Different behaviors of metallocene and Ziegler–Natta catalysts in ethylene/1,5‐hexadiene copolymerization

The behaviors of three different catalyst systems, TiCl₄/MgCl₂, Cp₂ZrCl₂ and Cp₂HfCl₂, were investigated in ethylene/1,5‐hexadiene copolymerization. In the Fourier transform infrared spectra of the copolymers, cyclization and branching were detected for 1,5‐hexadiene insertion in the metallocene and Ziegler–Natta systems, respectively. DSC and viscometry analyses results revealed that copolymers with lower T_m and crystallinity and higher molecular weight were obtained with metallocene catalysts. The sequence length distribution of the copolymers was investigated by using the successive self‐nucleation and annealing thermal fractionation technique. The continuous melting endotherms obtained from successive self‐nucleation and annealing analysis were employed to get information about short‐chain branching, the branching dispersity index, comonomer content and lamella thickness in the synthesized copolymers. The results established that metallocene catalysts were much more effective than Ziegler–Natta catalysts in the incorporation of 1,5‐hexadiene in the polyethylene structure. Metallocene‐based copolymers had higher short‐chain branching and comonomer content, narrower branching dispersity index and thinner lamellae. Finally, the tendency of the employed catalysts in the 1,5‐hexadiene incorporation and cyclization reaction was explored via molecular simulation. The energy results demonstrated that, in comparison to Ziegler–Natta, metallocene catalysts have a much higher tendency to 1,5‐hexadiene incorporation and cyclization. © 2018 Society of Chemical Industry     

Evolution of shell formation process in PP/PMMA/PS ternary blends: correlation between the melt rheology and phase morphology

Correlation between the melt rheology and phase morphology of PP/PMMA/PS ternary blends during the shell formation process were studied in detail. In this PP-matrix ternary system, theoretical predictions in agreement with the direct SEM observations demonstrated the core-shell morphology with PMMA and PS phases as core and shell phases, respectively. Morphological observations revealed that the complete shell formation takes place at about 12 and 9 wt% of PS minor phase in ternary blends composed of low and high viscosity PMMAs, respectively. In terms of rheological properties, this was corresponding to the maximum value on the storage modulus versus PS content (shell thickness) curves. Encapsulation of high viscosity PMMA core particles at lower PS contents was related to the bigger particles and low interfacial area in this system compared to the system with low viscosity PMMA core particles. At high PS contents, single and multi-core structures were observed for composite droplets of ternary blends containing low and high viscosity PMMAs, respectively. The single core morphology of low viscosity PMMA particles was related to the coalescence of core particles after the coalescence of the corresponding shells, while high viscosity PMMA cores are less likely to coalescence, leading to creation of multi-core morphology in latter system.     

Poly(Caprolactone)‐Poly(N‐Isopropyl Acrylamide)‐Fe3O4 Magnetic Nanofibrous Structure with Stimuli Responsive Drug Release

Poly(caprolactone; PCL)—poly(N‐isopropylacrylamie; PNIPAAm)—Fe₃O₄ fiber, that can be magnetically actuated, is reported. Here, a structure is engineered that can be utilized as a smart carrier for the release of chemotherapeutic drug via magneto‐thermal activation, with the aid of magnetic nanoparticles (MNPs). The magnetic measurement of the fibers revealed saturation magnetization values within the range of 1.2–2.2 emu g^?1. The magnetic PCL‐PNIPAAm‐Fe₃O₄ scaffold shows a specific loss power value of 4.19 W g^?1 at 20 wt% MNPs. A temperature increase of 40 °C led to a 600% swelling after only 3 h. Doxorubicin (DOX) as a model drug, demonstrates a controllable drug release profile. 39% ± 0.92 of the total drug loaded is released after 96 h at 37 °C, while 25% drug release in 3 h at 40 °C is detected. Cytotoxicity results show no significant difference in cell attachment efficiency between the MNP‐loaded fibers and control while the DOX‐loaded fibers effectively inhibited cell proliferation at 24 h matching the drug release profile. The noncytotoxic effect, coupled with the magneto‐thermal property and controlled drug release, renders excellent potential for these fibers to be used as a smart drug‐release agent for localized cancer therapy.     

Application of response surface methodology for modeling of reactive dye removal from solution using starch‐montmorillonite/polyaniline nanocomposite

In this study, starch‐montmorillonite/polyaniline (St‐MMT/PANI) nanocomposite was synthesized by chemical oxidative polymerization of aniline in the presence of St‐MMT nanocomposite dispersion. The prepared ternary nanocomposite was characterized using FTIR, XRD, and SEM techniques. Adsorption properties of the nanocomposite were investigated for removal of reactive blue (RB 194) as a model reactive dye from aqueous solution. Response surface methodology was employed for the modeling of adsorption capacity of the nanocomposite. A second‐order empirical relationship between adsorption capacity and independent variables (initial dye concentration, amount of the nanocomposite, and pH of the solution) was obtained. Pareto analysis for identification of the factors effect on the system revealed that initial dye concentration was the most effective parameter. The adsorption capacity value of reactive dye on St‐MMT/PANI nanocomposite was 91.74 mg g^?1. Further investigations indicated that the adsorption experimental data were well fitted to the Langmuir isotherm and pseudo‐second‐order kinetic model. POLYM. ENG. SCI., 54:1595–1607, 2014. © 2013 Society of Plastics Engineers     

Anticorrosion assessment of Al2O3‐TiO2 composite thin films derived from sol‐gel dipping technique

Metal surface protection by means of nanostructured ceramic coatings is considered an issue, which is variously scrutinized, and more efforts are made to improve steel performance in accordance with this method. In this respect, this study sought to examine the protective effects of a nanostructured coating containing TiO₂ and Al₂O₃. The optimization approach for obtaining a coating without any cracks with the highest efficiency of corrosion resistance is reported. The variables under assessment were as follows: weight ratio of the oxides, calcination temperature, and preparation parameters. The synthesized samples were analyzed utilizing XRD, FESEM, AFM, Tafel test, EIS, and microhardness measurement. The results revealed that the optimized conditions were as follows: (i) Ti:Al precursor mixture with a weight ratio of 75:25, (ii) heat treatment at 1000°C. This process yielded a uniform composite coating without any cracks with 5.1 nm roughness, containing crystalline rutile phase and amorphous alumina. Not only the intended coating improves the corrosion resistance of steel up to 97%, but it also increases its surface hardness up to 10 units.     

Bioinduced changes in the colored nitrocellulose‐coated cellophane films,induced by the Shewanella J18 143 strain

Two types of the nitrocellulose (NC)‐coated cellophane films, denoted 335 MS films (uncolored) and 335 MSC films (dyed with C.I. Direct Red 81), were incubated with Shewanella J18 143 for a period of 1 month at 50°C. The colored films were decolorized by Shewanella strain throughout this process. Changes in the NC coating of the films were studied by FTIR analysis, by determination of the surface wettability, and by ESEM evaluations. The colored films that were exposed to the Shewanella culture and decolorized, lost a significant amount of nitrate groups and became enriched in the hydroxyl group content. Moreover, the critical surface tension of the colored NC‐coated cellophane films increased, from 18.7 mN/m, for the original films, to 33.1 mN/m, for the film that was treated by the Shewanella strain. Unlike the colored film, the uncolored NC‐coated films did not give any considerable changes in their NC coating when exposed to the Shewanella culture, for the same time period. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Sound absorption characteristics of needle-punched sustainable Typha /polypropylene non-woven

Natural fibers are the acoustical sustainable materials used in blends with polypropylene as carded needle-punched non-woven for the automobile industry. Among the variety of natural fibers, studying the noise-absorptive properties of a novelty introduced fiber called Leafiran extracted from the Typha Australis plant has been aimed in this paper. Typha natural fibers were blended with polypropylene fibers in order to investigate the effect of this newly known natural fiber on the acoustic performance of producing non-woven composite structures. For this aim, five different blend ratios of Typha/polypropylene including 0:100, 30:70, 50:50, 70:30, and 100:0 were prepared. The non-woven porosity, areal density, and sound absorption properties were studied. Impedance Tube Method, which provides the normal incidence sound absorption coefficient (SAC) of materials, was used for determining the acoustic properties of produced non-woven samples. The results of SACs of Typha non-woven revealed that the Typha fibers have good acoustic performance with normal incidence absorption coefficient greater than 0.6 from 500 to 4 kHz. Finally, according to the obtained results from this research, it is claimed that Typha natural fibers could be an acceptable choice for sound reduction applications.     

Comparison of Global Food Traceability Regulations and Requirements

The food traceability regulations of 21 Organization for Economic Co‐Operation and Development (OECD) countries were examined with attention to whether these regulations are comprehensive for all food commodities and processed foods. The countries were evaluated based on responses to a series of questions that were developed to allow assessment of their traceability programs. The questions sought background information on whether: mandatory traceability regulation(s) exists at the national level within a given country; regulations include imported products, and the nature of required documentation for imports; an electronic database(s) for traceability exists and, if present, its accessibility; and labeling regulations allow consumer access and understanding of traceability. The examination ranked the countries that have specific traceability regulations for all commodities, both domestic and imports, as “Progressive,” while countries with less broad or stringent regulations were ranked as “Moderate,” and countries that were still in the developmental stage of mandatory or industry‐led traceability requirements were ranked as “Regressive.” Aggregate scores were developed from all of the rankings, determined on the basis of the questions, for each of the 21 countries, to provide an overall world ranking score. The aggregate scores were “Superior,” “Average,” or “Poor.”     

Implantation of HA into Superplastic Ti-6Al-4V: Kinetics and Mechanical Behaviors of Implanted Layer

An implanted layer is produced by implantation of hydroxyapatite (HA) into superplastic Ti-6Al-4V. X-ray diffraction (XRD) analysis indicates that the surface of the implanted layer is composed of HA and Ti-6Al-4V, and line-scanning analysis confirms a mutual elemental diffusion of HA and Ti-6Al-4V. According to the scanning electron microscope (SEM) images, by increasing the implantation temperature, the thickness of the implanted layer increases. The bonding strength between implanted layer and titanium substrate is examined by conducting a friction wear test. Higher surface removal of an implanted layer is observed when as-received Ti-6A1-4V was used in the implantation process, which is an indication of higher bonding strength between implanted layer and superplastic Ti-6A1-4V. The effect of implanted layer thickness on the wear resistance is also investigated. The reduction in thickness of the implanted layer is more evident in thicker implanted layers. The results suggest that the adhesion between the implanted layer and titanium substrate is stronger than the cohesion within the implanted layer.     

Improving the Spatiotemporal Resolution of Soil Moisture through a Synergistic Combination of MODIS and LANDSAT8 Data

Water Resources Management - Accurate soil moisture (SM) data with continuous spatiotemporal distribution has greatly contributed to various analyses in the fields of agricultural dryness and...