Preparation method and application of super-weather-resistant graphene PET coating material

Abstract

This invention discloses a method for preparing and applying an ultra-weather-resistant graphene PET coating material, belonging to the field of polymer composite materials technology. The method includes the following steps: S1: dispersing graphene oxide in a solvent, adding a modifier to perform a grafting reaction to obtain a functionalized graphene derivative; S2: performing an esterification reaction between terephthalic acid and ethylene glycol, adding the functionalized graphene derivative obtained in step S1 at the end of the esterification stage or the beginning of the polycondensation stage to disperse it in the polymer matrix; S3: performing a polycondensation reaction under the action of a catalyst, and extruding graphene PET sheets using a single-screw extruder. This invention can significantly improve the dispersibility and compatibility of graphene in a polyester matrix, induce the PET molecular chains to transform from coiled clusters to extended orientation, and reduce internal stress; the resulting material has excellent weather resistance, salt spray corrosion resistance, and a uniform matte appearance, making it particularly suitable for protective coatings on automotive windshield wiper wires.

Description

Technical Field

[0001] This invention relates to the field of polymer material modification technology, specifically to a method for preparing and applying an ultra-weather-resistant graphene PET coating material. Background Technology

[0002] Polyethylene terephthalate (PET) is often used as a protective coating material for metal core wires due to its excellent mechanical strength, dimensional stability, and chemical corrosion resistance. It is particularly suitable for structural components such as flat steel wires used to reinforce wiper blades, effectively improving the service life and reliability of the metal substrate. However, in practical applications of outdoor end products such as wipers, PET coatings need to withstand long-term exposure to ultraviolet radiation, high humidity, and salt spray corrosion. The weather resistance of conventional PET materials is insufficient to meet long-term service requirements, becoming a key issue restricting its application.

[0003] Existing ordinary PET coatings are prone to polymer chain degradation and breakage during outdoor aging, manifesting as surface cracking, powdering, and even peeling. Under neutral salt spray standard test conditions, coating edges are prone to blistering and decreased adhesion, and in severe cases, internal steel wires may develop red rust corrosion, generally failing the stringent salt spray resistance test of over 240 hours. Currently, the industry is attempting to modify PET using nanomaterials such as graphene, for example through simple physical melt blending or by directly adding graphene oxide in the early stages of esterification. However, simple physical blending is difficult to form strong interfacial bonds; while adding materials in the early stages of esterification not only easily leads to the aggregation of nanomaterials in strong acid and high-temperature moisture environments, but also causes the sensitive modifying groups with anti-aging functions to deactivate prematurely; in addition, graphene, as an excellent nucleating agent, easily induces high crystallization of PET during conventional molding and cooling processes, resulting in brittle coating materials and a sharp decrease in adhesion. Meanwhile, to avoid strong glare interfering with the driver's vision, wiper coatings typically require a uniform matte appearance, with a surface gloss level controlled below 45. Traditional matting methods often employ physical sandblasting or the addition of large amounts of inorganic matting fillers. The former involves complex processes and can easily damage the substrate, while the latter can cause uneven agglomeration of fillers, disrupting the continuity of the coating and significantly reducing the material's mechanical properties and protective effect.

[0004] Characterization analysis of commercially available high-performance black PET chips using FTIR, DSC, and XRF revealed that some products contained calcium (Ca) and exhibited an additional melting peak at approximately 122.7°C, suggesting the addition of low-melting-point lubricants or nucleating agents to improve processing performance. However, these low-melting-point components tend to migrate and precipitate to the surface during high-temperature processing or long-term aging, forming interface defects and weak points, further exacerbating the decline in coating weather resistance. Therefore, developing a PET coating material that does not rely on low-melting-point additives and possesses good dispersibility, excellent weather resistance, and self-matting properties has become a pressing technical challenge in this field.

[0005] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0006] The present invention aims to provide a method for preparing and applying an ultra-weather-resistant graphene PET coating material. By introducing a specific FGD, the problem of poor weather resistance, easy agglomeration of fillers, and easy foaming of existing PET coatings can be solved.

[0007] To achieve the above objectives, the present invention provides a method for preparing an ultra-weather-resistant graphene PET coating material, comprising the following steps: S1: Preparation of functionalized graphene derivatives: Graphene oxide (GO) was dispersed in a solvent, and a modifier was added to carry out a grafting reaction to obtain functionalized graphene derivatives (FGD). S2: In-situ polymerization: PTA terephthalic acid and EG ethylene glycol are esterified. In order to avoid the thermal degradation or deactivation of the hindered amine and other active groups in the modifier under long-term high temperature and water by-product environment, the functionalized graphene derivative FGD obtained in step S1 is added at the end of the esterification stage or at the beginning of the polycondensation stage to disperse it in the polymer matrix. S3: Melt polycondensation and extrusion: Polycondensation reaction is carried out under the action of a catalyst until the target intrinsic viscosity is reached. The product is then extruded through a T-die using a single screw extruder. The product is then rapidly cooled by a coolant to forcibly freeze the conformation of the PET molecular chain, suppress the tendency of graphene to spontaneously induce microcrystal formation, and keep it in an amorphous state, ultimately obtaining a sheet. S4: The extruded sheet is attached to the surface of the substrate through a hot pressing process.

[0008] Furthermore, preferably, the modifier in step S1 comprises a compatible component having a long-chain alkyl structure and a hindered amine (HALS) component having free radical scavenging function.

[0009] Furthermore, as a more preferred embodiment, the modifier in step S1 comprises monomers containing carboxyl or phenolic hydroxyl groups, such as 4-hydroxyacetophenone (4-HPE) or 3-carboxylic acid (MAA), and 2,2,6,6-tetramethylpiperidine derivatives.

[0010] Furthermore, preferably, the grafting reaction in step S1 is an amidation / esterification coupling reaction, with a reaction temperature of 80-110℃ and a time of 4-6h.

[0011] Furthermore, preferably, in step S2, the molar ratio of PTA to EG is 1:1 to 1:2, more preferably 1:1.2.

[0012] Furthermore, preferably, the amount of FGD added in step S2 is 1-5% of the total weight of the polymer.

[0013] Furthermore, preferably, the esterification reaction temperature in step S2 is 180-220℃, and the time is 1-3h.

[0014] Furthermore, preferably, the polycondensation reaction in step S3 is carried out in stages: the pre-polymerization stage is 270℃, 0.2-0.33MPa, and the final polycondensation stage is 280-285℃, 60-130Pa.

[0015] Furthermore, preferably, the coolant in step S3 is liquid nitrogen.

[0016] Furthermore, as a preferred embodiment, in step S3, the flow rate of liquid nitrogen is 8-15 L / min, the cooling distance is 110-160 mm, and the cooling time is 1-2 s.

[0017] Furthermore, as a preferred embodiment, the single-screw extruder in step S3 is divided into a feeding section, a compression section, a melting section, a homogenization section, and a die section for temperature control, as follows: feeding section 220-230℃, compression section 235-245℃, melting section 245-255℃, homogenization section 255-265℃, and die section 250-260℃.

[0018] Furthermore, preferably, the sheet thickness extruded by the single-screw extruder in step S3 is 0.8 mm.

[0019] Furthermore, preferably, the hot pressing process in step S4 includes preheating, surface treatment, and hot pressing. The preheating temperature is 120-130℃, and the preheating time is 15-45 min. The surface treatment includes corona treatment, plasma treatment, ultraviolet light treatment, flame treatment, and the use of a primer. The surface treatment can also be a synergistic effect of corona treatment and silane coupling agent. The hot pressing temperature is 260-290℃, the pressure is 1-3 MPa, the pressurization time is 20-40 s, and the cooling liquid is used for cooling.

[0020] Further, as a more preferred embodiment, the hot pressing temperature is 270-285℃, the pressure is 2-2.5 MPa, the pressurization time is 25-30s, and the cooling is achieved by flowing water; the cooling water flow rate is 5-15L / min, and the cooling time is 5-20s; more preferably, the cooling water flow rate is 8-12L / min, and the cooling time is 10-15s.

[0021] Furthermore, preferably, the functionalized graphene derivative induces the stretching of PET molecular chain segments in the PET matrix through van der Waals forces or chemical bonding.

[0022] Furthermore, preferably, the intrinsic viscosity of the PET coating material prepared by the method is between 1.30 and 1.65 dl / g, and it does not have an additional impurity melting peak below 240°C in differential scanning calorimetry testing.

[0023] Furthermore, preferably, the surface gloss (60° angle) of the PET coating material prepared by the method is less than 25.

[0024] This invention also provides a method for preparing an ultra-weather-resistant graphene PET coating material and the application of the material obtained, which is used as an automotive windshield wiper blade.

[0025] Furthermore, preferably, the automotive wiper blade includes a wire and a thermoplastic coating covering the wire, the thermoplastic coating being prepared by the method for preparing the ultra-weather-resistant graphene PET coating material.

[0026] Furthermore, preferably, the conductor is galvanized steel wire or galvanized aluminum alloy steel wire.

[0027] Furthermore, as a preferred embodiment, after the thermoplastic coating is applied to the conductor, the coating surface shows no red rust and no blistering except at the cut edges after the conductor is tested under a neutral salt spray test (Valeoswf11.015 standard) for 1924 hours.

[0028] Furthermore, as a preferred embodiment, after the thermoplastic coating is applied to the conductor, the surface gloss of the coating decreases slightly after the conductor is tested under QUV accelerated aging test (ISO 4892-2 standard) for 1200 hours, but no yellowing or cracking occurs.

[0029] Compared with the prior art, the present invention has the following beneficial effects: (1) The ester / amide groups on the surface of the FGD synthesized in this invention form hydrogen bonds and ester bonds with PET segments, which significantly reduces the interfacial energy, so that the FGD is uniformly dispersed in PET and has no obvious agglomeration. (2) The highly elastic interface of FGD synthesized in this invention can "stretch" PET chain segments, reduce the glass transition temperature (Tg) by about 2-4°C, and improve the flexibility of the material at low temperatures; (3) The two-dimensional structure of graphene in this invention forms a highly dense barrier channel, which can effectively capture and prevent active free radicals (·OH, ·O2). - It penetrates the PET matrix, significantly delaying the photo-oxidation reaction, and is then subjected to QUV accelerated aging (UV-B 340nm, light intensity 0.68W·m). -2 After 60°C for 1200 hours, the gloss reduction rate of the FGD-PET composite material was <5%, and the mechanical properties remained above 90% of the original values. (4) This invention improves the in-situ polymerization process, eliminating the need for additional high-temperature or high-pressure steps, and can be directly applied to existing extrusion, injection molding, and hot pressing production lines, with a cost increase of only 5-8%; (5) Unlike traditional graphene-modified PET processes, such as physical blending or initial feeding during esterification, this invention precisely controls the timing of in-situ feeding of FGD and the rapid cooling process during molding. On the one hand, feeding at the end of esterification / early stage of polycondensation perfectly avoids the damage of a large amount of water to free groups such as hindered amines (HALS), maximizing the preservation of their anti-aging activity. On the other hand, the nucleation and crystallization effect of graphene is forcibly suppressed by liquid nitrogen-level rapid cooling, solving the technical bias of traditional graphene-modified PET coatings being brittle and having low adhesion, and achieving a unity of highly flexible amorphous morphology and excellent chemical protection. Attached Figure Description

[0030] Figure 1 This is a flowchart of the preparation process of the present invention; Figure 2 A comparison chart of DSC curves of the materials prepared according to the present invention; Figure 3 This is a schematic diagram of the weather resistance mechanism of the present invention; Figure 4 This is a comparison chart of the salt spray test results of the present invention; Figure 5 The image shows the QUV accelerated aging test results of this invention. Detailed Implementation

[0031] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0032] The following provides a brief overview of one or more aspects to offer a basic understanding of them. This overview is not an exhaustive summary of all conceived aspects, nor is it intended to identify key or decisive elements of all aspects, nor to define the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form to prepare for the more detailed descriptions that follow.

[0033] Example 1:

[0034] A method for preparing an ultra-weather-resistant graphene PET coating material includes the following steps: S1: 5g of GO was dispersed in N,N-dimethylacetamide (DMF), 2g of 4-amino-2,2,6,6-tetramethylpiperidine (TAD) and 3g of 3-carboxylic acid (MA) were added, and the mixture was reacted at 90 °C for 5h. After centrifugation, washing and drying, functionalized FGD was obtained. S2: PTA and EG are mixed and pulped at a molar ratio of 1:1.2 and esterified at 220 °C and 0.2 MPa for 2 hours. Then, the FGD prepared in S1 (accounting for 2% of the total polymer weight) is dispersed in ethylene glycol, added to the reaction vessel and stirred evenly. S3: Add antimony trioxide catalyst to the reactor in step S2, heat to 270 °C, and pre-polymerize at 0.25 MPa for 2 hours. Then heat to 280 °C and gradually evacuate to 60 Pa. React until the intrinsic viscosity is about 1.4 dL / g. Then use a single screw extruder to extrude through a T-die and quench with liquid nitrogen to maintain its amorphous shape, finally obtaining 0.8 mm sheet. The segment parameters of the single screw extrusion are as follows: feed section temperature 220-230 °C, compression section temperature 235-245 °C, melting section temperature 245-255 °C, homogenization section temperature 255-265 °C, and die section temperature 250-260 °C. S4: The sheet extruded from S3 is attached to the substrate surface through a hot-pressing process. The hot-pressing process includes preheating, surface treatment, and hot pressing. The preheating temperature is 120-130 °C, and the preheating time is 0.5 h. Corona treatment and silane coupling agent are selected to work synergistically to improve the adhesion of the graphene PET film. The hot-pressing temperature is 270-285 °C, the pressure is 2-2.5 MPa, the pressing time is 25-30 s, and the cooling is carried out with flowing water. The cooling water flow rate is 8-12 L / min, and the cooling time is 10-15 s.

[0035] Example 2:

[0036] Unlike Example 1, the raw material ratio in S2 is as follows: PTA and EG in a molar ratio of 1:1, and FGD accounts for 1% of the total polymer weight.

[0037] Example 3:

[0038] Unlike Example 1, the proportions of raw materials in S2 are as follows: PTA to EG in a molar ratio of 1:2, and FGD accounts for 3% of the total weight of the polymer.

[0039] Comparative Example 1: Unlike Example 2, FGD was not added to the raw materials in S2.

[0040] Comparative Example 2: Unlike Example 3, the FGD added in S2 is in powder form and has not been dispersed in ethylene glycol.

[0041] Table 1 below shows the raw material formulas for Example 1, Example 2, Example 3, Comparative Example 1, and Comparative Example 2.

[0042] The materials prepared in Examples 1-3 and Comparative Examples 1-2 were tested, and their performance is shown in Table 2 below.

[0043] The above testing standards are as follows: viscosity is tested according to GB / T1632.1-2008 standard; tensile strength and elongation at break are tested according to ISO527-2 standard; elongation at break retention is tested according to GB / T 24135 standard; transparency and haze are tested according to ASTM D1003-13; gloss (60°) is tested according to ISO 2813 standard; melting point (DSC) is tested according to ISO 11357 standard; resistance to neutral salt spray (1924 h) is tested according to Valeo SWF11.015 standard; and QUV accelerated aging (1200 h) is tested according to ISO 4892-2 standard.

[0044] The test results above show that: 1. Examples 1-3 showed the best performance in the "neutral salt spray resistance (1924h)" and "QUV accelerated aging test (1200h)" tests, with no blistering, no rust, no yellowing, and no cracking. Simultaneously, the "elongation at break retention rate" was very high, reaching 88%-95%. Comparative Example 1 had the worst salt spray resistance, exhibiting "edge blistering"; its elongation at break retention rate was the lowest, only 70%. Comparative Example 2 fell between the two, showing "slight edge blistering" in salt spray resistance, with a retention rate of 73%. This indicates that the FGD added in Examples 1-3 significantly improved the corrosion resistance and weather resistance of the PET material. The main reason lies in the different dispersion processes in step S2. Examples 1-3 pre-dispersed FGD in ethylene glycol (EG), while Comparative Example 2 directly added the powder without dispersion. Good dispersion allowed FGD to form a denser barrier network in the polymer matrix, thereby preventing the penetration of moisture and salt.

[0045] 2. Examples 1-3 exhibited high tensile strengths, all exceeding 58 MPa (with a maximum of 59.5 MPa). Comparative Example 1 showed a tensile strength of 52.7 MPa, while Comparative Example 2 had the lowest tensile strength at only 50.1 MPa. This is because normally dispersed FGD (Examples 1-3) can enhance and toughen the polymer, resulting in higher strength than pure PET (Comparative Example 1). Although Comparative Example 2 incorporated FGD, the powder was added directly, making it prone to forming agglomerates (defects) in the polymer. These agglomerates became stress concentration areas under stress, causing its tensile strength to be even lower than that of pure PET without FGD.

[0046] 3. Comparative Example 1 exhibits extremely high transparency (92%) and high gloss (70%). Examples 1-3 and Comparative Example 2 show a significant decrease in transparency to approximately 67%-69%, and a substantial reduction in gloss to 12-25. This is because graphene itself is a carbon-based material with light-absorbing and light-blocking properties. Regardless of the dispersion effect (in the examples or comparative examples), as long as FGD is present in the matrix, a matte texture will be produced.

[0047] The following conclusions can be drawn: This application achieves structural strengthening and functional enhancement of the PET matrix by in-situ introduction of FGD; the "chain segment unfolding" effect of the grafted chains induces the PET molecular chains to transform from random coiling to directional orientation, which can effectively alleviate the internal stress of the material. At the same time, the high aspect ratio two-dimensional topology of graphene (physical barrier) and the free radical scavenging ability of hindered amines (chemical protection) are used to synergistically construct an oxygen / water vapor permeation barrier. The resulting composite material maintains a uniform matte finish while exhibiting excellent UV aging stability and salt spray corrosion resistance, making it highly suitable for the harsh working conditions required for protective coatings on automotive windshield wiper wires.

[0048] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for preparing an ultra-weather-resistant graphene PET coating material, characterized in that, Includes the following steps: S1: Preparation of functionalized graphene derivatives: Graphene oxide is dispersed in a solvent, and a modifier is added to carry out a grafting reaction. The modifier contains a compatible component with a long-chain alkyl structure and a hindered amine component with free radical scavenging function to obtain functionalized graphene derivatives. S2: In-situ polymerization: Terephthalic acid and ethylene glycol are esterified. At the end of the esterification stage or the beginning of the polycondensation stage, the functionalized graphene derivative obtained in step S1 is added to disperse it in the polymer matrix. S3: Melt polycondensation and extrusion: Polycondensation reaction is carried out under the action of a catalyst until the target intrinsic viscosity is reached, and graphene PET sheets are extruded through a single screw extruder.

2. The method for preparing an ultra-weather-resistant graphene PET coating material according to claim 1, characterized in that, In step S1, the modifier is 4-hydroxyacetophenone, 3-carboxylic acid monomer, or 2,2,6,6-tetramethylpiperidine derivative.

3. The method for preparing an ultra-weather-resistant graphene PET coating material according to claim 1, characterized in that, The grafting reaction in step S1 is an amidation / esterification coupling reaction, with a reaction temperature of 80-110℃ and a time of 4-6 hours.

4. The method for preparing an ultra-weather-resistant graphene PET coating material according to claim 1, characterized in that, The functionalized graphene derivatives induce the stretching of PET molecular chain segments in the PET matrix through van der Waals forces or chemical bonding.

5. The method for preparing an ultra-weather-resistant graphene PET coating material according to claim 1, characterized in that, The functionalized graphene derivatives account for 0.1% to 2.0% of the total PET.

6. The method for preparing an ultra-weather-resistant graphene PET coating material according to claim 1, characterized in that, The PET coating material prepared by the method has an intrinsic viscosity between 1.30 and 1.65 dl / g, and does not have an additional impurity melting peak below 240°C in differential scanning calorimetry testing.

7. The method for preparing an ultra-weather-resistant graphene PET coating material according to claim 6, characterized in that, The surface gloss of the PET coating material prepared by the method is less than 25.

8. The application of a material prepared by the method for preparing the ultra-weather-resistant graphene PET coating material according to any one of claims 1-7, characterized in that: Used as windshield wiper blades for automobiles.

9. The application of the material prepared by the method for preparing an ultra-weather-resistant graphene PET coating material according to claim 8, characterized in that: The automotive wiper blade includes a wire and a thermoplastic coating covering the wire, the thermoplastic coating being prepared by the method for preparing the ultra-weather-resistant graphene PET coating material.

10. The application of the material prepared by the method for preparing an ultra-weather-resistant graphene PET coating material according to claim 9, characterized in that: The conductor is galvanized steel wire or galvanized aluminum alloy steel wire.

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