1,3,5-Benzenetrisamide based nucleating agents for poly(vinylidene fluoride)

This paper presents 1,3,5-benzenetrisamides as colorless α-nucleating agents for poly(vinylidene fluoride). In order to screen a large variety of 1,3,5-benzenetrisamide derivatives with respect to their nucleating potential an efficient and reliable test based on polarized light microscopy was established. For selected promising compounds the concentration dependence of the PVDF crystallization temperature, the dissolution behavior of the additive in the polymer melt, and the crystallization of the additive from the polymer melt was investigated in a concentration range between 1 wt% (10,000 ppm) and 70 ppm. It was found, that only two of the investigated compounds were able to raise the crystallization temperature about 8 °C at a concentration of 140 ppm and 580 ppm, respectively. These trisamides have the advantage being soluble in the polymer melt, not featuring absorption of visible light and therefore allowing the preparation of uniform and colorless PVDF products.     

Phase behavior and optical- and mechanical properties of the binary system isotactic polypropylene and the nucleating/clarifying agent 1,2,3-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl) methylene]-nonitol

The phase behavior and optical- and selected mechanical properties of the binary system consisting of isotactic polypropylene (i-PP) and a new sorbitol-based nucleating and clarifying agent, 1,2,3-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl) methylene]-nonitol (TBPMN), were investigated. Temperature/composition diagrams of the binary were found to be of the simple monotectic type, similar to those of, among others, the previously investigated i-PP/1,3:2,4-bis(3,4-dimethyldibenzylidene)sorbitol (DMDBS). Liquid-liquid phase separation was observed in binaries comprising more than ∼5% w/w TBPMN, indicative of enhanced miscibility of the new additive with i-PP when compared with that of DMDBS. At TBPMN contents ≥0.1% w/w the optical properties haze and clarity progressively improved to remarkable levels with increasing concentration of the nucleating agent up to the onset of liquid-liquid phase separation, above which they deteriorated. The enhanced solubility in i-PP of the new clarifying agent on the one hand required uneconomically higher concentrations than previous members of the sorbitol family to be effective, but on the other, the superior optical properties of the system may permit manufacturing of clarified products of increased thickness.     

Nucleation and growth of the electrodeposited iron layers in the presence of an external magnetic field

The effect of an uniform magnetic field with a flux density up to 1 T and different configurations relative to the electrode surface on the electrocrystallization of Fe on polycrystalline Au(1 1 1) from acidic sulphate electrolyte has been investigated. It was found, irrespective of the applied parameters, that the deposition proceeds through successive nucleation and growth steps. The first one related to 2D growth was followed by a second nucleation and 3D diffusion controlled growth. At potential of −1500 and −1550 mV_MSE nucleation proceeds via a progressive mode, while at −1650 mV_MSE it follows an instantaneous mode. A strong influence of the parallel-to-electrode magnetic field on the nucleation processes was found for the progressive mode, which leads to the increase of the growth rate and as a consequence to retardation of the nucleation rate of the 3D step. Additionally, in this configuration at a sufficiently high magnetic flux density a third nucleation step could be observed (3D), which was found to be also affected by a magnetic field. No effect of a perpendicular-to-electrode magnetic field on the nucleation has been observed. The effects of a magnetic field on the nucleation and growth processes are discussed with respect to the magnetohydrodynamic effect (MHD) and confirmed by rotating disc electrode (RDE) experiments.     

Cryogels of cellulose derivatives prepared via UV irradiation of moderately frozen systems

Cryogels of non-ionic (hydroxypropyl)methylcellulose, 2-hydroxyethylcellulose, methylcellulose and cationic hydroxyethylcelluloses were prepared for the first time via UV irradiation of moderately frozen systems. The influence of the irradiation time, the concentration of the photoinitiator (4-benzoylbenzyl)trimethylammonium chloride, and the concentration of the polymer solution on the efficiency of the cross-linking process in moderately frozen systems was investigated. It was found that 2-min irradiation at an irradiation dose rate of 5.7 J/cm² min is adequate for cross-linking of 3 wt.% polymer solutions resulting in high quality cryogel.     

Efficient preparation of isotactic polypropylene/montmorillonite nanocomposites by in situ polymerization technique via a combined use of functional surfactant and metallocene catalysis

In order to promote efficiency of the preparation of isotactic polypropylene (i-PP)/montmorillonite (MMT) nanocomposites by in situ polymerization technique, a strategy was laid out to enhance both the intercalative selectivity and the catalyst activity of the in situ polymerization by a combined use of a functional surfactant for MMT modification and a metallocene catalyst system for isospecific propylene polymerization. Thus, (2-hydroxylethyl) hexadecyl diethylammonium iodine was involved in the ion-exchanged organic modification of MMT, leading to an implantation of catalyst-anchoring reactive sites (hydroxyl, OH) in the interlayer galleries of MMT (OMMT). By treating the OH-intercalated OMMT successively with excessive methylaluminoxane (MAO) and rac-Me₂Si(2-Me-4-Ph-Ind)₂ZrCl₂, the metallocene catalyst typical for i-PP polymerization was stabilized inside the interlayer galleries with a catalytically benign environment. The MMT-borne catalyst, upon further activation by MAO, released fairly high activities for propylene polymerization. The effective intercalative polymerization ensured an efficient preparation of i-PP/MMT nanocomposite. A series of i-PP/MMT nanocomposites containing completely disordered MMT at a loading range of 1.0-6.7 wt% (TGA measurement residue at 600 °C) were obtained in high yields.     

Parameter effects on wet ultrafine grinding of limestone through slurry rheology in a stirred media mill

Wet ultra-fine grinding of a limestone powder (< 100 μm) has been investigated in a stirred media mill with respect to the effect of slurry rheology. The grinding results obtained by various parameters (i.e., molecular weight of a dispersant, solids concentration, additive dosage, addition method and beads load) are evaluated in terms of energy efficiency and the fineness of a product. A polymeric dispersant called Dispersant S40 with a molecular weight of 5500 gives the best grinding results. For a certain level of beads load, an optimal solids concentration exists. In the case of the additive dosage of Dispersant S40 at 0.1 wt.% or more, a smaller additive amount of Dispersant S40 gives a higher energy efficiency and a smaller median size at a lower level of specific energy input. However, the excessive amount of the dispersant could cause a cushion layer formed on milling beads and thus lowers stress intensities from the collisions of milling beads, leading to an inefficient milling operation. This can be avoided by either the multi-point addition of the dispersant or a higher beads load (≥ 83 vol.%). In addition, it was found that the higher the beads load, the better the cumulative energy efficiency, and the smaller the product size at the same specific energy consumption. For a given solids concentration, the relationships between the specific surface area and the particle size of an FP product and the additive amount of Dispersant S40 are explored, respectively. Furthermore, an empirical particle size-energy model provides a good fit (R² > 0.991) to the grinding results under the experimental conditions investigated.     

Effects of zinc additive on the HPHT synthesis of diamond in Fe-Ni-C and Fe-C systems

In the series of experiments at 5.0-7.0 GPa and 1300-1800 °C with the duration from 15 min to 2 h, the diamond crystals were synthesized in the Fe-Ni-C and Fe-C systems with zinc additive and the capability of zinc for converting graphite to diamond were also investigated in this work. Compared with the diamond synthesis using conventional catalysts, much higher temperatures are required for the nucleation and growth of diamond in Fe-Ni-Zn-C and Fe-Zn-C systems. The morphology of synthesized diamond crystals changes regularly from cub-octahedron to octahedron in the Fe-Ni-C system with increasing zinc additive, while only octahedral diamonds form in the Fe-Zn-C system. The diamond growth is accelerated by appropriate addition of zinc in conventional catalysts while the excessive zinc additive may have a suppressive effect on the diamond nucleation. We also estabish the essential dependence of diamond nucleation and morphology on the composition of crystallization medium in the Fe-Ni-Zn-C and Fe-Zn-C systems. Based on our analysis of the diamond surface configuration, we suggest that the formation of the different defects on the {100} and {111} faces is most likely due to the two simultaneous growth process on the {111} faces.     

Correlation between retention and adsorption of phenolic compounds in nanofiltration membranes

Equilibrium adsorption experiments of phenol, 3-chlorophenol, 4-chlorophenol, and 3-nitrophenol aqueous solutions on NF90 membrane were conducted to obtain the corresponding adsorption isotherms at 25 ºC. Single-compound solutions with concentration ranging from 0.1 to 8 mmol L^− 1 were used. Freundlich and Langmuir models were compared to the experimental isotherms and their characteristic parameters were obtained from linear fits. In addition, the adsorptive behaviour of twelve aqueous phenolic compounds on the NF90 membrane was studied in order to investigate the relationship between adsorption and retention of selected solutes. An inverse correlation between the adsorbed amount, at the same equilibrium concentration (1 mmol L^− 1), and retention was found. The influence of the molecular hydrophobicity and dipole moment of phenolic compounds on membrane adsorption, solute retention and water flux decline was also investigated.     

Effect of 1-pentanol on the styrene emulsion polymerization

The influence of 1-pentanol (C₅OH) on the ST emulsion polymerization mechanisms and kinetics is investigated. The CMC of the ST emulsions first decreases rapidly and then levels off when the C₅OH concentration ([C₅OH]) increases from 0 to 72 mM. The effect of C₅OH increases to a maximum and then decreases when the SDS concentration ([SDS]) increases from 2 to 18 mM. At [SDS]=2 mM, homogeneous nucleation controls the polymerization kinetics regardless of [C₅OH]. At [SDS]=4 mM, the effect of [C₅OH] appears due to the transition from homogeneous nucleation to a mixed mode of particle nucleation (homogeneous nucleation and micellar nucleation) occurs when [C₅OH] increases from 0 to 72 mM. The effect of [C₅OH] is the strongest at [SDS]=6 mM since the particle nucleation mechanisms span homogeneous nucleation (low [C₅OH]), a mixed mode of particle nucleation (homogeneous nucleation and micellar nucleation) (medium [C₅OH]) and micellar nucleation (high [C₅OH]). At [SDS] >6 mM, in which micellar nucleation controls the polymerization kinetics, the effect of [C₅OH] decreases rapidly with increasing [SDS].     

Electrochemistry of Sn(II)/Sn in a hydrophobic room-temperature ionic liquid

The electrochemical reaction of Sn(II)/Sn was investigated in a room-temperature ionic liquid, 1-n-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMPTFSI) at 25 °C. The anodic dissolution of Sn metal proceeded by a two-electron transfer reaction with a current efficiency of nearly 100%. Electrodeposition of Sn on a Cu substrate is possible in BMPTFSI containing Sn(II). The formal potential of the Sn(II)/Sn is −0.57 V vs. Ag/Ag(I). The diffusion coefficient of Sn(II) was estimated to be ∼1 × 10⁻⁷ cm² s⁻¹ from chronoamperometric and chronopotentiometric techniques. The initial stage of nucleation of Sn on a polycrystalline Pt substrate was found to be classified into a three-dimensional progressive nucleation under diffusion control by chronoamperometry, suggesting the rate of nucleation is faster than that of crystal growth.     

Phase behavior, nucleation and optical properties of the binary system isotactic polypropylene/N,N′,N″-tris-isopentyl-1,3,5-benzene-tricarboxamide

The phase behavior of the binary system consisting of isotactic polypropylene (i-PP) and N,N′,N″-tris-isopentyl-1,3,5-benzene-tricarboxamide (1)—a selected member of a class of novel, versatile ‘designer’ nucleating/clarifying agents—was investigated over the entire additive concentration range by means of differential scanning calorimetry (DSC) and optical microscopy. Experimental phase diagrams were constructed from data obtained in melting and crystallization studies, and a simple monotectic is advanced, very similar to the previously studied binary system i-PP/1,3:2,4-bis(3,4-dimethylbenzylidene) sorbitol (DMDBS). In contrast to the latter, the crystallization temperature in the present system i-PP/1 was found to increase to ∼120 °C already at the lowest additive concentration employed and remained constant at further increasing additive concentration. Liquid-liquid phase separation was observed at elevated temperatures for i-PP/1 mixtures comprising more than ∼2 wt% of 1. A study on the optical properties of the i-PP/1 system revealed that the values for haze and clarity of injection-molded plaques progressively decreased and increased, respectively, in the concentration range up to 0.15 wt%. An intermediate region of fairly concentration-independent optical properties was found between 0.15 and 1 wt%, followed by a rapid increase in haze at concentrations exceeding 2 wt%.     

Lead electrodeposition from very alkaline media

The electrodeposition of lead from very alkaline media has been studied by cyclic voltammetry, chronoamperometry under stationary and convective conditions. Experimental parameters like lead concentration and temperature have been varied. From NaOH 6 M the metal deposition takes place at about −0.90 V versus SCE far from the hydrogen evolution reaction (HER) which is seen at −1.30 V, but both processes are favoured by the lead content increase and the NaOH concentration decrease. The analyses of the chronoamperometric responses support the view of a 3D growth and suggest a substantial influence of lead concentration on the type of nucleation. Progressive nucleation is observed for the deposition from solutions with low content in lead but as this concentration increases a tendency towards instantaneous nucleation is revealed. The voltammetry with the rotating platinum disc electrode has confirmed that the lead electrodeposition is a mass transfer controlled process, and also allowed the estimation of diffusion coefficients.     

Multifunctional antistatic and scratch resistant UV-cured acrylic coatings

Organic–inorganic antistatic hybrid acrylic coatings were prepared. Trialkoxy-silyl ammonium salt was added to the photocurable formulations in order to introduce an antistatic additive which could be covalently linked to the hybrid network through a co-condensation reaction involving the alkoxy groups. The influence of the antistatic additive on the radical photopolymerization reaction of the acrylic resin was evaluated by real time FTIR, keeping the inorganic precursor content constant at 20 phr and increasing the trialkoxy-silyl ammonium salt in the range between 5 and 15 phr. When the samples were cured under nitrogen atmosphere, a complete conversion of acrylic double bonds was achieved after 90 s of irradiation both for the acrylic resin and the formulations containing the ammonium salt. The scratch behavior of coatings was investigated by carrying out of progressive load scratch test. The penetration depth (Pd) and the residual depth patterns were investigated for all the hybrid films. A consistent improvement of penetration resistance by increasing alkoxy-ammonium salt content was noted in terms of Pd. Inorganic component and antistatic additives increase ε′ and σ_AC values of the hybrid coatings and decrease the resistivity ones, showing their efficiency for increasing antistatic properties of coatings, improved with respect to the pure acrylic resin.     

Silver electrocrystallization at polyaniline-coated electrodes

The initial stage of silver electrocrystallization is studied at polyaniline (PANI)-coated platinum electrodes by means of potentiostatic current transients and electron microscopic observations. Data for the nucleation frequency and the number of active sites for nucleation are obtained by interpreting of current transients according to the theory for nucleation and 3D growth under diffusion limitations. It is found that depending on the PANI layers thickness, d, two different regimes for silver nucleation and growth exist. For thin PANI coatings (d<0.3 μm), the crystallization occurs with high nucleation frequency at active sites located at the polymer layer/metal electrode interface, the number of active sites decreasing sharply with increasing PANI coverage. For thick PANI layers (d>0.3 μm), silver nucleation occurs with a two orders of magnitude lower nucleation frequency at active sites located most probably at the polymer surface, their number remaining constant for thicknesses up to 1.4 μm. It is established that reduction of the PANI layer occurring in parallel with the silver electrodeposition does not influence the number of active sites for nucleation. The results obtained by interpretation of current transients are in good agreement with results for the number of crystals obtained by microscopic observation.     

Electrochemical behavior of fission palladium in 1-butyl-3-methylimidazolium chloride

Electrochemical behavior of palladium (II) chloride in 1-butyl-3-methylimidazolium chloride has been investigated by various electrochemical transient techniques using glassy carbon working electrode at different temperatures (343-373 K). Cyclic voltammogram consisted of a prominent reduction wave at −0.61 V (vs. Pd) due to the reduction of Pd(II) to Pd, and two oxidation waves at −0.26 and 0.31 V. A nucleation loop is observed at −0.53 V. The diffusion coefficient of palladium (II) in bmimCl (∼10⁻⁷ cm²/s) was determined and the energy of activation (63 kJ/mol) was deduced from the cyclic voltammograms at various temperatures. Nucleation and growth of palladium on glassy carbon working electrode has been investigated by chronoamperometry and chronopotentiometry. The growth and decay of chronocurrents measured for palladium deposition has been found to follow the instantaneous nucleation model with three-dimensional growth of nuclei. The surface morphology of the deposit obtained at various applied potentials revealed the formation of dendrites immediately after nucleation and spread in all the directions with time.     

Structure and mechanical properties of W incorporated diamond-like carbon films prepared by a hybrid ion beam deposition technique

W incorporated diamond-like carbon films were prepared on silicon(1 0 0) wafers using a hybrid deposition system composed of an end-Hall-type hydrocarbon ion gun and a tungsten DC magnetron sputter source. The W concentration in the films was controlled by changing the fraction of Ar in the Ar and C₆H₆ reaction gas. The chemical composition, atomic bond structure, and mechanical properties were investigated for W concentrations ranging from 0 to 8.6 at.%. When the W concentration was <2.8 at.%, the W atoms were dissolved in the amorphous carbon matrix without forming a WC_1−x phase. Amorphous and crystalline WC_1−x nano-particles appeared when the W concentration was >2.8 and >3.6 at.%, respectively. It was found that the hardness and elastic modulus were not sensitive to the W concentration in this concentration range. On the other hand, the residual compressive stress was strongly dependent on the chemical state of the incorporated W atoms. The change in mechanical properties is discussed in terms of the microstructural changes induced by W incorporation.     

Fabrication of porous microspheres and network arrays of Zn–Al hydrotalcite-like compounds on Al substrate via facile hydrothermal method

The porous microspheres and network arrays of Zn–Al hydrotalcite-like compounds were synthesized on Al substrate using sodium oxalate via a facile one-step hydrothermal approach at low temperature (70 °C). The Zn–Al hydrotalcite-like microspheres assembled by numerous interlaced curved nanoplates with thickness of about 50 nm were generated when the concentration of sodium oxalate is 0.21 M. The XRD pattern indicates that the product was of good quality in terms of phase purity and crystallinity. The morphology of Zn–Al hydrotalcite-like compounds and the thickness of nanoplates varied with the concentration of sodium oxalate, which should be attributed to the different nucleation density and growth rate. When the concentration of Zn²⁺ and sodium oxalate was proportionally reduced the low nucleation density and growth caused the formation of porous network arrays. The reaction temperature directly affected the diffusion rates of ions and thus the density of the nucleation and growth is responsible for the morphology change when the reaction temperature is varied. Additionally, the Zn–Al hydrotalcite-like microspheres transformed into porous network arrays when the sodium oxalate was substituted by the equivalent sodium acetate, which should be attributed to the low alkalinity of sodium acetate. The density and thickness of nanoplates composed of the porous network arrays can be effectively tailored by adjusting the concentration of sodium acetate. On the basis of experimental results, the growth mechanism was proposed and discussed.     

Electrocrystallisation of tantalum in molten fluoride media

The electrochemical nucleation of tantalum in molten alkaline fluoride media is investigated using chronoamperometry in the 670-750 °C temperature range to optimize the operating conditions for preparing tantalum coatings for anode materials. Chronoamperometric results show that the electrodeposition process involves progressive nucleation with diffusion-controlled growth of the nuclei, which was confirmed by scanning electron microscopy. The influence of the temperature and the overpotential on the nucleation site densities is considered.Once the deposit has been obtained, plotting the roughness of the tantalum coatings as a function of the current densities reveals a minimum at about 80 mA/cm². This minimum is considered by the authors as a consequence of the progressive nucleation.     

On-site low-pressure diesel HDS for fuel cell applications: Deepening the sulfur content to ?1 ppm

This work investigates the feasibility of ultra-deep hydrodesulfurization (i.e. ?1 ppm of sulfur content) of several diesel feedstocks, viz., regular (R), premium (P) and hydrotreated straight-run (HSR) at low pressures, i.e. 10 bar, to lower significantly the operation costs. The premium and regular diesel contain additive packages with several components such as cetane boosters, antioxidants that show to negatively affect the sulfur conversion at low pressures. In the hydrotreated straight-run diesel fuel, which does not contain an additive package, total desulfurization can be obtained at 10 bar, T = 340 °C and LHSV = 1 h⁻¹. As a model for the additive package, FAME (fatty acid methyl ester), an ingredient that encounters the demands of a sustainable future, was added to the hydrotreated straight-run diesel (HSR + FAME) in order to check its influence on the total sulfur conversion. Results show that this biofuel component hindered tremendously the sulfur removal process by lowering the sulfur removal from 98% to zero at 10 bar, probably by competitive adsorption. At higher pressures, e.g. 30 bar, when FAME was present, new sulfur compounds were formed during the HDS process and the effective sulfur removal was very low.     

Reaction and nucleation mechanisms of copper electrodeposition on disposable pencil graphite electrode

The reaction and nucleation mechanism of copper electrodeposition on disposable pencil graphite electrode (PGE) in acidic sulphate solution were investigated using cyclic voltammetry (CV) and chronoamperometry (CA) techniques, respectively. Electrochemical experiments were followed by morphological studies with scanning electron microscopy (SEM). The effect of some experimental parameters, namely copper concentration, pH, scan rate, background electrolyte, deposition potential, and conditioning surface of the electrode were described. At the surface of PGE, Cu²⁺ ions were reduced at −250 mV vs. SCE. It was found that electrodeposition of copper is affected by rough surface of PGE. The nucleation mechanisms were examined by fitting the experimental CA data into Scharifker-Hills nucleation models. The nuclei population densities were also determined by means of two common fitting models developed for three-dimensional nucleation and growth (Scharifker-Mostany and Mirkin-Nilov-Herrman-Tarallo). It was found that deposition potential and background electrolyte affect the distribution of the deposited copper. The morphology of the deposited copper is affected by background electrolyte.