Polymerization of dicyclopentadiene: A new reaction injection molding system

Dicyclopentadiene was polymerized by reaction injection molding (RIM) using a catalyst system based on WCl₆ and diethylaluminium chloride. Ring opening polymerization results in formation of a crosslinked polymer with a high crosslink density. The kinetics of the fast exothermic reaction was followed by the adiabatic temperature rise method. In addition to the “adiabatic” polymerization, isothermal reactions were carried out in a thin mold. The properties of the cured samples were determined by dynamic mechanical measurements, solgel analysis, gas chromatography, mass spectrometry, DSC, and IR spectrometry. Gel fraction, glass transition temperature, content of the unreacted monomer, the modulus, and the degree of swelling were used to characterize the cured samples. The system shows very low critical conversion at the gel point (α_c < 0.01) proving a chainwise mechanism of the polymerization. Possible participation of a cationic mechanism is discussed. We found the specific reaction temperature range (T = 100–140°C) for optimum properties of the cured samples. Deterioration of properties (decrease in the crosslinking density, etc.) at a high temperature is a result of a faster deactivation of catalytic centers and a reversibility of the exothermic ring opening polymerization. Reverse cyclodegradation is preferred at a higher temperature.     

Kinetic experiments and modeling of NO oxidation and SCR of NOx with decane over Cu- and Fe-MFI catalysts

The kinetic model of the reduction of NO to N₂ with decane, developed based on the experimental data over Fe-MFI catalyst, has been applied for the oxidation of NO to NO₂ and reduction of NO₂ to N₂ with decane over Cu-MFI catalyst. The model fits well the experimental data of oxidation of NO as well as reduction of NO to N₂. Remarkable differences have been found in performance of Cu-MFI and Fe-MFI catalysts. While Fe-MFI is more active in oxidation of NO to NO₂, Cu-MFI exhibits much higher activity in the reduction of NO with decane. The kinetic model indicates that the significantly lower activity of Fe-MFI in comparison with Cu-MFI in transformation of NO_x to nitrogen is due to higher rate of transformation of NO₂, formed in the first step by the oxidation of NO, back to NO instead to molecular nitrogen.     

Application of water jet description on the de-scaling process

The paper is dealing with application of theoretical equations derived for rock disintegration onto materials with similar behavior—thick scales on hot metal rolling slabs. Penetration of water jet through a hot, rock-like material (e.g. scale) and work of the steam bubbles emerging from the water jet on the boundary between the scale layer and the hot metal material are described by a set of appropriate equations. The model is applied on the fan jets used for de-scaling process, and it provides both the qualitative and the quantitative results. These results make possible to determine the depth of penetration of water jet into the material of the scales and calculate the sizes of pieces of the disintegrated scales. Both mechanisms of water jet acting on scales, mechanical penetration to a certain depth in the material and the formation of steam bubbles inside the material, create mechanical stresses in the material of scales, especially the tensile and the shear ones. Pieces of scales are separated due to exceeding the limits of the stress and strain in the material of scales. The presented analytical equations describing the process in a simple way yield the quick and apprehensible calculation of applicable results. It is an alternative to solution of a rather complicated set of differential equations describing the mass and heat flow. The proposed theoretical base runs with technical factors and properties that can be obtained from tables or analogies with other materials or processes. The typical water pressure range of rolling mills is 16–24 MPa, the equivalent diameter of the applied water nozzle is 2 mm, the average traverse speed of the rolling slab is set to 1 m s^?1, and the mean stand-off distance of the nozzle from the steel slab surface is 150 mm. Calculated depth of penetration into scales is ranging from 5 to 18 mm for these parameters, while the real thickness of scales lies between 1 and 7 mm. Simultaneously, the calculated length of the peeled layer in the direction of the jet movement ranges from 30 to 70 mm and the cutting width determined from the jet shape and the stand-off distance is 80–120 mm. Therefore, the calculated size of the scale debris is 30?×?80 mm for layers thicker than 5 mm and 70?×?120 mm for the ones thinner than 2 mm. These theoretical values correspond with sizes of real scale debris picked at the rolling mill.     

Mixtures of l-Amino Acids as Reaction Medium for Formation of Iron Nanoparticles: The Order of Addition into a Ferrous Salt Solution Matters

Owing to Mössbauer spectroscopy, an advanced characterization technique for iron-containing materials, the present study reveals previously unknown possibilities using l-amino acids for the generation of magnetic particles. Based on our results, a simple choice of the order of l-amino acids addition into a reaction mixture containing ferrous ions leads to either superparamagnetic ferric oxide/oxyhydroxide particles, or magnetically strong Fe⁰-Fe₂O₃/FeOOH core-shell particles after chemical reduction. Conversely, when ferric salts are employed with the addition of selected l-amino acids, only Fe⁰-Fe₂O₃/FeOOH core-shell particles are observed, regardless of the addition order. We explain this phenomenon by a specific transient/intermediate complex formation between Fe²⁺ and l-glutamic acid. This type of complexation prevents ferrous ions from spontaneous oxidation in solutions with full air access. Moreover, due to surface-enhanced Raman scattering spectroscopy we show that the functional groups of l-amino acids are not destroyed during the borohydride-induced reduction. These functionalities can be further exploited for (i) attachment of l-amino acids to the as-prepared magnetic particles, and (ii) for targeted bio- and/or environmental applications where the surface chemistry needs to be tailored and directed toward biocompatible species.     

Ductile/brittle PA6/PS system: Effect of carbon nanoplatelets-modified interface on performance

Addition of rigid PS to ductile PA6 can lead to higher toughness provided plastic deformation of PS is achieved. The current study deals with upgrading of this system by graphene, graphene oxide (GO), and GO with grafted polystyrene (GO-g-PS). Low amount of these carbon nanoplatelets can enhance performance of the PA/PS 90/10 system with the best-balanced properties achieved with GO-g-PS by unique combination of reinforcement with the favorable effect of the GO-g-PS-modified interface on plastic deformation of the PS phase causing higher impact resistance. Simultaneous linking of PA chains and hydrogen bonding causes “anchoring” of PS inclusions in the PA6 phase. This results in support of hydrostatic pressure evolution during loading and thus extensive yielding of PS. Another positive effect is reduction of pullout of in situ formed fibrous inclusions, which is different from rigid short-fiber composites. The study highlights high potential of GO modified with polymer chains to upgrade polymer systems via tailoring the interface.     

Two-Step Preparation of Benzylacetone

Two-step preparation of benzylacetone has been investigated using layered double hydroxides (LDHs) as catalysts for aldol condensation of benzaldehyde and acetone and Ni supported catalysts for consecutive hydrogenation of benzylideneacetone. Activity and selectivity of LDHs of various Mg/Al ratios to desired product, benzylideneacetone, have been compared in the liquid phase at 333 K. An aldol condensation yield at 100 % conversion of benzaldehyde was 78 % using catalyst HT-2.0. In the following, optimal hydrogenation conditions—temperature of 353 K, hydrogen pressure of 5 MPa and 5 wt% of catalyst NiSAT^® 320 were found. At 95 % conversion of benzylideneacetone the selectivity to desired product was 99 %.     

System Condition Estimation Based on Selected Tribodiagnostic Data

The aim of the paper is to estimate a system‐soft failure occurrence and residual technical life. When estimating a residual technical life statistically, usually a big amount of tribodiagnostic data is used. Data include the information about particles contained in oil that testifies to oil and system conditions. We focus here on the particles that we consider to be interesting. They are ferrum (Fe) and lead (Pb) as contact degradation product. By modelling the occurrence of particles in oil, we expect to determine the expected moment for soft failure occurrence or adequate moment to perform preventive maintenance. The way of our modelling is based on the specific characteristics of diffusion processes, namely the Wiener process with positive drift and Ornstein–Uhlenbeck process. Following the modelling results, we could judge hazard rate and set‐up principles of ‘CBM ‐ Condition Based Maintenance’ (CBM). However, the possibilities are much wider, because we can also plan operation, mission and reduce life cost. Copyright © 2015 John Wiley & Sons, Ltd.