PET electrothermal cracking analogue simulation method under action of micro water

Abstract

The invention discloses a PET (Polyethylene Terephthalate) electrothermal cracking analogue simulation method under the action of micro water, which comprises the following steps: step 1, optimizing PET and H2O molecules to obtain a stable single-molecule configuration; step 2, respectively constructing electrothermal cracking structure models with H2O volume ratios of 0%, 1%, 5% and 10%; and step 3, simulating the electrothermal decomposition process of the PET under the micro-water condition by adopting Lammps software, comparing the decomposition intensity and reaction process information of the PET under different water contents, counting product information, and drawing a reaction path. Based on the microscopic atomic angle, the PET electrothermal cracking reaction process which cannot be completely observed in a macroscopic experiment can be obtained, the reaction path of PET-H2O is consistent with that observed in the experiment, and reliability is achieved.

Description

Technical Field

[0001] The invention relates to the field of electrical engineering insulation detection and polymer material aging analysis, and more specifically to a PET electrothermal cracking simulation method under the action of micro-water. Background Art

[0002] As the power system develops rapidly towards high voltage and large capacity, polymer insulation materials represented by polyethylene terephthalate (PET) are widely used in key equipment such as gas insulated closed lines (GIL) and power cable accessories due to their excellent dielectric properties and mechanical strength. However, during long-term operation, PET insulation materials will undergo irreversible aging due to the coupling of electrical, thermal and moisture multi-physical fields, which is manifested in molecular chain breakage, gas product escape and dielectric property degradation, eventually leading to insulation failure or even equipment failure.

[0003] At present, molecular dynamics simulation technology, especially ReaxFF reaction force field, has been widely used to study the thermal decomposition and aging mechanism of polymer materials. ReaxFF can effectively simulate the formation and breaking process of chemical bonds, providing an important tool for revealing complex reaction mechanisms. However, existing research focuses on material aging under a single thermal field or electric field, and there is still a lack of in-depth understanding of the microscopic cracking mechanism under electrothermal coupling conditions.

[0004] The present invention fills this research gap by combining ReaxFF reaction force field with thermal-electric field coupling simulation, and provides microscopic theoretical support for life prediction and fault warning of PET insulation materials in electrical equipment. Especially in high-voltage equipment such as gas-insulated closed lines (GIL), the aging and insulation failure of PET film are directly related to the reliability of the equipment, so the present invention has important practical application value. Summary of the invention

[0005] The purpose of this method is to propose a simulation method for the electrothermal cracking of PET under the action of micro-water, so as to solve the technical problem that the existing technology cannot accurately predict the aging and cracking behavior of PET insulating materials in a micro-water environment from a microscopic level.

[0006] To achieve the above objectives, the present invention provides a simulation method for the electrothermal cracking of PET under the action of micro-water. By constructing a PET molecular model and applying an electrothermal coupling field, the cracking process of PET in a micro-water environment is simulated, and its cracking path and product distribution are analyzed, thereby revealing its microscopic aging mechanism.

[0007] Compared with the prior art, the present invention has the following beneficial effects: the present invention can accurately simulate the cracking behavior of PET under the coupling of micro-water, electric field and thermal field at the atomic level, and provide theoretical support at the microscopic level for the life prediction and fault warning of PET insulating materials in electrical equipment, especially in the reliability research of high-voltage equipment such as gas-insulated closed lines (GIL). BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 The decomposition of CO at different water contents at 2000K 2 Quantity graph.

[0009] Figure 2 The decomposition of C at different water contents at 2000K 2 H 4 Quantity graph.

[0010] Figure 3 The decomposition of C at different water contents at 2000K 6 H 10 Quantity graph.

[0011] Figure 4 The decomposition of CO at different water contents at 2400K 2 Quantity graph.

[0012] Figure 5 It is the decomposition of C under different water contents at 2400K 2 H 4 Quantity graph.

[0013] Figure 6 It is the decomposition of C under different water contents at 2400K 6 H 10 Quantity graph.

[0014] Figure 7 This is a graph showing the change in the number of molecules in the system at different temperatures and water contents.

[0015] Figure 8 This is the electrothermal decomposition path diagram of PET under the action of micro-water.

[0016] Fig. 9 It is a flow chart of statistical decomposition products based on molecular dynamics simulation method. DETAILED DESCRIPTION

[0017] The following is a clear and complete description of the technical solution in the present invention in conjunction with the drawings 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.

[0018] The present invention proposes a PET electrothermal cracking simulation method under the action of micro-water, comprising the following steps:

[0019] Step 1: Construct PET and H in the molecular simulation software Materials Studio 2 The molecular model of O was constructed, and the geometry was optimized based on the first principles using PBE / DNP functional and basis set level to obtain the stable structure with the lowest molecular energy.

[0020] Step 2, construction of PET-H 2 O reaction system model, and perform geometry optimization to obtain the minimum energy system conformation, and adjust the PET-H 2 The initial temperature and density of the O reaction system model are adjusted;

[0021] Step 3: Use Lammps software to adjust the PET-H 2 The electrothermal cracking simulation was carried out using the O reaction system model, the decomposition severity and reaction process information of the PET molecular dynamics simulation under different water contents were compared, the decomposition products were counted, and the reaction path was drawn.

[0022] Embodiment 1

[0023] PET and H were constructed in the molecular simulation software Materials Studio. 2 The molecular model of O was constructed, and the geometry was optimized based on the first principles using PBE / DNP functional and basis set levels to obtain the stable structure with the lowest molecular energy.

[0024] In specific implementation, the initial molecular model provided by the ChemSpider database can be used, or the PET-H can be drawn in software such as GaussianView and AMS. 2 The molecular structure model of O was optimized using the PBE / DNP functional and basis set levels of the DMol3 module in Materials Studio software to obtain the stable configuration with the minimum energy.

[0025] Embodiment 2

[0026] Construction of PET-H 2O reaction system model, and perform geometry optimization to obtain the minimum energy system conformation, and adjust the PET-H 2 The initial temperature and density of the O reaction system model are adjusted;

[0027] In the specific implementation, the Amorphous Cell module of Materials Studio software was used to set the initial density to 0.8 g / cm3 and the initial temperature to 300 K to establish PET-H 2 The box model of the O system is based on the NVT ensemble. The molecular structure is relaxed to the equilibrium state by 5 ps relaxation at 300 K, and then the PET-H is adjusted by 5 ps relaxation in the NPT ensemble. 2 O reaction system model, and the adjusted PET-H 2 O-body reaction system model. The NVT ensemble uses the Nose-Hoover heat bath method to control temperature, with a temperature damping constant of 5 fs, and the NPT ensemble uses the Berendsen method to control pressure, with a pressure damping constant of 5 fs.

[0028] Embodiment 3

[0029] Lammps software was used to adjust the PET-H 2 The electrothermal cracking simulation was carried out using the O reaction system model, the decomposition severity and reaction process information of the PET molecular dynamics simulation under different water contents were compared, the decomposition products were counted, and the reaction path was drawn.

[0030] During the specific implementation, based on the reaction molecular kinetics theory, four different moisture content conditions were designed, namely 0%, 1%, 5% and 10%. Considering the key role of temperature in the electrothermal cracking process, the electrothermal cracking simulation of PET was carried out at temperatures of 2000K, 2400K, 2800K and 3200K to evaluate the influence of water content and temperature on the cracking behavior of PET, summarize the product distribution, and draw the reaction path.

[0031] The above content is merely an illustration of the structure of the present invention. The technicians in this technical field may make various modifications or additions to the specific structure described. As long as they do not deviate from the structure of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A simulation method for PET electrothermal cracking under the action of micro-water, characterized in that: The following steps are involved: Step 1: Build molecular models of PET and H2O in the molecular simulation software Materials Studio, and perform geometry optimization based on first principles using PBE / DNP functionals and basis set levels to obtain the stable structure with the lowest molecular energy; Step 2, constructing a PET-H2O reaction system model, and performing geometric optimization to obtain the minimum energy system conformation, and adjusting the initial temperature and density of the PET-H2O reaction system model according to the actual temperature and density; Step 3: Use Lammps software to perform electrothermal cracking simulation on the adjusted PET-H2O reaction system model, compare the decomposition severity and reaction process information of PET molecular dynamics simulation under different water contents, count the decomposition products, and draw the reaction path.

2. The method according to claim 1, characterized in that: In the step 2, the reaction system model is established using the Amorphous Cell module of the Materials Studio software, and the initial density is set to 0.8 g / cm3 and the initial temperature is set to 300 K; the density and temperature of the PET-H2O reaction system model are adjusted by performing 5 ps relaxation in the NVT ensemble and the NPT ensemble respectively.

3. The method according to claim 1, characterized in that: In step 3, the Lammps software is used to perform an electrothermal cracking simulation on the adjusted PET-H2O reaction system model, and the system energy of the ReaxFF force field is calculated as follows: AND system =And bond +E over +E under +E val +E pen +E tors +E lp +E coa +E vdWaals +E Coulomb +E Specific E val =f1(a BOij )·f1(a BOik )·f3(△ j )·{p val1 -p val1 ×exp[-p val2 ×(θ0-θ ijk ) 2 ]} From pen =p pen1 ·f4(△ j )·exp[-p pen2 (α BOij -2) 2 ]·exp[-p pen2 (α BOjk -2) 2 ] In the formula, E system is the total energy of the system, E bond is the bond energy, E over and E under represents the over- and under-coordination energy correction in the energy contribution, E val represents the energy of covalent bond angle bending, E pen represents the penalty energy for an atom sharing two double bonds to destabilize the system, E tors is the torsional energy, E conj represents the energy conjugation effect, E lp represents the energy of the lone pair of electrons, E coa represents the three-point conjugation energy, E Specific It represents the special energy contribution for a specific molecular system, such as the energy part affected by four-point conjugation, hydrogen bonding and C2 correction, E vdwaals and E coulomb are the non-bonded van der Waals interaction and the non-bonded Coulomb interaction, respectively. BOij , α BOik is the corrected bond order, D e is the key parameter, Δ j is the coordination number, θ0 is the equilibrium bond angle, θ ijk is the interatomic bond angle, P bond1 is a parameter used to describe the initial strength and stiffness of the bond, P val1 is the parameter associated with the initial value of the key level, P pen1 P is a parameter used to indicate the slope or curvature of the interatomic interaction force at a specific bond length. bond2 , P val2 , P pen2 These are parameters used to adjust the shape of the key curve.

4. The method according to claim 1, characterized in that: In step 3, PET molecular dynamics simulations were performed under different water contents, with the water contents being set to 0%, 1%, 5%, and 10%, respectively; the temperature was divided into four gradients of 2000K, 2400K, 2800K, and 3200K for control experiments; the electric field was uniformly set to 3kV / mm, and a molecular dynamics simulation of 100ps was performed based on the NVT ensemble.

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