Blends of propylene-ethylene and propylene-1-butene random copolymers: I. Morphology and structure

Samples of propylene-ethylene (EP) and propylene-(1-butene) (BP) random copolymers with various comonomer content (2-3.1 wt% ethylene, 9.9 wt% 1-butene), were melt-mixed in Brabender internal mixer at various compositions (25/75, 50/50, 75/25). Films of copolymers and blends, as well as of a homopolymer sample (iPP), obtained by compression moulding and with different thermal history were characterized by optical and scanning electron microscopy (OM, SEM), small-angle light scattering (SALS), small- and wide angle X-ray scattering (SAXS, WAXS) and differential scanning calorimetry (DSC). It was found that all copolymers and blends studied crystallized exclusively in monoclinic α-modification forming spherulitic structure in a very broad undercooling range. The average size of spherulites is smaller in the copolymer containing 1-butene as compared to those containing ethylene or to iPP homopolymer, due to enhanced heterogeneous nucleation in BP copolymer. SEM microscopic observations demonstrated that EP and BP copolymers were miscible at all examined compositions and form homogeneous blends. Structural and morphological analysis indicated that the comonomer units are incorporated into growing crystallites in both EP and BP copolymers, while the non-crystallizing material is rejected out of the crystallites. For small concentrations of comonomer some of non-crystallizing species are pushed ahead of the front of growing spherulite into interspherulitic regions. For higher comonomer concentration these species are mostly trapped in intraspherulitic regions. Melting behavior of copolymers reflects the incorporation of comonomer into crystalline phase: melting temperature and crystallinity degree decrease in copolymers and blends as compared to plain iPP.     

ECT图像分析法用于贮料仓卸料过程中剪切区域测量(英文)

The paper covers the electrical capacitance tomography(ECT) data analysis on shear zones formed during silo discharging process.This is due to the ECT aptitude for detection of slight changes of material concentration.On the basis of ECT visualisations,wall-adjacent shear zone profiles are analysed for different wall roughness parameters.The analysis on changes of material concentration,based on ECT images,enables the calculation for the characteristic parameters of shear zones-size and material concentration inside the shear zone in a dynamic process of silo discharging.In order to verify the methodology a series of experiments on gravitational flow of bulk solids under various conditions were conducted with different initial granular material packing densities and silo wall roughness.The investigation shows that the increase in container wall roughness is an effective method for reducing the dynamic effects during the material discharging,since these effects are resulted from the resonance between hopper construction and trembling material.Such effects will damage industrial equipment in practical applications and need further investigation.     

Sorption Behavior of Dowex PSR-2 and Dowex PSR-3 Resins of Different Structures for Metal(II) Removal

The sorption behavior of palladium(II) (Pd(II)) onto strongly basic anion exchange Dowex resins was studied depending on the concentration of hydrochloric acid (0.1–6.0 M HCl–100 mg Pd(II)/L), concentration of hydrochloric and nitric(V) acids (0.1–0.9 M HCl–0.9–0.1 M HNO₃–100 mg Pd(II)/L), and the time of contact of the solution with the anion exchange resin in the batch mode. Similar research was carried out also for the base metal ions such as cobalt(II) (Co(II)), copper(II) (Cu(II)), nickel(II) (Ni(II)), and zinc(II) (Zn(II)). The sorption process was also examined depending on the initial Pd(II) concentration, agitation rate, bead size distribution, and temperature. Pd(II) sorption was also checked in the column mode. The equilibrium and kinetic characteristics of the sorption of Pd(II) with the Dowex PSR-2 and Dowex PSR-3 anion exchange resins were determined. The possibilities of Pd(II) elution and reuse using the batch method was exploited. Pd(II) and Zn(II) sorption on the Dowex resins is time and concentration of acids dependent. Evaluating the determination coefficients, the kinetic studies showed that the pseudo-second-order equation and the Langmuir model described the data more appropriately than others. The maximum sorption capacity was 165.15 mg Pd(II)/g for Dowex PSR-2 and 184.39 mg Pd(II)/g for Dowex PSR-3. Dowex resins give quantitative Pd(II) removal from diluted acidic solutions.     

Effect of exfoliated graphite nanoplatelets’ size on the phase structure,electrical, and barrier properties of poly(trimethylene terephthalate)‐based nanocomposites

This article describes the preparation process of two series of poly(trimethylene terephthalate) (PTT) nanocomposites with an addition of exfoliated graphite nanoplatelets with two different platelets’ size (50 and 500 μm). The influence of their size on processing, physicochemical properties, morphology and, most importantly, electrical conductivity and barrier properties of thin polymer films has been studied. It was clearly found that smaller platelets enabled to obtain conductive thin polymer films with a nanoplatelet content of 0.3‐0.5 wt.%. However, nanocomposite based on PTT with 0.5 wt% of EG with the flake size of 500 μm proved to be nonconductive. At the same time smaller EG platelets demonstrated a more uniform distribution in the PTT matrix, which was confirmed by means of scanning and transmission electron microscopies, thus giving the samples in question barrier properties with respect to CO₂ and O₂. Moreover, it has been shown that both nanofillers did not have a significant influence on the phase transition temperatures and on the long period. They caused however a slight decrease of crystallinity which is an evidence of an antinucleating character of those nanoplatelets in the PTT matrix. POLYM. ENG. SCI., 55:2222–2230, 2015. © 2015 Society of Plastics Engineers     

Controlling the microstructure of lyophilized porous biocomposites by the addition of ZnO‐doped bioglass

The study presents the results of the study on porous composite biomaterials obtained using lyophilization method based on polymer solutions: chitosan solution, sodium alginate solution, or polylactide solution, and ZnO‐doped bioglass from CaO‐SiO₂‐P₂O₅ system. The properties of zinc ions were used, which have bactericidal, immune‐stimulating, and tissue‐regenerating functions in the organism. The effects of the polymer type, granulation, and bioglass amount, as well as the amount of solvent on composite microstructure, were studied. SEM‐EDS technique was used to visualize and describe the surface results occurring after incubation of composite in the Simulated Body Fluid (SBF). The selected method of preparation, used substrates, and the process conditions resulted in porous composites of the open, connected pore structure. It was proved that composite microstructure may be controlled by the appropriately selected amount of bioglass in relation to the polymer and its appropriate grain sizes. The morphology of the obtained composites is also affected by the amount of the solvent in lyophilizated dispersions. It was proved that bioactivity in composite material is induced by bioglass because after SBF incubation the surface layer is enriched with Ca and P, what may lead to a gradual formation of apatite layer. The obtained results enabled selection of the composites for further in vitro studies concerning cytotoxicity and antibacterial activity.     

Phase structure and viscoelastic properties of compatibilized blends of PET and HDPE recyclates

Immiscible blends of recycled poly(ethylene terephthalate) (R‐PET), containing some amount of polymeric impurities, and high‐density polyethylene (R‐PE), containing admixture of other polyolefins, in weight compositions of 75 : 25 and 25 : 75 were compatibilized with selected compatibilizers: maleated styrene–ethylene/butylene–styrene block copolymer (SEBS‐g‐MA) and ethylene–glycidyl methacrylate copolymer (EGMA). The efficiency of compatibilization was investigated as a function of the compatibilizer content. The rheological properties, phase structure, thermal, and viscoelastic behavior for compatibilized and binary blends were studied. The results are discussed in terms of phase morphology and interfacial adhesion among components. It was shown that the addition of the compatibilizer to R‐PET‐rich blends and R‐PE‐rich blends increases the melt viscosity of these systems above the level characteristic for the respective binary blends. The dispersion of the minor phase improved with increasing compatibilizer content, and the largest effects were observed for blends compatibilized with EGMA. Calorimetric studies indicated that the presence of a compatibilizer had a slight affect on the crystallization behavior of the blends. The dynamic mechanical analysis provided evidence that the occurrence of interactions of the compatibilizer with blend components occurs through temperature shift and intensity change of a β‐relaxation process of the PET component. An analysis of the loss spectra behavior suggests that the optimal concentration of the compatibilizers in the considered blends is close to 5 wt %. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1423–1436, 2001     

Deep levels in GaN studied by deep level transient spectroscopy and Laplace transform deep-level spectroscopy

In this study we present the results of investigations on Schottky Au-GaN diodes by means of conventional DLTS and Laplace DLTS methods within the temperature range of 77–350 K. Si-doped GaN layers were grown by Molecular Beam Epitaxy technique (MBE) on sapphire substrates. DLTS signal spectra revealed the presence of four majority traps: two hightemperature and two low-temperature peaks. Using LDLTS method and Arrhenius plots the activation energy and capture cross sections were obtained. For two high-temperature majority traps they are equal to E1 = 0.65 eV, σ₁ = 8.2 × 10^?16cm² and E2 = 0.58 eV, σ₂ = 2.6 × 10^?15 cm² whereas for the two low-temperature majority traps E3 = 0.18 eV, σ₃ = 9.72 × 10^?18 cm² and E4 = 0.13 eV, σ₄ = 9.17 × 10^?18 cm². It was also found that the traps are related to point defects. Possible origin of the traps was discussed and the results were compared with the data found elsewhere [1–5].     

Anisotropy of Gum Metal analysed by ultrasonic measurement and digital image correlation

ABSTRACT

The mechanical anisotropy of a multifunctional titanium alloy, Gum Metal, is investigated in this paper. The structural characterisation showed a strong <110> texture for Gum Metal, that is a result of the cold-swaging process applied during its manufacture. Gum Metal was treated as a transversally isotropic solid because of this texture. A significant difference from Young’s moduli of the alloy was detected from the ultrasonic measurement of parallel and perpendicular directions to the alloy swaging direction. Samples of Gum Metal cubes were compressed in two different orientations. During the deformation process, two perpendicular walls of each sample were monitored by two visible range cameras for further two-dimensional digital image correlation analysis, this confirmed a strong plastic anisotropy in Gum Metal.

This paper is part of a Thematic Issue on The Crystallographic Aspects of Metallic Alloys.     

Enhancement of sputtering yields due to C60 versus Ga bombardment of Ag[111] as explored by molecular dynamics simulations

The mechanism of enhanced desorption initiated by 15-keV C60 cluster ion bombardment of a Ag single crystal surface is examined using molecular dynamics computer simulations. The size of the model microcrystallite of 165,000 atoms and the sophistication of the interaction potential function yields data that should be directly comparable with experiment. The C60 model was chosen since this source is now being used in secondary ion mass spectrometry experiments in many laboratories. The results show that a crater is formed on the Ag surface that is approximately 10 nm in diameter, a result very similar to that found for Au3 bombardment of Au. The yield of Ag atoms is approximately 16 times larger than for corresponding atomic bombardment with 15-keV Ga atoms, and the yield of Ag3 is enhanced by a factor of 35. The essential mechanistic reasons for these differences is that the C60 kinetic energy is deposited closer to the surface, with the deeply penetrating energy propagation occurring via a nondestructive pressure wave. The numbers predicted by the model are testable by experiment, and the approach is extendable to include the study of organic overlayers on metals, a situation of growing importance to the SIMS community.     

Risk assessment for the supply chain of fast fashion apparel industry: a system dynamics framework

With the rapid progress of science and technology and continuously growing customer expectations, share of merchandise exhibiting characteristics of perishability is on the rise and a wide range of industries are affected by this phenomenon. This paper focuses on the fast fashion apparel industry due to its particular characteristics such as short life cycle products, volatile demand, low predictability, high level of impulse purchase, high level of price competition and global sourcing. A system dynamics model is proposed for analysing the behaviour and relationships of the fast fashion apparel industry with three supply chain levels. The Conditional Value at Risk measure is applied to quantify the risks associated with the supply chain of these products and also to determine the expected value of the losses and their corresponding probabilities. Multiple business situations for effective strategic planning and decision-making are generated. In particular, the impact of lead time and delivery delays on the supply chain performance (inventory, cost, backlog and risk) is analysed as the key to success for this industry is to satisfy customers’ needs in the shortest time.