Online monitoring of reactive compatiblization of poly(lactic acid)/polyamide 6 blend with different compatibilizers

Improvement of poly(lactic acid)/polyamide 6 (PLA/PA6) miscibility is approached by reactive compatibilization with using different reactive agents. Specifically, compatibilizing efficiency of commercially available Joncryl ADR-4368 (Joncryl) and free-radical initiator 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane (L101) is compared to that of laboratory synthesized compatibilizers (poly(lactic acid) grafted with itaconic anhydride (PLA-g-IAH) and poly(itaconic anhydride) (PIAH) by online rheology monitoring in internal mixer and oscillatory rheometer. The change of morphology and particle-size distribution is evaluated by scanning electron microscopy (SEM), the extent of PLA-PA6 miscibility is determined by differential scanning calorimetry (DSC), and newly formed polymer phases are identified by high-resolution thermogravimetric analysis (HR-TGA) and solvent extraction in formic acid. Although Joncryl exhibits the most promising results in PLA-PA6 compatibility, other compatibilizers also exhibit specific benefits for PLA/PA6 blend or individual polymers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48005.     

Preparation of TiAl15Si15 intermetallic alloy by mechanical alloying and the spark plasma sintering method

This work is devoted to the preparation of alloys based on intermetallic compounds in the Ti–Al–Si system by powder metallurgy using mechanical alloying and the spark plasma sintering (SPS) method. The aim was to describe the formation of intermetallic phases during mechanical alloying of TiAl15Si15 (wt-%) alloy and to consolidate the powder prepared by optimised conditions. Phase composition, microstructure and hardness of compacted alloy were determined. Four hours of mechanical alloying is sufficient time for preparation of pure elements free material composed only of intermetallic phases. After consolidation, the TiAl15Si15 alloy has a homogeneous structure composed of silicide (Ti₅Si₃) in aluminide (TiAl) matrix. The hardness of the material reaches 865?±?42 HV 5.     

Production of biogenic amines by lactic acid bacteria and bifidobacteria isolated from dairy products and beer

The aim was to monitor production of eight biogenic amines (BAs) (histamine, tyramine (TYR), tryptamine, putrescine, cadaverine (CAD), phenylethylamine, spermine and spermidine) by selected 81 lactic acid bacteria (LAB) strains: Lactobacillus, Lactococcus, Leuconostoc, Enterococcus, Pediococcus, Tetragenococcus and Bifidobacterium. The tested LAB and bifidobacteria were isolated from dairy products and beer. The decarboxylase activity of the micro‐organisms was studied in growth medium after cultivation. The activity was monitored by HPLC after the pre‐column derivatisation with dansylchloride. Fifty LAB showed decarboxylase activity. Thirty‐one strains produced low concentrations of CAD (≤10 mg L^?1). Almost 70% of beer isolates generated higher amounts of TYR (≤3000 mg L^?1). Most of the tested LAB demonstrated decarboxylase activity. The above micro‐organisms can contribute to the increase of content of BAs in dairy products or beer and thereby threaten food safety and health of consumers. Production of BAs even by the representatives of some probiotic strains (Bifidobacterium and Lactobacillus rhamnosus) was detected in this research. This study has also proved that contaminating LAB can act as sources of higher amounts of CAD and TYR in beer.     

Cavitation Rates in Water with Dissolved Gas and Other Impurities

Our objective is a better understanding of the role of physical properties of real fluids in the thermodynamics of cavitation in impure water. An extension to the classical homogenous nucleation theory suitable for mixtures is presented in attempt to address the discrepancy between the theoretical predictions and practical observations of cavitation rates in water at normal temperatures. The extension takes into account the non-equilibrium (dissipative) effects involved in nuclei formation through a substance dependent correction coefficient to be determined experimentally. The theory of thermodynamic fluctuations is applied to derive the work of formation of a bubble nucleus. The value of the correction coefficient is estimated using preliminary experimental data from a convergent-divergent nozzle. An application of the results to the numerical prediction of the cavitation zones in a radial-flow water pump is shown.     

A survey of eutectoid decomposition in ten Ti-X systems

The mechanism of eutectoid decomposition in ten Ti-X binary systems, wherein X was successively Bi, Co, Cr, Cu, Fe, Mn, Ni, Pb, Pd and Pt, has been investigated. In hypo-eutectoid alloys, the bainite reaction (defined in the present context as a nonlamellar dispersion of intermetallic compound particles amongst proeutectoid a) predominated in all alloys studied but Ti-Cu, where both bainite and pear lite were formed. In alloys of near eutectoid composition pearlite was the dominant product in some systems and bainite was in others. These results are essentially independent of reaction temperature. They are quite different from analogous ones in Fe-C alloys, where pearlite is the principal eutectoid structure formed at high temperatures and bainite plays this role at low tem-peratures. The difference between the Ti-X and Fe-C behaviors was explained in terms of the much more pronounced tendency for proeutectoid α plate formation in Ti-X than in Fe-C alloys and, on a theory due to Hillert, of the need for disordered interphase boundaries in order to develop the cooperative growth mode that leads to the evolution of pearlite.     

Magnetic Properties of ZnFe<Subscript>2</Subscript>O<Subscript>4</Subscript> Nanoparticles Synthesized by Starch-Assisted Sol–Gel Auto-combustion Method

In this paper, ZnFe₂O₄ spinel ferrite nanoparticles with different grain sizes at different annealing temperatures have been synthesized using the starch-assisted sol–gel auto-combustion method. The synthesized nanoparticles were characterized by conventional powder X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, and vibrating sample magnetometer. The X-ray diffraction (XRD) patterns demonstrated that the ZnFe₂O₄ nanoparticles consist of single-phase spinel structure with crystallite sizes 4.81, 8.72, 12.06, 29.32, and 72.60 nm annealed at 400, 600, 800, 1000, and 1200 °C, respectively. Field emission scanning electron microscopy reveals that particles are of spherical morphology at lower annealing temperature and hexagonal-like morphology at higher temperature. An infrared spectroscopy study shows the presence of two principal absorption bands in the frequency range around 525 cm^?1 (ν ₁) and around 350 cm^?1 (ν ₂), which indicate the presence of tetrahedral and octahedral group complexes, respectively, within the spinel ferrite nanoparticles. Raman spectroscopy study also indicated the change in octahedral and tetrahedral site-related Raman modes in zinc ferrite nanoparticles with change of particle size. The nanocrystalline ZnFe₂O₄ samples (4.81, 8.72, 12.06, 29.32 nm) show ferrimagnetic behavior, and bulk sample (72.60 nm) shows paramagnetic behavior. This change in magnetic behavior is due to change of cation distribution in ZnFe₂O₄ nanoparticles with decrease of particle size.     

The effect of lactose, NaCl and an aero/anaerobic environment on the tyrosine decarboxylase activity of Lactococcus lactis subsp. cremoris and Lactococcus lactis subsp. lactis

The aim of this work was to study, under model conditions, combined effects of the concentration of lactose (0-1% w/v), NaCl (0-2% w/v) and aero/anaerobiosis on the growth and tyramine production in 3 strains of Lactococcus lactis subsp. lactis and 2 strains of L. lactis subsp. cremoris. The levels of the factors tested were chosen with respect to the conditions which can occur during the real process of natural cheese production, including the culture temperature (10 ± 1 °C). In all strains tested, tyrosine decarboxylation was most influenced by NaCl concentration; the highest production of tyramine was obtained within the culture with the highest (2% w/v) salt concentration applied. Two of the strains L. lactis subsp. lactis produced tyramine only in broth with the highest NaCl concentration tested. In the remaining 3 strains of L. lactis, tyramine was detected under all conditions applied. The tested concentration of lactose and aero/anaerobiosis had a less significant effect on tyramine decarboxylation. However, it was also found that at the same concentrations of NaCl and lactose, a higher amount of tyramine was detected under anaerobic conditions. In all strains tested, tyramine decarboxylation started during the active growth phase of the cells.