Peel Adhesion of Natural Rubber Bonded to Polyethylene Terephthalate: Effect of Crosslinking on Rate/Temperature Response

Laminates consisting of natural rubber (NR) sandwiched between cloth fabric and polyester film were pulled apart at various rates and temperatures in a T-peel geometry. Peel energies for joints containing uncrosslinked or lightly-crosslinked NR did not obey simple time-temperature superposition. This behavior is attributed to strain-induced crystallization during peeling. However, when the rubber was highly crosslinked, strain crystallization seems to be absent, as peel energies now can be WLF shifted to form a mastercurve.     

Simulation of flow pulsations in a twin rectangular sub-channel geometry using unsteady Reynolds Averaged Navier-Stokes modelling

An unsteady Reynolds Averaged Navier-Stokes (URANS) based turbulence model, the Spalart-Allmaras (SA) model, was used to investigate the flow pulsation phenomena in compound rectangular channels for isothermal flows. The studied geometry was composed of two rectangular sub-channels connected by a gap, on which experiments were conducted by Meyer and Rehme (1994) and were used for the validation of numerical results. Two case studies were selected to study the effect of the advection scheme. The results from the first order upwind advection scheme had clear symmetry and periodicity. The frequency of flow pulsations was under predicted by almost a factor of two. Due to inevitable numerical diffusion of the first order upwind scheme, a second order accurate in space advection scheme was also considered. The span-wise velocity contours, velocity vector plots, and time traces of the velocity components showed the expected cross-flow mixing between the sub-channels through the gap. The predicted kinetic energy in the unsteady velocity fluctuations showed two clear peaks at the edges of the gap. The dynamics of the flow pulsations were quantitatively described through temporal auto-correlations and power spectral functions. The numerical predictions were in agreement with the experiments. Studies on the effect of the Reynolds number and the computational length of the domain were also performed. The numerical results reproduced the relationship between the Reynolds number and the frequency of the flow pulsations. The impact of the channel length was tested by simulating a longer channel with respect to the base case. It was found that the channel length did not significantly affect the numerical predictions. Simulations were also performed using the standard k-? model. While the flow pulsations were predicted with this model, the frequency of the pulsation was in poor agreement with the experimentally measured value.     

Photodegradation of low-density polyethylene with prooxidant and photocatalyst

Low-density polyethylene (LDPE) composite films with trisilver phosphate (Ag₃PO₄) and cadmium selenide (CdSe) particles as photocatalysts and manganese stearate as prooxidant were prepared. The film samples were irradiated under UV and visible light and their photodegradation were evaluated using Fourier-transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, and differential scanning calorimetry. The carbonyl index of the photocatalyst containing samples was very higher than the pure irradiated LDPE and even prooxidant containing film. The morphologies of the irradiated composite films were completely changed and had many cavities and cracks. The thermal stability of the composites was very lower than the pure polyethylene. However the crystallinity of the LDPE films with photocatalysts was enhanced contrarily the LDPE film with manganese stearate. Generally the results showed that the combination of the prooxidant with photocatalyst have synergistic effect on the photodegradation of the LDPE and can be used to accelerate the degradation of the polyethylene films.     

Silane Modification of Carbon Nanotubes and Preparation of Silane Cross‐Linked LLDPE/MWCNT Nanocomposites

The objective of this study is to investigate the effects of carbon nanotube (CNT) content, surface modification, and silane cross‐linking on mechanical and electrical properties of linear low‐density polyethylene/multiwall CNT nanocomposites. CNTs were functionalized by vinyltriethoxysilane to incorporate the ─O─C2H5 functional groups and were melt‐blended with polyethylene. Silane‐grafted polyethylene was then moisture cross‐linked. Silanization of CNT was confirmed by Fourier transform infrared spectroscopy, thermogravimetric analysis (TGA), and EDX analysis. Hot‐set test results showed that silane cross‐linking of polyethylene and incorporation of modified CNTs into polyethylene led to an increase in cross‐linking density and the number of entanglements resulting in a decrease in elongation. It was found that the addition of pristine multiwall carbon nanotubes (MWCNTs) and functionalized MWCNTs does not affect silane cross‐linking density. Silane modification resulted in a stronger adhesion of the silane cross‐linked LLDPE to silanized MWCNTs according to scanning electron microscopy micrographs. Additionally, the electrical tests revealed that the silane modification of CNTs results in an improvement in electrical properties of nanocomposites, while silane cross‐linking will not have an effect on electrical properties. Rheological properties of MWCNT/LLDPE nanocomposites have been studied thoroughly and have been discussed in this study. Moreover, according to TGA test results, modification of the MWCNTs led to a better dispersion of them in the LLDPE matrix and consequently resulted in an improvement in thermal properties of the nanocomposites. Crystallinity and melting properties of the nanocomposites have been evaluated in detail using DSC analysis. J. VINYL ADDIT. TECHNOL., 26:113–126, 2020. © 2019 Society of Plastics Engineers     

Study of performance and stability of hole transport layer-free perovskite solar cells with modified electron transport layer

Journal of Materials Science: Materials in Electronics - The electron transport layer (ETL) performs a functional role in the structure of perovskite solar cells (PSCs). Here in this study, various...     

Circularly/Linearly Polarized Low-Profile Plasma Microstrip Antenna for MIMO Applications

Wireless Personal Communications - A polarization reconfigurable square microstrip patch antenna (SMSPA) based on plasma is introduced in this paper. The antenna is designed for mobile...     

In situ synthesis of leucite-based feldspathic dental porcelain with minor kalsilite and Fe2O3 impurities

K-Feldspar was used as a raw material for in situ synthesis of leucite particles by solid-state reaction method. Prior to synthesis of leucite, K-Feldspar was treated by oxalic acid (C₂H₂O₄) to eliminate Fe content. The parameters affecting the structure and amount of Fe in K-Feldspar was investigated to reach an optimal leaching condition. Next, kasilite removal was studied by introducing CaF₂ to the composition of dental porcelain. To synthesis leucite, the prepared materials were heated up to 1450°C for 3 hours until fusion phenomena occurred, then cooled down to 865°C to permit the leucite crystals nucleate and grow. To find out the chemical composition of powder, XRF, EDX, and Atomic absorption spectroscopy were used. Fourier Transform Infrared Spectroscopy and X-Ray Diffractometer and Scanning Electron Microscopy were employed to study the structure of mineral. Spectrophotometry was chosen to analyze whiteness index of powder after acid treatment. Differential Thermal Analysis was employed to determine the crystallization temperature. Results indicated a dramatic decrease in Fe content (0.018%wt) by employing C₂H₂O₄ as a leachant at 50°C. In addition, whiteness index of 91% was achieved through this procedure for raw feldspar. Finally, 1%wt of CaF₂ prevented formation of kalsilite.     

Latent Dirichlet allocation (LDA) and topic modeling: models,applications, a survey

Multimedia Tools and Applications - Topic modeling is one of the most powerful techniques in text mining for data mining, latent data discovery, and finding relationships among data and text...     

Modeling the micro-scale static friction coefficient of the MEMS silicon surfaces affected by Ag and Au deposition using the thermal evaporation method

In different macro-scale applications, regarding what should be done, many of the prepared surfaces are immediately used after machining with no limitation. Since the micro-electromechanical applications have different conditions, their different properties, such as friction and adherence, must be checked. In the present study, using the thermal evaporation method, the silver and gold layers with different thicknesses were deposited on the silicon surfaces widely used in micromechanical systems (e.g. micro-assembly). Thereafter, the effects of the deposition on the geometrical properties of the surfaces were studied. Also, the effects of the deposition on the adherence and friction properties of the surfaces were examined by modeling the geometrical condition. To this end, the height function distribution was used to exploit the surface friction model in conjunction with the DMT surface adhesion model. The results show the extent to which gold affects the adhesion and friction properties of the coated surfaces.     

Toward a general framework for jointly processor-workload empirical modeling

The Journal of Supercomputing - The complexity of state-of-the-art processor architectures and their consequent vast design spaces have made it difficult and time-consuming to explore the best...