Volume 42, Issue 2

The effect of multi-walled carbon nanotubes (MWCNT) loading on the crystallization behavior of matrix polyamide 12 (PA-12), in PA-12/polypropylene-MWCNT (PP-MWCNT)-based nanocomposites were analyzed for their non-isothermal crystallization behavior at various cooling rates of 2.5–20 °C/min in differential scanning calorimetry (DSC). Several kinetic models such as Jeziorny (modified-Avrami), Mo and Tobin models were employed to analyze the crystallization behavioral trend with respect to time and temperature of the nanocomposites. The crystallization rate increased half-time of crystallization with MWCNT content as estimated from the Jeziorny theory. The linear agreement between Jeziorny model and experimental relative crystallinity outperforms the Tobin analysis where the coefficient of linear regression was found to be considerably trailing behind and off the satisfactory mark. The Mo model accounts for the percentage crystallinity and thereby successfully explained the crystallization behavior of PA-12 where the kinetic parameters increased with crystallinity indicating higher cooling rate for higher crystallinity. The MWCNT induced crystallization (nucleation activity) values were close to zero irrespective of MWCNT loading which reiterates the enhanced crystallization (rate) of PA-12 in the nanocomposites. Estimations based on Friedman approach showed inter-relationship between activation energy and crystallinity where the later was found to be governed by major (matrix) PA-12 phase.

In the present investigation, silica and talc were used as antiblock additives with slip additive to investigate their effects on tubular quenched polypropylene (TQPP) film properties. Polypropylene (PP) powder was compounded with additives in twin-screw extruder and subsequently processed through TQPP machine to prepare the films. Tear and tensile properties [in machine direction (MD) and transverse direction (TD)] and surface properties of the produced TQPP films were investigated in terms of optics and coefficient of friction (CoF). The effect of conditioning time on CoF was also studied. Addition of slip agent alone to PP did not show any significant change in tear strength, CoF and tensile properties, whereas CoF reduced drastically by adding both slip and antiblock agents in combination. Reduction in CoF values were found to be more pronounced in the presence of silica-based antiblock compared to talc-based antiblock. Film surface morphology was further examined by field-emission scanning electron microscopy. The tear strength and the gloss of TQPP film decreased slightly in presence of only antiblock agents, but the tensile strength was found to increase. It was also found that tensile properties of TQPP films were superior in silica-based formulation, whereas tear strength was better in talc-based formulation in MD and TD.

Composites of a biodegradable thermoplastic aliphatic polyester, polybutylene succinate (PBS), with bentonite were investigated for morphological and mechanical properties. The bentonite was modified with soybean oil (SBO) and lard oil (LO) (2:98 clay:oil % by weight) by mechanical stirring and ultrasonication. The PBS/modified bentonite composite was prepared by using an internal mixer and processed by compression molding. Under bentonite modification conditions, XRD and SEM showed that the bentonite layers were broken into small layers, and the d -spacing between the layers was increased by edible oil molecules. A small plate like structure of modified bentonite composite was observed by SEM micrograph, which revealed short and long layer silicate structure non-directionally throughout the matrix phase. The mechanical properties of PBS were reinforced by this structure. The tensile modulus and elongation at break seem to depend on its directional bentonite. Interestingly, considerable improvement in impact strength was observed at over 2 wt% of clay. The impact strengths of PBS, PBS/modified BTN with SBO composite, and PBS/modified BTN with LO composite were increased from 1 to 1.5 and 2 kJ/m 2 , respectively. Comparatively, using LO modified bentonite had a better performance for increased interlayer and resulted in higher impact strength of the composite than that of SBO composite. The results demonstrated that PBS/modified bentonite using edible oil could be a potential alternative low cost, eco-friendly material with superior impact properties useful for further applications.

Three-dimensional (3D) printing settings allow the existence of differently filled sections together within a piece. That means the use of inhomogeneous internal material structure. Knowing the load capacity that 3D printed plastic parts can withstand leads to the reduction of the filling degree, thus the amount of the used material in certain places. This approach has two advantages during production: (i) less material use and (ii) reduced manufacturing time, both being cost-reducing factors. The present research aims to find the optimal proportions for fabricating a bending test piece with varying filling degrees. To achieve this goal, experimental tests were performed for obtaining tensile strength and modulus of elasticity using different pairs of infill density and pattern. This provided a basis for creating a working mechanical model based on accurate and realistic material properties. Hence, a series of virtual bending test experiments were conducted on a sandwich structure specimen employing Ansys Workbench software. By doing so, the optimal thickness (of the sandwich’s inner layer) with the highest specific load capacity for the given filling patterns and densities were determined. To the best of our knowledge, the current procedure of experiments and method of settings optimization were not discussed elsewhere.

Most of bentonite used in modern drilling engineering is physically and chemically modified calcium bentonite. However, with the increase of drilling depth, the bottom hole temperature may reach 180 °C, thus a large amount of calcium bentonite used in the drilling fluid will be unstable. This paper covers three kinds of calcium bentonite with poor rheological properties at high temperature, such as apparent viscosity is greater than 45 mPa·s or less than 10 mPa·s, API filtration loss is greater than 25 mL/30 min, which are diluted type, shear thickening type and low-shear type, these defects will make the rheological properties of drilling fluid worse. The difference is attributed to bentonite mineral composition, such as montmorillonite with good hydration expansion performance. By adding three kinds of heat-resistant water-soluble copolymers Na-HPAN (hydrolyzed polyacrylonitrile sodium), PAS (polycarboxylate salt) and SMP (sulfomethyl phenolic resin), the rheological properties of calcium bentonite drilling fluids can be significantly improved. For example, the addition of 0.1 wt% Na-HPAN and 0.1 wt% PAS increased the apparent viscosity of the XZJ calcium bentonite suspension from 4.5 to 19.5 mPa·s at 180 °C, and the filtration loss also decreased from 20.2 to 17.8 mL.

Polyoxymethylene (POM) gears have significant roles in the accuracy, robustness and stability of diaphragm gas meters. Therefore, in an attempt to enhance the properties of POM, four different POM-Cloisite 20A nanocomposites were produced in this study. Later tensile and bending strengths, hardness and Vicat softening temperature test, TGA, DSC, SEM and XRD were employed to experimentally evaluate, compare and contrast the mechanical, thermal and morphological properties of those nano-composites. The results proved that proper melt-mixing of 1% nanoparticle into the polymer matrix could lead to an exfoliated nanocomposite that enhanced the mechanical properties (Young’s modulus, yield stress, tensile and bending strengths and hardness) more than the other samples; however it reduced the degradation temperature. Finally, it did not significantly affect the melting temperature. These experimental results provide promising indications that the nano-based POM gears can exhibit better mechanical properties; hence ensuring an extended and robust performance of diaphragm gas meters.

Cobalt, nickel, and their mixed hydroxides were electrochemically deposited on polythiophene-coated carbon-cloth substrate to develop new pseudo-capacitive electrodes for energy storage devices. Thiophene was electro-polymerized on carbon-cloth by the potentiodynamic method in acetonitrile containing 1-butyl-2,3-dimethylimidazolium hexafluorophosphate ionic-liquid as supporting electrolyte. The scanning-electron-microscopy images imply that flower-like Co(OH) 2 microstructures deposited on bamboo-like polythiophene coatings on carbon-fibers but they are covered by net curtain like thin Ni(OH) 2 layer. The Co-Ni layered-double-hydroxide deposited from their equimolar sulfate solutions is composed of large aggregates. The electron-dispersive-spectrum exhibits that Co/Ni ratio equals unity in the layered-double-hydroxide. The capacitances of Co, Ni, and Co-Ni hydroxide-coated PTh electrodes are 100, 569, and 221 F/g at 5 mA/cm 2 in 1 M KOH solution, respectively. Their corresponding oxides obtained by calcination at 450 °C in de-aerated medium possess higher capacitance up to 911, 643, and 696 F/g at 2 A/cm 2 . The shape of cyclic-voltammetry and galvanostatic-charge-discharge curves, as well as the Nyquist plots derived from electrochemical-impedance-spectroscopy measurements, reveal that hydroxide coatings on the polythiophene-coated carbon-cloth are more promising electrode materials for supercapacitor applications. The mixed hydroxide-coated electrode shows good cyclic stability of 100% after 400 cycles at 5 mA/cm 2 .

Cellulose derivatives are widely applied in the field of oil and gas exploration. However, this kind of natural polymers always shows poor temperature resistance due to their organic nature. To improve the temperature resistance of hydroxyethyl cellulose (HEC), inorganic nano-SiO 2 was introduced onto HEC polymer chains through the silylation coupling technique. And Fourier transform infrared spectrum (FTIR), X-ray photoelectron spectrum (XPS), and thermogravimetic analysis (TGA) were used to analyze the nanocomposite. As a result, nano-SiO 2 particle is chemically coupled onto hydroxyethyl cellulose molecule, and nano-SiO 2 /hydroxyethyl cellulose nanocomposite (RJ-HEC) shows excellent thermal stability comparing with HEC polymer. In experiment, thermal aging tests were utilized, and test results suggest that nano-SiO 2 /hydroxyethyl cellulose (RJ-HEC) nanocomposite can be utilized as thickening agent of water-based drilling fluid, which shows improved rheology stability at 210 °C and excellent salt (NaCl) tolerance.

The current investigation is focused on the removal of crystal violet (CV) from water by adsorption process (bach method). To achieve this purpose, specific membranes were prepared from poly acrylonitrile-co-sodium methallyl sulfonate (AN69) and poly acrylic acid (PAA) blends. The adsorption of CV onto AN69/PAA membranes was studied under various conditions: membrane composition, pH, contact time, initial concentration and temperature. To understand the effect of membrane morphology on adsorption process, scanning electronic microscopy (SEM) was employed to determine the features of section and membrane’s surface. From isotherm results, it was found that: the maximum adsorption capacity Q m was 1250 mg g −1 , the Langmuir separation factor R L was lying between 0.33 and 0.76, the Freundlich intensity was higher than Unit ( n  = 1.25) and the adsorption process follows preferentially the Langmuir model (correlation constant R 2  = 0.99). The mechanism of adsorption is perfectly fitted by pseudo second order. The obtained results tend to confirm that the removal of dye molecules is due to the establishment of strong electrostatic interactions between cationic dye molecules and anionic membrane groups. The high adsorption capacity (1250 mg g −1 ) for the small dye molecules may open wide opportunities to apply these membranes in the removal of various hazardous pollutants commonly present in water.