Membrane Separation of Gaseous Hydrocarbons by Semicrystalline Multiblock Copolymers: Role of Cohesive Energy Density and Crystallites of the Polyether Block

The energy-efficient separation of hydrocarbons is critically important for petrochemical industries. As polymeric membranes are ideal candidates for such separation, it is essential to explore the fundamental relationships between the hydrocarbon permeation mechanism and the physical properties of the polymers. In this study, the permeation mechanisms of methane, ethane, ethene, propane, propene and n-butane through three commercial multiblock copolymers PEBAX 2533, PolyActive1500PEGT77PBT23 and PolyActive4000PEGT77PBT23 are thoroughly investigated at 33 °C. This study aims to investigate the influence of cohesive energy density and crystallites of the polyether block of multiblock copolymers on hydrocarbon separation. The hydrocarbon separation behavior of the polymers is explained based on the solution–diffusion model, which is commonly accepted for gas permeation through nonporous polymeric membrane materials.

Determination of Mechanical and Fracture Properties of Silicon Single Crystal from Indentation Experiments and Finite Element Modelling

It is well-known that cracks are observed around the impression during indentation of brittle materials. The cracks inception depends on load conditions, material and indenter geometry. The paper aims to use experimental micro-indentation data, FE simulations with cohesive zone modelling, and an optimisation procedure to determine the cohesive energy density of silicon single crystals. While previous studies available in the literature, which use cohesive zone finite element techniques for simulation of indentation cracks in brittle solids, tried to improve methods for the evaluation of material toughness from the indentation load, crack size, hardness, elastic constants, and indenter geometry, this study focuses on the evaluation of the cohesive energy density 2Γ from which the material toughness can be easily determined using the well-known Griffith-Irwin formula. There is no need to control the premise of the linear fracture mechanics that the cohesive zone is much shorter than the crack length. Hence, the developed approach is suitable also for short cracks for which the linear fracture mechanics premise is violated.

Applications of Flory’s Statistical Theory to Ionic Liquids in the Extended Pressure Range and at Different Temperatures

Introduction: Flory’s statistical theory (FST) for the first time, has been applied successfully to two pure ionic liquids, [C3mim][NTf2] and [C5mim][NTf2] over an extended range of pressure (0.10 – 59.9) MPa and at different temperatures (298.15 – 333.15) K . Methods: : Density and sound speed data have been employed to compute a number of useful and important properties of these ionic liquids in the light of FST. Using Flory parameters (P*, T*, V*, P̃, T̃, Ṽ) the expression for the surface tension (σ) has been deduced in the form σ = σ* σ᷉ (Ṽ), σ* and σ᷉ (Ṽ) being the characteristic and reduced values of surface tension. Since the experimental σ of liquids is not known, the validity of FST has been tested by calculating u using four different u-ρ- σ correlations, namely Auerbach (1948), Altenberg (1950) Singh et al (1997) and Modified Auerbach (2016). Results: A number of useful and important properties of ionic liquids, under the varying physical conditions, have been deduced and compared with the observed ones with quite satisfactory agreement. Such properties include Pint, van der Waals constants (a & b), parachor [P], Eötvas constant (kB), energy (∆EV) and heat of vaporization (∆HV), cohesive energy density (ced), polarity index (n) and solubility parameter (δ). Conclusion: Thus the validity of FST to two ionic liquids under the present study, has been confirmed.

Crystallization of nanoparticles induced by precipitation of trace polymeric additives

Orthogonal to guided growth of nanoparticle (NP) crystals using DNA or supramolecules, a trace amount of polymeric impurities (<0.1 wt.%) leads to reproducible, rapid growth of 3D NP crystals in solution and on patterned substrates with high yield. When polymers preferentially precipitate on the NP surfaces, small NP clusters form and serve as nuclei for NP crystal growth in dilute solutions. This precipitation-induced NP crystallization process is applicable for a range of polymers, and the resultant 3-D NP crystals are tunable by varying polymeric additives loading, solvent evaporation rate, and NP size. The present study elucidates how to balance cohesive energy density and NP diffusivity to simultaneously favor nuclei formation energetically and kinetic growth in dilute solutions to rapidly crystalize NPs over multiple length scales. Furthermore, the amount of impurities needed to grow NP crystals (<0.1%) reminds us the importance of fine details to interpret experimental observations in nanoscience.

Evaluation of Thermodynamic and Optical Properties of Sixteen Ionic Liquids at Different Temperature

Based on the dimensional analysis ρ-u- thermodynamic and ρ-u- optical properties correlations have been applied to sixteen ionic liquids at different temperatures. The objective of the present work is to employ these relations to ionic liquids. The experimental values of ρ and u have been reported in the literature at different temperatures. We have computed thermal expansivity (α), isothermal compressibility (βT), heat capacities ratio (γ), internal pressure (Pint), pseudo-Grüneisen parameter (Г), energy of vaporization (ΔEV), enthalpy of vaporization (ΔHV), cohesive energy density (ced), solubility parameter (δ), refractive index (n), molar refraction (RM) and polarisability (αp) for these liquids. Results are found to quite satisfactory. Keeping in view of uncertainty in the experimental values of ρ and u, as well as some approximations used, the agreement between experimental and theoretical values is found to be quite satisfactory. The results are discussed critically. Introduction: In the present work, we are applying the ρ-u thermodynamic and ρ-u- optical properties correlations to sixteen ionic liquids to estimate thermodynamic and optical properties at different temperature. The experimental values of ρ and u have been reported in the literature at different temperatures. We have computed α, βT, γ, Pint, Г, ΔEV, ΔHV, ced, δ, n, RM and αp for these liquids. Method: Correlations between density-sound velocity and several thermodynamic properties have been derived on the basis of dimensional analysis On the basis of dimensional analysis, a number of useful and important thermodynamic relations were deduced in terms of density (ρ) and speed of sound (u). Result: Results are found to quite satisfactory. Keeping in view of uncertainty in the experimental values of ρ and u, as well as some approximations used, the agreement between experimental and theoretical values is found to be quite satisfactory. Discussion: Density (ρ) and ultrasonic speed (u) data of sixteen RTILs at different temperatures have been taken from the literature. Calculated values of α, βT, Pint, γ, CP-CV, and, Г obtained from empirical relations. The experimental values of α are given for making a comparative study. Conclusion: Based on the dimensional analysis our recently developed correlations between ρ-u- thermodynamic and ρ-uoptical properties have been found to be quite successful when applied to sixteen ionic liquids for the first time. α, βT, γ, Pint, ΔEVap, ΔHVap, ced, δ as well as RM and αp were calculated at various temperatures.

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

Crystallize Nanoparticles by Precipitating Trace Polymeric Additives

<p>Growing nanoparticle (NP) crystals has been pursued extensively using ligand chemistries such as DNA and supramolecules, controlled evaporation and patterned surfaces. Here, we show that a trace amount of polymeric impurities (<0.1 wt.%) leads to reproducible, rapid growth of high quality 3-D NP crystals in solution and on patterned substrates with high yield. The polymers preferentially precipitate on the NP surfaces inducing the formation of small NP clusters, which subsequently act as nuclei to initiate NP crystal growth in dilute solution. This precipitation-induced NP crystallization process is applicable for a range of polymers and the resultant 3-D NP crystals can be tuned by varying polymeric additives loading, solvent evaporation rate and NP size. Fundamentally, the present study elucidates how to balance cohesive energy density and NP diffusivity in the self-assembly to favor nuclei formation energetically and kinetic growth in dilute solutions. The results shown also opened up the process window to rapidly and reliably fabricate NP crystals over multiple length scales. Furthermore, the amount of these impurities needed to grow NP crystals (<0.1 %) reminds us the need to pay special attention to fine details to interpret experimental observations in nanoscience.</p>

Crystallize Nanoparticles by Precipitating Trace Polymeric Additives

<p>Growing nanoparticle (NP) crystals has been pursued extensively using ligand chemistries such as DNA and supramolecules, controlled evaporation and patterned surfaces. Here, we show that a trace amount of polymeric impurities (<0.1 wt.%) leads to reproducible, rapid growth of high quality 3-D NP crystals in solution and on patterned substrates with high yield. The polymers preferentially precipitate on the NP surfaces inducing the formation of small NP clusters, which subsequently act as nuclei to initiate NP crystal growth in dilute solution. This precipitation-induced NP crystallization process is applicable for a range of polymers and the resultant 3-D NP crystals can be tuned by varying polymeric additives loading, solvent evaporation rate and NP size. Fundamentally, the present study elucidates how to balance cohesive energy density and NP diffusivity in the self-assembly to favor nuclei formation energetically and kinetic growth in dilute solutions. The results shown also opened up the process window to rapidly and reliably fabricate NP crystals over multiple length scales. Furthermore, the amount of these impurities needed to grow NP crystals (<0.1 %) reminds us the need to pay special attention to fine details to interpret experimental observations in nanoscience.</p>