Localization of different types of organoclay montmorillonite in the compatibilized polyamide 6/carboxylated acrylonitrile butadiene rubber nanocomposites: Morphology and rheological properties

In this study, nanocomposites based on polyamide 6/carboxylated acrylonitrile butadiene rubber (PA6/XNBR) reinforced by the clay montmorillonite (OMMT) (Cloisite 20A and Cloisite 30B) were prepared by melt mixing. Glycidyl methacrylate-grafted XNBR (XNBR-g-GMA) compatibilizer was used for immiscible blends of PA6/XNBR. The results illustrated that OMMT wanted to be selectively present in the more hydrophilic PA6 phase. Also, by adding the XNBR-g-GMA compatibilizer and increasing OMMT content, tensile strength, rheological and dynamic mechanical properties of the nanocomposites improved. According to transmission electron microscopy (TEM) images, a few layers of OMMT (Cloisite 20A) in the XNBR-g-GMA compatibilizer phase was observed. The results of X-ray diffractometry and TEM analyses demonstrated that the formation of intercalated or exfoliated structures for both types of OMMT nanocomposites. In end of all analysis was found PA6/XNBR reinforced by the Cloisite 30B could be substantially improved by adding XNBR-g-GMA as a compatibilizer when compared to those reinforced by Cloisite 20A.     

Enhancement of thermal,morphological, and mechanical properties of compatibilized based on PA6-enriched graphene oxide/EPDM-g-MA/CR: Graphene oxide and EPDM-g-MA compatibilizer role

In this study, a series of elastomeric nanocomposites based on specific amounts of polyamide6 (PA6)/chloroprene rubber (CR) blends which are compatibilized with ethylene propylene diene monomer-grafted-maleic anhydride (EPDM-g-MA) and different amounts of graphene oxide (GO) were prepared with melt mixing method. The effect of compatibilizer and reinforcement concentration in the PA6/CR blend matrix was investigated using theoretical and experimental analysis. Dispersion of nanoplatelets within rubber blend matrix was proven with transmission electron microscopy and field emission-scanning electron microscopy. The modified microstructure of samples showed the significant effect of EPDM-g-MA and GO on the size reduction of CR droplets in the PA6 continuous phase. The results from differential scanning calorimetry and dynamic mechanical thermal analysis revealed the effect of EPDM-g-MA and GO as an effective nucleating agent in PA6-enriched GO/CR (PA6EGO/CR). The findings obtained from thermogravimetric analysis displayed that the GO in the presence of an EPDM-g-MA as a compatibilizer can cause a higher thermal stability in PA6EGO/CR. From mechanical properties, by adding a compatibilizer to the PA6/CR blend, the tensile strength changed from 39.0 to 45.1, the Young's modulus altered from 522.2 to 716.0 and the elongation at break changed from 246.8 to 222.2. While incorporation of 5 phr of GO to the compatibilized blend, the tensile strength increased by 25.2%, the Young's modulus increased by 36.6% and the elongation at break decreased by 20%. The Christensen–Lo model used for analyzing the stiffness of PA6EGO/EPDM-g-MA/CR with emphasis on the influence of the interphase region to predict the effect of various loadings of GO and EPDM-g-MA of Young's modulus. The rheology and creep tests showed a significant effect of EPDM-g-MA and GO content on the rheology behavior of nanocomposites.     

Effect of drawing temperature on the structure and free volume of semicrystalline polyester yarns

Supercritical carbon dioxide (scCO₂), an environmentally friendly solvent, can change the fine structure of fibers depending on treatment temperature and pressure. This article presents the results of an investigation into the effects of drawing temperature, scCO₂ exposure and tension on structural changes, and mesomorphic transitions in partially oriented yarn (POY) and oriented poly(ethylene terephthalate) (PET) yarns. Samples of POY and PET yarns were uniaxially drawn at different temperatures to obtain filaments with different structures for subsequent exposure to scCO₂ in the presence and absence of tension at a temperature of 80^oC and under a pressure of 220 bar. Structural investigation of the samples was performed by combining the results obtained from differential scanning calorimetry, Fourier transform infrared, mechanical deformation, and density and birefringence measurements, all of which exhibited a good correlation. The fractional free volume in the PET samples was considered for interpreting structure–property relations. Results showed that the development of a transient structure strongly depends on process temperature and that for an identical draw ratio, PET yarns drawn at 23^oC are significantly more oriented than those drawn at 68^oC. Two crystallization mechanisms, that is strain‐induced and thermal‐induced crystallization, are involved that are frequently used to explain the structural changes during yarn deformation at different temperatures. The degree of crystallinity and orientation factors for PET yarns does not proportionally increase with increasing temperature of the drawing process; indeed, the highest value is obtained at a temperature of 100^oC, whereas the lowest is observed at a temperature of 68^oC, which is near the glass transition temperature. Tension under scCO₂ exposure also produces significant effects in term of causing structural changes. POLYM. ENG. SCI., 55:2030–2041, 2015. © 2014 Society of Plastics Engineers     

Comparison of methods for estimating loss from water storage by evaporation and impacts on reservoir management

Reservoirs are the key infrastructure of water resources management. A controlling variable of reservoir operation is evaporation, which in semi‐arid and arid regions may consume a large fraction of reservoir storage annually. This paper assesses the role of evaporation and the choice of evaporation methods on reservoir operation. The operation of the reservoir is calculated with the standard operation policy (SOP). Several efficiency criteria are employed to rank the evaporation‐calculation methods with the technique for the order of preference by similarity to ideal solution (TOPSIS). The method presented in this paper is illustrated by applying its application to Karkheh reservoir, the largest in Iran.     

Significance of thermodynamics and rheological characteristics of dope solutions on the morphological evolution of polyethersulfone ultrafiltration membranes

Herein, the effect of solvent type and polymer concentration on the thermodynamic and viscoelastic properties, and performance of polyethersulfone (PES) ultrafiltration (UF) membranes are investigated. The morphology and mechanical properties of the membranes are examined too. Rheological measurements indicated that solidification and instantaneous demixing occurred fast for PES/N-methyl-2-pyrrolidone (NMP) dope solution. This resulted in a dense skin layer with a finger-like structure confirmed by the scanning electron microscopy images. In comparison, PES/dimethylformamide (DMF) exhibited a delayed solidification and demixing with a sponge-like structure. Rheological characteristics and ternary phase diagrams of two systems are examined to gain insights and make correlations with the morphology of resultant membranes. Performance analysis revealed that membranes derived from PES/NMP system exhibited both improved pure water flux and bovine serum albumin rejection suggesting the superiority of NMP compared to DMF as the solvent of choice for the preparation of PES UF membranes.     

Facile route for synthesis of strontium hexaborate crystalline powders

In this paper, a solid-state reaction route was developed to synthesize SrB₆O₁₀ crystalline powders. Regarding the last preparation methods, a short process time of synthesis was achieved that has not reported before. The prepared sample was characterized using various methods, such as X-ray diffraction, Raman spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, and diffuse reflection spectroscopy. The obtained results proved that the prepared sample at temperature 840°C with 2.5 h duration consists of SrB₆O₁₀ crystalline powders with 4.96 eV bandgap.     

n-Fold obstinate filters in BL-algebras

In this paper, we introduced the notion of n-fold obstinate filter in BL-algebras and we stated and proved some theorems, which determine the relationship between this notion and other types of n-fold filters in a BL-algebra. We proved that if F is a 1-fold obstinate filter, then A/F is a Boolean algebra. Several characterizations of n-fold fantastic filters are given, and we show that A is a n-fold fantastic BL-algebra if A is a MV-algebra (n ≥ 1) and A is a 1-fold positive implicative BL-algebra if A is a Boolean algebra. Finally, we construct some algorithms for studying the structure of the finite BL-algebras and n-fold filters in finite BL-algebras.