Method for evaluating permeation effect of adhesive based on contact angle

Abstract

The invention discloses a method for evaluating the permeation effect of an adhesive based on a contact angle, the permeation effect of the adhesive is evaluated through the average contact angle attenuation rate, the permeation effect comprises rapid permeation, medium permeation and slow permeation, the contact angle attenuation rate of the rapid permeation is greater than 0.1, the contact angle attenuation rate of the medium permeation is greater than 0.01, and the contact angle attenuation rate of the slow permeation is greater than 0.01. The attenuation rate of the contact angle is less than or equal to 0.1, and the attenuation rate of the contact angle of the slow penetration is less than or equal to 0.01. According to the method, complex microscopic observation or weight measurement is not needed, the contact angle measuring instrument is utilized, after the adhesive is dropwise added to the surface of the material, the change of the contact angle is continuously monitored, the permeation effect of the adhesive is rapidly obtained through data analysis, and the method is simple, convenient, efficient and accurate.

Description

Technical Field

[0001] This patent belongs to the field of adhesive technology, and specifically relates to a method for evaluating the penetration effect of adhesives based on contact angle. Background Art

[0002] Adhesives are widely used in modern industrial manufacturing, and their performance directly affects product quality and durability. To ensure that adhesives can perform optimally in practical applications, accurately evaluating their penetration properties is crucial.

[0003] Currently, there are two main methods for testing the penetration effect of adhesives: microscopic observation and weight method.

[0004] Microscopic observation uses a microscope to observe the penetration of adhesives into the material. This method can directly determine the penetration depth and distribution of the adhesive, but it requires a high-magnification microscope and specialized technicians. The process is complex and requires sample-by-sample observation, which is time-consuming and inefficient. It can only detect surface or shallow penetration, making it difficult to fully reflect the penetration effect.

[0005] The gravimetric method measures the weight change of the material before and after adhesive penetration. This method is relatively simple to operate, but the weight change is affected by many factors, making it difficult to accurately reflect the penetration effect. It can only provide an overall penetration amount and cannot be refined into the details of the penetration process.

[0006] Due to the above-mentioned shortcomings of the microscopic observation method and the weight method, it is necessary to provide a simpler, more efficient and accurate method for detecting the penetration effect of the adhesive. Summary of the Invention

[0007] The purpose of this patent is to provide a method for evaluating the penetration effect of adhesives based on contact angle, so as to simplify the existing complex and time-consuming detection process and improve the accuracy and efficiency of detection.

[0008] In order to solve the above technical problems, this patent adopts the following technical solutions:

[0009] A method for evaluating adhesive penetration based on contact angle comprises the following steps:

[0010] Step A: Add the adhesive to the clean substrate surface to form droplets;

[0011] Step B: Use a contact angle meter to immediately measure the initial contact angle between the droplet and the surface of the material to be tested;

[0012] Step C: within a fixed time interval after the adhesive is added, continuously monitor the change of the contact angle using a contact angle meter and record the contact angle value at each time point;

[0013] Step D: Import the contact angle value recorded in step C into the computer system and calculate the contact angle decay rate k (s-1) within a fixed time interval according to the following formula (1):

[0014] k(s-1)=(㏑θ n -㏑θ n+1 ) / (t n+1 -t n ) (1)

[0015] Where n is the time number marked at each fixed time interval starting from the initial contact angle value, and n is a continuous integer from small to large; θ n is the contact angle value measured at the nth fixed time interval after the adhesive is dropped;

[0016] Step F: Evaluate the penetration effect of the adhesive by calculating the average contact angle decay rate, which includes fast penetration, medium penetration and slow penetration.

[0017] The contact angle decay rate of fast penetration is greater than 0.1,

[0018] The contact angle decay rate of medium penetration is greater than 0.01, and the contact angle decay rate is less than or equal to 0.1,

[0019] The contact angle decay rate of slow penetration is less than or equal to 0.01.

[0020] Furthermore, the contact angle half-life of rapid penetration is less than 7s;

[0021] The contact angle half-life for medium penetration is greater than or equal to 7s and less than 70s;

[0022] The contact angle half-life of slow penetration is greater than 70s.

[0023] Furthermore, step D also includes calculating the contact angle change rate V according to the following formula (2):

[0024] V=dθ / dt (2)

[0025] Wherein, θ is the contact angle change from the initial contact angle value to the stable contact angle value, t is the time from the initial contact angle value to the stable contact angle value,

[0026] The contact angle change rate for rapid penetration is greater than 5.0° / s;

[0027] The contact angle change rate for medium penetration is greater than 0.9° / s and less than or equal to 5.0° / s;

[0028] The contact angle change rate of slow penetration is less than or equal to 0.9° / s.

[0029] Furthermore, step D also includes:

[0030] The contact angle change curve is drawn according to the contact angle values ​​measured at each time point between the initial contact angle value and the stable contact angle value to judge the penetration process, which includes initial wetting, expansion stage and penetration stage.

[0031] Furthermore, the initial contact angle value to the stable contact angle value successively goes through the initial wetting stage, the expansion stage and the penetration stage.

[0032] The contact angle changing rate in the initial wetting stage is greater than that in the expansion stage, and the contact angle changing rate in the expansion stage is greater than that in the penetration stage.

[0033] Furthermore, the method further comprises step E:

[0034] Step E: Based on the measured contact angle value, calculate the penetration ability P of the adhesive on the substrate according to the following formula (3):

[0035]

[0036] Wherein, θ is the contact angle change from the initial contact angle value to the stable contact angle value, γL is the surface tension of the adhesive, η is the viscosity of the adhesive, rp is the pore diameter, and Ra is the roughness of the substrate.

[0037] Furthermore, the penetration capacity of fast penetration is P>0.008, the penetration capacity of medium penetration is 0.002<P≤0.008, and the penetration capacity of slow penetration is P≤0.002.

[0038] This patent detects and calculates the overall average contact angle decay rate, half-life, penetration capacity P and contact angle change rate to quickly classify the penetration characteristics of adhesives with unknown characteristics, and further quickly match them to applicable materials based on the classification. The applicable materials include wood materials, composite materials, paper substrates or non-porous or low water absorption substrates.

[0039] This patent further claims protection for a method for screening adhesives suitable for wood materials. According to any of the above-mentioned methods for evaluating the penetration effect of adhesives based on contact angle, adhesives with slow penetration or medium penetration are screened out. Such adhesives are adhesives suitable for wood materials (hereinafter referred to as wood).

[0040] As a natural material, wood has unique surface energy and pore structure, which significantly influence the penetration behavior of adhesives. Key influencing factors include surface energy, porosity and structure, roughness, and humidity and environmental conditions. Wood typically has a low surface energy, typically between 30 and 50 mN / m. This low surface energy means poor wettability, necessitating adhesives with higher surface tension for optimal penetration and bonding. When selecting an adhesive, it is important to choose one with a higher surface tension or to use appropriate surface treatment techniques (such as plasma treatment or flame treatment) to improve the wood surface's compatibility. The porosity and structure of wood vary by species, typically ranging from 10% to 80%. This porous structure makes wood highly hygroscopic, particularly in softwoods, where adhesives can penetrate quickly. However, excessive penetration can lead to reduced bond strength. Therefore, when selecting an adhesive, it is important to assess the wood's pore structure and hygroscopicity to determine the appropriate adhesive type (e.g., water-based or solvent-based). The surface roughness of wood varies depending on the wood type and treatment. A rough surface may trap adhesive more effectively, improving adhesion, but it may also limit penetration. Surface polishing or surface treatment can help control penetration depth. Wood is highly hygroscopic, and high humidity can alter its surface energy, affecting adhesive penetration. When using adhesives in high-humidity environments, it's important to select adhesives with strong moisture resistance to prevent surface moisture from adversely affecting adhesive performance. While wood is relatively uncommon in the tobacco industry, it does have some specific uses, particularly as a component of a material or in specific manufacturing processes, such as cigarette boxes and packaging, cigarette filter rods, and wooden pipes. Wood is used in the exterior of some cigarette boxes and packaging, particularly in high-end, customized cigarette boxes, where its unique texture and premium feel are a selling point. Adhesives in these applications require rapid penetration and good weather resistance. Wood may also be part of filter rod assemblies. While not directly used as a filter material, it is sometimes incorporated as a structural component in complex filtration systems. This type of application requires adhesives that can firmly bond to the wood surface while ensuring that filtration performance is not affected. In traditional pipe manufacturing, wood is the main material, and adhesives are used during the manufacturing process to connect different parts of the wood and ensure the structural stability of the pipe.

[0041] Suitable adhesives for wood include slow-penetrating or medium-penetrating water-based adhesives, solvent-based adhesives, and hot melt adhesives. Hot melt adhesives are also common in wood applications, especially in packaging and craft production. Hot melt adhesives cure quickly and provide a strong bond.

[0042] This patent further claims protection for a method for screening adhesives suitable for composite materials, and according to any of the above methods for evaluating the penetration effect of adhesives based on contact angles, an adhesive with a slow penetration effect is screened out, and the adhesive is an adhesive suitable for composite materials. Composite materials have low porosity and limited permeability, so slow-penetrating adhesives are required. The applications of composite materials in the tobacco field include filter materials, high-barrier packaging for cigarette boxes, or high-barrier packaging for cigarette boxes. Filter material: multi-layer composite structure, the adhesive needs to penetrate slowly to ensure interlayer bonding without affecting air permeability. High-barrier packaging for cigarette boxes: Some cigarette boxes use composite materials (such as aluminum foil / plastic / paper composite structures), and the adhesive needs to penetrate slowly to ensure interlayer stability without destroying the material structure.

[0043] This patent further claims protection for a method for screening adhesives suitable for paper substrates, and according to any of the above methods for evaluating the penetration effect of adhesives based on contact angles, an adhesive with a medium penetration effect is screened out, and the adhesive is an adhesive suitable for paper substrates. Paper substrates, that is, paper, have a certain water absorption, but require moderate penetration to ensure the bonding effect without excessive absorption. The application of paper substrates in the tobacco industry includes cigarette paper, filter rod wrapping paper or tobacco packaging paper. Cigarette paper: To control the burning rate, the adhesive needs to penetrate moderately to enhance the mechanical strength of the paper without affecting the burning performance. Filter rod wrapping paper: The outer wrapping paper needs to penetrate moderately to ensure stability without affecting the air permeability. Tobacco packaging paper: Suitable for cigarette outer packaging, stable bonding but not excessive penetration to avoid print-through or affect the printing quality.

[0044] This patent further claims protection for a method for screening adhesives suitable for non-porous or low-water-absorbent substrates, and screens out adhesives with fast penetration according to any of the above-mentioned methods for evaluating adhesive penetration based on contact angle. Non-porous or low-water-absorbent substrates (such as glass, plastic, and metal) have low surface energy, and adhesives need to wet and penetrate quickly. The application of low-water-absorbent materials in the tobacco industry includes cigarette box packaging, electronic cigarette shells, or inkjet coatings. Cigarette box packaging: Transparent plastic film (BOPP film) is used to package cigarettes, which requires adhesives with high wettability and fast penetration. Electronic cigarette shell: Plastic or metal shell structure bonding requires fast penetration to provide bonding strength. Inkjet coating: Inkjet printing of production date and other labels, the wetting properties of the adhesive or ink determine the adhesion effect.

[0045] In this patent, the term "contact angle" is the angle formed by a liquid droplet on a solid surface and is used to measure the wettability of a liquid on a solid.

[0046] In this patent, the term "wettability" refers to the degree of spreading of a liquid on a solid surface and is an indicator of the interaction between the liquid and the solid.

[0047] In this patent, the term "permeability" refers to the ability of a liquid to pass through the pores or microscopic channels of a solid material.

[0048] In this patent, the term "dynamic contact angle" refers to the contact angle of a liquid droplet on a solid surface that changes with time and is used to analyze the penetration behavior of a liquid.

[0049] To simplify operations and improve detection efficiency, this patent proposes a method for evaluating adhesive penetration based on detecting contact angle changes. This method, which does not require complex microscopic observation or weight measurement, utilizes a contact angle meter to continuously monitor changes in contact angle after the adhesive is added to the material surface. The method then rapidly derives the adhesive's penetration effect through data analysis. This method is simple, efficient, and accurate, and can be used to detect adhesive penetration on different material surfaces. By providing a technical approach based on contact angle change detection, this patent not only simplifies the detection process and improves detection efficiency, but also enhances the precise characterization of adhesive penetration effects. This method offers significant technical protection benefits, enabling better evaluation and selection of adhesives, and improving their practical application performance and durability.

[0050] This patent achieves the following technical effects:

[0051] Easy operation: No complicated microscopic observation or weight measurement is required, just add the adhesive and measure the change in contact angle.

[0052] Efficient testing: Testing can be completed in a short time, providing real-time information on adhesive penetration. High-precision contact angle meters can accurately measure the contact angle of a droplet on a solid surface, providing reliable data. They can also perform dynamic measurements, recording contact angle changes in real time to provide real-time information on the adhesive penetration process.

[0053] Accurate Characterization: The contact angle curve provides a detailed reflection of the penetration process, enabling a more accurate assessment of penetration effectiveness through the computer system. The computer system's data logging module efficiently stores contact angle measurement data, ensuring data integrity and continuity. The data analysis module rapidly processes and analyzes large amounts of data, generating contact angle curves and related parameters. The penetration effectiveness assessment module analyzes the contact angle curve to assess the penetration effectiveness of the adhesive, providing a scientific basis for adhesive performance evaluation.

[0054] Widely applicable: Suitable for evaluating the penetration effect between various types of adhesives and different substrate materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The above content of this patent and the following specific embodiments will be better understood when read in conjunction with the accompanying drawings. It should be noted that the drawings are only examples of the technical solutions claimed.

[0056] Figure 1 Schematic diagram of the contact angle penetration process of this patent;

[0057] Figure 2 Schematic diagram of the curve showing the change of contact angle with time for medium penetration in this patent. DETAILED DESCRIPTION

[0058] The detailed features and advantages of this patent are described in detail below in the specific implementation method. The content is sufficient to enable any technical personnel in this field to understand the technical content of this patent and implement it accordingly. Based on the description, claims and drawings disclosed in this specification, technical personnel in this field can easily understand the relevant purposes and advantages of this patent.

[0059] Prior to this patent being proposed, some technologies have attempted to evaluate the wettability and permeability of liquids by changing the contact angle.

[0060] Dynamic contact angle measurement: Some studies use dynamic contact angle measurement technology to analyze the wetting properties of liquids by recording the changes in contact angle during the expansion or contraction of droplets on solid surfaces. Although dynamic contact angle measurement can provide some information during the expansion of droplets, its application in the evaluation of adhesive penetration effects is not comprehensive due to the high viscosity of adhesives, especially for the evaluation of deep penetration. Because the contact angle can only reflect the surface wetting, it cannot reveal the penetration behavior of the adhesive inside the material, the penetration depth and the influence of the pore structure. In addition, the change of contact angle is often relatively rapid, and it is impossible to accurately capture the deep expansion of the adhesive during long-term penetration. It is necessary to combine other technologies (such as microscopic imaging, X-ray imaging, etc.) for comprehensive analysis.

[0061] Static contact angle measurement: Another area of ​​research focuses on static contact angle measurement, which assesses the wettability of liquids by measuring the contact angle of a droplet at equilibrium. This only provides information on initial wettability and cannot reflect the time-dependent penetration process, making it inaccurate for evaluating the penetration properties of adhesives.

[0062] An analysis of the shortcomings of existing technical solutions reveals that existing contact angle measurement technology still has certain limitations in evaluating adhesive penetration. This patent proposes a method for characterizing adhesive penetration based on contact angle change detection. This method aims to provide a simple, efficient, and accurate means of evaluating penetration by continuously monitoring the change in contact angle over time. This method not only overcomes the shortcomings of microscopic observation and gravimetric methods but also fills a gap in existing contact angle measurement technology for evaluating penetration, thus possessing significant practical application value.

[0063] Basic properties of adhesives: Adhesives penetrate into the micropores or capillaries of a substrate to form a strong bond. The effectiveness of this penetration depends on a variety of factors, including the adhesive's viscosity, the substrate's pore structure, and its surface energy.

[0064] The viscosity of an adhesive determines how easily it flows. Higher viscosities typically result in slower adhesive expansion on the paper surface, slower changes in the contact angle, and potentially poorer penetration. Low-viscosity adhesives, on the other hand, easily expand on the paper surface, with a rapidly decreasing contact angle and potentially better permeability. The pore structure of the paper (porosity, pore size distribution, etc.) directly affects the expansion and penetration of the adhesive on the paper surface. Paper with a larger porosity typically exhibits higher permeability because the adhesive can more easily penetrate the material, causing the contact angle to drop rapidly. Paper with a smaller pore size may prevent the adhesive from penetrating deeply into the pores, resulting in slower or smaller changes in the contact angle.

[0065] The surface energy (polar and non-polar components) of paper affects the wettability and adhesion of adhesives. Paper with high surface energy generally attracts adhesives with low surface energy (such as oil-based adhesives), resulting in a smaller contact angle and better penetration. On the other hand, paper with low surface energy may result in less penetration, resulting in a larger contact angle and poorer penetration.

[0066] Good penetration can enhance the bonding between the adhesive and the substrate, improving bond strength and durability. Insufficient penetration may lead to problems such as weak adhesion and easy peeling, affecting product quality.

[0067] This patent reflects the wettability of liquids on solid surfaces by measuring the contact angle formed by a liquid droplet on the solid surface. High-precision contact angle meters can quickly and accurately measure changes in the contact angle of a liquid droplet, making them an effective tool for evaluating the behavior of liquids on solid surfaces. Table 1 further allows for a comprehensive evaluation of the adhesive's ability to penetrate the substrate.

[0068] Table 1: Evaluation table of factors affecting the penetration ability of adhesives on substrates

[0069] Influencing factors variable Physical meaning Influence Adhesive viscosity η Adhesive flow resistance The higher the viscosity, the lower the penetration rate Adhesive surface tension γL Affects wettability The higher the value, the stronger the wettability. Substrate surface energy γS Affects the degree of wetting The higher the value, the smaller the contact angle. Substrate porosity φ Pore ​​volume ratio The larger the value, the faster the penetration rate. Pore ​​diameter rp Main factors of capillary effect The smaller the size, the stronger the capillary effect. Substrate roughness Ra Affects the actual contact area Hydrophilic surfaces enhance wetting, while hydrophobic surfaces reduce wetting. Ambient temperature T Affects viscosity and surface tension As the temperature increases, the viscosity decreases and the wetting increases

[0070] In order to unify the adhesive penetration performance under different experimental conditions, the dimensionless wetting penetration index can be introduced as a quantitative analysis model of the adhesive penetration effect to unify the analysis standard.

[0071] The dimensionless wetting penetration index is expressed by the P value:

[0072]

[0073] Among them, P reflects the penetration ability of the adhesive on the substrate.

[0074] Experimental method: Measure θ, η, rp, and γL to determine P.

[0075] This patent can be used to select suitable adhesives, optimize coating formulations, and evaluate the compatibility of different substrates through analysis of P values.

[0076] In order to further illustrate the advantages of this patent, contact angle detection tests are conducted on different types of adhesives and different substrates.

[0077] 1. Experimental equipment:

[0078] Contact Angle Meter: A high-precision instrument used to measure the contact angle between the adhesive and the surface of the material to be tested. It can quickly and accurately measure the contact angle of the droplet on the solid surface and record the contact angle change data.

[0079] Computer and data analysis software: used to record contact angle change data and draw contact angle change curves. The computer system records and analyzes the data of contact angle changes over time, generates change curves, and analyzes the penetration effect of the adhesive based on the curve characteristics.

[0080] 2. Experimental materials:

[0081] Adhesive materials to be tested (paper, wood and composites).

[0082] 3. Experimental steps:

[0083] Prepare the experimental setup: Install a high-precision contact angle meter and ensure that the instrument is calibrated and functions properly to ensure the accuracy and real-time nature of the measurement, which is the basis of the entire method.

[0084] Add adhesive dropwise: Add the adhesive dropwise onto the clean surface of the substrate to be tested to form droplets. This step ensures the uniformity and consistency of the adhesive droplets. Use a titration device to ensure the accuracy of the adhesive dosage.

[0085] Measure the initial contact angle: After the adhesive is added, use a contact angle meter to immediately measure the initial contact angle between the adhesive droplet and the surface of the material to be tested, and record the contact angle value at this time (time t0).

[0086] Dynamic monitoring: At fixed time intervals (e.g., every second) after the adhesive is added, a contact angle meter is used to continuously monitor the change in contact angle. The contact angle value at each time point (t1, t2, t3...tn) is recorded. This is the data on the change in contact angle over time. Continuously measuring the change in contact angle reflects the penetration process of the adhesive in real time.

[0087] Data recording and analysis: Use a computer and data analysis software to ensure efficient and accurate data processing. Import the measured contact angle data into the computer system, record the contact angle, and save it through the data recording module. Plot a graph of the contact angle change over time and analyze the relationship between the contact angle change trend and the adhesive penetration effect. Taking the time point numbered t1 at the first second after the adhesive is added and the time point numbered t2 at the second second as an example, the contact angle decay rate is calculated according to the following formula (1):

[0088] k (s-1)=(㏑θ1-㏑θ2) / (t2-t1) (1)

[0089] According to the contact angle value at each time point, the overall average contact angle change rate, contact angle change value, contact angle decay rate and contact angle half-life were calculated.

[0090] The classification results of adhesive penetration effect evaluation are shown in Table 2.

[0091] Table 2: Adhesive penetration effect evaluation classification table

[0092]

[0093]

[0094] Contact angle curve: Record and plot the contact angle over time to observe the trend of contact angle changes. If the adhesive penetrates well, the contact angle will gradually decrease, indicating that the adhesive has penetrated the material surface. If the contact angle changes slightly, it indicates that the adhesive has not penetrated effectively.

[0095] Quantification of penetration effect: The penetration effect of the adhesive can be quantitatively evaluated by the rate of change and final value of the contact angle.

[0096] Penetration Effect Evaluation: Evaluate the adhesive's penetration effect based on the contact angle change curve and its analysis results. On porous materials (such as paper), penetration is often manifested as a slow change in contact angle, resulting in medium or slow penetration. On non-porous or low-absorbency materials, the contact angle changes more rapidly, and rapid penetration may more directly reflect the penetration effect.

[0097] Through this method, the penetration effect of adhesives can be evaluated quickly and accurately, providing important experimental basis for the research and development and application of adhesives.

[0098] Contact angle reduction rate: If the contact angle decreases rapidly, it means that the adhesive has strong permeability and can quickly penetrate the material surface.

[0099] Final contact angle (i.e. stable contact angle): If the contact angle becomes stable and low after a certain period of time, it means that the adhesive has fully penetrated into the material surface.

[0100] Differences between different materials: Different materials have different surface energies, and the penetration effect of adhesives on the surfaces of different materials may also be different. The adaptability of the adhesive can be judged by comparing the changes in contact angles on different materials.

[0101] Assuming that the contact angle θ changes with time t, the rate of change of the contact angle is: rate = dθ / dt.

[0102] In actual experiments, the expansion process of the adhesive droplet can be continuously filmed, the contact angle values ​​at different time points can be recorded, and the contact angle change rate can be calculated using numerical methods (such as numerical differentiation).

[0103] Influence of adhesive properties on penetration effect: By analyzing the changes in contact angles of different types of adhesives, the penetration performance of different adhesives can be evaluated, thereby selecting the most suitable adhesive type.

[0104] 4. Experimental results:

[0105] Adhesives with different viscosities, curing times, and chemical compositions can be effectively evaluated, showing a wide range of applicability. The results are shown in Table 3.

[0106] Table 3: Penetration effects of different types of adhesives

[0107]

[0108]

[0109] Through the above experiments, it can be seen that the contact angle change method can effectively evaluate the penetration effect of different adhesives on different substrates:

[0110] Adhesive A is suitable for paper, has good wettability and permeability, and has a faster contact angle change rate.

[0111] Adhesive B is suitable for wood, has poor permeability, and has a slower rate of contact angle change.

[0112] C adhesive is suitable for composite materials, mainly provides strong adhesion rather than permeability, and the contact angle changes slowly.

[0113] This patent can obtain a large amount of data in a short time through dynamic contact angle measurement, quickly complete the penetration effect evaluation, and improve the detection efficiency. The automatic data processing and analysis of the computer system avoids the tediousness and errors of manual operation, further improving the efficiency. The contact angle change curve can reflect the penetration process of the adhesive in detail, such as Figure 1As shown, the various stages including initial wetting, spreading and penetration are included to provide accurate characterization of the penetration effect.

[0114] Incipient Wetting: The contact angle decreases rapidly, indicating that the droplet begins to wet the surface.

[0115] Extension stage: The contact angle continues to decrease and the extension gradually slows down, indicating that the droplet is extending on the surface.

[0116] Penetration stage: The contact angle changes slowly and tends to be stable, indicating that the adhesive may begin to penetrate into the material.

[0117] Taking the medium penetration effect as an example, a curve diagram of the contact angle changing with time is provided, such as Figure 2 As shown, the time period 0-T1 represents the initial wetting phase of adhesive penetration, the time period T1-T2 represents the expansion phase of adhesive penetration, and the time period T2-stable contact angle represents the penetration phase of adhesive penetration. This patent can calculate key parameters such as the rate of contact angle change, providing a quantitative basis for adhesive performance evaluation. A rapidly changing contact angle generally indicates rapid wetting and expansion of the adhesive on the surface, indicating good adhesion and permeability. This method is applicable to various types of adhesives and substrates of different materials, whether metal, plastic, wood, or composite materials, and can be used to evaluate penetration effects.

[0118] The high-precision contact angle measuring instrument and computer system data processing capabilities ensure the reliability of measurement and analysis. Dynamic monitoring and continuous data recording avoid measurement errors caused by accidental factors and improve the reliability of evaluation results.

[0119] This patent is a method for characterizing the penetration effect of adhesives based on contact angle change detection. Through a high-precision contact angle measuring instrument and a computer system, it achieves a simple, efficient and accurate penetration effect evaluation, overcomes the shortcomings of existing technologies, and has significant technical advantages and broad application prospects.

[0120] The terms and expressions used herein are for descriptive purposes only, and this patent should not be limited to these terms and expressions. The use of these terms and expressions does not exclude any equivalent features of the illustrations and descriptions (or portions thereof), and it should be recognized that various modifications that may exist should also be included within the scope of the claims. Other modifications, variations, and substitutions are also possible. Accordingly, the claims should be deemed to cover all such equivalents.

[0121] Similarly, it should be pointed out that although this patent has been described with reference to the current specific embodiments, ordinary technicians in this technical field should realize that the above embodiments are only used to illustrate this patent, and various equivalent changes or substitutions can be made without departing from the spirit of this patent. Therefore, as long as the changes and modifications to the above embodiments are within the scope of the essential spirit of this patent, they will fall within the scope of the claims of this patent.

Claims

1. A method for evaluating the penetration effect of an adhesive based on the contact angle, characterized in that, It includes the following steps: Step A: Drop the adhesive onto the surface of a clean substrate to form a droplet; Step B: Immediately measure the initial contact angle value between the droplet and the surface of the material to be tested using a contact angle measuring instrument; Step C: Continuously monitor the change of the contact angle within a fixed time interval after the adhesive is dropped using the contact angle measuring instrument, and record the contact angle value at each time point; Step D: Import the contact angle values recorded in Step C into a computer system, and calculate the contact angle decay rate k (s-1) within the fixed time interval according to the following formula (1): k(s - 1) = (lnθ n - lnθ n+1 ) / (t n+1 - t n ) (1) where n is the time number marked at each of the fixed time intervals starting from the initial contact angle value, and n is a consecutive integer in ascending order; θ n is the contact angle value measured at the nth fixed time interval after the adhesive is dropped; Step F: Evaluate the penetration effect of the adhesive by calculating the average contact angle decay rate. The penetration effect includes rapid penetration, medium penetration, and slow penetration. The contact angle decay rate of the rapid penetration is greater than 0.

1. The contact angle decay rate of the medium penetration is greater than 0.01 and less than or equal to 0.

1. The contact angle decay rate of the slow penetration is less than or equal to 0.

01.

2. The method for evaluating the penetration effect of an adhesive based on the contact angle according to claim 1, wherein The contact angle half-life of the rapid penetration is less than 7 s; The contact angle half-life of the medium penetration is greater than or equal to 7 s and less than 70 s; The contact angle half-life of the slow penetration is greater than 70 s.

3. The method for evaluating the penetration effect of an adhesive based on the contact angle according to claim 1, wherein In Step D, it also includes calculating the contact angle change rate V according to the following formula (2): V = dθ / dt (2) where θ is the contact angle change value between the initial contact angle value and the stable contact angle value, and t is the time between the initial contact angle value and the stable contact angle value. The contact angle change rate of the rapid penetration is greater than 5.0° / s; The contact angle change rate of the medium penetration is greater than 0.9° / s and less than or equal to 5.0° / s; The contact angle change rate of the slow penetration is less than or equal to 0.9° / s.

4. The method for evaluating the penetration effect of an adhesive based on the contact angle according to claim 3, characterized in that, Step D also includes: Draw a contact angle change curve based on the contact angle values measured at each time point between the initial contact angle value and the stable contact angle value to judge the penetration process, and the penetration process includes initial wetting, spreading stage, and penetration stage.

5. The method for evaluating the penetration effect of an adhesive based on the contact angle according to claim 4, wherein The initial contact angle value to the stable contact angle value successively experiences the initial wetting, the spreading stage, and the penetration stage. The contact angle change rate in the initial wetting stage is greater than the contact angle change rate in the spreading stage, and the contact angle change rate in the spreading stage is greater than the contact angle change rate in the penetration stage.

6. The method for evaluating the penetration effect of an adhesive based on the contact angle according to claim 1, characterized in that, It also includes Step E: Step E: Calculate the penetration ability P of the adhesive on the substrate according to the measured contact angle value according to the following formula (3): where θ is the contact angle change value between the initial contact angle value and the stable contact angle value, γL is the surface tension of the adhesive, η is the viscosity of the adhesive, rp is the pore diameter, and Ra is the substrate roughness. The penetration ability P of the rapid penetration is > 0.

008. The penetration ability of the medium penetration is 0.002 < P ≤ 0.

008. The penetration ability of the slow penetration is P ≤ 0.

002.

7. A method for screening adhesives suitable for wood materials, characterized in that, According to the method for evaluating the penetration effect of an adhesive based on the contact angle described in any one of claims 1 to 6, select the adhesive with the penetration effect being the slow penetration or the medium penetration.

8. A method for screening adhesives suitable for composite materials, characterized in that, According to the method for evaluating the penetration effect of an adhesive based on the contact angle described in any one of claims 1 to 6, select the adhesive with the penetration effect being the slow penetration.

9. A method for screening adhesives applicable to paper substrates, characterized in that, According to the method for evaluating the penetration effect of an adhesive based on the contact angle described in any one of claims 1 to 6, select the adhesive with the penetration effect being the medium penetration.

10. A method for screening adhesives suitable for non-porous or low water-absorbing substrates, characterized in that, According to the method for evaluating the penetration effect of an adhesive based on the contact angle described in any one of claims 1 to 6, select the adhesive with the penetration effect being the fast penetration.

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