Effect of rolling deformation on the structures and properties of multi‐walled carbon nanotube filled isotactic polypropylene

Isotactic polypropylene filled with various contents of multi‐walled carbon nanotubes (MWCNTs) were fabricated by the injection molding technique and then rolled at room temperature. The unrolled samples (URS) and rolled samples (RS) were characterized by X‐ray diffraction studies, scanning electron microscopy, mechanical and micromechanical tests and differential thermal analyses. Although the URS exhibit the lamellar α‐crystal with a*‐axis orientation, the RS show the same crystals with both a*‐ and c‐axis orientation, which is explained by interlamellar and intralamellar slips and lamellar destruction. Scanning electron micrographs display distinct surface morphological features for both URS and RS. While the tensile strength of RS is higher than that of URS, the Young's modulus (Y) is found to be lower than that of URS. Anisotropy in microharness (H) parallel and perpendicular to the rolled direction has been detected, although H for both samples increases with increasing MWCNT contents. The average relationship H/Y ≈ 0.18 as estimated for URS is closer to the predicted value of 0.10 for polymers than the H/Y ≈ 0.22 obtained for RS. The lamellar thickness for URS increases with increase of MWCNT content and that for RS decreases, as evaluated from both differential thermal analyses and X‐ray diffraction data. Copyright © 2011 Society of Chemical Industry     

Thermal and mechanical behavior of natural rubber latex‐silica aerogel film

A major problem in most natural rubber latex (NRL) commonly encountered like other polymer is susceptibility to mechanical properties and thermal degradation; particularly in thin film due to the presence of double bonds in the main chain. Therefore, it is desirable to seek for ways of improving these properties. Silica aerogel is a material with extraordinary properties was believed to have potential enhance properties in NRL films because of its high specific surface area. Therefore, based on the unique character of silica aerogel, NRL‐silica aerogel film was developed by latex compounding and dry coagulant dipping to form thin film where silica aerogel acts as filler. Silica aerogel, synthesized from rice husk was dispersed in a ball‐mill using distilled water for NRL compounding. Results indicate that increasing silica aerogel loading enhances the mechanical properties of the NRL‐silica aerogel film. Effects of postvulcanization processes were also investigated, whereby the best reinforcing effect was obtained at 4 phr silica aerogel loading with leaching postvulcanization condition. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effects of partial replacement of commercial fillers by recycled poly(ethylene terephthalate) powder on the properties of natural rubber composites

Commercial fillers, including carbon black (N550), halloysite nanotubes (HNTs), and precipitated silica, were replaced by recycled poly(ethylene terephthalate) powder (R‐PET) in natural rubber (NR) composites. Five different compositions of NR/N550/R‐PET, NR/HNTs/R‐PET, and NR/silica/R‐PET compounds, i.e., 100/20/0, 100/15/5, 100/10/10, 100/5/15, and 100/0/20 parts per hundred rubber (phr), were prepared on a two‐roll mill. The curing behavior, tensile properties, and morphological characteristics of the natural rubber composites were investigated. The results indicated that the replacement of carbon black, HNTs, and silica by R‐PET decreased the tensile strength and tensile modulus, such that NR/silica/R‐PET composites showed the lowest effect, followed by NR/HNTs/R‐PET and NR/N550/R‐PET composites. The negative effect on these properties can be explained by the decrease of crosslink density. The curing results revealed that with the replacement of carbon black by R‐PET, the scorch time and cure time decreased, but that the NR/HNTs/R‐PET and NR/silica/R‐PET composites exhibited the opposite trend. Scanning electron microscopy investigation of tensile fracture surfaces confirmed that the co‐incorporation of N550/R‐PET improved the dispersion of R‐PET and enhanced the interaction between the fillers and NR matrix more than R‐PET and silica/R‐PET hybrid fillers. J. VINYL ADDIT. TECHNOL., 2012. © 2012 Society of Plastics Engineers     

Stability of SiN<Subscript>X</Subscript>/SiN<Subscript>X</Subscript> double stack antireflection coating for single crystalline silicon solar cells

Double stack antireflection coatings have significant advantages over single-layer antireflection coatings due to their broad-range coverage of the solar spectrum. A solar cell with 60-nm/20-nm SiN_X:H double stack coatings has 17.8% efficiency, while that with a 80-nm SiN_X:H single coating has 17.2% efficiency. The improvement of the efficiency is due to the effect of better passivation and better antireflection of the double stack antireflection coating. It is important that SiN_X:H films have strong resistance against stress factors since they are used as antireflective coating for solar cells. However, the tolerance of SiN_X:H films to external stresses has never been studied. In this paper, the stability of SiN_X:H films prepared by a plasma-enhanced chemical vapor deposition system is studied. The stability tests are conducted using various forms of stress, such as prolonged thermal cycle, humidity, and UV exposure. The heat and damp test was conducted for 100 h, maintaining humidity at 85% and applying thermal cycles of rapidly changing temperatures from -20°C to 85°C over 5 h. UV exposure was conducted for 50 h using a 180-W UV lamp. This confirmed that the double stack antireflection coating is stable against external stress.     

Quantum chemical studies on corrosion inhibition for series of thio compounds on mild steel in hydrochloric acid

Quantum chemical calculations were performed on ten thio compounds using semi-empirical method PM3 within program package of Material Studio 5.5. The effect of molecular structure on the corrosion inhibition efficiency was investigated using the quantum chemical calculations. The electronic properties such as highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO) energy levels, (LUMO–HOMO) energy gap, dipole moment (λ) and fraction of electron transfer (ΔN) were calculated and discussed. A relationship between the corrosion inhibition efficiency and several quantum parameters was established with coefficient correlation (R²) of 0.8894.     

A General Method for the Synthesis of 5H‐Benzo[b]‐, Carbazolo[2,3‐b]‐ and Indolo[2,3‐b]carbazole Derivatives via Copper(II) Triflate‐Catalyzed Heteroannulation

A straightforward approach for the construction of 5H‐benzo[b]‐, carbazolo[2,3‐b]‐ and indolo[2,3‐b]carbazole derivatives has been developed by using copper(II) triflate‐catalyzed heteroannulation.     

Composite mixed matrix membranes incorporating microporous carbon molecular sieve as filler in polyethersulfone for CO2/CH4 separation

Membrane technology has been considered a key factor for sustainable growth in high-efficiency gas separation. Current mixed matrix membranes (MMMs) technology is rising, but these membranes in the dense structure are having difficulties in operating at high pressures and scale up for commercialization. The purpose of this research is to synthesize composite MMMs (CMMMs) consisting of polyethersulfone (PES), carbon molecular sieve (CMS 1–5 wt %), and Novatex 2471 nonwoven fabric (support layer). The membranes' physical, chemical, and thermal properties were evaluated by different analytical equipment. The morphology of both PES and PES-CMS composite membranes had a porous and asymmetric structure, in which CMS was uniformly distributed in the polymer matrix. The thermal properties showed that the membranes were stable up to 350 °C with a single glass transition temperature. The functional groups in the membrane were confirmed by spectral analysis. The gas performance results showed that carbon dioxide permeance increased with increased CMS concentration and methane permeance decreased due to the hindering effect of CMS under similar operating conditions. The highest selectivity achieved was 12.774 using CMMM of 5 wt % of CMS at 10 bar, which on average was 137.80%, improved selectivity compared to pure PES membrane. The support layer was able to withstand high operating pressures and showed the ability to scale up. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48476.     

Studies on batch adsorptive removal of cadmium and nickel from synthetic waste water using silty clay originated from Balochistan–Pakistan

The potentials of silty clay(SC), acquired from Chaman, Balochistan, were investigated as adsorbent for Ni(Ⅱ)and Cd(Ⅱ) removal from contaminated media. The influence of different operating factors like dose, pH, temperature, and time of contact was explored, and optimum values were noted under batch adsorption method. Isothermal study was conducted with varying concentrations of solutions on optimized conditions and different adsorption models i.e., Langmuir, Freundlich, Temkin and Dubinin–Radushkevich(D–R) isotherm, which were employed to interpret the process. The isothermal data of both Ni(Ⅱ) and Cd(Ⅱ) were well fitted to Langmuir isotherm suggesting the formation of monolayer of metal ions on silty clay. The values of adsorption capacity noted for Ni(Ⅱ) and Cd(Ⅱ) were 3.603 mg·g~(-1) and 5.480 mg·g~(-)1, respectively. Kinetic studies affirmed that pseudo second order(PSO) kinetics was being obeyed by the removal of Ni(Ⅱ) and Cd(Ⅱ). Thermodynamic variables like free energy change(ΔG°), enthalpy change(ΔH°) and entropy change(ΔS°) were calculated. The negative value of ΔG° and the positive values of ΔH° and ΔS° unfolded that the removal process of both metal ions of by SC was spontaneous, endothermic and feasible.     

Fly Ash-based Geopolymer Lightweight Concrete Using Foaming Agent

In this paper, we report the results of our investigation on the possibility of producing foam concrete by using a geopolymer system. Class C fly ash was mixed with an alkaline activator solution (a mixture of sodium silicate and NaOH), and foam was added to the geopolymeric mixture to produce lightweight concrete. The NaOH solution was prepared by dilute NaOH pellets with distilled water. The reactives were mixed to produce a homogeneous mixture, which was placed into a 50 mm mold and cured at two different curing temperatures (60 °C and room temperature), for 24 hours. After the curing process, the strengths of the samples were tested on days 1, 7, and 28. The water absorption, porosity, chemical composition, microstructure, XRD and FTIR analyses were studied. The results showed that the sample which was cured at 60 °C (LW2) produced the maximum compressive strength for all tests, (11.03 MPa, 17.59 MPa, and 18.19 MPa) for days 1, 7, and 28, respectively. Also, the water absorption and porosity of LW2 were reduced by 6.78% and 1.22% after 28 days, respectively. The SEM showed that the LW2 sample had a denser matrix than LW1. This was because LW2 was heat cured, which caused the geopolymerization rate to increase, producing a denser matrix. However for LW1, microcracks were present on the surface, which reduced the compressive strength and increased water absorption and porosity.     

Rapid synthesis of thermally stable hydroxyapaptite

We have optimized the wet precipitation synthesis of hydroxyapaptite to obtain thermally stable powder in the short time span of 3 min. Exposure of the reaction mixture to 1000 W microwave for 3 min furnished hydroxyapatite, which was thermally stable at temperatures up to 1200 °C. Powders were analyzed for phase purity using X-ray crystallography; chemical composition was studied using Fourier transform infrared spectroscopy while particle morphology was analyzed using scanning electron microscopy.