scholarly journals Molecular Dynamics Investigation of the Thermo-Mechanical Properties of the Moisture Invaded and Cross-Linked Epoxy System

Polymers ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 103
Author(s):  
Can Sheng ◽  
Gai Wu ◽  
Xiang Sun ◽  
Sheng Liu
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Diffusion Coefficient ◽  
Hydrogen Bonds ◽  
Epoxy Polymer ◽  
Uniaxial Tensile ◽  
Cross Linking ◽  
Water Molecules ◽  
Moisture Concentration

In spite of a high market share of plastic IC packaging, there are still reliability issues, especially for the effects of moisture. The mechanism between moisture and epoxy polymer is still obscure. A multi-step cross-linking approach was used to mimic the cross-linking process between the DGEBA resin and JEFFAMINE®-D230 agent. Based on the molecular dynamics method, the thermo-mechanical properties and microstructure of epoxy polymer were analyzed. In this paper, the degree of cross-linking ranged from 0% to 85.4% and the moisture concentration ranged from 0 wt.% to 12 wt.%. The hydrogen bonds were investigated in the moisture invaded epoxy polymer. Although most of the hydrogen bonds were related to water molecules, the hydrogen bonds between the inside of epoxy polymer were reduced only a little as the concentration of moisture increased. The diffusion coefficient of the water molecules was found to increase with the increase of moisture concentration. When the moisture concentration was larger than 12 wt.% or smaller than 1.6 wt.%, the diffusion coefficient was less affected by the epoxy polymer. In addition, the free volume and the thermal conductivity of the epoxy polymer were considered. It was found that the moisture could increase the thermal conductivity from 0.24 to 0.31 W/m/K, identifying a coupling relationship between moisture and thermal properties. Finally, the mechanical properties of epoxy polymer were analyzed by uniaxial tensile simulation. The COMPASS and DREIDING force fields were used during the uniaxial tensile simulation. A better result was achieved from the DREIDING force field compared with the experiment. The degree of cross-linking was positively correlated with mechanical properties. For the system with the largest degree of cross-linking of 85.4%, the Young’s modulus was 2.134 ± 0.522 GPa and the yield strength was 0.081 ± 0.01 GPa. There were both plasticizing and anti-plasticizing effects when the water molecules entered the epoxy polymer. Both the Young’s moduli and yield strength varied in a large range from 1.38 to 2.344 GPa and from 0.062 to 0.128 GPa, respectively.

MOLECULAR DYNAMICS STUDY OF THE DISRUPTION OF H-BONDS BY WATER MOLECULES AND ITS DIFFUSION BEHAVIOR IN AMORPHOUS CELLULOSE

2012 ◽  
Vol 26 (14) ◽  
pp. 1250088 ◽  
Author(s):  
RUIJIN LIAO ◽  
MENGZHAO ZHU ◽  
XIN ZHOU ◽  
FUZHOU ZHANG ◽  
JIAMING YAN ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Hydrogen Bonding ◽  
Diffusion Coefficient ◽  
Hydrogen Bonds ◽  
Water Molecule ◽  
Free Volume ◽  
Water Molecules ◽  
Amorphous Cellulose ◽  
Diffusion Behavior ◽  
Bonding Structure

Hydrolysis is an important component of the aging of cellulose, and it severely affects the insulating performance of cellulosic materials. The diffusion behavior of water molecules in amorphous cellulose and their destructive effect on the hydrogen bonding structure of cellulose were investigated by molecular dynamics. The change in the hydrogen bonding structure indicates that water molecules have a considerable effect on the hydrogen bonding structure within cellulose: both intermolecular and intramolecular hydrogen bonds decreased with an increase in ingressive water molecules. Moreover, the stabilities of the cellulose molecules were disrupted when the number of intermolecular hydrogen bonds declined to a certain degree. Both the free volumes of amorphous cells and water molecule-cellulose interaction affect the diffusion of water molecules. The latter, especially the hydrogen bonding interaction between water molecules and cellulose, plays a predominant role in the diffusion behavior of water molecules in the models of which the free volume rarely varies. The diffusion coefficient of water molecules has an excellent correlation with water molecule-cellulose interaction and the average hydrogen bonds between each water molecule and cellulose; however, this relationship was not apparent between the diffusion coefficient and free volume.

scholarly journals Molecular Dynamics Simulation of Improving the Physical Properties of Polytetrafluoroethylene Cable Insulation Materials by Boron Nitride Nanoparticle under Moisture-Temperature-Electric Fields Conditions

Polymers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 971 ◽  
Author(s):  
Xu Hua ◽  
Li Wang ◽  
Shanshui Yang
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Physical Properties ◽  
Electric Fields ◽  
Breakdown Strength ◽  
Relative Dielectric Constant ◽  
Water Molecules ◽  
Cable Insulation ◽  
Insulation Materials

The physical properties in amorphous regions are important for the insulation aging assessment of polytetrafluoroethylene (PTFE) cable insulation materials. In order to study the effect of boron nitride (BN) nanoparticles on the physical properties of PTFE materials under moisture, temperature, and electric fields conditions at the molecular level, the amorphous region models of PTFE, BN/PTFE, water/PTFE, and water/BN/PTFE were respectively constructed by molecular dynamics (MD) simulation. The mechanical properties including Young’s modulus, Poisson’s ratio, bulk modulus, and shear modulus, along with glass transition temperature, thermal conductivity, relative dielectric constant, and breakdown strength of the four models have been simulated and calculated. The results show that the mechanical properties and the glass transition temperature of PTFE are reduced by the injection of water molecules, whereas the same, along with the thermal conductivity, are improved by incorporating BN nanoparticles. Moreover, thermal conductivity is further improved by the surface grafting of BN nanoparticles. With the increase of temperature, the mechanical properties and the breakdown strength of PTFE decrease gradually, whereas the thermal conductivity increases linearly. The injection of water molecules increases the water content in the PTFE materials, which causes a gradual increase in its relative dielectric constant. This work has shown that this effect is significantly reduced by incorporation of BN nanoparticles. The variation of physical properties for PTFE and its composites under the action of moisture, temperature, and electric fields is of great significance to the study of wet, thermal, and electrical aging tests as well as the life prediction of PTFE cable insulation materials.

scholarly journals Molecular Dynamics Simulations for Effects of Fluoropolymer Binder Content in CL-20/TNT Based Polymer-Bonded Explosives

Molecules ◽  
2021 ◽  
Vol 26 (16) ◽  
pp. 4876
Author(s):  
Shenshen Li ◽  
Jijun Xiao
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Correlation Function ◽  
Binding Energy ◽  
Hydrogen Bonds ◽  
Bond Length ◽  
Pair Correlation Function ◽  
Pair Correlation ◽  
Binder Content ◽  
Polymer Bonded Explosives

In order to better understand the role of binder content, molecular dynamics (MD) simulations were performed to study the interfacial interactions, sensitivity and mechanical properties of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane/2,4,6-trinitrotoluene (CL-20/TNT) based polymer-bonded explosives (PBXs) with fluorine rubber F2311. The binding energy between CL-20/TNT co-crystal (1 0 0) surface and F2311, pair correlation function, the maximum bond length of the N–NO2 trigger bond, and the mechanical properties of the PBXs were reported. From the calculated binding energy, it was found that binding energy increases with increasing F2311 content. Additionally, according to the results of pair correlation function, it turns out that H–O hydrogen bonds and H–F hydrogen bonds exist between F2311 molecules and the molecules in CL-20/TNT. The length of trigger bond in CL-20/TNT were adopted as theoretical criterion of sensitivity. The maximum bond length of the N–NO2 trigger bond decreased very significantly when the F2311 content increased from 0 to 9.2%. This indicated increasing F2311 content can reduce sensitivity and improve thermal stability. However, the maximum bond length of the N–NO2 trigger bond remained essentially unchanged when the F2311 content was further increased. Additionally, the calculated mechanical data indicated that with the increase in F2311 content, the rigidity of CL-20/TNT based PBXs was decrease, the toughness was improved.

scholarly journals SPECTRAL FEATURES AND HYDROGEN BOND STRUCTURE OF AQUEOUS SOLUTIONS OF ETHANOL

2021 ◽  
pp. 30-33
Keyword(s):  
Molecular Dynamics ◽  
Hydrogen Bonds ◽  
Aqueous Solutions ◽  
Gaseous Medium ◽  
Water Molecules ◽  
Structural Reorganization ◽  
Intermolecular Hydrogen Bonds ◽  
Method Of Molecular Dynamics ◽  
Combined Use ◽  
Structure Of Aqueous Solutions

The aim of this work is develop an approach that makes it possible to study the spectral properties and structure of intermolecular hydrogen bonds in aqueous solutions of ethanol formed in systems whose existence in a gaseous medium or an isolated state is practically impossible. This approach bases on the combined use of infrared spectroscopy and molecular dynamics (MD) methods. An analysis give the structural reorganization of water molecules depending on the concentration of ethanol alcohol. It has been shown that the method of molecular dynamics with classical force fields makes it possible to explicitly take into account the molecules of the solvent and solute, and, thus, to investigate hydrogen bonds in the system and to interpret with the experimental data obtained by vibrational spectroscopy.

scholarly journals Molecular Dynamics Simulation Study of the Mechanical Properties of Nanocrystalline Body-Centered Cubic Iron

Surfaces ◽  
2020 ◽  
Vol 3 (3) ◽  
pp. 381-391
Author(s):  
Jan Herman ◽  
Marko Govednik ◽  
Sandeep P. Patil ◽  
Bernd Markert
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Strain Rate ◽  
Tensile Tests ◽  
Dynamics Simulation ◽  
Uniaxial Tensile ◽  
Body Centered Cubic ◽  
Bcc Iron ◽  
Average Grain Size ◽  
Study Results

In the present work, the mechanical properties of nanocrystalline body-centered cubic (BCC) iron with an average grain size of 10 Å were investigated using molecular dynamics (MD) simulations. The structure has one layer of crystal grains, which means such a model could represent a structure with directional crystallization. A series of uniaxial tensile tests with different strain rates and temperatures was performed until the full rupture of the model. Moreover, tensile tests of the models with a void at the center and shear tests were carried out. In the tensile test simulations, peak stress and average values of flow stress increase with strain rate. However, the strain rate does not affect the elasticity modulus. Due to the presence of void, stress concentrations in structure have been observed, which leads to dislocation pile-up and grain boundary slips at lower strains. Furthermore, the model with the void reaches lower values of peak stresses as well as stress overshoot compared to the no void model. The study results provide a better understanding of the mechanical response of nanocrystalline BCC iron under various loadings.

Structure, Mechanical Properties, and Thermal Transport in Microporous Silicon Nitride Via Parallel Molecular Dynamics

1995 ◽  
Vol 408 ◽  
Author(s):  
Andrey Omeltchenko ◽  
Aiichiro Nakano ◽  
Rajiv K. Kalia ◽  
Priya Vashishta
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Silicon Nitride ◽  
Elastic Constants ◽  
Thermal Transport ◽  
Entire System ◽  
Amorphous Silicon Nitride ◽  
Parallel Molecular Dynamics ◽  
Dynamics Simulations

AbstractMolecular dynamics simulations are performed to investigate structure, mechanical properties, and thermal transport in amorphous silicon nitride under uniform dilation. As the density is lowered, we observe the formation of pores below ρ = 2.6 g/cc and at 2.0 g/cc the largest pore percolates through the entire system. Effects of porosity on elastic constants, phonons and thermal conductivity are investigated. Thermal conductivity and Young's modulus are found to scale as ρ1.5 and ρ3.6, respectively.

scholarly journals Molecular Dynamics Modeling of Mechanical Properties of Polymer Nanocomposites Reinforced by C7N6 Nanosheet

Surfaces ◽  
2021 ◽  
Vol 4 (3) ◽  
pp. 240-254
Author(s):  
Qinghua Zhang ◽  
Bohayra Mortazavi ◽  
Fadi Aldakheel
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Thermal Effects ◽  
Carbon Nitride ◽  
Maximum Strength ◽  
Uniaxial Tensile ◽  
Dynamics Modeling ◽  
Cohesive Model ◽  
Molecular Dynamics Modeling ◽  
Carbon Nitride Nanosheets

Carbon-nitride nanosheets have attracted remarkable attention in recent years due to their outstanding physical properties. C7N6 is one of the hotspot nanosheets which possesses excellent mechanical, electrical, and optical properties. In this study, the coupled thermo-mechanical properties of the single nanosheet C7N6 are systematically investigated. Although temperature effects have a strong influence on the mechanical properties of C7N6 monolayer, thermal effects were not fully analyzed for carbon-nitride nanosheet and still an open topic. To this end, the presented contribution aims to highlight this important aspect and investigate the temperature influence on the mechanical stress-strain response. By using molecular dynamics (MD) simulation, we have found out that the C7N6 monolayer’s maximum strength decreases as the temperature increase from 300 K to 1100 K. In the current contribution, 5% to 15% volume fractions of C7N6/P3HT composite were employed to investigate the C7N6 reinforcing ability. Significantly, the uniaxial tensile of C7N6/P3HT composite reveals that 10%C7N6 can enhance the maximum strength of the composite to 121.80 MPa which is 23.51% higher than the pure P3HT matrix. Moreover, to better understand the enhanced mechanism, we proposed a cohesive model to investigate the interface strength between the C7N6 nanosheet and P3HT matrix. This systematic study provides not only a sufficient method to understand the C7N6 thermo-mechanical properties, but also the reinforce mechanism of the C7N6 reinforced nanocomposite. Thus, this work provides a valuable method for the later investigation of the C7N6 nanosheet.

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