scholarly journals Molecular Dynamics Study of Anti-Wear Erosion and Corrosion Protection of PTFE/Al2O3 (010) Coating Composite in Water Hydraulic Valves

Coatings ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1214
Author(s):  
Masoud Kamoleka Mlela ◽  
He Xu ◽  
Haihang Wang
Keyword(s):  
Binding Energy ◽  
Energy Density ◽  
Bulk Modulus ◽  
Chain Length ◽  
Solubility Parameter ◽  
Cohesive Energy ◽  
Solubility Parameters ◽  
Cohesive Energy Density ◽  
Water Hydraulic ◽  
Hydraulic Valves

Cavitation erosion and corrosion commonly occur on the surface of fluid dynamic system components, mostly water hydraulic valves, causing the failure of metal parts. Coating of polytetrafluoroethylene (PTFE) on Al2O3 (010) was created by varying the chain length of polytetrafluoroethylene. Calculations were conducted by molecular dynamic (MD) simulations. This study shows that the K10 and K20 chain lengths’ mechanical properties possess negative elastic, shear, and bulk modulus values. We have found that the K10 chain length composition shows the high results of binding energy and negative bulk modulus of 6267.16 kJ/mol and −3709.54 GPa, respectively. The K10 chain length was observed to possess a higher cohesive energy density (CED) and solubility parameter of (6.885 ± 0.00076) × 109 J/m3 and (82.974 ± 0.005) (J/cm3)0.5, respectively. It was also found that increasing the chain length contributes to decreasing the binding energy and solubility parameter of PTFE/Al2O3 (010) composition. These results are vital for overcoming the repetitive regime of high compressive strength of water microjets on the valves’ material surface. Improved values of the cohesive energy density and solubility parameters imply the water’s superior hydrophobic effect.

Study of the effects of water content and temperature on polyacrylamide/polyvinyl alcohol interpenetrating network hydrogel performance by a molecular dynamics method

e-Polymers ◽  
2015 ◽  
Vol 15 (5) ◽  
pp. 301-309 ◽  
Author(s):  
Qinghua Wei ◽  
Yingfeng Zhang ◽  
Yanen Wang ◽  
Weihong Chai ◽  
Mingming Yang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Binding Energy ◽  
Energy Density ◽  
Water Content ◽  
Cohesive Energy ◽  
Pair Correlation ◽  
Cohesive Energy Density ◽  
Pva Hydrogel ◽  
Hydrogel System

AbstractAn investigation of the molecular interaction within a hydrogel system was conducted using molecular dynamics simulation, and the interaction mechanism of a polyacrylamide/polyvinyl alcohol (PAM/PVA) hydrogel system was examined specifically at the molecular level. Several characteristics of the PAM/PVA composite hydrogel system that are largely dependent on water content and temperature were studied in this paper, such as cohesive energy density, binding energy, mechanical properties and pair correlation function. The cohesive energy density and binding energy of the hydrogel system increased with higher water content. Results also showed that increased temperatures led to a decrease in the cohesive energy density of the system, while binding energy remained unchanged. The mechanical properties of the system were evaluated by analyzing the static mechanic performance. Results showed that elastic coefficients, engineering modulus and ductility decreased with increasing water content and temperature. In addition, analysis of the pair correlation function revealed mainly hydrogen bonding interactions between H2O molecules and surrounding atoms or functional groups. Results also indicated that the strength of these hydrogen bonds was Owater>OPVA>OPAM>NPAM, confirming both the potential and the difficulty of hydrogen bond formation. The aforementioned findings help in understanding the interaction mechanisms between the components of a hydrogel system and in demonstrating the effects of water content and temperature on the PAM/PVA hydrogel system, which provides useful information on the possible operating windows of a biomedical hydrogel-making process.

Liquid Structure, Thermodynamics, and Mixing Behavior of Saturated Hydrocarbon Polymers. 1. Cohesive Energy Density and Internal Pressure

1998 ◽  
Vol 31 (20) ◽  
pp. 6991-6997 ◽  
Author(s):  
Janna K. Maranas ◽  
Maurizio Mondello ◽  
Gary S. Grest ◽  
Sanat K. Kumar ◽  
Pablo G. Debenedetti ◽  
...  
Keyword(s):  
Energy Density ◽  
Internal Pressure ◽  
Cohesive Energy ◽  
Saturated Hydrocarbon ◽  
Liquid Structure ◽  
Cohesive Energy Density ◽  
Mixing Behavior ◽  
Hydrocarbon Polymers

The Interaction between Rubber and Liquids. III. The Swelling of Vulcanized Rubber in Various Liquids

1943 ◽  
Vol 16 (2) ◽  
pp. 263-267 ◽  
Author(s):  
G. Gee
Keyword(s):  
Energy Density ◽  
Cohesive Energy ◽  
Molecular Volume ◽  
Substantial Agreement ◽  
Swelling Power ◽  
Cohesive Energy Density ◽  
Vulcanized Rubber ◽  
A Value

Abstract The entropy of swelling of vulcanized rubber is estimated, and assumed independent of the nature of the swelling liquid. The heat of swelling is related to the cohesive energy of the liquid, and a value of 66 calories per cc. deduced for the cohesive energy density of rubber. The swelling power of a liquid can be calculated approximately if its cohesive energy and molecular volume are known. Substantial agreement with theory is found in most cases, although it is necessary to consider aliphatic and aromatic liquids separately. The anomalously high swelling power of acids and alcohols arises from their association.

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