A method for evaluating adhesive penetration based on contact angle

Abstract

This patent discloses a method for evaluating the penetration effect of adhesives based on contact angle. The method assesses the penetration effect by measuring the average contact angle decay rate, which is categorized as rapid penetration, moderate penetration, and slow penetration. Rapid penetration is characterized by a contact angle decay rate greater than 0.1, moderate penetration by a contact angle decay rate greater than 0.01 and less than or equal to 0.1, and slow penetration by a contact angle decay rate less than or equal to 0.01. This patent eliminates the need for complex microscopic observation or weight measurement. The method utilizes a contact angle measuring instrument to continuously monitor changes in the contact angle after the adhesive is dropped onto the material surface, and quickly determines the adhesive penetration effect through data analysis. This method is simple, efficient, and accurate.

Description

Technical Field

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

[0002] Adhesives have wide applications in modern industrial manufacturing, and their performance directly affects the quality and durability of products. Accurately assessing the penetration properties of adhesives is crucial to ensuring they perform optimally in practical applications.

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

[0004] Microscopic observation is the method of observing the penetration of adhesives into the interior of materials using a microscope. This method can directly see the penetration depth and distribution of adhesives, but it requires a high-magnification microscope and professional technicians. It is highly demanding in terms of technical expertise, and the operation is relatively complex, requiring observation of each sample individually. This method is both time-consuming and inefficient, and can only observe 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. Furthermore, it can only provide an overall penetration amount and cannot provide details of the penetration process.

[0006] Due to the aforementioned drawbacks of microscopic observation and gravimetric methods, there is a need for a simpler, more efficient, and more accurate method for detecting adhesive penetration. 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, thereby simplifying the existing complex and time-consuming testing process and improving the accuracy and efficiency of testing.

[0008] To solve the above-mentioned technical problems, this patent adopts the following technical solution: A method for evaluating adhesive penetration based on contact angle includes the following steps: Step A: Apply the adhesive to a clean substrate surface to form droplets; Step B: Immediately measure the initial contact angle between the droplet and the surface of the material to be tested using a contact angle meter; Step C: At fixed time intervals after the adhesive is applied, continuously monitor the changes in the contact angle using a contact angle measuring instrument and record the contact angle value at each time point; Step D: Import the contact angle value recorded in step C into the computer system, and calculate the contact angle decay rate k within a fixed time interval according to the following formula (1).(s-1) : k (s-1) =(lnθ) n -㏑θ n+1 ) / (t n+1 -t n (1) Where n is the time number marked at each fixed time interval starting from the initial contact angle value, and n is a consecutive integer in ascending order; θ n The contact angle value is measured at the nth fixed time interval after the adhesive is applied. Step F: Evaluate the adhesive's penetration effect by calculating the average contact angle decay rate, which includes fast penetration, medium penetration, and slow penetration. The contact angle decay rate of rapid penetration is greater than 0.1. For medium penetration, the contact angle decay rate is greater than 0.01, and the contact angle decay rate is less than or equal to 0.1. The contact angle decay rate of slow penetration is less than or equal to 0.01.

[0009] Furthermore, the contact angle half-life of rapid penetration is less than 7 s; The contact angle half-life of moderate penetration is greater than or equal to 7 s and less than 70 s; The contact angle half-life of slow penetration is greater than 70 s.

[0010] Furthermore, step D also includes calculating the contact angle change rate V according to the following formula (2): V=dθ / dt (2) Where θ is the change in contact angle from the initial contact angle value to the stable contact angle value, and t is the time from the initial contact angle value to the stable contact angle value. The contact angle change rate of rapid penetration is greater than 5.0 ° / s; The contact angle change rate for moderate penetration is greater than 0.9 ° / s and less than or equal to 5.0 ° / s; The contact angle change rate of slow penetration is less than or equal to 0.9 ° / s.

[0011] Furthermore, step D also includes: A contact angle change curve is plotted based on the contact angle values ​​measured at each time point between the initial contact angle value and the stable contact angle value, in order to determine the penetration process, which includes the initial wetting, spreading, and penetration stages.

[0012] Furthermore, the transition from the initial contact angle value to the stable contact angle value sequentially involves the initial wetting, spreading, and penetration stages. The rate of change of the contact angle during the initial wetting stage is greater than that during the spreading stage, and the rate of change of the contact angle during the spreading stage is greater than that during the penetration stage.

[0013] Furthermore, it also includes step E: 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): (3) Where θ is the change in contact angle from the initial contact angle value to the stable contact angle value, and γ L η is the surface tension of the adhesive, η is the viscosity of the adhesive, and r is the surface tension of the adhesive. p Where is the pore diameter and Ra is the substrate roughness.

[0014] Furthermore, the permeability of rapid infiltration is P > 0.008, the permeability of medium infiltration is 0.002 < P ≤ 0.008, and the permeability of slow infiltration is P ≤ 0.002.

[0015] This patent classifies the penetration characteristics of adhesives with unknown properties by detecting and calculating the overall average contact angle decay rate, half-life, penetration capacity P, and contact angle change rate, and further quickly matches them to applicable materials based on the classification. The applicable materials include wood materials, composite materials, paper substrates, or non-porous or low-absorbency substrates.

[0016] This patent further claims a method for screening adhesives suitable for wood materials, wherein adhesives with slow or medium penetration effects are screened according to any of the above-described methods for evaluating the penetration effect of adhesives based on contact angle, and such adhesives are suitable for wood materials (hereinafter referred to as wood).

[0017] Wood, as a natural material, possesses unique surface energy and pore structure characteristics that 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 low surface energy, usually between 30-50 mN / m. Lower surface energy means poor wettability, thus requiring adhesives with higher surface tension for better penetration and bonding. When selecting adhesives, it's necessary to choose those with higher surface tension or use appropriate surface treatment techniques (such as plasma treatment or flame treatment) to improve the affinity of the wood surface. The porosity and structure of wood vary depending on the species, generally ranging from 10% to 80%. This pore structure makes wood highly hygroscopic, especially on softwoods, where adhesives may penetrate rapidly, but excessive penetration can lead to reduced bond strength. Therefore, when selecting adhesives, it's necessary to evaluate the wood's pore structure and hygroscopicity to determine the appropriate adhesive type (such as water-based or solvent-based adhesives). The surface roughness of wood varies depending on the type of wood and the processing method. A rough surface may allow adhesives to be more trapped on the surface, increasing adhesive strength, but it may also limit penetration. Surface polishing or treatment can help control the penetration depth. Wood is highly hygroscopic; in high humidity, the surface energy of the wood may change, affecting the penetration of adhesives. When using adhesives in high-humidity environments, it is necessary to choose adhesives with strong moisture resistance to prevent the moisture on the wood surface from adversely affecting the adhesive performance. Wood is used relatively less in the tobacco industry, but there are some specific uses, especially as part of the material or in certain manufacturing processes, such as in cigarette boxes and packaging materials, cigarette filters, and wooden pipes. Wood is used in the exterior materials of some cigarette boxes or packaging boxes, especially in high-end custom cigarette boxes, where the unique texture and premium feel of wood are selling points. Adhesives used in this application need to have rapid penetration and good weather resistance. Wood may be used as part of filter rod components; although it is not used directly as a filter material, it is sometimes used as a structural component in complex filtration systems. Such applications require adhesives that can bond firmly to the wood surface while ensuring that filtration performance is not compromised. In traditional pipe manufacturing, wood is the primary material, and adhesives are used during the manufacturing process to connect different parts of the wood, ensuring the pipe's structural stability.

[0018] Adhesives suitable 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 crafts making. Hot melt adhesives cure quickly, providing strong adhesion.

[0019] This patent further claims a method for screening adhesives suitable for composite materials. Based on any of the aforementioned methods for evaluating adhesive penetration based on contact angle, adhesives with slow penetration are screened; these adhesives are then suitable for composite materials. Composite materials have low porosity and limited permeability, thus requiring slow-penetrating adhesives. Applications of composite materials in the tobacco industry include filter materials, high-barrier cigarette packaging, and other similar applications. Filter materials: multi-layered composite structures require slow adhesive penetration to ensure interlayer bonding without affecting air permeability. High-barrier cigarette packaging: some cigarette boxes use composite materials (such as aluminum foil / plastic / paper composite structures); adhesives require slow penetration to ensure interlayer stability without damaging the material structure.

[0020] This patent further claims a method for screening adhesives suitable for paper-based substrates. Based on any of the aforementioned methods for evaluating adhesive penetration based on contact angle, adhesives with moderate penetration are screened; these adhesives are then considered suitable for paper-based substrates. Paper-based substrates, i.e., paper, have a certain degree of absorbency, but moderate penetration is required to ensure adhesion without excessive absorption. Applications of paper-based substrates in the tobacco industry include cigarette paper, filter rod wrapping paper, or tobacco packaging paper. Cigarette paper: To control the burning rate, the adhesive needs moderate penetration to enhance the paper's mechanical strength without affecting its combustion performance. Filter rod wrapping paper: The outer wrapping paper needs moderate penetration to ensure stability without affecting air permeability. Tobacco packaging paper: Suitable for cigarette packaging, it provides stable adhesion without excessive penetration to avoid bleed-through or affecting print quality.

[0021] This patent further claims a method for screening adhesives suitable for non-porous or low-absorbency substrates, screening adhesives with rapid penetration based on the contact angle-based method described above. Non-porous or low-absorbency substrates (such as glass, plastic, and metal) have low surface energy, requiring adhesives to wet and penetrate quickly. Applications of low-absorbency materials in the tobacco industry include cigarette case packaging, e-cigarette casings, and inkjet coatings. Cigarette case packaging: Using a transparent plastic sealing film (BOPP film) to package cigarettes requires adhesives with high wettability and rapid penetration. E-cigarette casings: Bonding plastic or metal casing structures requires rapid penetration to provide adhesive strength. Inkjet coatings: For inkjet printing of production dates and other markings, the wetting properties of the adhesive or ink determine the adhesion effect.

[0022] In this patent, the term "contact angle" refers to the angle at which a droplet forms on a solid surface, and is used to measure the wettability of a liquid on a solid.

[0023] In this patent, the term "wetting property" refers to the degree to which a liquid spreads on a solid surface, and is a characterizing indicator of the interaction between a liquid and a solid.

[0024] In this patent, the term "permeable" refers to the ability of a liquid to pass through the pores or tiny channels of a solid material.

[0025] In this patent, the term "dynamic contact angle" refers to the contact angle of a droplet on a solid surface that changes over time, and is used to analyze the permeation behavior of the liquid.

[0026] To simplify operation and improve testing efficiency, this patent proposes a method for evaluating adhesive penetration based on changes in contact angle. This method eliminates the need for complex microscopic observation or weight measurement. Utilizing a contact angle meter, it continuously monitors changes in the contact angle after the adhesive is dropped onto the material surface and quickly determines the adhesive penetration effect through data analysis. This method is simple, efficient, and accurate, and can be used to detect the penetration effect of adhesives on different material surfaces. By providing a contact angle change-based detection technique, this patent not only simplifies the testing process and improves testing efficiency but also enhances the accurate characterization of adhesive penetration effects, providing significant technical protection. It allows for better evaluation and selection of adhesives, improving their practical application performance and durability.

[0027] This patent achieves the following technical effects: Simple operation: No complicated microscopic observation or weight measurement is required. Simply add adhesive and measure the change in contact angle.

[0028] High-efficiency detection: Capable of completing detection in a short time, providing real-time information on adhesive penetration. The high-precision contact angle meter accurately measures the contact angle of droplets on solid surfaces, providing a reliable data foundation. It also enables dynamic measurement, recording contact angle changes in real time to reflect real-time information about the adhesive penetration process.

[0029] Precise Characterization: The contact angle variation curve provides a detailed reflection of the penetration process, offering a more accurate assessment of penetration effectiveness through a 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 variation curves and related parameters. The penetration effectiveness assessment module evaluates the adhesive's penetration effect through analysis of the contact angle variation curve, providing a scientific basis for adhesive performance evaluation.

[0030] Widely applicable: Suitable for evaluating penetration effects between various types of adhesives and different substrate materials. Attached Figure Description

[0031] The above content of this patent and the following detailed embodiments will be better understood when read in conjunction with the accompanying drawings. It should be noted that the drawings are merely examples of the claimed technical solution.

[0032] Figure 1This is a schematic diagram of the contact angle penetration process of this patent; Figure 2 This is a schematic diagram showing the change of the contact angle over time for moderate penetration according to this patent. Detailed Implementation

[0033] The detailed features and advantages of this patent are described below in the specific embodiments. The content is sufficient to enable any person skilled in the art to understand the technical content of this patent and implement it accordingly. Based on the specification, claims and drawings disclosed in this specification, a person skilled in the art can easily understand the related objectives and advantages of this patent.

[0034] Prior to this patent, some technologies had attempted to assess the wettability and permeability of liquids by measuring changes in contact angle.

[0035] Dynamic contact angle measurement: Some studies employ dynamic contact angle measurement technology to analyze the wetting properties of liquids by recording changes in the contact angle during the expansion or contraction of droplets on solid surfaces. While dynamic contact angle measurement can provide some information about the droplet expansion process, its application in assessing adhesive penetration is limited due to the high viscosity of adhesives, particularly in evaluating deep penetration. This is because the contact angle only reflects surface wetting and cannot reveal the adhesive's penetration behavior, penetration depth, or the influence of pore structure within the material. Furthermore, changes in the contact angle are often rapid, failing to accurately capture the deep expansion of adhesives during long-term penetration. Therefore, a comprehensive analysis combining other techniques (such as microscopic imaging and X-ray imaging) is necessary.

[0036] Static contact angle measurement: Another part of the research focuses on measuring the static contact angle, which assesses the wettability of a liquid by measuring the contact angle of a droplet when it reaches equilibrium. However, this only provides initial wettability information and cannot reflect the penetration process over time, making it insufficiently accurate for evaluating the penetration performance of adhesives.

[0037] Analysis of existing technical solutions reveals limitations in evaluating adhesive penetration. This patent proposes a method for characterizing adhesive penetration based on contact angle change detection. By continuously monitoring the change in contact angle over time, it provides a simple, efficient, and accurate means of evaluating penetration. This method not only overcomes the shortcomings of microscopic observation and gravimetric methods but also fills a gap in existing contact angle measurement techniques for penetration evaluation, possessing significant practical application value.

[0038] The basic characteristics of adhesives: Adhesives penetrate into the micropores or capillaries of the substrate to form a strong bond. The penetration effect depends on various factors such as the viscosity of the adhesive, the pore structure of the substrate, and surface energy.

[0039] The viscosity of an adhesive determines its ease of flow. Higher viscosity generally results in slower spread of the adhesive on the paper surface, a more gradual change in the contact angle, and potentially poorer penetration. Conversely, lower viscosity adhesives spread more easily on the paper surface, with a rapid decrease in the contact angle, potentially exhibiting better penetration. The pore structure of the paper (porosity, pore size distribution, etc.) directly affects the spread and penetration of the adhesive on the paper surface. Paper with higher porosity typically exhibits higher penetration because the adhesive can more easily penetrate into the material's interior, causing the contact angle to decrease rapidly. Paper with smaller pore sizes may result in the adhesive being unable to penetrate the pores deeply, leading to a slower or smaller change in the contact angle.

[0040] 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) better, resulting in a smaller contact angle and better penetration. Conversely, paper with low surface energy may result in adhesives not penetrating well, having a larger contact angle and poorer penetration.

[0041] Good penetration enhances the adhesion between the adhesive and the substrate, improving bond strength and durability. Insufficient penetration can lead to problems such as weak adhesion and easy peeling, affecting product quality.

[0042] This patent reflects the wettability of a liquid on a solid surface by detecting the contact angle formed by a droplet on the surface. A high-precision contact angle measuring instrument can quickly and accurately measure changes in the contact angle of a droplet, making it an effective tool for evaluating the behavior of liquids on solid surfaces. Furthermore, the penetration ability of adhesives on substrates can be comprehensively evaluated using Table 1.

[0043] Table 1: Evaluation Table of Factors Affecting the Penetration Ability of Adhesives on Substrates

[0044] To standardize the penetration performance of adhesives under different experimental conditions, a dimensionless wetting and penetration index can be introduced as a quantitative analysis model for the penetration effect of adhesives to unify the analysis standard.

[0045] The dimensionless wetting and permeability index is represented by the P-value:

[0046] P reflects the adhesive's ability to penetrate the substrate.

[0047] Experimental method: Measurement of θ, η, r p γ L To find P.

[0048] This patent, through the analysis of P-values, can be used to select suitable adhesives, optimize coating formulations, and evaluate the compatibility with different substrates.

[0049] To further illustrate the advantages of this patent, contact angle testing was conducted on different types of adhesives and different substrates.

[0050] 1. Experimental equipment: Contact angle meter: A high-precision instrument used to measure the contact angle between an adhesive and the surface of a material to be tested. It can quickly and accurately measure the contact angle of a droplet on a solid surface and record the contact angle change data.

[0051] Computer and data analysis software: used to record contact angle change data and plot 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 adhesives based on the curve characteristics.

[0052] 2. Experimental materials: Adhesives tested on materials (paper, wood, and composites).

[0053] 3. Experimental steps: Prepare the experimental setup: Install a high-precision contact angle measuring instrument, ensuring that the instrument is calibrated and functioning properly. Ensuring the accuracy and real-time nature of the measurement is the foundation of the entire method.

[0054] Adding adhesive: The adhesive is added dropwise to the clean surface of the substrate to be tested, forming droplets. This step ensures the uniformity and consistency of the adhesive droplets, and a titration device is used to ensure the accuracy of the adhesive dosage.

[0055] Measure the initial contact angle: After the adhesive is added, immediately measure the initial contact angle between the adhesive droplet and the surface of the material to be tested using a contact angle meter, and record the contact angle value at this time (t0).

[0056] Dynamic monitoring: At fixed time intervals (e.g., every second) after the adhesive is added, the change in contact angle is continuously monitored using a contact angle meter, and the contact angle value at each time point (t1, t2, t3...tn) is recorded. This data represents the change in contact angle over time. Continuous measurement of the change in contact angle reflects the real-time penetration process of the adhesive.

[0057] Data Recording and Analysis: Using computers and data analysis software, the efficiency and accuracy of data processing are ensured. The measured contact angle data are imported into the computer system, the contact angle is recorded, and it is saved through the data recording module. A curve of the contact angle changing over time is plotted to analyze the relationship between the trend of contact angle change and the penetration effect of the adhesive. Taking the first second time point t1 and the second second time point t2 after the adhesive is added as examples, the contact angle decay rate is calculated according to the following formula (1): k (s-1) =(㏑θ1-㏑θ2) / (t2-t1) (1) Based on 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 are calculated.

[0058] The results of the adhesive penetration effect assessment are shown in Table 2.

[0059] Table 2: Classification Table for Adhesive Penetration Effect Evaluation

[0060] Contact angle variation curve: Record and plot the contact angle change over time to observe the trend. If the adhesive penetration is good, the contact angle will gradually decrease, indicating that the adhesive has penetrated to the material surface. If the contact angle change is small, it indicates that the adhesive penetration is poor and has failed to penetrate effectively.

[0061] Quantitative Penetration Effect: The penetration effect of adhesives can be quantitatively evaluated by the rate of change and final value of the contact angle.

[0062] Penetration effect assessment: The penetration effect of the adhesive is evaluated based on the contact angle change curve and its analysis results. In porous materials (such as paper), penetration is often manifested as a slow change in contact angle, and the penetration effect is moderate or slow penetration. In non-porous or low-absorbency materials, the contact angle changes more quickly, and rapid penetration may more directly reflect the penetration effect.

[0063] This method allows for the rapid and accurate evaluation of adhesive penetration, providing important experimental evidence for the research and application of adhesives.

[0064] Contact angle reduction rate: If the contact angle decreases rapidly, it indicates that the adhesive has strong permeability and can quickly penetrate into the material surface.

[0065] Final contact angle (i.e. stable contact angle): If the contact angle tends to stabilize and become low after a certain period of time, it indicates that the adhesive has fully penetrated the material surface.

[0066] Differences between different materials: Different materials have different surface energies, and the penetration effect of adhesives on the surfaces of different materials may also vary. The suitability of an adhesive can be judged by comparing the changes in contact angle on different materials.

[0067] Assume that the contact angle θ changes with time t, and the rate of change of the contact angle is: rate = dθ / dt.

[0068] In actual experiments, the contact angle value at different time points can be recorded by continuously photographing the expansion process of adhesive droplets, and the rate of change of the contact angle can be calculated using numerical methods (such as numerical differentiation).

[0069] The influence of adhesive properties on penetration effect: By analyzing the contact angle changes of different types of adhesives, the penetration performance of different adhesives can be evaluated, thereby selecting the most suitable type of adhesive.

[0070] 4. Experimental Results: It can effectively evaluate adhesives with different viscosities, curing times, and chemical compositions, and has wide applicability. The results are shown in Table 3.

[0071] Table 3: Penetration Effect of Different Types of Adhesives

[0072] The above experiments demonstrate that the contact angle variation method can effectively evaluate the penetration effect of different adhesives on different substrates. Adhesive A is suitable for paper, has good wettability and penetration, and a fast rate of contact angle change.

[0073] B-type adhesives are suitable for wood, but have poor penetration and a slow rate of change in contact angle.

[0074] C-type adhesives are suitable for composite materials, primarily providing strong adhesion rather than penetration, and exhibiting a slower change in contact angle.

[0075] This patent utilizes dynamic contact angle measurement to acquire a large amount of data in a short time, enabling rapid assessment of penetration effectiveness and improving testing efficiency. The automated data processing and analysis by the computer system avoids the tediousness and errors of manual operation, further enhancing efficiency. The contact angle variation curve can provide a detailed reflection of the adhesive penetration process, such as... Figure 1 As shown, it includes various stages such as initial wetting, spreading and penetration, providing accurate characterization of penetration effect.

[0076] Initial wetting: The contact angle decreases rapidly, indicating that the droplet has begun to wet the surface.

[0077] Expansion phase: The contact angle continues to decrease, and the expansion gradually slows down, indicating that the droplet is expanding on the surface.

[0078] Penetration stage: The contact angle changes slowly and tends to stabilize, indicating that the adhesive may begin to penetrate into the material.

[0079] Taking moderate penetration as an example, a schematic diagram of the contact angle changing over time is provided, such as... Figure 2As shown, the time period from 0 to T1 represents the initial wetting stage of adhesive penetration, the time period from T1 to T2 represents the expansion stage of adhesive penetration, and the time period from T2 to the stable contact angle represents the penetration stage of adhesive penetration. This patent can calculate key parameters such as the rate of change of the contact angle, providing a quantitative basis for evaluating adhesive performance. A rapidly changing contact angle usually indicates rapid wetting and expansion of the adhesive on the surface, indicating good adhesion and penetration. It is applicable to various types of adhesives and different substrate materials, whether metal, plastic, wood, or composite materials, and can be used to evaluate penetration effects.

[0080] The high-precision contact angle measuring instrument and the data processing capabilities of the computer system ensure the reliability of measurement and analysis. Dynamic monitoring and continuous data recording avoid measurement errors caused by accidental factors, thus improving the reliability of the evaluation results.

[0081] This patented method for characterizing adhesive penetration based on contact angle change detection achieves a simple, efficient, and accurate assessment of penetration effect through a high-precision contact angle measuring instrument and a computer system. It overcomes the shortcomings of existing technologies and has significant technical advantages and broad application prospects.

[0082] The terminology 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 imply the exclusion of any illustrative and descriptive equivalent features (or parts thereof), and it should be recognized that various possible modifications should also be included within the scope of the claims. Other modifications, variations, and substitutions may also exist. Accordingly, the claims should be considered to cover all such equivalents.

[0083] Similarly, it should be noted that although this patent has been described with reference to the specific embodiments described above, those skilled in the art should recognize 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, any changes or modifications to the above embodiments within the essential spirit of this patent will fall within the scope of the claims of this patent.

Claims

1. A method for evaluating the penetration effect of adhesives based on contact angle, characterized in that, Includes the following steps: Step A: Apply the adhesive to a clean substrate surface to form droplets; Step B: Immediately measure the initial contact angle between the droplet and the surface of the material to be tested using a contact angle measuring instrument; Step C: Within a fixed time interval after the adhesive is applied, continuously monitor the change in the contact angle using the contact angle measuring instrument and record the contact angle value at each time point; Step D: Import the contact angle value recorded in step C into the computer system, and calculate the contact angle decay rate k within a fixed time interval according to the following formula (1). (s-1) : k (s-1) =(㏑θ n -㏑θ n+1 ) / (t n+1 -t n ) (1) Wherein, n is the time number marked at each fixed time interval starting from the initial contact angle value, and n is a consecutive integer in ascending order; θ n The contact angle value is measured at the nth fixed time interval after the adhesive is applied; Step F: Evaluate the penetration effect of the adhesive by calculating the average contact angle decay rate, which includes rapid penetration, moderate 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-permeability medium is greater than 0.01, and the contact angle decay rate is less than or equal to 0.

1. The contact angle decay rate of the slow penetration is less than or equal to 0.01; 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): （3） Where θ is the change in contact angle between the initial contact angle value and the stable contact angle value, and γ L η is the surface tension of the adhesive, and r is the viscosity of the adhesive. p Where is the pore diameter and Ra is the substrate roughness; The permeability P of the rapid penetration is greater than 0.

008. The term "medium permeability" refers to a permeability capacity of 0.002 < P ≤ 0.

008. The permeability of the slow-permeability is P≤0.

002.

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

3. The method for evaluating adhesive penetration based on contact angle according to claim 1, characterized in that, Step D further includes calculating the contact angle change rate V according to the following formula (2): V=dθ / dt (2) Where θ is the change in contact angle from the initial contact angle value to the stable contact angle value, and t is the time from the initial contact angle value to 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-permeability 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 adhesive penetration based on contact angle according to claim 3, characterized in that, Step D further includes: A contact angle variation curve is plotted based on the contact angle values ​​measured at each time point between the initial contact angle value and the stable contact angle value, in order to determine the penetration process, which includes the initial wetting, the expansion stage and the penetration stage.

5. The method for evaluating adhesive penetration based on contact angle according to claim 4, characterized in that, The transition from the initial contact angle value to the stable contact angle value sequentially involves the initial wetting stage, the spreading stage, and the penetration stage. The contact angle change rate during the initial wetting stage is greater than that during the expansion stage, and the contact angle change rate during the expansion stage is greater than that during the penetration stage.

6. A method for screening adhesives suitable for wood materials, characterized in that, According to any one of claims 1 to 5, the method for evaluating the penetration effect of adhesives based on contact angle is used to screen out adhesives whose penetration effect is either slow penetration or medium penetration.

7. A method for screening adhesives suitable for composite materials, characterized in that, According to any one of claims 1 to 5, the method for evaluating the penetration effect of adhesives based on contact angle is used to screen out adhesives with the slow penetration effect.

8. A method for screening adhesives suitable for paper-based substrates, characterized in that, According to any one of claims 1 to 5, the method for evaluating the penetration effect of adhesives based on contact angle is used to screen out adhesives with the penetration effect of medium penetration.

9. A method for screening adhesives suitable for non-porous or low-absorbency substrates, characterized in that, According to any one of claims 1 to 5, the method for evaluating the penetration effect of adhesives based on contact angle is used to screen out adhesives with the rapid penetration effect.

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