Method for evaluating stability of EVA (Ethylene Vinyl Acetate) film through thermal shrinkage characteristic

Abstract

The invention discloses a method for evaluating the stability of an EVA film through thermal shrinkage characteristics, and particularly relates to the field of EVA film detection.The method comprises the steps that an EVA film sample to be detected is obtained, initial detection data are obtained based on the EVA film sample, and the initial detection data comprise a thermodynamic behavior layer and a structural evolution layer; the thermodynamic behavior level in the initial detection data comprises evaluation of the thermal shrinkage rate and the thermal shrinkage rate of the EVA film sample; a first reference condition is established based on the thermal shrinkage rate and the thermal shrinkage rate. Through initial detection reference conditions established in combination with a thermodynamic behavior level and a structural evolution level and a comprehensive evaluation model, thermal shrinkage behavior difference and stability problems caused by uneven distribution of the photo-thermal stabilizer are quantified; according to the method, the defect that the distribution influence of the photo-thermal stabilizer cannot be effectively detected in the traditional technology is overcome, and the anti-aging performance evaluation capability of the EVA film is relatively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of EVA film detection, and more particularly to a method for evaluating the stability of an EVA film through thermal shrinkage characteristics. Background Art

[0002] EVA film is made of ethylene-vinyl acetate copolymer, which has excellent flexibility, heat resistance, transparency and adhesion properties, and is widely used in photovoltaic module encapsulation, packaging materials and functional films. The light and heat stabilizer added to EVA film is an additive used to improve the light and heat resistance of the film, mainly by absorbing ultraviolet light, slowing down thermal oxidation decomposition and stabilizing the molecular chain structure, thereby extending the life of the film. In order to improve the anti-aging properties of EVA films, photothermal stabilizers are usually added. However, these additives may affect the thermal motion characteristics of the molecular chains, resulting in performance changes. Therefore, there is an urgent need for a method to evaluate the stability of EVA films through thermal shrinkage characteristics in order to detect the differences in thermal shrinkage behavior and stability evaluation deviations caused by the uneven distribution of photothermal stabilizers. Summary of the invention

[0003] In order to overcome the above-mentioned defects of the prior art, an embodiment of the present invention provides a method for evaluating the stability of EVA film through thermal shrinkage characteristics. By combining the initial inspection reference conditions established at the thermodynamic behavior level and the structural evolution level, and a comprehensive evaluation model, the thermal shrinkage behavior differences and stability problems caused by the uneven distribution of photothermal stabilizers are quantified to solve the problems raised in the above-mentioned background technology.

[0004] To achieve the above object, the present invention provides the following technical solution: a method for evaluating the stability of an EVA film by thermal shrinkage characteristics, comprising: Obtain the EVA film sample to be tested, and obtain preliminary inspection data based on the EVA film sample, the preliminary inspection data including the thermodynamic behavior level and the structural evolution level; The thermodynamic behavior level in the initial inspection data includes evaluating the thermal shrinkage rate and thermal shrinkage rate of the EVA film sample; establishing reference condition 1 based on the thermal shrinkage rate and thermal shrinkage rate; The structural evolution level in the initial inspection data includes evaluating the molecular chain crystallinity and optical transmittance of the EVA film sample; establishing reference condition 2 based on the molecular chain crystallinity and optical transmittance; If reference condition 1 or reference condition 2 is judged to be abnormal, a comprehensive evaluation model is established, otherwise the EVA film sample is judged to be normal; the comprehensive evaluation model is used to quantify the comprehensive effect of the distribution of light and heat stabilizers on the thermal shrinkage behavior and stability of the EVA film; A comprehensive evaluation value is obtained based on the comprehensive evaluation model. If the comprehensive evaluation value is greater than the comprehensive evaluation threshold, the EVA film sample is marked.

[0005] In a preferred embodiment, the reference condition 1 includes: if the thermal shrinkage rate is greater than a preset thermal shrinkage rate threshold, and the thermal shrinkage rate is greater than a preset thermal shrinkage rate threshold, then the EVA film sample is judged to be abnormal; Reference condition two includes: if the molecular chain crystallinity is less than a preset molecular chain crystallinity threshold, and the optical transmittance is less than a preset optical transmittance threshold, the EVA film sample is judged to be abnormal.

[0006] In a preferred embodiment, the comprehensive evaluation model includes evaluating the thermal shrinkage rate, thermal shrinkage rate, thermal stress concentration rate, thermal expansion coefficient, and thermal stability time in the thermodynamic behavior level; The comprehensive evaluation model includes the evaluation of molecular chain crystallinity, optical transmittance, molecular chain orientation, cross-linking distribution uniformity, and structural porosity at the structural evolution level.

[0007] In a preferred embodiment, the thermal shrinkage rate in the thermodynamic behavior level is calculated, and the thermal shrinkage rate is ; ; in is the initial reference length; Indicates at time The length of the film; is the thermal expansion correction coefficient; For time The ambient temperature at is the molecular chain shrinkage resistance coefficient; is the temperature sensitive factor; Calculate the thermal shrinkage rate in the thermodynamic behavior level and propose the thermal shrinkage rate as ; ; in For time The shrinkage rate at is the rate amplification factor of the photothermal stabilizer; is the rate temperature attenuation coefficient; is the time attenuation coefficient; Indicates the interval between two adjacent time points.

[0008] In a preferred embodiment, the molecular chain crystallinity in the structural evolution level is calculated, and the molecular chain crystallinity is proposed to be ; ; in is the scattering angle X-ray intensity at ; is the lower limit of the scattering angle of the crystalline region; is the upper limit of the scattering angle of the crystalline region; is the crystallinity correction factor; is the molecular chain arrangement irregularity coefficient; Calculate the optical transmittance in the structural evolution layer and propose the optical transmittance as ; ; in is the light intensity transmitted through the film; is the incident light intensity; is the transmittance attenuation factor; is the structural porosity; is the compensation factor of light transmittance of the light and heat stabilizer; is the temperature sensitivity coefficient of optical performance.

[0009] In a preferred embodiment, the thermal stress concentration rate in the thermodynamic behavior level is calculated, and the thermal stress concentration rate is ; ; in For time The instantaneous stress; For time The bearing area of ​​the lower film; is the peak stress during heat treatment; is the area difference of the local stress concentration area; Indicates the total duration of the film during the heat treatment process; Calculate the thermal expansion coefficient in the thermodynamic behavior level and propose the thermal expansion coefficient as ; ; in is the length change caused by thermal expansion; is the temperature change; is the molecular chain flexibility factor; is the expansion rate correction factor; is the initial length before heat treatment; Calculate the thermal stability time in the thermodynamic behavior level and propose the thermal stability time as ; ; in The time to reach a steady state; is the stabilization time rate constant; is the influence coefficient of temperature on stabilization time; is the yield stress of the film.

[0010] In a preferred embodiment, the molecular chain orientation degree in the structural evolution level is calculated, and the molecular chain orientation degree is proposed to be ; ; in Angle under polarizing microscope The light intensity at is the molecular chain orientation compensation coefficient; is the orientation temperature sensitivity coefficient; Calculate the uniformity of cross-linking degree distribution in the structural evolution level, and propose the uniformity of cross-linking degree distribution as ; ; in For the The cross-linking ratio of the region; is the correction factor for dynamic distribution of cross-linking degree; is the correlation factor between cross-linking uniformity and structural porosity; Calculate the structural porosity in the structural evolution level and propose the structural porosity ; ; in is the change in pore volume of the film before and after heat treatment; is the total volume of the film; is the porosity distribution correction factor; is the sensitivity coefficient of temperature to porosity.

[0011] In a preferred embodiment, based on the thermal shrinkage in the thermodynamic behavior , thermal shrinkage rate , thermal stress concentration rate , thermal expansion coefficient , Thermal stability time , and the molecular chain crystallinity at the structural evolution level , Optical transmittance , molecular chain orientation , uniformity of cross-linking degree distribution , structural porosity Establish a comprehensive evaluation model; obtain comprehensive evaluation values ​​based on the comprehensive evaluation model ; ; in For the The weight of the parameters; For the The value of the evaluation parameter; For the Normalization factor for each parameter; is the nonlinear adjustment factor; is the compensation factor; is the temperature sensitivity factor.

[0012] Technical effects and advantages of the present invention: By combining the initial inspection reference conditions established at the thermodynamic behavior level and the structural evolution level, as well as the comprehensive evaluation model, the differences in thermal shrinkage behavior and stability problems caused by the uneven distribution of photothermal stabilizers were quantified; this method not only makes up for the defect that traditional technologies cannot effectively detect the influence of photothermal stabilizer distribution, but also relatively improves the ability to evaluate the anti-aging performance of EVA films; The parameters introduced in the comprehensive evaluation model cover the thermodynamic behavior level and the structural evolution level. The parameter design includes dynamic characteristics and microstructural characteristics. Through nonlinear models and compensation coefficients, the performance fluctuations of the film under different working conditions are captured, which relatively improves the reliability of the test results. By designing reference conditions 1 and 2, abnormal samples can be identified in advance, simplifying the initial inspection process; if the sample is abnormal, further in-depth analysis can be performed through a comprehensive evaluation model, which relatively improves the detection efficiency; By coupling the thermal shrinkage characteristics with the optical properties through optical transmittance and structural porosity, it is possible to evaluate the mechanical stability of the film and quantify the changes in optical properties; Dynamic characteristics such as temperature sensitivity factor and time attenuation coefficient are introduced into the comprehensive evaluation model to simulate the effects of photothermal stabilizers under different temperature and time conditions, which relatively improves the adaptability of the model. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0014] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0015] Refer to the instruction manual Figure 1 A method for evaluating the stability of an EVA film by thermal shrinkage characteristics according to an embodiment of the present invention comprises: Obtain the EVA film sample to be tested, and obtain preliminary inspection data based on the EVA film sample, the preliminary inspection data including the thermodynamic behavior level and the structural evolution level; The thermodynamic behavior level in the initial inspection data includes evaluating the thermal shrinkage rate and thermal shrinkage rate of the EVA film sample; establishing reference condition 1 based on the thermal shrinkage rate and thermal shrinkage rate; The structural evolution level in the initial inspection data includes evaluating the molecular chain crystallinity and optical transmittance of the EVA film sample; establishing reference condition 2 based on the molecular chain crystallinity and optical transmittance; If reference condition 1 or reference condition 2 is judged to be abnormal, a comprehensive evaluation model is established, otherwise the EVA film sample is judged to be normal; the comprehensive evaluation model is used to quantify the comprehensive effect of the distribution of light and heat stabilizers on the thermal shrinkage behavior and stability of the EVA film; A comprehensive evaluation value is obtained based on the comprehensive evaluation model. If the comprehensive evaluation value is greater than the comprehensive evaluation threshold, the EVA film sample is marked.

[0016] Reference condition 1 includes: if the thermal shrinkage rate is greater than a preset thermal shrinkage rate threshold, and the thermal shrinkage rate is greater than a preset thermal shrinkage rate threshold, the EVA film sample is judged to be abnormal; Reference condition two includes: if the molecular chain crystallinity is less than a preset molecular chain crystallinity threshold, and the optical transmittance is less than a preset optical transmittance threshold, the EVA film sample is judged to be abnormal.

[0017] The comprehensive evaluation model includes the evaluation of thermal shrinkage rate, thermal shrinkage rate, thermal stress concentration rate, thermal expansion coefficient, and thermal stability time in the thermodynamic behavior level; The comprehensive evaluation model includes the evaluation of molecular chain crystallinity, optical transmittance, molecular chain orientation, cross-linking distribution uniformity, and structural porosity at the structural evolution level; It should be noted that in the process of initial data inspection, reference condition 1 is established based on the heat shrinkage rate and heat shrinkage rate because these two parameters directly reflect the macroscopic dimensional changes and dynamic processes of the EVA film under the action of heat; a heat shrinkage rate that is too large indicates that the film has severe dimensional shrinkage, which may be a thermal stability problem caused by disordered molecular chain arrangement or uneven distribution of light and heat stabilizers; a heat shrinkage rate that is too large indicates that the thermal shrinkage process of the film is abnormally violent, which further points to dynamic instability caused by uncontrolled molecular chain movement; The second reference condition is established based on the molecular chain crystallinity and optical transmittance, which focuses on the microstructural characteristics of the film. Low molecular chain crystallinity indicates that the molecular chains of the film are disordered and lack an ordered structure, which directly affects the thermal stability. Low optical transmittance indicates that there may be defects inside the film or that the molecular chain arrangement is disordered due to the uneven distribution of the light and heat stabilizer. The 10 parameters referenced in the comprehensive evaluation model are to comprehensively cover the two levels of thermodynamic behavior and structural evolution; the 5 parameters at the thermodynamic behavior level (thermal shrinkage, thermal shrinkage rate, thermal stress concentration rate, thermal expansion coefficient, thermal stability time) quantify the complexity of thermal shrinkage behavior from the perspective of macroscopic dynamic and static thermal stability; the 5 parameters at the structural evolution level (molecular chain crystallinity, optical transmittance, molecular chain orientation, cross-linking distribution uniformity, structural porosity) start from the microscopic structural integrity to evaluate the potential impact of photothermal stabilizer distribution on film performance; the comprehensive selection of these parameters ensures that the model can capture both thermal shrinkage characteristics and analyze the multidimensional impact of photothermal stabilizer distribution on stability; the reason why the model's abnormality judgment is based on the comprehensive evaluation value being greater than the comprehensive evaluation threshold is that the larger the evaluation value, the higher the degree of abnormality in thermodynamic behavior and structural evolution, indicating that the overall stability of the film is worse, so it is measured by being greater than; The comprehensive evaluation model uses thermal shrinkage characteristics as the core parameter and quantifies the impact of the inhomogeneity of the distribution of photothermal stabilizers on stability through multi-dimensional supplementation of microstructure and dynamic response. By integrating thermal shrinkage behavior and structural evolution data, the model can systematically evaluate the overall performance of the film. In addition, photothermal stabilizers may cause changes in the thermal motion characteristics of molecular chains, which in turn leads to performance instability and evaluation deviations. The solution screens out samples with abnormalities in thermodynamics and structural evolution through initial inspections, and introduces a comprehensive evaluation model to deeply quantify the differences in thermal shrinkage behavior and stability issues caused by the uneven distribution of photothermal stabilizers, thereby solving the problem of detection deviation.

[0018] Calculate the thermal shrinkage in the thermodynamic behavior level and propose the thermal shrinkage rate as ; Characterize the degree of dimensional change of the film under heat treatment and reflect the reaction ability of the film molecular chain in the thermal environment; ; in is the initial reference length, indicating the initial length of the film before heat treatment; Indicates at time The length of the film, which reflects the shrinkage state under the action of heat; is the thermal expansion correction coefficient, Used to consider the enhancement effect of light and heat stabilizers on thermal shrinkage; For time The ambient temperature at is the molecular chain shrinkage resistance coefficient, which is used to indicate the inhibitory effect of the cohesive force between molecular chains on thermal shrinkage; is the temperature sensitivity factor, It is used to adjust the nonlinear response of temperature to shrinkage. The higher the value, the more sensitive the molecular chain is to temperature changes. is an exponential temperature response term, which is used to describe the rapid response behavior of the molecular chain to temperature changes. The exponential form reflects the common nonlinear change law in thermodynamics. In order to introduce the nonlinear influence of size effect, the square treatment amplifies the weight of the initial length of the film on the thermal shrinkage correction term, reflects the relative hysteresis effect of large-sized film on temperature response during thermal expansion, and simulates the difference in the influence of light and heat stabilizers on films of different sizes; exist The formula includes three terms. The first term is a standardized formula based on length change, which is used to reflect the basic change of thermal shrinkage rate. The second term is used to consider the accelerating effect of temperature on shrinkage rate, thereby introducing a temperature correction term. The third term describes the resistance effect of molecular chain cohesion with temperature change through an exponential temperature dependence. In addition, the addition in the formula is to express the trend that the heat shrinkage rate increases with the increase of temperature and the enhancement of the effect of light and heat stabilizer; the subtraction in the formula is to describe the reverse inhibition effect of molecular chain cohesion on heat shrinkage; Calculate the thermal shrinkage rate in the thermodynamic behavior level and propose the thermal shrinkage rate as ; ; in is the shrinkage rate at time, which is used to reflect the dynamic changes of the thermal shrinkage process; Indicates at time The length of the film; For time The ambient temperature at is the rate amplification factor of the photothermal stabilizer, which is directly related to the distribution of the additive; is the rate temperature attenuation coefficient, which is used to quantify the effect of temperature on the shrinkage rate; is the time attenuation coefficient, Used to describe the rate-reducing effect of long-term heat treatment; Indicates the interval between two adjacent time points; is an exponential decay term, which is used to describe the effect of temperature on the thermal shrinkage rate; It is used as a normalization factor for rate correction, which weakens the extreme effect of too large or too small time interval on the rate. The above equation contains two terms, the first of which is the basic expression of the rate, and the second term is modified by exponential and time decay to capture the nonlinear effect of uneven distribution of photothermal stabilizers on the rate.

[0019] Calculate the molecular chain crystallinity at the structural evolution level and propose the molecular chain crystallinity as ; ; in For scattering X-ray intensity at ; is the lower limit of the scattering angle of the crystalline region, indicating the lowest deflection angle; is the upper limit of the scattering angle of the crystalline region, indicating the highest deflection angle; is the crystallinity correction factor, which is used to quantify the effect of the distribution of light and heat stabilizers on the crystal structure. The higher it is, the greater the correction value; is the molecular chain arrangement irregularity coefficient, which is used to reflect the inhibitory effect of the non-ideal structure of the molecular chain on crystallinity. The larger it is, the smaller the correction value is; It represents the weighted integration result of the scattered signal of the molecular chain in the crystal region. is the weight function of the scattering angle, which is used to adjust the contribution of different scattering angles to the crystallization signal; Represents the weighted integration result of all scattered signals of the film, which is used to normalize the crystallization signal. It is another weight function of the scattering angle, which is used to describe the contribution of the non-crystalline region signal. In the above formula, the denominator adopts a weighted integral model to reflect the coupling relationship between the total intensity at the scattering angle and the molecular chain orientation. In addition, the second term adds a nonlinear correction factor to quantify the effect of the photothermal stabilizer on the molecular chain arrangement, forming a nonlinear model. Calculate the optical transmittance in the structural evolution layer and propose the optical transmittance as ; ; in is the light intensity transmitted through the film; is the incident light intensity; is the transmittance attenuation factor, which characterizes the effect of structural porosity on optical properties; is the structural porosity, Used to characterize the degree of microscopic defects inside the film. express The cube root of , which specifically means quantifying the influence of structural pores on optical transmittance through nonlinear scaling of porosity; is the compensation factor of light transmittance of the light and heat stabilizer; is the temperature sensitivity coefficient of optical properties, which represents the dynamic effect of temperature on optical properties. The above formula includes two terms, the first of which adopts the attenuation model to describe the negative effect of structural porosity on optical transmittance; the second term is corrected by exponential compensation to capture the distribution and temperature dynamic effect of photothermal stabilizer.

[0020] Calculate the thermal stress concentration rate in the thermodynamic behavior level and propose the thermal stress concentration rate as ; ; in For time The instantaneous stress, It can be obtained through stress testing to reflect the stress caused by thermal expansion or contraction in the local area of ​​the film; For time The bearing area of ​​the lower film; is the peak stress during heat treatment; is the area difference of the local stress concentration area, where The calculation method is: , is the initial total area of ​​the film, It represents the area of ​​the region that actually bears stress due to stress concentration; represents the total duration of the film during the heat treatment process and is used to evaluate the time range of stress distribution; Indicated in Inside, the sum of the dynamic coupling of the instantaneous stress distribution and the bearing area; The molecular chain produces stress concentration due to uneven distribution of light and heat stabilizers during heat treatment. The formula captures the abnormal stress distribution through time integration and area normalization. Calculate the thermal expansion coefficient in the thermodynamic behavior level and propose the thermal expansion coefficient as ; ; in is the length change caused by thermal expansion; is the temperature change; is the molecular chain flexibility factor, which is used to reflect the regulation of the expansion freedom by the photothermal stabilizer; is the expansion correction factor, which is used to quantify the additional effect of temperature on expansion; is the initial length before heat treatment; the above formula describes the composite effect of the distribution of photothermal stabilizers on the expansion behavior by combining the logarithmic expansion model with the linear correction; Calculate the thermal stability time in the thermodynamic behavior level and propose the thermal stability time as ; Used to indicate the time required for a film to reach a stable state during heat treatment; ; in The time to reach a steady state; is the stabilization time rate constant, which is a constant used to characterize the rate at which a film transitions from an unstable state to a stable state during heat treatment; is the influence coefficient of temperature on stabilization time; The yield stress of the film refers to the minimum stress value at which the film begins to undergo permanent deformation under the action of external force. The higher the yield stress, the more the film can resist deformation caused by thermal effects. For time The ambient temperature at represents the additional effect of temperature on the stabilization time, when Increase or When it decreases, the additional effect becomes stronger and the thermal stability time Extend, if If it is large enough, the influence of temperature on the stabilization time will be weakened; in summary, the above formula describes the stabilization time process by integration, and adds the correction terms of temperature and yield stress to reflect the complex dynamic characteristics of molecular chain motion; In addition, in determining It can be obtained by experimental fitting, measuring the film at different times Substitute the data into the following fitting model: ; In the formula For time A physical quantity when the temperature is high, including but not limited to shrinkage rate, stress, etc.; is the limit value under stable state; according to the experimental data fitting , to characterize the rate of the stabilization process.

[0021] Calculate the molecular chain orientation degree at the structural evolution level and propose the molecular chain orientation degree as ; ; in Angle under polarizing microscope The light intensity at is the molecular chain orientation compensation coefficient, which is used to compensate for the molecular chain arrangement deviation caused by the uneven distribution of the light and heat stabilizer; is the orientation temperature sensitivity coefficient, which is used to control The sensitivity to the adjustment of molecular chain orientation. The higher the value, the more sensitive the molecular chain is to temperature fluctuations. The orientation temperature sensitivity coefficient is used to characterize the effect of temperature on the orientation of the molecular chain. Take Angle The square of the sine value of represents the contribution of molecular chain alignment in the direction perpendicular to the main orientation; Take Angle The square of the cosine value of represents the contribution of molecular chain arrangement in the main orientation direction; The weighted integral of the light intensity multiplied by the sine square term represents the overall alignment strength of the molecular chains in the vertical direction; The weighted integral of the light intensity multiplied by the cosine square term represents the overall alignment strength of the molecular chain in the main orientation direction; It is used to normalize the orientation degree of the main direction to a maximum value of 1. The smaller the ratio (the stronger the main axis direction), the closer the result is to 1; By compensating for the molecular chain deviation, the orientation calculation is closer to the actual distribution state; the above formula reflects the distribution of polarization intensity with orientation angle through integration, and combines the compensation factor to capture the orientation change caused by the light and heat stabilizer; Calculate the uniformity of cross-linking degree distribution in the structural evolution level, and propose the uniformity of cross-linking degree distribution as ; ; in For the The cross-linking ratio of the region; Represents the logarithmic value of the proportion of cross-linking points, which is used to amplify the impact of low-probability events on the distribution; is the correction factor for the dynamic distribution of the degree of crosslinking, which indicates the dynamic effect of the photothermal stabilizer on the distribution of the degree of crosslinking, and can generally be obtained by fitting experimental data; is the correlation factor between cross-linking uniformity and structural porosity, which is used to describe the negative impact of porosity on the uniformity of cross-linking degree distribution. A larger porosity will significantly reduce the uniformity of cross-linking point distribution. For time The ambient temperature at is the structural porosity; Represents the total number of regions into which the film is divided; the above formula consists of two parts. The first part uses the entropy term to capture the non-uniformity of the crosslinking point distribution, and the second part quantifies the coupling effect between the photothermal stabilizer and the structural porosity through the correction term; Calculate the structural porosity in the structural evolution level and propose the structural porosity ; ; in is the change in pore volume of the film before and after heat treatment; is the total volume of the film; is the porosity distribution correction factor; is the sensitivity coefficient of temperature to porosity; is an exponential decay term, which represents the dynamic response of porosity to temperature change; the role of the cubic root is to reduce the impact of extreme data (such as pore volume that is too large or too small), and is related to the estimation of the actual physical pore diameter; the above formula captures the combined impact of pore distribution and temperature dynamic effects on stability through the cubic root model and logarithmic correction.

[0022] Thermal shrinkage based on thermodynamic behavior , thermal shrinkage rate , thermal stress concentration rate , thermal expansion coefficient , Thermal stability time , and the molecular chain crystallinity at the structural evolution level , Optical transmittance , molecular chain orientation , uniformity of cross-linking degree distribution , structural porosity Establish a comprehensive evaluation model; obtain comprehensive evaluation values ​​based on the comprehensive evaluation model ; ; in Indicates the summation operation of the 10 evaluation parameters, which is the comprehensive contribution of each parameter; For the The weight of the parameters, Indicates the relative importance of different evaluation directions in the overall stability; is a natural logarithmic function, which represents a nonlinear scaling process of the parameter value and is used to adjust the amplitude differences of different parameters; It is a parameter standardization processing item used to ensure the comparability of various evaluation parameters; For the The value of the evaluation parameter; For the The normalization factor of the parameters is used to adjust the parameters of different dimensions to a uniform range; is a nonlinear adjustment factor used to control the The nonlinear amplification or compression effect of a parameter in the model. For example, when the effect of a parameter on stability is significantly nonlinear, Strengthen its nonlinear weight; is a dynamic temperature compensation term, which is used to describe the nonlinear effect of the photothermal stabilizer on stability at different temperatures; is the compensation factor, indicating the The maximum compensation amount of each parameter affected by the light and heat stabilizer; is an exponential decay function, used to simulate Dynamic inhibition effect on the distribution of photothermal stabilizers; is the temperature sensitivity factor, which is used to quantify the effect of temperature on the The influence strength of each parameter; For time The ambient temperature at In summary, the first part of the formula is the evaluation value of nonlinear scaling; the second part of the formula It is the dynamic compensation value of light and heat stabilizer.

[0023] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for evaluating the stability of EVA film by thermal shrinkage characteristics, characterized in that: include: Obtain the EVA film sample to be tested, and obtain preliminary inspection data based on the EVA film sample, the preliminary inspection data including the thermodynamic behavior level and the structural evolution level; The thermodynamic behavior level in the initial inspection data includes evaluating the thermal shrinkage rate and thermal shrinkage rate of the EVA film sample; establishing reference condition 1 based on the thermal shrinkage rate and thermal shrinkage rate; The structural evolution level in the initial inspection data includes evaluating the molecular chain crystallinity and optical transmittance of the EVA film sample; establishing reference condition 2 based on the molecular chain crystallinity and optical transmittance; If reference condition 1 or reference condition 2 is judged to be abnormal, a comprehensive evaluation model is established, otherwise the EVA film sample is judged to be normal; the comprehensive evaluation model is used to quantify the comprehensive effect of the distribution of light and heat stabilizers on the thermal shrinkage behavior and stability of the EVA film; A comprehensive evaluation value is obtained based on the comprehensive evaluation model. If the comprehensive evaluation value is greater than the comprehensive evaluation threshold, the EVA film sample is marked.

2. The method for evaluating the stability of an EVA film by thermal shrinkage characteristics according to claim 1, characterized in that: Reference condition 1 includes: if the thermal shrinkage rate is greater than a preset thermal shrinkage rate threshold, and the thermal shrinkage rate is greater than a preset thermal shrinkage rate threshold, the EVA film sample is judged to be abnormal; Reference condition two includes: if the molecular chain crystallinity is less than a preset molecular chain crystallinity threshold, and the optical transmittance is less than a preset optical transmittance threshold, the EVA film sample is judged to be abnormal.

3. A method for evaluating the stability of an EVA film by thermal shrinkage characteristics according to claim 2, characterized in that: The comprehensive evaluation model includes the evaluation of thermal shrinkage rate, thermal shrinkage rate, thermal stress concentration rate, thermal expansion coefficient, and thermal stability time in the thermodynamic behavior level; The comprehensive evaluation model includes the evaluation of molecular chain crystallinity, optical transmittance, molecular chain orientation, cross-linking distribution uniformity, and structural porosity at the structural evolution level.

4. The method for evaluating the stability of an EVA film by thermal shrinkage characteristics according to claim 3, characterized in that: Calculate the thermal shrinkage in the thermodynamic behavior level and propose the thermal shrinkage rate as ; ； in is the initial reference length; Indicates at time The length of the film; is the thermal expansion correction coefficient; For time Ambient temperature at is the molecular chain shrinkage resistance coefficient; is the temperature sensitive factor; Calculate the thermal shrinkage rate in the thermodynamic behavior level and propose the thermal shrinkage rate as ; ； in For time The shrinkage rate at is the rate amplification factor of the photothermal stabilizer; is the rate temperature attenuation coefficient; is the time attenuation coefficient; Indicates the interval between two adjacent time points.

5. The method for evaluating the stability of an EVA film by thermal shrinkage characteristics according to claim 4, characterized in that: Calculate the molecular chain crystallinity at the structural evolution level and propose the molecular chain crystallinity as ; ； in is the scattering angle X-ray intensity at ; is the lower limit of the scattering angle of the crystalline region; is the upper limit of the scattering angle of the crystalline region; is the crystallinity correction factor; is the molecular chain arrangement irregularity coefficient; Calculate the optical transmittance in the structural evolution layer and propose the optical transmittance as ; ； in is the light intensity transmitted through the film; is the incident light intensity; is the transmittance attenuation factor; is the structural porosity; is the compensation factor of light transmittance of the light and heat stabilizer; is the temperature sensitivity coefficient of optical performance.

6. The method for evaluating the stability of an EVA film by thermal shrinkage characteristics according to claim 5, characterized in that: Calculate the thermal stress concentration rate in the thermodynamic behavior level and propose the thermal stress concentration rate as ; ； in For time The instantaneous stress; For time The bearing area of ​​the lower film; is the peak stress value during heat treatment; is the area difference of the local stress concentration area; Indicates the total duration of the film during the heat treatment process; Calculate the thermal expansion coefficient in the thermodynamic behavior level and propose the thermal expansion coefficient as ; ； in is the length change caused by thermal expansion; is the temperature change; is the molecular chain flexibility factor; is the expansion rate correction factor; is the initial length before heat treatment; Calculate the thermal stability time in the thermodynamic behavior level and propose the thermal stability time as ; ； in The time to reach a steady state; is the stabilization time rate constant; is the influence coefficient of temperature on stabilization time; is the yield stress of the film.

7. The method for evaluating the stability of an EVA film by thermal shrinkage characteristics according to claim 6, characterized in that: Calculate the molecular chain orientation degree in the structural evolution level and propose the molecular chain orientation degree as ; ； in Angle under polarizing microscope The light intensity at is the molecular chain orientation compensation coefficient; is the orientation temperature sensitivity coefficient; Calculate the uniformity of cross-linking degree distribution in the structural evolution level, and propose the uniformity of cross-linking degree distribution as ; ； in For the The cross-linking ratio of the region; is the correction factor for dynamic distribution of cross-linking degree; is the correlation factor between cross-linking uniformity and structural porosity; Calculate the structural porosity in the structural evolution level and propose the structural porosity ; ； in is the change in pore volume of the film before and after heat treatment; is the total volume of the film; is the porosity distribution correction factor; is the sensitivity coefficient of temperature to porosity.

8. The method for evaluating the stability of an EVA film by thermal shrinkage characteristics according to claim 7, characterized in that: Thermal shrinkage based on thermodynamic behavior , thermal shrinkage rate , thermal stress concentration rate , thermal expansion coefficient , Thermal stability time , and the molecular chain crystallinity at the structural evolution level , Optical transmittance , molecular chain orientation , uniformity of cross-linking degree distribution , structural porosity Establish a comprehensive evaluation model; obtain comprehensive evaluation values ​​based on the comprehensive evaluation model ; ； in For the The weight of the parameters; For the The value of the evaluation parameter; For the Normalization factor for each parameter; is the nonlinear adjustment factor; is the compensation factor; is the temperature sensitivity factor.

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