Study of marine bacteria adhesion on sea-immersed 304 and 316 stainless steels: experimental and theoretical investigations

In this study, we investigated the potential adhesion of marine bacteria isolated from seawater in the port of Chmaâla, Morocco, to sea-immersed 304 and 316 stainless steels using thermodynamic approach and the Environmental Scanning Electron Microscopy (ESEM). Furthermore, the physicochemical properties including hydrophobicity and electron donor / electron acceptor (Lewis acid-base) of bacterial isolates and both substrates were evaluated using the contact angle measurements. The molecular identification indicated that the isolated strains were Bacillus thuringiensis and Bacillus amyloliquefascience. Results also showed that both bacterial strains’s cells have a hydrophilic character with Δ_Giwi values of 29.30 and 24.12 mJ m^?2 respectively for Bacillus thuringiensis and Bacillus amyloliquefascience, and are strong electron donating (γ^?) and weakly electron accepting (γ⁺). For substrates surfaces, we found that both sea-immersed stainless steels types were hydrophilic and present strong electron-donor character (γ^? = 49 ± 0.2 mJ m^?2 for 304 and γ^? = 55.07 ± 0.02 mJ m^?2 for 316) and weak electron-acceptor character (γ⁺ = 5.4 ± 0.1 mJ m^?2 for 304 and γ⁺ = 8.3 ± 0.06 mJ m^?2 for 316). The theoretical prediction showed that both tested strains, B. thuringiensis and B. amyloliquefascience, exhibited positive values of ΔG^Total vis-à-vis the two sea-immersed stainless steels types which indicates unfavorable adhesion while the ESEM electro-micrographs show that both strains were able to adhere to both strainless steels surfaces.     

Investigations on matrix network characteristics in NBR/silica nanocomposites: Resolving matrix bulk density and network molecular weight and their alterations due to filler‐curing agent interactions

Presence of filler in an elastomeric composite can affect curing characteristics due to possible interaction with curing agents. Alteration of the curing characteristics can change intrinsic properties of elastomer including its bulk density and swelling behavior. In this study, a series of acrylonitrile butadiene rubber (NBR) with various curing levels was prepared. From the experimental data the bulk density and network molecular weight (M_c,sw) were specified and a relationship was established between these parameters. In order to determine the swelling characteristics of NBR in presence of filler, another series of NBR/silica nanocomposites was prepared with various nanosilica loadings under a constant content of curing agents and curing conditions. With the use of the swelling data and applying the obtained relationship, the M_c,sw and bulk density of the filled NBR matrix were resolved. The M_c,sw values obtained by considering the influence of nanosilica on curing characteristics of NBR were compared with those obtained simply based on bulk density of raw rubber. This comparison confirmed that there are considerable differences between these values. With increasing nanosilica contents, and hence, increasing the negative impact of the filler on reducing curing degree of NBR, the bulk density of filled NBR matrix was decreased. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46170.     

Temperature dependency of gas barrier properties of biodegradable PP/PLA/nanoclay films: Experimental analyses with a molecular dynamics simulation approach

Polypropylene (PP)/poly(lactic acid) (PLA)/clay nanocomposite films with various compositions (PP‐rich and PLA‐rich) were prepared. Their structural and barrier properties against CO₂, O₂, and N₂ were investigated. The microstructure of the nanocomposites was studied by scanning electron microscopy, transmission electron microscopy, and wide angle X‐ray scattering. The PP‐rich with 75/25 composition revealed the best barrier properties against all the gases which could be justified according to its microstructure. Selectivity of O₂/N₂ and CO₂/N₂ was also measured. It was found that the addition of nanoclay as a gas barrier component reduced the permeability in both systems. The permselectivity was also reduced in the PP‐rich films while it was increased in the PLA‐rich system. Moreover, the temperature dependency of permeability, selectivity, and permselectivity for PP, PLA, and PP/PLA (75/25) samples was examined. The results showed that the temperature dependence of permeability obeyed an Arrhenius equation and order of activation energy of permeability for O₂, CO₂, and N₂ gases was found to be E_P < E_P/PLA < E_PLA. According to solubility measurements, the order of solubility coefficient for gases was as follows: CO₂ > O₂ > N₂. Finally, the molecular dynamics (MD) simulation was performed to estimate the diffusivity coefficients of the gases and showed that solubility increases with increasing temperature, which was in accordance with the experiments. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46665.     

Synthesis,characterization, rheological and thermal behavior of metallocene ethylene − norbornene copolymers with low norbornene content using pentafluorophenol modified methylaluminoxane

Ethylene ? norbornene copolymers were synthesized using rac‐ethylene bis(indenyl) zirconium dichloride/pentafluorophenol modified methylaluminoxane. First, the effect of using a modifier in combination with a low ratio of Al/Zr on the catalyst activity and co‐monomer incorporation was studied. The results of copolymerization reveal a 20% co‐monomer incorporation improvement and a rise of activity by 2‐fold in the presence of the modifier. Rheological measurements show a higher molecular weight in copolymers synthesized using modified methylaluminoxane. The alternative and dyad block microstructures of copolymers become possible in the case of a norbornene content of more than 14 mol%. Second, the effect of co‐monomer content on the rheological and thermal behavior of the synthesized copolymers was investigated. The results of the rheological study indicate a lower molecular weight in samples containing a higher norbornene content. Dynamic mechanical thermal analysis confirms the influence of different microstructures on the glass transition temperature. The crystal structure of copolymers having a higher molecular weight is emphasized using wide angle X‐ray scattering and DSC even with a greater incorporation of norbornene. © 2015 Society of Chemical Industry     

Statistical Optimization for Production of Light Olefins in a Fluidized‐Bed Reactor

The methanol‐to‐olefins reaction (MTO) was studied in a small‐scale fluidized‐bed reactor over synthesized silicoaluminophosphate (SAPO‐34) catalysts. Mesoporous nanocrystalline SAPO‐34 molecular sieves were synthesized hydrothermally by ultrasonic and microwave‐assisted aging processes in the presence of hexadecyltrimethylammonium bromide (CTAB) and tetradecyldimethyl(3‐trimethoxysilylpropyl)ammonium chloride (TPOAC) as surfactant agents. The Box‐Behnken experimental design method was applied to determine the optimum operating parameters of this process conducted in the fluidized‐bed reactor. The optimum conditions in terms of reaction temperature, ratio of inlet gas velocity to minimum fluidizing velocity, and MeOH weight fraction were evaluated.     

Multivariate Modeling of a Chemical Toner Manufacturing Process

Modeling, optimization, process monitoring, and product development in a toner process using multiway principal component analysis and multiway partial least square method is described. Process measurements and product quality values of past successful batches were collected in a data matrix and preprocessed through time alignment, centering, and scaling. Following the identification of latent variables, an empirical model was built through a fourfold cross validation that can represent the operation of a successful batch. The prepared model provided a realistic prediction of process behavior, realistically represented the operation of the industrial unit, and is mathematically simple enough to be used in online optimization and for automatic control strategies of selected abnormal batches.     

High‐performance carboxylate superplasticizers for concretes: Interplay between the polymerization temperature and properties

Polycarboxylate superplasticizers based on acrylic acid (AA) and maleic anhydride (MAn) were synthesized via free‐radical copolymerization with an ethylene glycol monomer and characterized. The copolymerization temperature (ranging from 50 to 90 °C) appeared to be the key operating factor governing the chemical structure of the superplasticizers. The chemical structures of the products were analyzed by gel permeation chromatography, whereas an optimized sample was further analyzed by Fourier transform infrared spectroscopy and ¹H‐NMR. Superplasticizers of the AA and MAn classes were then incorporated into concrete, and their performances were measured by slump and slump loss tests, where a large dependency of the microstructure on the synthesis temperature was recognized. The optimum temperatures were found to be 50 and 80 °C for the AA and MAn modifiers, respectively. At their own optimum temperatures, the AA and MAn superplasticizer revealed slump losses from 23 to 4 cm and 15 to 5 cm, respectively, after 45 min. The chemical structures of the plasticizers were patterned illustratively to speculate the performance of each superplasticizer according to changes that took place in the backbone length and side‐chain density. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44908.     

Microfunnel magnetic stirring-assisted dispersive liquid–liquid microextraction-derivatization technique,for the determination of 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (Mutagen X) in aqueous samples by GC-ECD

A simple, highly sensitive and reliable microfunnel magnetic stirring-assisted dispersive liquid–liquid microextraction method (MF-MSA-DLLME) was developed based on the derivatization of mutagen X in aqueous samples and determined using gas chromatography with electron capture (GC-ECD). The effects of different variables on the extraction efficiency were investigated and optimized. The calibration curve showed good linearity in the concentration range of 0.05–400 μgL^?1 (r² = 0.998) and precision (RSD = 5.0%). Under optimum conditions, the limit of detection (LOD) and the limit of quantification in drinking water were 0.015 and 0.05 µg L^?1, respectively. The developed method was successfully applied for the determination of six Mutagen X (MX) in real samples.