scholarly journals Micro-Structure and Thermomechanical Properties of Crosslinked Epoxy Composite Modified by Nano-SiO2: A Molecular Dynamics Simulation

Polymers ◽  
2018 ◽  
Vol 10 (7) ◽  
pp. 801 ◽  
Author(s):  
Qing Xie ◽  
Kexin Fu ◽  
Shaodong Liang ◽  
Bowen Liu ◽  
Lu Lu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Particle Size ◽  
Rational Design ◽  
Thermomechanical Properties ◽  
Composite Model ◽  
Dynamics Simulation ◽  
Thermal And Mechanical Properties ◽  
Micro Structure ◽  
Nano Sio2

Establishing the relationship among the composition, structure and property of the associated materials at the molecular level is of great significance to the rational design of high-performance electrical insulating Epoxy Resin (EP) and its composites. In this paper, the molecular models of pure Diglycidyl Ether of Bisphenol A resin/Methyltetrahydrophthalic Anhydride (DGEBA/MTHPA) and their nanocomposites containing nano-SiO2 with different particle sizes were constructed. The effects of nano-SiO2 dopants and the crosslinked structure on the micro-structure and thermomechanical properties were investigated using molecular dynamics simulations. The results show that the increase of crosslinking density enhances the thermal and mechanical properties of pure EP and EP nanocomposites. In addition, doping nano-SiO2 particles into EP can effectively improve the properties, as well, and the effectiveness is closely related to the particle size of nano-SiO2. Moreover, the results indicate that the glass transition temperature (Tg) value increases with the decreasing particle size. Compared with pure EP, the Tg value of the 6.5 Å composite model increases by 6.68%. On the contrary, the variation of the Coefficient of Thermal Expansion (CTE) in the glassy state demonstrates the opposite trend compared with Tg. The CTE of the 10 Å composite model is the lowest, which is 7.70% less than that of pure EP. The mechanical properties first increase and then decrease with the decreasing particle size. Both the Young’s modulus and shear modulus reach the maximum value at 7.6 Å, with noticeable increases by 12.60% and 8.72%, respectively compared to the pure EP. In addition, the thermal and mechanical properties are closely related to the Fraction of Free Volume (FFV) and Mean Squared Displacement (MSD). The crosslinking process and the nano-SiO2 doping reduce the FFV and MSD value in the model, resulting in better thermal and mechanical properties.

Atomic simulation of mechanical properties of irradiated iron

2019 ◽  
Vol 31 (02) ◽  
pp. 2050027
Author(s):  
Lei Ma ◽  
Changsheng Li ◽  
Ailong Zhang ◽  
Wangyu Hu
Keyword(s):  
Crystal Structure ◽  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Tensile Test ◽  
Room Temperature ◽  
Stacking Faults ◽  
Dynamics Simulation ◽  
Stress And Strain ◽  
Micro Structure ◽  
Atomic Simulation

The mechanical properties of irradiated iron are studied by molecular dynamics simulation. The initial models are irradiated with the energy of primary knocked-on atoms (PKA) of 10[Formula: see text]keV at 100, 300, 500 and 600 K, and then all the irradiated models are subjected to tensile test. The results reveal that the mechanical properties of irradiated iron are changed compared with un-irradiated iron, the yield stress and strain decrease after irradiation, and the irradiation causes the hardening of micro-structure at low temperature and high temperature, but it results in the softening of structure at room temperature. The plastic reduces for irradiated iron under tensile test, more stacking faults are formed in the crystal structure as the temperature increases.

scholarly journals The Mechanical Properties of Poly (Urea-Formaldehyde) Incorporated with Nano-SiO2 by Molecular Dynamics Simulation

Polymers ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1447
Author(s):  
Yanfang Zhang ◽  
Youyuan Wang ◽  
Yudong Li ◽  
Zhanxi Zhang
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Hydrogen Bonds ◽  
Urea Formaldehyde ◽  
Interfacial Interaction ◽  
Dynamics Simulation ◽  
Self Healing ◽  
Fractional Free Volume ◽  
Sio2 Surface ◽  
Nano Sio2

Self-healing materials can promote the sustainable reuse of resources. Poly (urea-formaldehyde) (PUF) microcapsules can be incorporated into dielectric materials for self-healing. However, the mechanical properties of PUF microcapsules need to be improved due to insufficient hardness. In this paper, PUF models incorporated with nano-SiO2 of different filler concentrations (0, 2.6, 3.7, 5.3, 6.7, 7.9 wt.%) were designed. The density, the fractional free volume, and the mechanical properties of the PUF-SiO2 models were analyzed at an atomic level based on molecular dynamics simulation. The interfacial interaction model of PUF on the SiO2 surface was also constructed to further investigate the interaction mechanisms. The results showed that the incorporation of nano-SiO2 had a significant effect on the mechanical properties of PUF. Density increased, fractional free volume decreased, and mechanical properties of the PUF materials were gradually enhanced with the increase of nano-SiO2 concentration. This trend was also confirmed by experimental tests. By analyzing the internal mechanism of the PUF–SiO2 interfacial interaction, it was found that hydrogen bonds play a major role in the interaction between PUF and nano-SiO2. Moreover, hydrogen bonds can be formed between the polar atoms of the PUF chain and the hydroxyl groups (–OH) as well as O atoms on the surface of SiO2. Hydrogen bonds interactions are involved in adsorption of PUF chains on the SiO2 surface, reducing the distance between PUF chains and making the system denser, thus enhancing the mechanical properties of PUF materials.

scholarly journals Synthesis of Bio-Based Poly(Butylene Adipate-co-Butylene Itaconate) Copolyesters with Pentaerythritol: A Thermal, Mechanical, Rheological, and Molecular Dynamics Simulation Study

Polymers ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2006
Author(s):  
Chin-Wen Chen ◽  
Hsu-I Mao ◽  
Zhi-Yu Yang ◽  
Kuan-Wei Huang ◽  
Hao-Chen Yan ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Mechanical Property ◽  
Molecular Dynamics ◽  
Amorphous State ◽  
Polyester Fabric ◽  
Angular Frequency ◽  
Dynamics Simulation ◽  
Thermal And Mechanical Properties ◽  
Frequency Range ◽  
Glass Transition Temperatures

Bio-based unsaturated poly(butylene adipate-co-butylene itaconate) (PBABI) aliphatic copolyesters were synthesized with pentaerythritol (PE) as a modifier, observing the melting point, crystallization, and glass transition temperatures were decreased from 59.5 to 19.5 °C and 28.2 to −9.1 °C as an increase of itaconate concentration, and Tg ranged from −54.6 to −48.1 °C. PBABI copolyesters tend to the amorphous state by the existence of the BI unit above 40 mol%. The yield strength, elongation, and Young’s modulus at different BA/BI ratios were valued in a range of 13.2–13.8 MPa, 575.2–838.5%, and 65.1–83.8 MPa, respectively. Shear-thinning behavior was obtained in all BA/BI ratios of PBABI copolyesters around an angular frequency range of 20–30 rad s−1. Furthermore, the thermal and mechanical properties of PBABI copolyesters can be well regulated via controlling the itaconic acid contents and adding the modifier. PBABI copolyesters can be coated on a 3D air mesh polyester fabric to reinforce the mechanical property for replacing traditional plaster applications.

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