore, developing a treatment process that can impart a smooth, sealed, and self-cleaning superhydrophobic surface to polyamide parts in a single step has urgent technical demand and market value. To this end, we propose an integrated superhydrophobic treatment method for polyamide 3D printed parts. Summary of the Invention

[0013] The purpose of this invention is to provide a superhydrophobic integrated treatment method for polyamide 3D printed parts, which solves the problems mentioned in the background art.

[0014] To achieve the above objectives, the present invention provides the following technical solution: a method for integrated superhydrophobic treatment of polyamide 3D printed parts, comprising the following steps:

[0015] S1. A composite solvent system containing long-chain fluorinated silanes is prepared. This composite solvent system is used to achieve surface swelling, micropore filling, and hydrophobic precursor loading of the part. Preferably, it is heptadecafluorodecyltriethoxysilane (PFDS) or similar long-chain fluorinated silanes. These substances can condense onto the part surface in the vapor phase. After hydrolysis, their ethoxy groups can form strong Si-OC covalent bonds with the polar groups on the polyamide surface. Simultaneously, the outwardly arranged fluorocarbon chains form a stable low surface energy layer. The composite solvent system uses two or three of trifluoroethanol, ethanol, and ethyl acetate as base solvents. The combination of trifluoroethanol and ethanol / ethyl acetate can adjust the solvent swelling rate and the solubility of the fluorinated silanes, avoiding excessive swelling or fluorinated silane precipitation problems caused by a single solvent.

[0016] S2. Immerse the polyamide 3D printed part in the above composite solvent system, and control the immersion temperature and time to ensure that the solvent fully acts on the surface and internal micropores of the part. The immersion temperature is set to 20℃-60℃. If the temperature is below 20℃, the solvent penetration will be insufficient and it will not be able to fill the 1-50μm micropores. If the temperature is above 60℃, the part will be easily deformed, affecting the dimensional accuracy. The immersion time is set to 10min-60min. If the time is too short, the hydrophobic precursor load will be insufficient, and if the time is too long, the surface of the part will be excessively swollen.

[0017] S3. After impregnation, the parts are dried by gradient heating to remove volatile solvents in the system, thoroughly remove water and ethanol, and avoid affecting the efficiency of steam action. The gradient heating drying temperature range is 30℃-80℃. Starting from a low temperature can prevent the rapid evaporation of solvents on the surface of the parts from causing incomplete micropore sealing. The high temperature stage accelerates the removal of deep solvents. The total drying time is 30min~120min. During the drying process, the ambient humidity is controlled to be ≤60%. Excessive humidity can easily cause water to be re-adsorbed, affecting the subsequent thermosetting effect.

[0018] S4. Perform thermosetting treatment on the dried part to form a stable hydrophobic film layer on the surface of the part and the inner wall of the micropores of the long-chain fluorinated silane. This completes the integrated construction of surface smoothing, micropore sealing and superhydrophobic function, promotes the complete hydrolysis-condensation reaction of PFDS, strengthens the covalent bond of Si-OC, avoids the hydrophobic layer from falling off, and removes residual solvent to prevent the part from deforming. The thermosetting temperature is set at 80℃-150℃. Below 80℃, the reaction is incomplete and the hydrophobic film layer has weak bonding force; above 150℃, it is easy to cause aging of polyamide substrate. The curing time is 20min-90min. The curing process is carried out in an inert gas, nitrogen or argon protection or in an air atmosphere.

[0019] Preferably, the composite solvent system uses two or three of trifluoroethanol, ethanol and ethyl acetate as base solvents, the amount of long-chain fluorinated silane added is 0.5% to 5% of the mass fraction of the base solvent, the mass fraction of trifluoroethanol is 10% to 18% of the total mass fraction of the base solvent, and trifluoroethanol is a strongly polar main solvent that causes surface swelling.

[0020] Preferably, in step S2, the immersion temperature is 20℃-60℃ and the immersion time is 10min-60min, ensuring that the solvent penetrates into the 1-50μm microporous structure inside the part.

[0021] Preferably, in step S3, the temperature range of the gradient heating drying is 30℃-80℃, the total drying time is 30min-120min, and the ambient humidity is controlled to be ≤60% during the drying process.

[0022] Preferably, in step S4, the thermosetting temperature is 80℃-150℃, the curing time is 20min-90min, and the curing process is carried out under inert gas protection or in an air atmosphere.

[0023] Preferably, the long-chain fluorinated silane is a silane coupling agent containing perfluoroalkyl groups, and the length of the fluorocarbon chain in its molecular chain is C6-C12.

[0024] Preferably, the surface roughness Ra of the treated polyamide 3D printed part is ≤5μm, the static water contact angle is ≥150°, the test conditions are 25℃ and 50% relative humidity, tested according to GB / T 30693-2014 standard, the water absorption dimensional change rate is ≤0.5%, and the tensile strength retention rate is ≥90%, tested according to GB / T 1040.1-2018 standard.

[0025] Preferably, the polyamide 3D printed part is a PA6, PA12, PA11 or a blend thereof formed by selective laser sintering (SLS), and the initial porosity of the part is 10% to 30%.

[0026] This invention provides a method for integrating superhydrophobic treatment of polyamide 3D printed parts. This method for integrating superhydrophobic treatment of polyamide 3D printed parts has the following beneficial effects:

[0027] This invention integrates long-chain fluorinated silanes into an optimized solvent system and employs a key thermosetting step to successfully achieve the integrated construction of polyamide 3D printed parts with smooth surface, micropore sealing, and superhydrophobicity. The treated parts exhibit excellent waterproofness (24h water absorption rate ≤0.25%), self-cleaning ability, static water contact angle ≥150°, and antifouling and anti-adhesion properties. The antifouling and anti-adhesion properties (no hydrophobic layer peeling off after 100 rubs with a 500g heavy cotton cloth) demonstrate significant technical effectiveness and possess high industrial application value. Attached Figure Description

[0028] Figure 1 This is a flowchart of the steps involved in the method. Detailed Implementation

[0029] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described with reference to the accompanying drawings.

[0030] like Figure 1 As shown, the present invention has the following three specific embodiments.

[0031] Example 1: PA12 outdoor electronic device housing

[0032] Part parameters: dimensions 100mm×80mm×5mm, surface roughness Ra=13.8μm, untreated part 24h water absorption rate=1.8%, static water contact angle=75°, no hydrophobicity after 50 cycles of rubbing with 500g weighted cotton cloth.

[0033] Compound solvent formulation, total 1000mL:

[0034] Solvent base: Trifluoroethanol (TFE), 150 mL, 15%; NMP, 100 mL, 10%; n-Butanol, 25%; 1,4-Dioxane, 200 mL, 20%; Xylene, 28.5%;

[0035] Hydrophobic functional system: PFDS, 1.5% per 15 mL;

[0036] Process parameters:

[0037] Steam temperature: 65℃, processing time: 120 seconds;

[0038] Heat curing: 110℃, 45 minutes;

[0039] Performance test results:

[0040] Surface roughness Ra=3.7μm, a reduction of 73.2%;

[0041] The water absorption rate was 0.18% in 24 hours, a decrease of 90%. After 50 cycles of hot and cold cycling from -30℃ to 80℃, the water absorption rate was still <0.25%.

[0042] Abrasion resistance test, 500g load, 100 rubs with cotton cloth: contact angle = 152°, no hydrophobic layer peeling off.

[0043]

[0044] Example 2: PA66 glass fiber reinforced fluid valve components

[0045] Part parameters: dimensions 50mm×30mm×10mm, surface roughness Ra=14.5μm, glass fiber content 15%, untreated part leaks after holding under 0.1MPa water pressure for 10 minutes, water absorption rate = 1.5% after 24 hours;

[0046] Compound solvent formulation, total 1000mL:

[0047] Solvent base: Trifluoroethanol (TFE), 120 mL, 12%; NMP, 80 mL, 8%; n-Butanol, 28%; 1,4-Dioxane, 220 mL, 22%; Xylene, 290 mL, 29%; Ethyl acetate, 10 mL, 1%.

[0048] Hydrophobic functional system: PFDS, 1.0% per 10 mL;

[0049] Process parameters:

[0050] Steam temperature: 68℃, processing time: 100 seconds;

[0051] Heat curing: 105℃, 40 minutes;

[0052] Performance test results:

[0053] Surface roughness Ra=4.1μm, a reduction of 71.7%, and no residual solvent on the inner wall of the flow channel;

[0054] 24-hour water absorption rate = 0.22%;

[0055] Water pressure test: No leakage was observed after holding the water pressure at 0.2MPa for 30 minutes, while traditional untreated parts leaked at 0.1MPa.

[0056] Chemical resistance: After immersion in a 5% sulfuric acid solution for 24 hours, no surface corrosion was observed, and the contact angle remained >145°.

[0057]

[0058] Example 3: PA11 catheter connector was selected.

[0059] Part parameters: dimensions 20mm×10mm×3mm, surface roughness Ra=10.2μm, porosity 15%; static water contact angle of untreated part = 72°; after wiping 20 times with 75% ethanol, surface hydrophilicity is enhanced; surface roughness requirement for application: Ra ≤ 5μm.

[0060] Compound solvent formulation, total 1000mL:

[0061] Solvent base: Trifluoroethanol (TFE), 18% in 180 mL; NMP, 12% in 120 mL; n-Butanol, 20% in 200 mL; 1,4-Dioxane, 18% in 180 mL; Xylene, 30% in 300 mL.

[0062] Hydrophobic functional system: PFDS, 2.0% in 20mL;

[0063] Process parameters:

[0064] Steam temperature: 70℃, processing time: 90 seconds;

[0065] Heat curing: 100℃, 35 minutes;

[0066] Performance test results:

[0067] Surface roughness Ra = 2.2 μm. Roughness is reduced by 78%, meeting the requirements for medical-grade surfaces;

[0068] The static water contact angle is 160°, and the water rolls off the surface in a spherical shape without leaving any residue.

[0069] Disinfection resistance: After wiping with 75% ethanol 50 times, the contact angle is still >155%, with no functional degradation.

[0070]

[0071] The above description is merely an illustrative embodiment of the present invention and is not intended to limit the scope of the invention. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of the present invention should fall within the scope of protection of the present invention. Furthermore, it should be noted that the components of the present invention are not limited to the overall application described above. Each technical feature described in the specification can be used individually or in combination as needed. Therefore, the present invention naturally covers other combinations and specific applications related to this case.

[0072] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0073] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for integrated superhydrophobic treatment of polyamide 3D printed parts, characterized in that: Includes the following steps: S1. Configure a composite solvent system containing long-chain fluorinated silanes, wherein the composite solvent system is used to achieve surface swelling, micropore filling and hydrophobic precursor loading of the part; S2. Place the polyamide 3D printed part into the reaction chamber for steam treatment, control the steam temperature and time, and ensure that the solvent vapor fully acts on the surface and internal micropores of the part. S3. The impregnated parts are dried by gradient heating to remove volatile solvents from the system; S4. Perform thermosetting treatment on the dried part to form a stable hydrophobic film layer on the surface of the part and the inner wall of the micropores with long-chain fluorinated silane, thus completing the integrated construction of surface smoothing, micropore sealing and superhydrophobic function.

2. The method for integrated superhydrophobic treatment of polyamide 3D printed parts according to claim 1, characterized in that: The composite solvent system uses two or three of trifluoroethanol, ethanol and ethyl acetate as base solvents, and the amount of long-chain fluorinated silane added is 0.5% to 5% of the mass fraction of the base solvents. The mass fraction of trifluoroethanol is 10% to 18% of the total mass fraction of the base solvents.

3. The method for integrated superhydrophobic treatment of polyamide 3D printed parts according to claim 1, characterized in that: In step S2, the immersion temperature is 20℃-60℃ and the immersion time is 10min-60min, ensuring that the solvent penetrates into the 1-50μm microporous structure inside the part.

4. The method for integrated superhydrophobic treatment of polyamide 3D printed parts according to claim 1, characterized in that: In S3, the temperature range of gradient heating drying is 30℃-80℃, the total drying time is 30min~120min, and the ambient humidity is controlled to be ≤60% during the drying process.

5. The method for integrated superhydrophobic treatment of polyamide 3D printed parts according to claim 1, characterized in that: In S4, the thermosetting temperature is 80℃-150℃, the curing time is 20min-90min, and the curing process is carried out under inert gas protection or in an air atmosphere.

6. The method for integrated superhydrophobic treatment of polyamide 3D printed parts according to claim 1, characterized in that: The long-chain fluorinated silane is a silane coupling agent containing perfluoroalkyl groups, and the length of the fluorocarbon chain in its molecular chain is C6-C12. Specifically, the long-chain fluorinated silane is heptadecafluorodecyltriethoxysilane.

7. The method for integrated superhydrophobic treatment of polyamide 3D printed parts according to claim 1, characterized in that: The surface roughness Ra of the treated polyamide 3D printed parts is ≤5μm, the static water contact angle is ≥150°, the test conditions are 25℃, relative humidity is 50%, the water absorption dimensional change rate is ≤0.5%, and the tensile strength retention rate is ≥90%.

8. The method for integrated superhydrophobic treatment of polyamide 3D printed parts according to claim 1, characterized in that: The polyamide 3D printed parts are PA6, PA12 or their blends formed by selective laser sintering (SLS), and the initial porosity of the parts is 10% to 30%.

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