A simulation method for analyzing the changes in flame retardant properties of polymer insulation materials during aging based on intermolecular forces

Abstract

This invention provides a simulation method for analyzing changes in the flame retardant properties of polymer insulation materials during aging based on intermolecular forces. The method involves three aspects: 1) simulating and analyzing microscopic parameters related to intermolecular forces during the aging process of polymer insulation materials; 2) analyzing the evolution of intermolecular forces during the aging process of polymer insulation materials; and 3) establishing a structure-activity relationship between intermolecular forces and flame retardant properties of polymer insulation materials. This method provides theoretical guidance for understanding the influence of intermolecular forces on the properties of polymer insulation materials during aging.

Description

Technical Field

[0001] The present invention belongs to the technical field of molecular simulation, and in particular relates to a simulation method for analyzing changes in flame retardant properties of polymer insulating materials during aging based on intermolecular forces. Background Art

[0002] Due to their excellent physical, chemical, and electrical properties, polymer insulation materials such as resins and rubbers are widely used in power equipment. However, polymer insulation materials inevitably age in complex environments, leading to performance degradation. Power equipment is subject to various stresses during operation, such as electrical and thermal stresses. Under these stresses, insulation materials gradually age over time, causing a decrease in flame retardancy and significantly increasing the risk of fire.

[0003] Currently, aging analysis of polymer insulation materials primarily relies on macroscopic methods such as infrared spectroscopy, gas chromatography, and nuclear magnetic resonance. These methods can only reveal patterns in the changes in specific polymer groups, molecular bonds, and atomic numbers before and after aging, but are unable to accurately characterize the evolution of intermolecular forces within polymer insulation materials. Furthermore, macroscopic testing requires significant human and material resources, resulting in significant costs. Microscopic mechanistic analysis of the impact of the evolution of intermolecular forces on the flame retardant properties of polymer insulation materials during aging is rare. Summary of the Invention

[0004] The purpose of the present invention is to provide a simulation method for analyzing the changes in flame retardant properties of polymer insulating materials during aging based on intermolecular forces. The simulation method of the present invention constructs a structure-activity relationship between intermolecular forces and flame retardant properties of polymer insulating materials, providing theoretical guidance for understanding the influence of intermolecular forces on the performance of polymer insulating materials during aging.

[0005] A simulation method for analyzing changes in flame retardant properties of polymer insulation materials during aging based on intermolecular forces includes the following steps:

[0006] A) constructing and optimizing the molecular structure of a polymer insulating material using Gaussian View software, placing the optimized polymer insulating material molecular model within a periodic structure, and performing reaction kinetics simulation of the polymer insulating material using GULP software based on the ReaxFF force field. The polymer insulating material structures corresponding to different simulation times are extracted to obtain n polymer insulating material molecular models with different aging degrees;

[0007] B) geometrically optimizing n molecular models of polymer insulating materials at different aging degrees, placing the n optimized molecular models of polymer insulating materials at the same aging degree in the same periodic system using Packmol software, obtaining TOP files required for the GAFFL force field during molecular dynamics simulations of the n polymer insulating materials at different aging degrees using Sobtop software, calculating RESP charges of the polymer insulating materials using Multiwfn software, assigning the charges to the TOP files, performing molecular dynamics simulations using Gromacs software, and performing molecular dynamics simulations based on the NPT ensemble;

[0008] C) calculating the free volume fraction, self-diffusion coefficient, density, cohesive energy density, and gyration radius of the polymer insulating material molecules at different aging degrees based on the molecular dynamics simulation trajectories of the n polymer insulating material molecules at different aging degrees obtained in step B);

[0009] D) constructing a structure-activity relationship between intermolecular forces and flame retardancy of the polymer insulating material based on the free volume fraction, self-diffusion coefficient, density, cohesive energy density, and radius of gyration data of the polymer insulating material molecules at different aging levels obtained in step C), combined with the pattern of changes in the flame retardancy of the polymer insulating material with aging.

[0010] Preferably, in the step A), the degree of polymerization of the polymer insulating material molecular model is not less than 10, and both ends of the polymer insulating material molecules are subjected to hydrogenation and saturation treatment.

[0011] Preferably, in step A), the molecular structure of the polymer insulating material is geometrically optimized using Gaussian software M062X functional and 6-311G (d, p) basis set method.

[0012] Preferably, in step A), the lowest temperature at which the polymer insulating material molecular model reacts is used as the reaction kinetics simulation temperature.

[0013] Preferably, the geometry optimization of the n molecular models of polymer insulating materials with different aging degrees in step B) is performed using Gaussian software M062X functional and 6-311G (d, p) basis set method.

[0014] Preferably, in the step B), the simulation time of the molecular dynamics simulation based on the NPT ensemble is ≥20 ns, and the simulation trajectory after 10 ns is selected for data extraction.

[0015] Preferably, the free volume fraction FFV is calculated according to formula I:

[0016]

[0017] In formula I, FFV is the free volume fraction, V free is the total free volume of the polymer insulating material, V occ is the total occupied volume of the polymer insulating material.

[0018] Preferably, the self-diffusion coefficient D is calculated according to Formula II:

[0019]

[0020] In formula II, D is the self-diffusion coefficient, r i (t) and r i (0) represents the position vector of the i-th atom at time t and time 0, respectively, and N is the total number of atoms.

[0021] Preferably, the cohesive energy density CED is calculated according to Formula III and Formula IV:

[0022] E coh =- <E inter >= <E intra >- <E total > Formula III;

[0023]

[0024] In Formula III and Formula IV, E coh is the cohesive energy of the model, V is the volume of the model, E inter is the energy between model molecules, E intra is the intramolecular energy, E total is the total energy of the model.

[0025] Preferably, the radius of rotation (R g ) is calculated according to formula V:

[0026]

[0027] In formula V, m i is the mass of atom i, r i is the coordinate of atom i, r c are the coordinates of the center of mass of the system, and m is the mass of atom j.

[0028] This invention provides a simulation method for analyzing changes in the flame retardant properties of polymer insulation materials during aging based on intermolecular forces. The method involves three aspects: 1) simulating and analyzing microscopic parameters related to intermolecular forces during the aging process of polymer insulation materials; 2) analyzing the evolution of intermolecular forces during the aging process of polymer insulation materials; and 3) establishing a structure-activity relationship between intermolecular forces and flame retardant properties of polymer insulation materials. This method provides theoretical guidance for understanding the influence of intermolecular forces on the properties of polymer insulation materials during aging. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0030] Figure 1 The structural change process of the silicone rubber under the conditions of wet heat aging in the embodiment of the present invention;

[0031] Figure 2 is the oxygen index of the silicone rubber at different aging times in the embodiment of the present invention. DETAILED DESCRIPTION

[0032] The present invention provides a simulation method for analyzing the change of flame retardant properties of polymer insulation materials during aging based on intermolecular forces, comprising the following steps:

[0033] Step 1: Simulate and analyze the microscopic parameters related to intermolecular forces during the aging process of polymer insulation materials.

[0034] Gaussian View software was used to construct the single molecular structure of the polymer insulation material. To ensure the accuracy of the simulation results, the polymerization degree of the monomer model of the polymer insulation material was not less than 10, and both ends of the polymer were hydrogenated and saturated.

[0035] Based on density functional theory, the constructed polymer insulating material monomer model was geometrically optimized using the Gaussian software M062X functional and 6-311G(d,p) basis set method to make the model closer to the actual structure. The M062X functional is very suitable for the binding optimization of organic matter, and the high-quality 6-311G(d,p) basis set ensures the accuracy of the results.

[0036] The optimized monomer model of the polymer insulation material was placed in a periodic structure, and the reaction dynamics of the polymer insulation material were simulated using GULP software based on the ReaxFF force field. The temperature during the simulation was higher than the actual temperature. Based on the target temperature in actual use, the temperature was tested in 50K increments during the simulation to determine the lowest temperature at which the polymer insulation material model reacted. This lowest temperature was set as the simulation temperature. Water and oxygen molecules were added to the model to simulate humidity and a nutrient-rich environment, and the electric field strength was set to simulate an electric field environment.

[0037] Based on the reaction kinetics simulation process of the polymer insulation material model, the main structural evolution process of the polymer insulation material during the aging process is extracted, and the aging level of the polymer insulation material is named according to the degree of structural degradation, that is, n molecular models of polymer insulation materials with different aging levels are obtained.

[0038] The geometry optimization of polymer insulation materials with different aging levels was performed using the Gaussian M062X functional and the 6-311G(d,p) basis set. Packmol software was used to place n identical polymer insulation materials with the same aging level in the same periodic system. For example, 30 polymer insulation material molecules with aging level 1 were placed in one periodic box, and 30 polymer insulation material molecules with aging level 2 were placed in another periodic box. Molecular dynamics simulations of polymer insulation materials with different aging levels were then performed.

[0039] The GAFFL force field was used in molecular dynamics simulations of polymer insulation materials at different aging levels. The GAFF force field provides a more accurate simulation of polymers. Sobtop software was used to obtain the TOP files required for molecular dynamics simulations of polymer insulation materials at different aging levels. Based on the wave function files obtained after geometric optimization of the polymer insulation material models at different aging levels, Multiwfn software was used to calculate the RESP charges of the polymer insulation materials and assign the charges to the TOP files. The RESP charges of the polymer insulation materials are better compatible with the GAFF force field, resulting in more accurate molecular dynamics simulation results.

[0040] This study uses Gromacs software to perform molecular dynamics simulations of polymer insulation materials with varying aging levels. Based on the NPT ensemble, the simulations last no less than 20 nanoseconds. The first 10 nanoseconds are used to equilibrate the model and achieve a more reasonable density. The simulations after 10 nanoseconds are used to analyze various properties of the model. Gromacs software can perform nanosecond-scale molecular dynamics simulations, significantly reducing randomness and improving simulation accuracy.

[0041] Step 2: Obtain the evolution behavior of intermolecular forces during the aging process of polymer insulation materials.

[0042] Based on the molecular dynamics simulation trajectories of polymer insulation materials with different aging grades obtained in the first step, the changes in free volume fraction, self-diffusion coefficient, density, cohesive energy density and gyration radius of polymer insulation materials with different aging grades are calculated.

[0043] The total volume of the polymer insulating material is given by the occupied volume V occ and the free volume V free Composition, the free volume is dispersed throughout the polymer in the form of voids. Different polymer insulating materials have different sizes, dimensions, and densities. The free volume fraction (FFV) is introduced to measure the free volume of different types of insulating oil molecules. The free volume fraction is shown in Formula I.

[0044]

[0045] The mean square displacement (MSD) of polymer insulating material molecules can be calculated by the following formula:

[0046]

[0047] Among them, r i (t) and r i (0) represents the position vector of the i-th atom at time t and time 0 respectively.

[0048] The self-diffusion coefficient of polymer insulating materials can be solved using the Einstein formula, as shown in Formula II:

[0049]

[0050] Where N is the total number of atoms. In order to make the calculation of the self-diffusion coefficient more accurate, 10% to 90% of the MSD curve is selected for linear fitting.

[0051] The cohesive energy density of polymer insulation materials can be calculated using formulas III and IV:

[0052] E coh =- <E inter >= <E intra >- <E total > Formula III;

[0053]

[0054] Where E coh is the cohesive energy of the model, V is the volume of the model, E inter is the total energy of the model, Eintra is the intermolecular energy, E total is the total energy of the model.

[0055] The radius of gyration of the polymer (R g ) can be calculated by formula V, where mi is the mass of atom i, ri is the coordinate of atom i, rc is the coordinate of the center of mass of the system, and m j is the mass of atom j.

[0056]

[0057] Step 3: Construct the structure-activity relationship between the intermolecular forces and flame retardant properties of polymer insulation materials.

[0058] Based on the calculation results of the free volume fraction, self-diffusion coefficient, density, cohesive energy density and gyration radius of polymer insulation materials with different aging grades in the second step, the change rules of the microscopic parameters of polymer insulation materials with different aging grades are summarized.

[0059] The flame retardant properties of polymer insulation materials at different aging stages are tested according to GBT 5169.16-2017 Fire hazard tests for electric and electronic products - Part 16: Test flame 50W horizontal and vertical flame test method.

[0060] Combining the changing pattern of flame retardant properties of polymer insulation materials with aging degree and the simulation results of microscopic parameters, the structure-activity relationship between intermolecular forces and flame retardant properties of polymer insulation materials is constructed.

[0061] This invention provides a simulation method for analyzing changes in the flame retardant properties of polymer insulation materials during aging based on intermolecular forces. The method involves three aspects: 1) simulating and analyzing microscopic parameters related to intermolecular forces during the aging process of polymer insulation materials; 2) analyzing the evolution of intermolecular forces during the aging process of polymer insulation materials; and 3) establishing a structure-activity relationship between intermolecular forces and flame retardant properties of polymer insulation materials. This method provides theoretical guidance for understanding the influence of intermolecular forces on the properties of polymer insulation materials during aging.

[0062] To further illustrate the present invention, a simulation method for analyzing changes in flame retardant properties of polymer insulating materials during aging based on intermolecular forces provided by the present invention is described in detail below in conjunction with examples, but it should not be understood as limiting the scope of protection of the present invention.

[0063] Example

[0064] This embodiment takes the change in flame retardant properties of silicone rubber polymer insulation material under the action of wet heat aging as an example.

[0065] According to the molecular structure of silicone rubber, a monomer model of silicone rubber polymer insulating material was constructed using Gaussian View software with a degree of polymerization of 10. The constructed monomer model of silicone rubber polymer insulating material was geometrically optimized using Gaussian software M062X functional and 6-311G(d,p) basis set method.

[0066] A silicone rubber molecule is placed in a periodic structure. Considering the hygrothermal aging under the action of moisture and temperature, one water molecule is added to the model. According to the test, silicone rubber can decompose at a temperature of 500K. Therefore, the simulation temperature is set to 500K.

[0067] Based on the ReaxFF force field, GULP software was used to simulate the polymer aging under hygrothermal aging conditions, and the structural change process of silicone rubber under hygrothermal aging conditions was extracted. Figure 1 As shown. Figure 1 The five silicone rubber structures shown in 0 to 4 are named aging degree 0 to aging degree 4 respectively.

[0068] Based on the results obtained for the five silicone rubbers described above, density functional theory simulations were performed using the M062X-6-311G(d,p) method and Gaussian software. Each of the five silicone rubber structures was optimized, and the RESP atomic charges for each structure were obtained using Multiwfn software. Using Packmol software, 30 silicone rubbers of the same structure and aging grade were placed in a periodic system. Energy minimization of the model was performed using Gromacs software and the steepest gradient method. Molecular dynamics simulations were then performed for 20 ns in the NPT ensemble using the GAFF force field, with a temperature setting of 473 K and a step size of 1.5 fs. The changes in the free volume fraction, self-diffusion coefficient, density, cohesive energy density, and radius of gyration of the silicone rubbers for the different structures were calculated using the selected 10 ns simulation trajectory. The results are shown in Table 1.

[0069] The results show that as the structure of silicone rubber changes during the wet-heat aging process, its microscopic parameters also change accordingly. The changing trend of the microscopic parameters is not completely monotonically decreasing or increasing, but presents a fluctuating trend, which indicates that as the degree of aging increases, the intermolecular force of silicone rubber shows a trend of first decreasing, then increasing, and then decreasing.

[0070] Table 1 Microscopic parameters of silicone rubber under different aging degree structures

[0071]

[0072] Conduct humidity and heat aging tests on silicone rubber and test its flame retardant properties to further verify the simulation results. Refer to "Environmental Test Part 2: Test Method Test Cab: Constant Humidity and Heat Test" to conduct humidity and heat aging tests on samples. The ambient temperature is set to 85±5℃, the ambient relative humidity is set to 90±10%, and the aging days are 0-56d. Flame retardant performance tests are conducted on samples with different aging degrees. Refer to "GBT 5169.16-2017 Fire Hazard Tests for Electrical and Electronic Products Part 16: Test Flame 50W Horizontal and Vertical Flame Test Method" to conduct vertical combustion tests on silicone rubber test samples, and obtain the changes in oxygen index during the test, such as Figure 2 As shown in Figure 2, it can be found that the flame retardant performance of silicone rubber shows a trend of first decreasing and then increasing.

[0073] Combining experimental and simulation results reveals that the density and cohesive energy density of silicone rubber first decrease and then increase, while the intermolecular forces on the surface first decrease and then increase with increasing aging. The free volume fraction and self-diffusion coefficient first increase and then decrease, indicating that the thermal stability of silicone rubber first decreases and then increases. During the test, the higher the oxygen index, the stronger the surface flame retardancy. The experimental results show that the flame retardancy of silicone rubber first decreases and then increases with increasing aging days, and the simulation results well reflect the experimental phenomena.

[0074] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A simulation method for analyzing the change in flame retardant properties of polymer insulation materials during aging based on intermolecular forces, comprising the following steps: A) constructing and optimizing the molecular structure of a polymer insulating material using Gaussian View software, placing the optimized polymer insulating material molecular model within a periodic structure, and performing reaction kinetics simulation of the polymer insulating material using GULP software based on the ReaxFF force field. The polymer insulating material structures corresponding to different simulation times are extracted to obtain n polymer insulating material molecular models with different aging degrees; B) geometrically optimizing n molecular models of polymer insulating materials at different aging degrees, placing the n optimized molecular models of polymer insulating materials at the same aging degree in the same periodic system using Packmol software, obtaining TOP files required for the GAFFL force field during molecular dynamics simulations of the n polymer insulating materials at different aging degrees using Sobtop software, calculating RESP charges of the polymer insulating materials using Multiwfn software, assigning the charges to the TOP files, performing molecular dynamics simulations using Gromacs software, and performing molecular dynamics simulations based on the NPT ensemble; C) calculating the free volume fraction, self-diffusion coefficient, density, cohesive energy density, and gyration radius of the polymer insulating material molecules at different aging degrees based on the molecular dynamics simulation trajectories of the n polymer insulating material molecules at different aging degrees obtained in step B); D) constructing a structure-activity relationship between intermolecular forces and flame retardancy of the polymer insulating material based on the free volume fraction, self-diffusion coefficient, density, cohesive energy density, and radius of gyration data of the polymer insulating material molecules at different aging levels obtained in step C), combined with the pattern of changes in the flame retardancy of the polymer insulating material with aging.

2. The simulation method according to claim 1, wherein: In the step A), the degree of polymerization of the polymer insulating material molecular model is not less than 10, and both ends of the polymer insulating material molecules are subjected to hydrogenation saturation treatment.

3. The simulation method according to claim 1, wherein: In the step A), the molecular structure of the polymer insulating material is geometrically optimized using the Gaussian software M062X functional and the 6-311G (d, p) basis set method.

4. The simulation method according to claim 1, wherein: In the step A), the lowest temperature at which the polymer insulating material molecular model reacts is used as the reaction kinetics simulation temperature.

5. The simulation method according to claim 1, wherein: The Gaussian software M062X functional and 6-311G (d, p) basis set method are used to perform geometry optimization on the molecular models of n polymer insulating materials with different aging degrees in step B).

6. The simulation method according to claim 1, wherein: In the step B), the simulation time of the molecular dynamics simulation based on the NPT ensemble is ≥20 ns, and the simulation trajectory after 10 ns is selected for data extraction.

7. The simulation method according to claim 1, wherein: The free volume fraction FFV is calculated according to formula I: In formula I, FFV is the free volume fraction, V free is the total free volume of the polymer insulating material, V occ is the total occupied volume of the polymer insulating material.

8. The simulation method according to claim 1, wherein: The self-diffusion coefficient D is calculated according to formula II: In formula II, D is the self-diffusion coefficient, r i (t) and r i (0) represents the position vector of the i-th atom at time t and time 0, respectively, and N is the total number of atoms.

9. The simulation method according to claim 1, wherein: The cohesive energy density CED is calculated according to Formula III and Formula IV: E coh =- <E inter >= <E intra >- <E total > Formula III; In Formula III and Formula IV, E coh is the cohesive energy of the model, V is the volume of the model, E inter is the energy between model molecules, E intra is the intramolecular energy, E total is the total energy of the model.

10. The simulation method according to claim 1, wherein: Radius of rotation (R g ) is calculated according to formula V: In formula V, m i is the mass of atom i, r i is the coordinate of atom i, r c is the coordinate of the center of mass of the system, m j is the mass of atom j.

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