Self-cleaning coating for post-treatment of 3D printed part and synthesis method

Abstract

The invention belongs to the technical field of 3D printing post-treatment, and particularly relates to a synthesis method of a self-cleaning coating for post-treatment of 3D printed parts, and the coating is composed of a WPUA emulsion and an sn-SiO2 ethanol solution; the synthesis method comprises the following steps: step 1, preparing a WPUA emulsion; step 2, preparing an Sn-SiO2 ethanol solution; and (3) mixing the WPUA emulsion prepared in the step (1) and the sn-SiO2 ethanol solution, so as to prepare the WPUA / sn-SiO2 coating. According to the method, the TPU / WPUA / sn-SiO2 workpiece is obtained by coating the surface of the 3D printing TPU workpiece with the WPU / sn-SiO2 coating, the hydrophobicity of the TPU workpiece is effectively improved, meanwhile, the TPU workpiece has photocatalytic performance, organic pollutants on the surface of the TPU workpiece can be automatically removed, and the requirement for the surface self-cleaning function of the TPU workpiece in other high-performance 3D printing application fields such as intelligent wearing is well met.

Description

Technical Field

[0001] This invention relates to the field of 3D printing post-processing technology, and in particular to a self-cleaning coating and its synthesis method for post-processing 3D printed parts. Background Technology

[0002] 3D printing (also known as additive manufacturing) is a digital manufacturing technology based on the principle of discrete-addition forming. In stark contrast to traditional subtractive and equal-material manufacturing, 3D printing relies on a three-dimensional digital model to build a three-dimensional solid by layering materials. Currently, the most widely used 3D printing technology for thermoplastic materials is SLS (Surface Mount Technology). Compared to other technologies, SLS's main advantages are high design freedom, simplified process, no need for molds, and a wide variety of materials. It also boasts high material utilization, fast forming speed, the ability to manufacture various complex components, and high precision in the produced products.

[0003] Thermoplastic polyurethane (TPU) is a polymer with high elongation at break and excellent abrasion resistance. Due to its combination of plastic and rubber properties, SLS-printed TPU parts currently show promising application prospects in fields such as smart wearables, electronics, and automobiles. For economic, aesthetic, and environmental reasons, 3D-printed TPU products in these fields have an urgent need for self-cleaning properties. Because SLS technology only melts the powder using a laser without applying external stress, the outer surface of the part has micropores and a large surface roughness, exhibiting a certain degree of hydrophobicity. Therefore, the hydrophobic properties of TPU parts can be improved by adding hydrophobic metal oxide fillers to the TPU powder.

[0004] However, due to the differences in shape, size, and surface properties between hydrophobic fillers and TPU printing powder, the performance of SLS molding processes such as powder spreading and sintering deteriorates, leading to a decrease in the mechanical properties and other surface properties of the parts. On the other hand, the TPU powder used for printing does not possess photocatalytic properties, making it difficult to remove surface organic contaminants from the final printed TPU parts, which makes it difficult to meet the self-cleaning requirements of TPU parts in applications such as smart wearables.

[0005] To address the aforementioned issues, taking advantage of the numerous micropores on the surface of SLS-printed TPU parts, a post-treatment coating method is introduced. This method involves infiltrating a self-cleaning modified waterborne polyurethane coating into the micropores on the surface of the pure TPU printed part, and then implanting superhydrophobic SiO2 into the part surface to achieve the self-cleaning effect of the TPU part. Summary of the Invention

[0006] 1. Technical problems to be solved

[0007] The purpose of this invention is to solve the problem that it is difficult to remove organic contaminants from the surface of 3D printed TPU parts in the prior art, and it is difficult to meet the self-cleaning function requirements of TPU parts in applications such as smart wearables. Therefore, this invention proposes a self-cleaning coating for post-processing of 3D printed parts and a synthesis method therein.

[0008] 2. Technical Solution

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A self-cleaning coating for post-processing of 3D printed parts, the coating being WPUA / sn-SiO2, wherein the WPUA / sn-SiO2 coating is composed of WPUA emulsion and sn-SiO2 ethanol solution.

[0011] Preferably, the content of the WPUA emulsion is 80%, and the content of the sn-SiO2 ethanol solution is 20%.

[0012] Preferably, the WPUA emulsion is composed of WPU emulsion and AEAPTMS, wherein the R value of the WPU emulsion is 1.2, and the R value is the NCO / OH ratio.

[0013] Preferably, the sn-SiO2 ethanol solution is composed of sn-SiO2 and ethanol, wherein the sn-SiO2 content is 5-25% and the ethanol content is 75-95%.

[0014] This invention also proposes a method for synthesizing a self-cleaning coating for post-processing of 3D printed parts, comprising the following steps:

[0015] Step 1: Preparation of WPUA emulsion. IPDI and PTMG were added to a flask and reacted at 80°C under a nitrogen atmosphere with a stirring speed of 320 rpm for 4 hours. Then, 2,2-dimethylolpropionic acid (DMPA) and a few drops of DBDTL were added, and the reaction was carried out at 70°C and 320 rpm for 2 hours. Subsequently, butanediol (BDO) was added, and the reaction was continued at 70°C and 320 rpm for 2 hours. Finally, AEAPTMS was added, and the reaction was carried out at 35°C and 320 rpm. The reaction was carried out for 30 min. Then, TEA was added to the flask and the neutralization reaction was maintained at 35°C and 320 r / min for 30 min. During the neutralization reaction, a small amount of acetone was added to reduce the viscosity of the system. Then, EDA was added and the reaction was carried out at 35°C and 320 r / min for 5 min. After the reaction was completed, distilled water was added under vigorous stirring at 1200 r / min and the reaction was carried out for 5 min. Finally, acetone was removed under reduced pressure using a rotary evaporator to obtain a WPUA emulsion containing AEAPTMS.

[0016] Step 2: Preparation of sn-SiO2 ethanol solution. Sn-SiO2 was placed in a vacuum oven and dried at 80°C for 24 hours. After drying, ethanol was weighed according to the above ratio and poured into a beaker. Then, dried sn-SiO2 powder was weighed and slowly added to the beaker. The mixture was magnetically stirred for 30 minutes and then ultrasonically dispersed for 30 minutes to obtain a uniformly dispersed sn-SiO2 ethanol solution.

[0017] Step 3: Mix the WPUA emulsion and sn-SiO2 ethanol solution prepared in the above steps according to the above content ratio to obtain the WPUA / sn-SiO2 coating.

[0018] The present invention also proposes a self-cleaning TPU / WPUA / sn-SiO2 coated TPU self-cleaning part having the above-mentioned coating.

[0019] Preferably, the method for preparing a self-cleaning TPU / WPUA / sn-SiO2 coated TPU self-cleaning part includes the following steps:

[0020] S1: Pour WPUA emulsion into a silicone mold, then place the TPU part into the WPUA emulsion in the silicone mold and immerse it for 10 minutes. Take it out and wait for the liquid on the surface to drip off naturally. Place it in a 75℃ forced-air oven for pre-drying for 10 minutes and then take it out to obtain a TPU / WPUA part with WPUA emulsion coated on the surface.

[0021] S2: Pour sn-SiO2 ethanol solution into a silicone mold, then place the TPU / WPUA part into the silicone mold and immerse it for 10 minutes. Remove it and wait for the surface liquid to drip off naturally. Place it in a 75℃ forced-air oven to cure for 6 hours to obtain a part with sn-SiO2 implanted on the outer surface of the WPUA coating of the TPU / WPUA part.

[0022] Preferably, the preparation steps of the 3D printed TPU part are as follows: TPU composite powder is deposited layer by layer and then laser sintered to obtain the 3D printed part; the SLS printing steps are as follows: a sample model of the required shape is drawn using 3D modeling software, and then imported into the SLS printer computer. The printing process parameters are set to achieve the best molding effect. After sintering, when the temperature inside the molding cavity cools to 50°C, the TPU printed part is taken out of the cavity and placed in a powder cleaning machine. After 30 minutes of rolling sandblasting, the residual powder on the surface of the part is blown away, and finally the molded TPU part is obtained.

[0023] 3. Beneficial effects

[0024] Compared with the prior art, the advantages of this invention are:

[0025] (1) In this invention, WPUA emulsion can easily enter the gaps on the surface of SLS printed parts. After the WPUA emulsion is cured, it forms a "plug" structure. The WPUA coating will be "anchored" on the surface of TPU parts, which effectively improves the coating's adhesion performance.

[0026] (2) In this invention, sn-SiO2 is implanted into the surface of TPU / WPUA parts, and sn-SiO2 is “captured” by AEAPTMS on the surface of TPU / WPUA parts, thereby constructing a surface nanostructure, improving the roughness of TPU parts, and effectively improving the self-cleaning performance of TPU parts.

[0027] (3) In this invention, TPU / WPUA / sn-SiO2 coated parts were prepared by implanting nano-sn-SiO2 on the surface of TPU / WPUA coated parts, which effectively improved the hydrophobicity of TPU parts and also had photocatalytic performance, enabling TPU parts to self-clean up organic pollutants on the surface, which well met the requirements of TPU parts for self-cleaning function in application fields such as smart wearables. Attached Figure Description

[0028] Figure 1 These are digital photographs of WPU emulsions with different R values ​​proposed in Embodiment 2 of the present invention;

[0029] Figure 2 The particle size distribution of WPU emulsions with different R values ​​proposed in Example 2 of this invention is shown.

[0030] Figure 3 The tensile strength and elongation at break of WPU coatings with different R values ​​proposed in Embodiment 2 of the present invention are shown in the figure.

[0031] Figure 4 The infrared spectrum of WPUA proposed in Embodiment 2 of the present invention;

[0032] Figure 5 The following are the proton nuclear magnetic resonance spectra proposed in Example 2 of this invention: (a) WPUA-0; (b) AEAPTMS; (c) WPUA-0.5;

[0033] Figure 6 (a) Digital photographs of emulsions with different WPUA contents; (b) Particle size distribution diagrams of emulsions with different WPUA contents as proposed in Example 2 of this invention;

[0034] Figure 7 The water contact angles of WPUA membranes with different AEAPTMS contents proposed in Example 2 of this invention;

[0035] Figure 8 The mechanical properties of WPUA films with different AEAPTMS contents proposed in Example 2 of this invention are shown in the figure.

[0036] Figure 9 The following are the TG data of WPUA membranes with different contents of AEAPTMS proposed in Example 2 of this invention: (a) TGA; (b) DTG;

[0037] Figure 10 The water contact angle of TPU / WPUA parts with different AEAPTMS contents proposed in Example 2 of this invention;

[0038] Figure 11 The above are digital photographs of coffee droplets on the surface of TPU / WPUA parts with different AEAPTMS contents as presented in Example 2 of this invention.

[0039] Figure 12 The mechanical properties of TPU / WPUA parts with different AEAPTMS contents proposed in Example 2 of this invention;

[0040] Figure 13 SEM images of the surface of the TPU / WPUA / sn-SiO2 part proposed in Embodiment 3 of the present invention; Figures: (a) TPU; (b) TPU / WPUA-0.5; (c) TPU / WPUA-0.5 / sn-SiO2-20; (d) Enlarged view of Figure c;

[0041] Figure 14 The water contact angle of TPU / WPUA / sn-SiO2 parts with different sn-SiO2 contents proposed in Example 3 of this invention;

[0042] Figure 15 Digital photographs of coffee droplets on the surface of TPU / WPUA / sn-SiO2 parts with different sn-SiO2 contents as proposed in Example 3 of this invention;

[0043] In the picture: (a)TPU / WPUA-0.5(b)TPU / WPUA-0.5 / sn-SiO2-5(c)TPU / WPUA-0.5 / sn-SiO2-10(d)TP U / WPUA-0.5 / sn-SiO2-15(e)TPU / WPUA-0.5 / sn-SiO2-20(f)TPU / WPUA-0.5 / sn-SiO2-25;

[0044] Figure 16 The mechanical properties of TPU / WPUA / sn-SiO2 parts with different sn-SiO2 contents proposed in Example 3 of this invention;

[0045] Figure 17Digital photographs of coffee droplets on the surface of TPU / WPUA-0.5 / sn-SiO2-20 parts at different curing temperatures as proposed in Example 3 of this invention: (a) 55℃ (b) 65℃ (c) 75℃ (d) 85℃;

[0046] Figure 18 The mechanical properties of TPU / WPUA-0.5 / sn-SiO2-20 parts with different curing temperatures as proposed in Example 3 of this invention;

[0047] Figure 19 Digital photographs of coffee droplets on the surface of TPU / WPUA-0.5 / sn-SiO2-20 parts with different curing times as proposed in Example 3 of the present invention (a) 2h;

[0048] (b) 4h; (c) 6h; (d) 8h;

[0049] Figure 20 The mechanical properties of TPU / WPUA-0.5 / sn-SiO2-20 parts with different curing times as proposed in Example 3 of this invention;

[0050] Figure 21 Anti-fouling tests were conducted on different TPU lattice components proposed in Embodiment 3 of the present invention: (a) TPU lattice component; (b) TPU / WPUA-0.5 lattice component; (c) TPU / WPUA-0.5 / sn-SiO2-20 lattice component;

[0051] Figure 22 This is a schematic diagram of the TPU lattice component compression process proposed in Embodiment 3 of the present invention;

[0052] Figure 23 This is a compressive stress-strain curve of the TPU / WPUA / sn-SiO2 lattice component proposed in Example 3 of the present invention;

[0053] Figure 24 This is a schematic diagram of the TPU / WPUA / sn-SiO2 self-cleaning mechanism proposed in Embodiment 3 of the present invention. Detailed Implementation

[0054] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0055] Example 1:

[0056] A self-cleaning coating for post-processing of 3D printed parts is disclosed. The coating is WPUA / sn-SiO2, which consists of WPUA emulsion and sn-SiO2 ethanol solution. The content of WPUA emulsion is 80%, and the content of sn-SiO2 ethanol solution is 20%. The WPUA emulsion is composed of WPU emulsion and AEAPTMS. The R value of WPU emulsion is 1.2, where R is the NCO / OH ratio. The sn-SiO2 ethanol solution is composed of sn-SiO2 and ethanol, with the sn-SiO2 content being 5-25% and the ethanol content being 75-95%.

[0057] In this embodiment, a method for synthesizing a self-cleaning coating for post-processing of 3D printed parts includes the following steps:

[0058] Step 1: Preparation of WPU emulsion. IPDI and PTMG were added to a flask and reacted at 320 r / min for 4 h under a nitrogen atmosphere at 80 °C. Then, 2,2-dimethylolpropionic acid (DMPA) and a few drops of DBDTL were added, and the reaction was carried out at 70 °C and 320 r / min for 2 h. Butylene glycol (BDO) was then added and the reaction was continued at 70 °C and 320 r / min for 2 h. TEA was then added to the flask and the reaction was maintained at 35 °C and 320 r / min for 30 min for neutralization. A small amount of acetone was added to reduce the viscosity of the system. EDA was then added and the reaction was carried out at 35 °C and 320 r / min for 5 min. After the reaction was completed, distilled water was added under vigorous stirring at 1200 r / min and the reaction was carried out for 5 min. Finally, acetone was removed under reduced pressure using a rotary evaporator to obtain the WPU emulsion.

[0059] Step 2: Preparation of WPUA emulsion. IPDI and PTMG were added to a flask and reacted at 80°C under a nitrogen atmosphere with a stirring speed of 320 rpm for 4 hours. Then, 2,2-dimethylolpropionic acid (DMPA) and a few drops of DBDTL were added, and the reaction was carried out at 70°C and 320 rpm for 2 hours. Subsequently, butanediol (BDO) was added, and the reaction was continued at 70°C and 320 rpm for 2 hours. Finally, AEAPTMS was added, and the reaction was carried out at 35°C and 320 rpm. The reaction was carried out for 30 min. Then, TEA was added to the flask and the neutralization reaction was maintained at 35°C and 320 r / min for 30 min. During the neutralization reaction, a small amount of acetone was added to reduce the viscosity of the system. Then, EDA was added and the reaction was carried out at 35°C and 320 r / min for 5 min. After the reaction was completed, distilled water was added under vigorous stirring at 1200 r / min and the reaction was carried out for 5 min. Finally, acetone was removed under reduced pressure using a rotary evaporator to obtain a WPUA emulsion containing AEAPTMS.

[0060] Step 3: Preparation of sn-SiO2 ethanol solution. Sn-SiO2 is placed in a vacuum oven and dried at 80℃ for 24 hours. After drying, ethanol is weighed according to the above content ratio and poured into a beaker. Then, dried sn-SiO2 powder is weighed and slowly added to it. The mixture is magnetically stirred for 30 minutes and then ultrasonically dispersed for 30 minutes to obtain a uniformly dispersed sn-SiO2 ethanol solution.

[0061] Step 4: Mix the WPUA emulsion and sn-SiO2 ethanol solution prepared in the above steps according to the above content ratio to obtain the WPUA / sn-SiO2 coating.

[0062] In this embodiment, a self-cleaning TPU / WPUA / sn-SiO2 coated TPU self-cleaning part with the above-mentioned coating is prepared by the following steps:

[0063] S1: Pour WPUA emulsion into a silicone mold, then place the TPU part into the WPUA emulsion in the silicone mold and immerse it for 10 minutes. Take it out and wait for the liquid on the surface to drip off naturally. Place it in a 75℃ forced-air oven for pre-drying for 10 minutes and then take it out to obtain a TPU / WPUA part with WPUA emulsion coated on the surface.

[0064] S2: Pour sn-SiO2 ethanol solution into a silicone mold, then place the TPU / WPUA part into the silicone mold and immerse it for 10 minutes. Remove it and wait for the surface liquid to drip off naturally. Place it in a 75℃ forced-air oven to cure for 6 hours to obtain a part with sn-SiO2 implanted on the outer surface of the WPUA coating of the TPU / WPUA part.

[0065] In this embodiment, the preparation steps of SLS-printed TPU parts are as follows: TPU composite powder is deposited layer by layer and then laser sintered to obtain 3D printed parts; the SLS printing steps are as follows: a sample model of the required shape is drawn using 3D modeling software, and then imported into the SLS printer computer. Printing process parameters are set to achieve the best molding effect. After sintering, when the temperature inside the molding cavity cools to 50°C, the TPU printed parts are taken out of the cavity and placed in a powder cleaning machine. After 30 minutes of rolling sandblasting, the residual powder on the surface of the parts is blown away, and finally the molded TPU parts are obtained.

[0066] In this embodiment, the WPUA emulsion can easily penetrate the gaps on the surface of the SLS-printed part. After the WPUA emulsion cures, it forms a "plug" structure, and the WPUA coating will be "anchored" to the surface of the TPU part, which effectively improves the coating's adhesion performance.

[0067] In this embodiment, sn-SiO2 is implanted into the surface of the TPU / WPUA part, and the sn-SiO2 is "captured" by AEAPTMS on the surface of the TPU / WPUA part, thereby constructing a surface nanostructure, improving the roughness of the TPU part, and effectively improving the self-cleaning performance of the TPU part.

[0068] In this embodiment, a TPU / WPUA / sn-SiO2 coated part was prepared by implanting nano-sn-SiO2 onto the surface of the TPU / WPUA coated part. This effectively improved the hydrophobicity of the TPU part and also provided photocatalytic performance, enabling the TPU part to self-clean up organic pollutants on its surface. This well meets the self-cleaning function requirements of TPU parts in applications such as smart wearables.

[0069] Example 2:

[0070] In this embodiment, the influence of the R value (NCO / OH value) on the properties of WPU emulsion and its influence on the particle size of WPU emulsion are as follows: Figure 1 Digital photographs of WPU emulsions with different R values. Figure 2 Particle size distribution of WPU emulsions with different R values.

[0071] In this embodiment, from Figure 1 As the R value increases, the color of the WPU emulsion changes from light blue to bluish-white from left to right. This color change reflects the particle size of the WPU emulsion. When the particle size is small, longer wavelength red light is scattered, while shorter wavelength blue light easily passes through, resulting in a light blue color. As the particle size increases, total internal reflection occurs, and the WPU emulsion gradually turns bluish-white. Figure 2 It can be seen that the particle size of the WPU emulsion continuously increases with the increase of the R value. This is because, with the increase of the R value, there are more rigid segments in the WPU chain, and the flexibility of the WPU chain decreases. During emulsification, the dispersion effect of the WPU chain deteriorates, resulting in an increase in the particle size of the WPU emulsion. Simultaneously, with the increase of the R value, there is an increase in the number of unreacted -NCO groups remaining in the WPU emulsion. These -NCO groups readily react with water to form urea groups, generating heat. During emulsification, the heat of reaction increases, the viscosity increases, and the emulsion is not easily dispersed by shear force, further increasing the particle size of the WPU emulsion. Therefore, with the increase of the R value, the particle size of the WPU emulsion increases, and the WPU emulsion gradually changes from light blue to bluish-white.

[0072] In this embodiment, the impact on the mechanical properties of TPU / WPU parts is as follows: Figure 2 The effect of coatings with different R-value contents on the mechanical properties of TPU / WPUA / sn-SiO2 parts was studied. Figure 2It can be seen that the tensile strength of the pure TPU part is 3.60 MPa and the elongation at break is 371.1%. After coating with WPU, the tensile strength of the TPU / WPUA-0.5 printed part is 3.67 MPa and the elongation at break is 385.6%. This is because when coating with WPU, the coating penetrates into the voids on the TPU surface during the coating process, making up for surface defects and enhancing the mechanical properties of the part.

[0073] In this embodiment, the effect of AEAPTMS content on the properties of WPUA emulsion: its effect on the chemical structure of WPUA emulsion; Figure 4 Infrared spectra of WPUA films with different contents of AEAPTMS, 3320 cm⁻¹ -1 -NH tensile vibration on WPUA, 2945cm -1 2850cm -1 For the -CH tensile vibration on WPUA, 1720cm -1 C=O tensile vibration on WPUA, 1535cm -1 The bending vibrations of the NH group in the amide bond of WPUA represent the formation of the carbamate group, indicating the successful synthesis of WPUA. (1112 cm) -1 For the COC tensile vibration on WPUA, 2260cm -1 The left and right sides show the characteristic absorption bands of NCO, indicating the presence of unreacted NCO in the WPUA membrane. At 1112 cm⁻¹... -1 The absorption intensity of the WPUA-0.5 absorption peak is stronger than that of WPUA-0. This is because the -OCH3 group of AEAPTMS hydrolyzes to form Si-O-Si, and the vibrational frequency of Si-O-Si is similar to that of the COC group. This indicates that AEAPTMS has been successfully introduced onto WPUA.

[0074] In this embodiment, Figure 5 These are the proton NMR spectra of WPUA-0 (i.e., WPU-1.2), AEAPTMS, and WPUA-0.5. Figure 5 In sample a, the 7.26 ppm peak represents the solvent peak of CDCl3. WPUA without AEAPTMS shows a weak peak at 6.99 ppm, a characteristic peak for the hydrogen atom on the -NH- group of ethyl carbamate. The characteristic peaks for the hydrogen atom on the methylene group of DMPA and BDO in WPUA are at 4.07 ppm. The characteristic peak for the proton atom on the methyl hydrogen atom of IPDI appears at 0.87–0.93 ppm. The peaks at 1.25 ppm and 3.41 ppm are characteristic peaks for the hydrogen atom on the -CH2- group of PTMG. The peaks near 1.05 ppm represent hydrogen atoms on the methyl group of DMPA and some methylene groups of IPDI. AEAPTMS... 1HNMR spectrum as follows Figure 5 As shown in b, the chemical shift at δ 3.20 ppm is associated with the hydrogen atom of Si-OCH3, representing the methoxysilyl moiety of AEAPTMS. Multiple signals at δ 0.30, 1.20, and 2.39 ppm characterize the hydrogen atoms of the first, second, and third methylene groups associated with the silicon atom in –SiCH2-. Figure 5 c is WPUA-0.5 1 The ¹H NMR spectrum shows a peak at 0.78 ppm, which is a characteristic peak of the hydrogen atom in the -CH₂- group on silicon. No characteristic peaks were observed at 3.50 ppm and 5.0 ppm, indicating that -SiOCH₃ underwent hydrolysis and condensation.

[0075] In this embodiment, the effect on WPUA emulsion particle size is shown in Table 1, which presents the corresponding data on AEAPTMS content and average particle size of WPUA emulsion. Figure 6 Digital photographs and particle size distribution diagrams of WPUA emulsions with different contents. Figure 6 Photo A shows that as the AEAPTMS content increases, the color of the WPUA emulsion changes from blue to white from left to right. This color change reflects the particle size of the WPUA emulsion. When the particle size is small, longer wavelength red light is scattered, while shorter wavelength blue light easily passes through, resulting in a blue, translucent emulsion. As the particle size increases, total internal reflection occurs, and the WPUA emulsion appears milky white. The average particle size of the WPUA-0 emulsion is 31.14 nm, and its color is blue and translucent. After adding AEAPTMS, the average particle size of the WPUA-0.5 emulsion increases to 44.23 nm, and while it remains blue and translucent, its transparency decreases. This is because with the addition of AEAPTMS, the -SiOCH3 groups in the side chains are easily hydrolyzed into -Si-OH groups in water. These -Si-OH groups then react with each other to form Si-O-Si groups, increasing the internal cross-linking degree of WPUA. This makes it more difficult for the polyurethane chains in WPUA to move, leading to emulsification difficulties, a continuously increasing particle size in the WPUA emulsion, and a decrease in its transparency. As the AEAPTMS content increases, the particle size of the WPUA emulsion increases from 44.23 nm to 227.37 nm, and the color of the WPUA emulsion gradually changes from blue and translucent to milky white, with a continuous decrease in transparency. This is because the increasing AEAPTMS content increases the cross-linking degree in WPUA, making it more difficult for the polyurethane chains to move, leading to emulsification difficulties, a continuously increasing particle size in the WPUA emulsion, and a gradual change in the appearance of the WPUA emulsion from blue and translucent to milky white.

[0076] Table 1. Average particle size of WPUA emulsions with different AEAPTMS contents.

[0077]

[0078] In this embodiment, Figure 2 The water contact angles of WPUA membranes with different AEAPTMS contents are shown. The contact angles of WPUA-0, WPUA-0.25, WPUA-0.5, WPUA-0.75, and WPUA-1 are 78.0°, 81.5°, 83.0°, 84.5°, and 86.5°, respectively. With increasing AEAPTMS content, the water contact angle of the WPUA membrane increases, and the self-cleaning performance improves. On the one hand, the increased AEAPTMS content introduces AEAPTMS as a side chain into the waterborne polyurethane, which lowers the surface energy and increases the hydrophobicity of the membrane. On the other hand, AEAPTMS also contains silicon atoms, which have low surface tension and strong hydrophobicity, making it more difficult for water molecules to wet the membrane surface, thus increasing the hydrophobicity of the membrane.

[0079] Table 2. TG data of WPUA membranes with different AEAPTMS contents.

[0080]

[0081]

[0082] In this embodiment, the effect of AEAPTMS content on other properties of the WPUA membrane is as follows: Effect on the mechanical properties of the WPUA membrane: Figure 8 The tensile properties of WPUA membranes with different AEAPTMS contents are shown in the figure. As can be seen from the figure, the tensile strength of WPUA-0 is 6.52 MPa, and the elongation at break is 205%. The tensile strength of the WPU-0.25 membrane increases to 8.51 MPa, and the elongation at break increases to 623%. WPUA-0 without AEAPTMS is a linear polymer. When the WPUA-0 membrane is subjected to external tensile force, the WPU chains move easily. When AEAPTMS is incorporated into the WPU chains, the siloxane groups of AEAPTMS are hydrolyzed into a Si-O-Si crosslinked network, thereby enhancing the crosslink density and stiffness of the film. This improves the tensile strength and elongation at break of the WPUA membrane. With increasing AEAPTMS content, the tensile strength and elongation at break of the WPUA membrane initially increase and then decrease. This is because the hard segments in the WPUA membrane provide strength, while the soft segments provide ductility. Excessive AEAPTMS leads to an overly dense crosslinked network, restricting the movement of molecular chains, disrupting the microphase separation structure of the WPUA membrane, making the material brittle, and reducing its mechanical properties.

[0083] In this embodiment, the effect on the thermal stability of WPUA film is shown in Table 2, which contains TG data for WPUA films with different AEAPTMS contents. Figure 9The figures show the TGA and DTG curves of WPUA films with different contents of AEAPTMS. As can be seen from the figures, each curve has two decomposition stages. The first stage is the decomposition of the hard segments of the polyurethane bonds, starting at approximately 300°C; the second stage is the decomposition of the soft segments of the polyurethane bonds, starting at approximately 400°C, occurring in the soft segments. The figures also show that the TGA of WPUA-0... 1max The temperature was 312.6℃. With the addition of AEAPTMS, the T of WPUA-0.5 was... 1max The temperature was 315.7℃. This is because the addition of AEAPTMS, which acts as a side chain attached to the WPUA chain, strengthens the interaction forces between chain segments. Furthermore, the increased crosslinking degree of WPUA leads to an increase in the thermal stability of the WPUA film. With increasing AEAPTMS content, the thermal stability of WPUA... 1max The T of WPUA-4 continues to increase. 1max The temperature reached 322.2℃. This is because with the increase of AEAPTMS content, the number of Si-O-Si groups in WPUA increases, the degree of cross-linking of WPUA chains increases, the interaction force between chain segments strengthens, and the thermal stability of the WPUA film increases. In summary, the thermal stability of the WPUA film continuously increases with the increase of AEAPTMS content.

[0084] In this embodiment, the effect of AEAPTMS content on the self-cleaning performance of TPU / WPUA parts: the effect on the water contact angle of TPU / WPUA parts: from Figure 10 It can be seen that the water contact angle of TPU / WPUA-0 is 95.0°. After adding AEAPTMS, the water contact angle of TPU / WPUA-0.25 is 100.8°, indicating an increase in the water contact angle of the TPU / WPUA part. Furthermore, as the AEAPTMS content increases, the water contact angle of the TPU / WPUA part continuously rises from 100.8° to 107.3°, demonstrating improved self-cleaning performance. This is because the addition of AEAPTMS introduces low-surface-energy Si elements into the -SiOCH3 groups. Due to the low surface tension and strong hydrophobicity of Si, water molecules have difficulty wetting the surface of the TPU / WPUA part, thus increasing the water contact angle. With further increases in AEAPTMS content, the Si element content increases, making it even more difficult for water molecules to wet the surface of the TPU / WPUA part, resulting in an even greater increase in the water contact angle.

[0085] In this embodiment, the impact on removing surface contaminants from TPU / WPUA parts is as follows: Figure 11 Digital photographs of coffee droplets on the surface of TPU / WPUA parts with different AEAPTMS contents. Figure 11As can be seen, the coffee droplets on TPU / WPUA-0.5 are hemispherical. This is because after the TPU part is coated with a polyurethane coating, the voids on the surface of the TPU composite material are filled, the surface roughness is reduced, and the adhesion area and adhesion force between the droplets and the rough surface increase. The coffee droplets on TPU / WPUA-2 are also flat. With the increase of AEAPTMS content in WPUA, the coffee droplets on the surface of the TPU / WPUA part become hemispherical with increased curvature. This is because with the increase of AEAPTMS content, the Si element content on the part surface increases, and silicon atoms have low surface tension and strong hydrophobicity. Therefore, water is difficult to wet the surface of the TPU / WPUA part, the hydrophobicity of the TPU / WPUA part increases, and the coffee droplets on the surface of the TPU / WPUA part are closer to spherical.

[0086] In this embodiment, the effect of AEAPTMS content on the mechanical properties of TPU / WPUA parts is as follows: Figure 12 The tensile strength and elongation at break of TPU / WPUA parts with different AEAPTMS contents are shown in the figure. As can be seen from the figure, the tensile strength of TPU / WPUA-0 is 3.6 MPa and the elongation at break is 385.6%. The addition of AEAPTMS increases the tensile strength and elongation at break of TPU / WPUA-0, while the tensile strength and elongation at break of TPU / WPUA-0 parts decrease slightly with increasing AEAPTMS content. This is because WPUA-0 without AEAPTMS is a linear polymer. When the TPU / WPUA-0 part is subjected to external tensile force, the WPU chains move easily. When AEAPTMS is incorporated into the WPUA chains, the siloxane groups of AEAPTMS are hydrolyzed into a Si-O-Si crosslinked network, thereby enhancing the crosslink density and stiffness of the film, thus increasing the tensile strength and reducing the elongation at break. However, with the continuous increase of AEAPTMS content, the crosslinked network of the WPUA coating on the surface of the TPU / WPUA part becomes too dense, restricting the movement of molecular chains, making the material brittle, and reducing its mechanical properties.

[0087] In this embodiment, as the R value increases, the particle size of the WPU emulsion increases continuously, and the mechanical properties first rise and then fall. Among them, the WPU-1.2 emulsion has the best performance with a particle size of 31.14 nm. Therefore, the WPU emulsion with an R value of 1.2 is selected in the subsequent process.

[0088] In this embodiment, as the AEAPTMS content increases, the particle size of the WPUA emulsion increases, and the water contact angle and thermal stability of the WPUA membrane improve. However, the mechanical properties of the WPUA membrane first increase and then decrease. The WPUA-0.5 membrane with an emulsion particle size of 65.81 nm exhibits the best mechanical properties, with a water contact angle of 83.0°.

[0089] In this embodiment, as the AEAPTMS content increases, the water contact angle of the TPU / WPUA part continuously increases from 95.0° to 107.3°, and the self-cleaning performance continuously improves with the continuous increase in the water contact angle. Therefore, the introduction of AEAPTMS can improve the self-cleaning performance of the TPU / WPUA part.

[0090] Example 3:

[0091] In this embodiment, the surface microstructure and morphology characteristics of the TPU / WPUA / sn-SiO2 part are described.

[0092] : Figure 13 This is a SEM image of the surface of the TPU / WPUA / sn-SiO2 part. It can be observed that the surface of the TPU part contains a large amount of incompletely fused TPU powder. Figure 13 a) The surface of the TPU part coated with WPUA-0.5 becomes smooth. Figure 13 b), after coating with WPUA-0.5 / sn-SiO2-20, the unmelted TPU powder on the surface of the part is encapsulated by the coating. Figure 13 c), and many superhydrophobic SiO2 particles exist on the surface of the TPU part. Figure 13 d). The reason for the above results is that sn-SiO2 itself has superhydrophobicity. When sn-SiO2 is implanted into the surface of WPUA-0.5, many tiny particles are distributed on the surface of the WPUA-0.5 / sn-SiO2-20 coating. The size of these tiny particles is at the nanoscale, and it can be basically determined that these tiny particles are sn-SiO2 particles. These sn-SiO2 particles result in a high surface roughness and a high water contact angle of the part.

[0093] In this embodiment, the effect of sn-SiO2 content on the self-cleaning performance of TPU / WPUA / sn-SiO2 parts and its effect on the water contact angle are as follows: Figure 14 These are the water contact angles of TPU / WPUA / Sn-SiO2 parts with different Sn-SiO2 contents. From... Figure 14 It can be seen that the contact angle of the pure TPU part is 123.8°. After coating with WPUA, the water contact angle of the TPU / WPUA-0.5 printed part is 105.0°. The water contact angle of the part decreases because when coating with WPUA, the voids on the surface of the TPU part are filled by WPUA emulsion, the surface roughness of the part decreases, and the contact angle of the part decreases.

[0094] In this embodiment, after superhydrophobic Sn-SiO2 was implanted onto the surface of the TPU / WPUA-0.5 part, the water contact angle of the TPU / WPUA / sn-SiO2 part was significantly higher than that of the TPU / WPUA-0.5 part. This indicates that the self-cleaning performance of the TPU / WPUA-0.5 part was significantly improved after superhydrophobic Sn-SiO2 was implanted onto its surface. This is because after coating, the surface of the TPU / WPUA-0.5 / sn-SiO2-5 printed part has raised Sn-SiO2 particles, which increases the surface porosity of the TPU composite material and increases the surface roughness.

[0095] In this embodiment, as the sn-SiO2 content increases, the water contact angle of the part first increases and then decreases. When the sn-SiO2 content is 20%, the TPU / WPUA-0.5 / sn-SiO2 part has the largest water contact angle of 153.3°, reaching superhydrophobicity. This is because as the sn-SiO2 content increases, more sn-SiO2 particles are distributed on the surface of the TPU / WPUA-0.5 / sn-SiO2 printed part, increasing the surface roughness of the TPU composite material and thus increasing the contact angle. When the sn-SiO2 content increases to 20%, on the one hand, the sn-SiO2 content continues to increase, resulting in too many sn-SiO2 particles on the part surface. This leads to agglomeration of the sn-SiO2 particles and subsequent shedding, causing the water contact angle of the part to decrease. On the other hand, excessive sn-SiO2 fills the "depressions" between particles, actually reducing the roughness originally increased by the implanted sn-SiO2. According to the Cassie-Baxter model, when a liquid comes into contact with a rough surface, the gas in the gaps between the rough structures will not be expelled. Due to the high surface tension of water, the increase in roughness reduces the adhesion area and force between the water droplet and the rough surface, resulting in an increased water contact angle, thus improving hydrophobicity and self-cleaning properties.

[0096] In this embodiment, the effect on the performance of removing surface contaminants from TPU / WPUA / sn-SiO2 parts is as follows: Figure 15 Digital photographs of coffee droplets on the surface of TPU / WPUA / sn-SiO2 parts with different SiO2 contents. Figure 15It can be seen that after coating with WPUA emulsion, the coffee droplets on TPU / WPUA-0.5 are flattened hemispherical. This is because after the TPU part is coated with a polyurethane coating, the surface voids are filled, the surface roughness is reduced, and the adhesion area and adhesion force between the droplets and the rough surface increase. The coffee droplets on TPU / WPUA-2 are flattened hemispherical. With the surface coating of sn-SiO2, the coffee droplets on the surface of TPU / WPUA-2 / sn-SiO2-6 parts are approximately spherical. This is because with the addition of sn-SiO2, the surface of the part is covered with raised SiO2 particles, which increases the surface roughness of the TPU composite material. The coffee droplets on the surface of TPU / WPUA-0.5 / sn-SiO2-5 parts are approximately spherical. As the sn-SiO2 content increases, the coffee droplet shape on the TPU / WPUA-0.5 / sn-SiO2 surface becomes more spherical. This is because the sn-SiO2 particles on the TPU part surface increase, which increases the surface roughness of the TPU composite material and the contact angle of the part.

[0097] In this embodiment, as can be seen from the above, compared with pure TPU parts, the surface coating of WPUA / sn-SiO2 can make the coffee droplets on the TPU parts approximately spherical, improve the self-cleaning performance of the TPU parts, and enable the TPU parts to cope with complex contaminants.

[0098] In this embodiment, the effect of sn-SiO2 content on the mechanical properties of TPU / WPUA / sn-SiO2 parts is as follows: Figure 16 This study investigates the effect of coatings with different sn-SiO2 contents on the mechanical properties of TPU / WPUA / sn-SiO2 parts. Figure 16 It can be seen that the tensile strength of the pure TPU part is 3.60 MPa and the elongation at break is 371.1%. After coating with WPUA, the tensile strength of the TPU / WPUA-0.5 printed part is 3.67 MPa and the elongation at break is 385.6%. This is because when coating with WPUA, the coating penetrates into the voids on the TPU surface during the coating process, making up for surface defects and enhancing the mechanical properties of the part.

[0099] In this embodiment, after superhydrophobic sn-SiO2 is implanted on the surface of the TPU / WPUA-2 part, the tensile strength of the TPU / WPUA-0.5 / sn-SiO2-5 printed part is 4.89 MPa, and the elongation at break is 412.3%. This is because after coating with sn-SiO2, sn-SiO2 particles are distributed on the surface of the TPU / WPUA-0.5 / sn-SiO2-5 printed part. These sn-SiO2 particles are connected to the WPUA coating through Si-O-Si bonds, which enhances the mechanical properties of the WPUA coating and improves the mechanical properties of the TPU / WPUA / sn-SiO2 part.

[0100] In this embodiment, as the sn-SiO2 content increases, the mechanical properties of the part first increase and then decrease. When the sn-SiO2 content is 20%, the TPU / WPUA-0.5 / sn-SiO2-20 part exhibits the best mechanical properties, with a tensile strength of 5.60 MPa and an elongation at break of 477.2%. This is because as the sn-SiO2 content increases, the number of sn-SiO2 particles distributed on the surface of the TPU / WPUA-0.5 / sn-SiO2-20 printed part increases, the content of Si-O-Si bonds between the sn-SiO2 particles and the WPUA coating increases, and the mechanical properties of the TPU / WPUA-2 / sn-SiO2 part increase. As the sn-SiO2 content continues to increase, there are too many sn-SiO2 particles on the surface of the part, and the sn-SiO2 particles on the surface of the part will agglomerate. The uneven distribution of sn-SiO2 particles will lead to stress concentration and a decrease in the mechanical properties of the part.

[0101] In this embodiment, the effect of curing temperature on the performance of TPU self-cleaning material is as follows: Effect on self-cleaning performance: Figure 17 Digital photographs of coffee droplets on the surface of TPU / WPUA-0.5 / sn-SiO2-20 parts at different curing temperatures show that the coffee droplets on the surface of the TPU / WPUA-0.5 / sn-SiO2-20 parts are approximately spherical with changes in curing temperature. The curing temperature has little effect on the coffee droplets on the part surface. This is because the curing of the emulsion mainly involves two aspects: first, the evaporation of water and the aggregation of emulsion particles (film formation); second, the hydrolysis of the -SiOCH3 groups in the WPUA matrix into -SiOH groups, which form hydrogen bonds with the hydroxyl functional groups on the sn-SiO2 surface. Among these, the evaporation of water and the aggregation of emulsion particles (film formation) are physical changes rather than violent chemical reactions, and therefore have relatively low temperature dependence. The evaporation of water is greatly affected by factors such as ambient temperature, humidity, and air flow. Once the water evaporates to a certain extent, the emulsion particles will rapidly aggregate to form a continuous film. This process is usually relatively fast and has low dependence on curing temperature. The hydrogen bonding reaction between the -SiOH groups and the hydroxyl functional groups on the sn-SiO2 surface occurs at high temperatures, where molecular thermal motion intensifies and the stability of the hydrogen bonds decreases. However, due to the narrow experimental range of curing temperature, the difference in the number of hydrogen bonds is small, and the effect on coffee droplets on the surface of the part is not significant. Therefore, the curing temperature has no significant effect on coffee droplets on the surface of TPU / WPUA-0.5 / sn-SiO2-20 parts.

[0102] In this embodiment, the impact on mechanical properties is as follows: Figure 18 This study investigates the effect of different curing temperatures on the mechanical properties of TPU / WPUA-0.5 / sn-SiO2-20 parts. Figure 18 It can be seen that as the curing temperature increases from 55℃ to 85℃, the mechanical properties of the TPU / WPUA-0.5 / sn-SiO2-20 parts first increase and then slightly decrease. When the curing temperature is 75℃, the TPU / WPUA-0.5 / sn-SiO2-20 parts exhibit the best mechanical properties, with a tensile strength of 5.60 MPa and an elongation at break of 477.2%. This is because the curing of the emulsion mainly involves two aspects: firstly, the evaporation of water and the aggregation of emulsion particles (film formation); secondly, the hydrolysis of the -SiOCH3 groups in the WPUA matrix into -SiOH groups, which form hydrogen bonds with the hydroxyl functional groups on the surface of sn-SiO2. The evaporation of water and the aggregation of emulsion particles (film formation) are physical changes. Once the water evaporates to a certain extent, the emulsion particles will rapidly aggregate to form a continuous film. This process is usually relatively fast and has low dependence on the curing temperature. The reaction in which the -SiOH group forms hydrogen bonds with the hydroxyl functional groups on the surface of sn-SiO2 leads to incomplete curing at low temperatures. As the temperature increases, the mechanical properties of the part improve. However, at high temperatures, the thermal motion of molecules intensifies, the stability of hydrogen bonds decreases, and some hydrogen bonds break. As the temperature further increases, the mechanical properties of the part decrease.

[0103] In this embodiment, the effect of curing time on the performance of TPU self-cleaning material is as follows: Effect on self-cleaning performance: Figure 19 Digital photographs of coffee droplets on the surface of TPU / WPUA-0.5 / sn-SiO2-20 parts at different curing times show that the coffee droplets on the surface of the TPU / WPUA-0.5 / sn-SiO2-20 parts are approximately spherical with varying curing time. The curing time has little effect on the coffee droplets on the part surface. This is because the curing of the emulsion mainly involves two aspects: first, the evaporation of water and the aggregation of emulsion particles (film formation); second, the hydrolysis of the -SiOCH3 groups in the WPUA matrix into -SiOH groups, which form hydrogen bonds with the hydroxyl functional groups on the sn-SiO2 surface. Among these, the evaporation of water and the aggregation of emulsion particles (film formation) are physical changes, and therefore have relatively low time dependence. The evaporation of water is greatly affected by factors such as ambient temperature, humidity, and air flow, while the length of curing time has little effect on the rate of water evaporation. Once the water has evaporated to a certain extent, the emulsion particles will rapidly aggregate to form a continuous film. This process is usually fast and has low dependence on curing time. The formation of hydrogen bonds between the -SiOH groups and the hydroxyl functional groups on the sn-SiO2 surface is typically very rapid, occurring on a picosecond (ps) to nanosecond (ns) timescale, and the curing time has a negligible impact on it. Therefore, the curing time has a relatively small effect on the coffee droplets on the surface of TPU / WPUA-0.5 / sn-SiO2-20 parts.

[0104] In this embodiment, the impact on mechanical properties is as follows: Figure 20 This study investigates the effect of different curing times at 75℃ on the mechanical properties of TPU / WPUA-0.5 / sn-SiO2-20 parts. Figure 20 It can be seen that the mechanical properties of the TPU / WPUA-0.5 / sn-SiO2-20 parts changed little as the curing time increased from 2 hours to 8 hours. The tensile strength of the TPU / WPUA-0.5 / sn-SiO2-20 parts was around 5.60 MPa, and the elongation at break was around 470.0%. This is because the curing of the emulsion mainly involves two aspects: first, the evaporation of water and the aggregation of emulsion particles (film formation); second, the hydrolysis of the -SiOCH3 groups in the WPUA matrix into -SiOH groups, which form hydrogen bonds with the hydroxyl functional groups on the surface of sn-SiO2. Among these, the evaporation of water and the aggregation of emulsion particles (film formation) are physical changes rather than violent chemical reactions, so their time dependence is relatively low. The evaporation of water is greatly affected by factors such as ambient temperature, humidity, and air flow, while the curing time has a relatively small impact on the rate of water evaporation. Once the moisture evaporates to a certain extent, the emulsion particles rapidly aggregate to form a continuous film. This process is usually quite fast and has low dependence on curing time. The formation rate of hydrogen bonds between the -SiOH groups and the hydroxyl functional groups on the surface of sn-SiO2 is typically very fast. Therefore, curing time has a relatively small impact on the mechanical properties of TPU / WPUA-0.5 / sn-SiO2-20 parts.

[0105] In this embodiment, the effect on the self-cleaning performance of TPU lattice structure components is as follows: Figure 21 Anti-fouling tests for different TPU lattice components. Figure 21 A is a TPU lattice component. After being immersed in coffee solution, a large amount of coffee solution remains in the lattice of the TPU lattice component, and a large number of lattices are blocked. Figure 21 b is a TPU / WPUA-0.5 lattice component. After being immersed in coffee solution, a lot of coffee solution remains in the lattice of the TPU lattice component, and a large number of lattices are blocked. Figure 21 c represents a TPU / WPUA-0.5 / sn-SiO2-20 lattice component. The TPU lattice component has almost no coffee solution residue, indicating that the TPU / WPUA-0.5 / sn-SiO2-20 lattice component has excellent anti-fouling properties and can maintain good self-cleaning performance in coffee solution.

[0106] In this embodiment, after coating with sn-SiO2, the surface of the TPU / WPUA-0.5 / sn-SiO2-20 printed part is covered with numerous protruding sn-SiO2 particles. This increases the porosity on the TPU lattice surface, resulting in increased surface roughness. According to the Cassie-Baxter model, the increased roughness leads to a reduction in the area of ​​contact between the surface and the liquid, thus decreasing the adhesion area and force between the coffee solution and the rough surface. Due to this reduced adhesion area and force, when the TPU lattice part is immersed in coffee solution, the amount of coffee droplets remaining on the surface is significantly reduced, resulting in better self-cleaning ability. Therefore, increased surface roughness increases the water contact angle on the TPU part surface, improving self-cleaning ability.

[0107] Effect on the compressibility of TPU lattice structure components

[0108] In this embodiment, the TPU lattice component exhibits excellent elastic properties, effectively resisting compressive loads during compression tests, and can recover its original shape even when compressed to a completely flat state. Figure 23 The compressive stress-strain curves of TPU lattice components at room temperature are shown, revealing three typical stages of compressive deformation: When 0% < ε < 20%, the TPU lattice component is in the linear elastic stage, with all lattice structures within the component deforming collaboratively, exhibiting good elastic response; when 20% < ε < 40%, the TPU lattice component is in the plastic plateau stage, with the middle lattice gradually compacted, and the compressive pressure increases slowly with strain, exhibiting typical energy absorption characteristics; when ε > 40%, the TPU lattice component enters the densification stage, with the top and bottom lattices compacted, and the compressive stress begins to rise sharply, with the material stiffness approaching the properties of the matrix material. This is because in the densification stage, all lattices are compacted, and the compressive performance of the lattice component is mainly determined by the TPU matrix material, whose stiffness is generally better than that in the lattice structure stage. This unique stage characteristic gives TPU lattice components both good elastic recovery and energy absorption characteristics.

[0109] In this embodiment, at room temperature, the compressive strength of the pure TPU lattice structure is 0.273 MPa, while the compressive strengths of the TPU / WPUA-0.5 and TPU / WPUA-0.5 / sn-SiO2-20 components are 0.421 Pa and 0.733 MPa, respectively, representing increases of 54% and 168% compared to the compressive strength of the pure TPU lattice structure. These results are attributed to the implantation of nano-sn-SiO2 on the TPU / WPUA-0.5 surface. The -sn-SiOCH3 groups in the WPU matrix hydrolyze to form -sn-SiOH groups, which then form hydrogen bonds with the hydroxyl functional groups on the sn-SiO2 surface. This strengthens the interfacial bonding between the nano-sn-SiO2 and the WPU matrix, thus improving the compressive performance of the TPU components.

[0110] In this embodiment, Figure 24 This diagram illustrates a TPU / WPUA / sn-SiO2 self-cleaning process. First, a WPUA emulsion is coated onto the TPU. Then, sn-SiO2 is "captured" by AEAPTMS. The addition of sn-SiO2 increases the surface roughness of the TPU part. According to the Wenzel model formula, when the static contact angle is greater than 90°, θ... r The size is proportional to the roughness coefficient of the rough surface, i.e., θ r As r increases, the surface roughness decreases. According to the Cassie-Baxter model, an increase in r leads to a reduction in the area of ​​contact between the surface and the liquid, decreasing the adhesion area and force between the water droplet and the rough surface, and increasing the water contact angle. Therefore, increased surface roughness leads to a larger water contact angle on the TPU part surface, improving its self-cleaning ability. When water comes into contact with the part surface, due to the high surface roughness, the water droplet forms a near-spherical shape and easily rolls off. During this rolling process, surface contaminants adhere to the water droplet surface and are thus rolled off.

[0111] In this embodiment, the contact angle of the pure TPU part is 123.8°. As the content of sn-SiO2 implanted on the surface of the TPU / WPUA part increases, the hydrophobic angle of TPU / WPUA-0.5 / sn-SiO2 continuously increases. When the sn-SiO2 content is 20%, the water contact angle of the TPU / WPUA-0.5 / sn-SiO2-20 part is the largest, at 153.3°, exhibiting superhydrophobic properties. After sn-SiO2 implantation, the hydrophobic and antifouling properties of TPU can be further improved, thereby enhancing its self-cleaning performance.

[0112] In this embodiment, superhydrophobic sn-SiO2 is implanted onto the surface of the TPU / WPUA part, which improves the mechanical properties of the part. When the sn-SiO2 content is 20%, the tensile strength of the TPU / WPUA-0.5 / sn-SiO2-20 part is 5.60 MPa, and the elongation at break is 477.2%, which are 55% and 28% higher than those of the TPU / WPU part without superhydrophobic sn-SiO2 implantation, respectively.

[0113] In this embodiment, the TPU / WPUA-0.5 / sn-SiO2-20 lattice part exhibits very little residual contaminant after impregnation in contaminants, demonstrating superior antifouling performance compared to pure TPU and TPU / WPUA-0.5 lattice part. The compressive strengths of the TPU / WPUA-0.5 and TPU / WPUA-0.5 / sn-SiO2-20 parts are 0.421 Pa and 0.733 MPa, respectively, representing increases of 54% and 168% compared to the pure TPU lattice part.

[0114] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A self-cleaning coating for post-processing of 3D printed parts, the coating being WPUA / sn-SiO2, characterized in that, The WPUA / sn-SiO2 coating is composed of WPUA emulsion and sn-SiO2 ethanol solution.

2. The self-cleaning coating for post-processing of 3D printed parts according to claim 1, characterized in that, The content of the WPUA emulsion is 80%, and the content of the sn-SiO2 ethanol solution is 20%.

3. The self-cleaning coating for post-processing of 3D printed parts according to claim 2, characterized in that, The WPUA emulsion is composed of WPU emulsion and 3-(2-aminoethyl)-aminopropyltrimethoxysilane (AEAPTMS), wherein the R value of the WPU emulsion is 1.2, and the R value is the NCO / OH ratio.

4. A self-cleaning coating for post-processing of 3D printed parts according to claim 2, characterized in that, The sn-SiO2 ethanol solution is composed of sn-SiO2 and ethanol, wherein the sn-SiO2 content is 5-25% and the ethanol content is 75-95%.

5. A method for synthesizing a self-cleaning coating for post-processing of 3D printed parts according to any one of claims 1-4, characterized in that, Includes the following steps: Step 1: Preparation of WPUA emulsion. Isophorone diisocyanate (IPDI) and polytetrahydrofuran (PTMG) were added to a flask and reacted at 80°C under a nitrogen atmosphere with a stirring speed of 320 rpm for 4 hours. Then, 2,2-dimethylolpropionic acid (DMPA) and a few drops of dibutyltin dilaurate (DBDTL) were added, and the reaction was carried out at 70°C and 320 rpm for 2 hours. Subsequently, butanediol (BDO) was added, and the reaction was continued at 70°C and 320 rpm for 2 hours. Finally, AEAPTMS was added, and the reaction was carried out at 35°C and 320 rpm. The reaction was carried out for 30 minutes under the condition of 35°C and 320 rpm. Then, TEA triethylamine was added to the flask and the neutralization reaction was maintained at 35°C and 320 rpm for 30 minutes. During the neutralization reaction, a small amount of acetone was added to reduce the viscosity of the system. Then, EDA ethylenediamine was added and the reaction was carried out at 35°C and 320 rpm for 5 minutes. After the reaction was completed, distilled water was added under vigorous stirring at 1200 rpm and the reaction was carried out for 5 minutes. Finally, acetone was removed under reduced pressure using a rotary evaporator to obtain a WPUA emulsion containing AEAPTMS. Step 2: Preparation of sn-SiO2 ethanol solution. Sn-SiO2 was placed in a vacuum oven and dried at 80°C for 24 hours. After drying, ethanol was weighed according to the above ratio and poured into a beaker. Then, dried sn-SiO2 powder was weighed and slowly added to the beaker. The mixture was magnetically stirred for 30 minutes and then ultrasonically dispersed for 30 minutes to obtain a uniformly dispersed sn-SiO2 ethanol solution. Step 3: Mix the WPUA emulsion and sn-SiO2 ethanol solution prepared in the above steps according to the above content ratio to obtain the WPUA / sn-SiO2 coating.

6. A self-cleaning TPU / WPUA / sn-SiO2 coated thermoplastic polyurethane elastomer (TPU) self-cleaning part having the coating of claim 1.

7. The method for preparing a self-cleaning TPU / WPUA / sn-SiO2 coated TPU self-cleaning part according to claim 6, characterized in that, Includes the following steps: S1: Pour WPUA emulsion into a silicone mold, then place the TPU part into the WPUA emulsion in the silicone mold and immerse it for 10 minutes. Take it out and wait for the liquid on the surface to drip off naturally. Place it in a 75℃ forced-air oven for pre-drying for 10 minutes and then take it out to obtain a TPU / WPUA part with WPUA emulsion coated on the surface. S2: Pour sn-SiO2 ethanol solution into a silicone mold, then place the TPU / WPUA part into the silicone mold and immerse it for 10 minutes. Remove it and wait for the surface liquid to drip off naturally. Place it in a 75℃ forced-air oven to cure for 6 hours to obtain a part with sn-SiO2 implanted on the outer surface of the WPUA coating of the TPU / WPUA part.

8. The method for preparing a self-cleaning TPU / WPUA / sn-SiO2 coated TPU self-cleaning part according to claim 7, characterized in that, The preparation steps of the TPU part are as follows: TPU powder is deposited layer by layer and selectively laser sintered (SLS) to obtain 3D printed TPU parts; the SLS printing steps are as follows: a sample model of the required shape is drawn using 3D modeling software, and then imported into the SLS printer computer. The printing process parameters are set to achieve the best molding effect. After sintering, when the temperature inside the molding cavity cools to 50°C, the TPU printed part is taken out of the cavity and placed in a powder cleaning machine. After 30 minutes of rolling sandblasting, the residual powder on the surface of the part is blown away, and the final molded TPU part is used for subsequent coating with TPU / WPUA / sn-SiO2.

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