Study of motional processes in polymer blends composed of isotactic polypropylene and ethylene–propylene–diene monomer rubber by broad‐line 1H‐NMR

The broad‐line ¹H‐NMR study of the polymer blend composed of isotactic polypropylene and ethylene–propylene–diene monomer rubber was carried out. The NMR measurements were performed on the samples of the polymer blend and on the components of the blend in the temperature range covering the glass‐transition regions of all studied polymers. Conclusions were drawn from the temperature dependencies of the second moment M₂ and of the data obtained by the decomposition of the spectra into the components related to the motionally distinct regions of the partially crystalline polymer. The mass fractions of the amorphous, intermediate, and crystalline domains and the widths of the spectra related to the particular phases were computed from the spectra. A double glass transition was revealed for the polymer blend. Different mechanisms of the motional processes related to the glass transition were deduced from the data. The gradual increase of the number of the chains and the enhancement of the chain mobility within noncrystalline regions of the polymer blend are responsible for the motion related to the lower glass transition and only transformation of the hindered motion into free motion was found in the temperature region of the upper glass transition. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 247–252, 2004     

Tribological Properties of TiN/Ag Nanocomposite Coatings

Morphology, structure, and tribological behavior of magnetron co-sputtered TiN/Ag nanocomposite coatings deposited at 150 °C with an Ag content in the range of 7–45 at.% were characterized. The coatings show a columnar structure with embedded Ag crystallites of 3–50 nm in diameter, where the columns are characterized by a layered structure with Ag-poor and Ag-rich layers. These layers originate from sample rotation during deposition, where the layer thickness increases with increasing Ag content. These Ag layers become continuous over a critical Ag content. At room temperature the friction coefficient is determined by the film structure, whereas friction and wear at high temperature depend on segregation of Ag to the surface.     

Effect of vanadium on grain boundary segregation of phosphorus in low alloy steels

The phosphorus grain boundary segregation at 853 K was investigated in three low alloy steels with different vanadium content. Kinetic dependence of the phosphorus grain boundary concentration was determined experimentally by means of AES and described theoretically, as well. To assess the influence of the individual alloying elements on the phosphorus segregation, the metal composition of carbide phases at 853 K was predicted by means of thermodynamic calculations and confirmed by experimental measurements (TEM + EDX). The vanadium was found to enhance the phosphorus grain boundary segregation by reducing the amount of dissolved and segregated carbon. Thereby, the equilibrium of mutual displacement C (segregated) ? P (segregated) was shifted to more phosphorus segregation. The results achieved indicate that vanadium indirectly increases sensitivity of low alloy steels to intergranular embrittlement.     

Catalytic and thermal cracking of selected polyolefins

Feedstock recycling is a promising alternative for the management of plastic wastes, as it may allow these residues to be transformed into valuable products for refinery and/or petrochemical industry. Catalytic degradation of polyolefin was carried out in a pilot scale reactor Blowdec® operating in the temperature range of 340–470°C. The catalysts used in this study were natural zeolite Clinoptilolite, ZSM-5, HZSM-5 and their mixture in various volume ratios. Both thermal and catalytic cracking of low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP) and their mixture have been investigated. Liquid products were checked in selected refinery and petrochemical processes as feedstocks on the model pyrolysis equipment and with the help of MAT test (microactivity test).     

Determination of sorption isotherm based on the measurements of contaminant outflow

In this paper, we present a method for determining the sorption isotherm from experimental measurements. The sorption isotherm is not assumed to be a member of any specific finite dimensional class (e.g. Freundlich isotherm, Langmuir isotherm). Instead, an infinite-dimensional space of functions is considered with limited a priori assumptions (e.g. smoothness, monotonicity). Consequently, we face a more challenging problem compared to the finite-dimensional case, in which only few tuning parameters need to be determined. We consider the case of flow of the contaminated water into the unsaturated porous media sample; we assume that the data are collected at the outflow. The sorption isotherm is determined in an iterative way. We minimize the cost functional reflecting the discrepancy between measured and computed data. In doing so, we use the Gateaux differential to obtain the direction of descent.     

An electromagnetism-like metaheuristic for the uncapacitated multiple allocation p-hub median problem

This paper deals with the uncapacitated multiple allocation p-hub median problem (UMApHMP). An electromagnetism-like (EM) method is proposed for solving this NP-hard problem. Our new scaling technique, combined with the movement based on the attraction–repulsion mechanism, directs the EM towards promising search regions. Numerical results on a battery of benchmark instances known from the literature are reported. They show that the EM reaches all previously known optimal solutions, and gives excellent results on large-scale instances. The present approach is also extended to solve the capacitated version of the problem. As it was the case in the uncapacitated version, EM also reached all previously known optimal solutions.     

Phase transformations and microstructure changes in a 12%Cr-steel during tempering at 1053 K

The evolution of the microstructure and the phase transformations in a 12% Cr-steel during tempering at 1053 K for 30 s, 0.25, 1 and 2 h were studied. The investigations were carried out by transmission electron microscopy. For the identification of the different phases and the determination of their chemical composition electron diffraction and energy dispersive X-ray spectroscopy were used. Four different types of precipitates were found: MX, M₃C, M₂X and M₂₃C₆. They showed the following time dependent precipitation sequence: MX → MX + M₃C → MX + M₂X + M₂₃C₆ → MX + M₂₃C₆. Changes in the chemical composition of the various precipitates were determined. The chemical composition of the M₂₃C₆ carbide was nearly constant, whereas it varied with time for the M₂X and MX carbonitrides. Two different types of MX particles were identified: Ti,V-rich precipitates in the quenched and short-term tempered states and V,Cr-rich particles in the longer-term tempered states. Two types of orientation relationships between the ferrrite and the M₂₃C₆ were observed: and .     

Study of thermophysical and mechanical properties of particulate composite polyethylene-CaCO3

Starting from the formulae for effective parameters of the particulate composite derived within the average field approximation, the formula for the percolation threshold is derived. The maximum value of the percolation threshold is ⅓ in the case of the isotropic granules of globular shape. Further, the experimental data obtained from the measurement of effective thermal conductivity and elastic shear modulus of the particulate composite polyethylene-CaCO₃ cannot be interpreted in the framework of the average field approximation. For this reason it was necessary to modify the formulae for effective parameters, and they were able to describe the experiment. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1525–1530, 1997     

Effect of 1-Ethyl-3-methylimidazolium Tetrafluoroborate and Acetate Ionic Liquids on Stability and Amyloid Aggregation of Lysozyme

Amyloid fibrils draw attention as potential novel biomaterials due to their high stability, strength, elasticity or resistance against degradation. Therefore, the controlled and fast fibrillization process is of great interest, which raises the demand for effective tools capable of regulating amyloid fibrillization. Ionic liquids (ILs) were identified as effective modulators of amyloid aggregation. The present work is focused on the study of the effect of 1-ethyl-3-methyl imidazolium-based ILs with kosmotropic anion acetate (EMIM-ac) and chaotropic cation tetrafluoroborate (EMIM-BF₄) on the kinetics of lysozyme amyloid aggregation and morphology of formed fibrils using fluorescence and CD spectroscopy, differential scanning calorimetry, AFM with statistical image analysis and docking calculations. We have found that both ILs decrease the thermal stability of lysozyme and significantly accelerate amyloid fibrillization in a dose-dependent manner at concentrations of 0.5%, 1% and 5% (v/v) in conditions and time-frames when no fibrils are formed in ILs-free solvent. The effect of EMIM-BF₄ is more prominent than EMIM-ac due to the different specific interactions of the anionic part with the protein surface. Although both ILs induced formation of amyloid fibrils with typical needle-like morphology, a higher variability of fibril morphology consisting of a different number of intertwining protofilaments was identified for EMIM-BF_4.