Effects of Different Polypropylene Momeni, Vahid; Shahroodi, Zahra; Gonzalez-Gutierrez, Joamin ...
Polymers,
07/2023, Letnik:
15, Številka:
14
Journal Article
Recenzirano
The current study presents the effect of the backbone as an important binder component on the mechanical, rheological, and thermal properties of Aluminium (Al) alloy feedstocks. A thermoplastic ...elastomer (TPE) main binder component was blended with either polypropylene (PP), grafted-maleic anhydride-PP (PPMA), or grafted-maleic anhydride-PPwax (PPMAwax) plus PP, as the backbone. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) tests were performed to investigate the thermal properties of binder systems and feedstocks. Fourier-transform infrared (FTIR) spectroscopy was used to study the chemical interaction between the binder and the Al alloy. After making feedstock filaments, tensile tests, scanning electron microscopy (SEM), and fused filament fabrication (FFF) printing were done. The results showed that although the PP printability was acceptable, the best mechanical properties and printed quality can be achieved by PPMA. TGA test showed that all binder systems in the feedstocks could be removed completely around 500 °C. From FTIR, the possibility of chemical reactions between Al alloy particles and maleic anhydride groups on the grafted PP backbone could explain the better dispersion of the mixture and higher mechanical properties. Tensile strength in PP samples was 3.4 MPa which was improved 1.8 times using PPMA as the backbone.
► Synthesis and characterization of alumina–copper hybrid particles using a thermo-chemical method. ► Preparation of alumina–copper/water hybrid nanofluids by dispersion of synthesized hybrid ...particles in deionised water. ► Heat transfer and pressure drop studies of prepared hybrid nanofluid with volume concentration 0.1%. ► Significant enhancement in convective heat transfer due to the addition of synthesised hybrid particles compared to water. ► Empirical correlations proposed for Nusselt number and friction factor agree well with the experimental results.
In this experimental work, a fully developed laminar convective heat transfer and pressure drop characteristics through a uniformly heated circular tube using Al2O3–Cu/water hybrid nanofluid is presented. For this we synthesized Al2O3–Cu nanocomposite powder in a thermo chemical route that involves a hydrogen reduction technique and then dispersed the prepared hybrid nano powder in deionised water to form a stable hybrid nanofluid of 0.1% volume concentration. The prepared powder was characterized by X-ray diffraction and Scanning Electron Microscope to confirm the chemical composition, to determine the particle size and to study the surface morphology. The convective heat transfer experimental results showed a maximum enhancement of 13.56% in Nusselt number at a Reynolds number of 1730 when compared to Nusselt number of water. The experimental results also show that 0.1% Al2O3–Cu/water hybrid nanofluids have slightly higher friction factor when compared to 0.1% Al2O3/water nanofluid. The empirical correlations proposed for Nusselt number and friction factor are in good agreement with the experimental data.
We study the structural phase transition, elastic and thermodynamic properties of HfCr.sub.2 from first-principles calculations. The simulated results are very close to those of previous studies. The ...phase transition from C.sub.15 to C.sub.36 occurs at about 202.7 GPa, while the phase transition pressure from C.sub.36 to C.sub.14 is about 283.9 GPa. It can be seen from the phonon spectra and elastic constants that HfCr.sub.2 is mechanically stable at C.sub.15 phase. It can be concluded that C.sub.15 phase HfCr.sub.2 is ductile from 0 to 200 GPa, and the bigger the pressure, the greater the ductility from G/B value and Poisson's ratio. Then, through the analysis of density of states, the mechanism of metal properties is discussed. Finally, the relation of thermal expansion coefficient, Debye temperature and thermal capacity to pressure and temperature is discussed.
We have measured the pressure drop and convective heat transfer coefficient of water-based Al2O3 nanofluids flowing through a uniformly heated circular tube in the fully developed laminar flow ...regime. The experimental results show that the data for nanofluid friction factor show a good agreement with analytical predictions from the Darcy's equation for single-phase flow. However, the convective heat transfer coefficient of the nanofluids increases by up to 8% at a concentration of 0.3 vol% compared with that of pure water and this enhancement cannot be predicted by the Shah equation. Furthermore, the experimental results show that the convective heat transfer coefficient enhancement exceeds, by a large margin, the thermal conductivity enhancement. Therefore, we have discussed the various effects of thermal conductivities under static and dynamic conditions, energy transfer by nanoparticle dispersion, nanoparticle migration due to viscosity gradient, non-uniform shear rate, Brownian diffusion and thermophoresis on the remarkable enhancement of the convective heat transfer coefficient of nanofluids. Based on scale analysis and numerical solutions, we have shown, for the first time, the flattening of velocity profile, induced from large gradients in bulk properties such as nanoparticle concentration, thermal conductivity and viscosity. We propose that this flattening of velocity profile is a possible mechanism for the convective heat transfer coefficient enhancement exceeding the thermal conductivity enhancement.
The electronic structure and elastic and thermodynamic properties of the AgMO.sub.3 (M = Nb, Ta) were investigated using first-principles calculations. The lattice parameters and volumes are in ...reasonable agreement with the experimental results. The calculated Cauchy's pressure, Poisson's ratio, and B/G ratio confirm the ductile nature of both the compounds. The variation in entropy (S), thermal expansion coefficient (alpha), constant volume heat capacity (C.sub.v), and the constant pressure heat capacity C.sub.p with temperature have been studied.
Aqueous nanofluids containing low volume concentrations of Al2O3 nanoparticles in the 0.01-0.3 vol.% range were produced and characterized. Measurements of zeta potential and TEM micrograph of the ...alumina nanoparticles in the Al2O3-water nanofluids show that the alumina nanoparticles can be best dispersed and stabilized in DI water with little evidence of aggregation at 5 h of ultrasonic vibration. Viscosity measurements show that the viscosity of the Al2O3-water nanofluids significantly decreases with increasing temperature. Furthermore, the measured viscosities of the Al2O3-water nanofluids show a nonlinear relation with the concentration even in the low volume concentration (0.01%-0.3%) range, while the Einstein viscosity model clearly predicts a linear relation, and exceed the Einstein model predictions. In contrast to viscosity, the measured thermal conductivities of the dilute Al2O3-water nanofluids increase nearly linearly with the concentration, agree well with the predicted values by the Jang and Choi model, and are consistent in their overall trend with previous data at higher concentrations.
Residual polymer (here, poly(methyl methacrylate), PMMA) left on graphene from transfer from metals or device fabrication processes affects its electrical and thermal properties. We have found that ...the amount of polymer residue left after the transfer of chemical vapor deposited (CVD) graphene varies depending on the initial concentration of the polymer solution, and this residue influences the electrical performance of graphene field-effect transistors fabricated on SiO2/Si. A PMMA solution with lower concentration gave less residue after exposure to acetone, resulting in less p-type doping in graphene and higher charge carrier mobility. The electrical properties of the weakly p-doped graphene could be further enhanced by exposure to formamide with the Dirac point at nearly zero gate voltage and a more than 50% increase of the room-temperature charge carrier mobility in air. This can be attributed to electron donation to graphene by the -NH2 functional group in formamide that is absorbed in the polymer residue. This work provides a route to enhancing the electrical properties of CVD-grown graphene even when it has a thin polymer coating.
The radical statistical copolymerization of N-vinyl pyrrolidone (NVP) and 2-chloroethyl vinyl ether (CEVE) was conducted using the Reversible Addition-Fragmentation chain Transfer (RAFT) ...polymerization technique, employing (O-ethylxanthyl)methylbenzene (CTA-1) and O-ethyl S-(phthalimidylmethyl) xanthate (CTA-2) as the Chain Transfer Agents (CTAs), leading to P(NVP-stat-CEVE) products. After optimizing copolymerization conditions, monomer reactivity ratios were estimated using various linear graphical methods, as well as the COPOINT program, which was applied in the framework of the terminal model. Structural parameters of the copolymers were obtained by calculating the dyad sequence fractions and the monomers' mean sequence lengths. Thermal properties of the copolymers were studied by Differential Scanning Calorimetry (DSC) and kinetics of their thermal degradation by Thermogravimetric Analysis (TGA) and Differential Thermogravimetry (DTG), applying the isoconversional methodologies of Ozawa-Flynn-Wall (OFW) and Kissinger-Akahira-Sunose (KAS).
