A study on the use of phenoxy resins as compatibilizers of polyamide 6 (PA6) and polybutylene terephthalate (PBT)

In this study we investigated the potential of phenoxy resins as compatibilizers in the blending of two high‐volume engineering thermoplastics—polyamide 6 (PA6) and polybutylene terephthalate (PBT), in an effort to establish the usefulness of blending as a method of recycling of mixed plastic wastes. It was found that phenoxy resins formed miscible blends with PBT, formed grafted copolymers with PBT through ester exchange reactions, and—though formed immiscible blends with PA6—produced energetic interactions in the form of hydrogen bonding with PA6. The ternary blend systems of 70 parts PA6, 30 parts PBT, and respectively 5, 10, and 30 parts phenoxy resins, all by weight, revealed at two‐phase nature—PA6 as the continuous phase and miscible blends of PBT and phenoxy resins as the dispersed phase—and were found to be stable to phase coarsening by annealing with mechanical properties at least as good as those of the component polymers.     

Thermoreversible gelation of poly(vinylidene fluoride)/poly(methyl acrylate) blends in diethyl azelate: a thermodynamic investigation

The thermodynamic behaviour of poly(vinylidene fluoride) (PVF₂)/poly(methyl acrylate) (PMA) blend gels in diethyl azelate (DEAZ) was studied by differential scanning calorimetry at three different blend compositions (x (weight fraction of PVF₂ in the blend) = 0.75, 0.5 and 0.25). Transmission electron microscopy together with optical microscopy indicate the presence of fibrillar network morphology in the gels. The quasi‐binary phase diagrams drawn from both the heating and cooling processes are almost similar, with a hysteresis of 50–60 °C. The possibility of polymer–solvent compound formation in the blend gels have been explored from the composition dependency of enthalpy of gel fusion and enthalpy of gel formation data. Extending the procedure of the pure PVF₂/DEAZ gel systems to blend gels, it has been surmised that polymer–solvent compound formation also occurs in blend gels, but the stoichiometry of the complexes varies with blend composition. The shapes of the quasi‐binary phase diagrams of the blend gels are different in some cases from that of pure PVF₂/DEAZ, gel indicating that the polymer–solvent compounds are incongruent or singular type depending on the blend compositions. A possible explanation for this behaviour has been offered from entropic and enthalpic viewpoints. Copyright © 2003 Society of Chemical Industry     

The Veterinary Anti-Parasitic Selamectin Is a Novel Inhibitor of the Mycobacterium tuberculosis DprE1 Enzyme

Avermectins are macrocyclic lactones with anthelmintic activity. Recently, they were found to be effective against Mycobacterium tuberculosis, which accounts for one third of the worldwide deaths from antimicrobial resistance. However, their anti-mycobacterial mode of action remains to be elucidated. The activity of selamectin was determined against a panel of M. tuberculosis mutants. Two strains carrying mutations in DprE1, the decaprenylphosphoryl-β-D-ribose oxidase involved in the synthesis of mycobacterial arabinogalactan, were more susceptible to selamectin. Biochemical assays against the Mycobacterium smegmatis DprE1 protein confirmed this finding, and docking studies predicted a binding site in a loop that included Leu275. Sequence alignment revealed variants in this position among mycobacterial species, with the size and hydrophobicity of the residue correlating with their MIC values; M. smegmatis DprE1 variants carrying these point mutations validated the docking predictions. However, the correlation was not confirmed when M. smegmatis mutant strains were constructed and MIC phenotypic assays performed. Likewise, metabolic labeling of selamectin-treated M. smegmatis and M. tuberculosis cells with ¹⁴C-labeled acetate did not reveal the expected lipid profile associated with DprE1 inhibition. Together, our results confirm the in vitro interactions of selamectin and DprE1 but suggest that selamectin could be a multi-target anti-mycobacterial compound.     

Irreversible step growth polymerization having segmental diffusion limitations in HCSTRs—simulation and steady state multiplicity

The effect of various parameters on the overall rate constant, number average chain length, and polydispersity index of isothermal, irreversible, step growth polymerization of ARB monomers, exhibiting segmental diffusional limitations and carried out in HCSTRs, are studied. A phenomenological model which has proved useful for chain polymerization is adapted for step growth polymerizations and simulations for several values of the different parameters are carried out. The number average chain length μ_n and the polydispersity index ρ are obtained as a function of the dimensionless time t^*. It is found that, even though the behavior of μ_n and ρ vs. t^* depends on the values of the parameters, the plot of μ_n vs. ρ is unique as expected from statistical considerations. An attempt has been made to investigate the multiplicity of steady states under conditions of infinitely rapid heat transfer from a jacket, using singularity and bifurcation theory. It is found from the analysis that there is no multiplicity of steady states for this system, which is confirmed by simulations using a wide range of parameter values.     

Nonlinear model-based control algorithm for a distillation column using software sensor

This paper presents the design of model-based globally linearizing control (GLC) structure for a distillation process within the differential geometric framework. The model of a nonideal binary distillation column, whose characteristics were highly nonlinear and strongly interactive, is used as a real process. The classical GLC law is comprised of a transformer (input-output linearizing state feedback), a nonlinear state observer, and an external PI controller. The tray temperature based short-cut observer (TTBSCO) has been used as a state estimator within the control structure, in which all tray temperatures were considered to be measured. Accordingly, the liquid phase composition of each tray was calculated online using the derived temperature-composition correlation. In the simulation experiment, the proposed GLC coupled with TTBSCO (GLC-TTBSCO) outperformed a conventional PI controller based on servo performances with and without measurement noise as well as on regulatory behaviors. In the subsequent part, the GLC law has been synthesized in conjunction with tray temperature based reduced-order observer (GLC-TTBROO) where the distillate and bottom compositions of the distillation process have been inferred from top and bottom product temperatures respectively, which were measured online. Finally, the comparative performance of the GLC-TTBSCO and the GLC-TTBROO has been addressed under parametric uncertainty and the GLC-TTBSCO algorithm provided slightly better performance than the GLC-TTBROO. The resulting control laws are rather general and can be easily adopted for other binary distillation columns.     

Nano-gold supported on Fe2O3: A highly active catalyst for low temperature oxidative destruction of methane green house gas from exhaust/waste gases

A number of nano-gold catalysts were prepared by depositing gold on different metal oxides (viz. Fe₂O₃, Al₂O₃, Co₃O₄, MnO₂, CeO₂, MgO, Ga₂O₃ and TiO₂), using the homogeneous deposition precipitation (HDP) technique. The catalysts were evaluated for their performance in the combustion of methane (1 mol% in air) at different temperatures (300–600 °C) for a GHSV of 51,000 h⁻¹. The supported nano-gold catalysts have been characterized for their gold loading (by ICP) and gold particle size (by TEM/HRTEM or XRD peak broadening). Among these nano-gold catalysts, the Au/Fe₂O₃ (Au loading = 6.1% and Au particle size = 8.5 nm) showed excellent performance. For this catalyst, temperature required for half the methane combustion was 387 °C, which is lower than that required for Pd(1%)/Al₂O₃ (400 °C) and Pt(1%)/Al₂O₃ (500 °C) under identical conditions. A detailed investigation on the influence of space velocity (GHSV = 10,000–100,000 cm³ g⁻¹ h⁻¹) at different temperatures (200–600 °C) on the oxidative destruction of methane over the Au/Fe₂O₃ catalyst has also been carried out. The Au/Fe₂O₃ catalyst prepared by the HDP method showed much higher methane combustion activity than that prepared by the conventional deposition precipitation (DP) method. The XPS analysis showed the presence of Au in the different oxidation states (Au⁰, Au¹⁺ and Au³⁺) in the catalyst.     

使用环境可接受的酞菁控制冷却水循环中的藻类和藻青菌

本研究的目的是发现一种环境友好的处理方法减少来自循环冷却水的藻青菌和藻类,同时抑制它们的繁殖。该处理应该能够代替目前常用的需要频繁大剂量投加的化学试剂。一种适合的取代物是纯态氧,其通过光和溶解在循环水中的功能燃料的相互作用来生产。     

Effect of functionalised core–shell microgels prepared by emulsion polymerisation on acrylic coatings properties

The influence of hydroxyl-functionalised acrylic core–shell microgels incorporated into a solvent-borne acrylic binder system on the properties of coatings is described in this paper. Our approach has been to show the usefulness of prepared functionalised microgels as coating modifiers. This subject was shown to be connected with the selection of an appropriate solvent with good affinity for microgels and the film-forming polymer. Therefore the swelling behaviour of microgels in selected solvents as a function of microgel composition is discussed as well. The structured microgels were prepared by first making an aqueous emulsion via the semi-batch emulsion copolymerisation, then dehydrating the system by air drying followed by grinding in a mill. The resulting agglomerates of spherical microgel particles were dispersed in convenient organic solvent media and after that added to the thermosetting solvent-borne acrylic binder system. It was shown that the application of core–shell microgels did not affect the surface appearance and transparency of coatings. Moreover, the presence of microgel network precursors improved corrosion resistance of coatings.     

Investigation of the Microstructural Changes and Hardness Variations of Sub-Zero Treated Cr-V Ledeburitic Tool Steel Due to the Tempering Treatment

The microstructure and tempering response of Cr-V ledeburitic steel Vanadis 6 subjected to sub-zero treatment at ??196 °C for 4 h have been examined with reference to the same steel after conventional heat treatment. The obtained experimental results infer that sub-zero treatment significantly reduces the retained austenite amount, makes an overall refinement of microstructure, and induces a significant increase in the number and population density of small globular carbides with a size 100-500 nm. At low tempering temperatures, the transient M₃C-carbides precipitated, whereas their number was enhanced by sub-zero treatment. The presence of chromium-based M₇C₃ precipitates was evidenced after tempering at the temperature of normal secondary hardening; this phase was detected along with the M₃C. Tempering above 470 °C converts almost all the retained austenite in conventionally quenched specimens while the transformation of retained austenite is rather accelerated in sub-zero treated material. As a result of tempering, a decrease in the population density of small globular carbides was recorded; however, the number of these particles retained much higher in sub-zero treated steel. Elevated hardness of sub-zero treated steel can be referred to more completed martensitic transformation and enhanced number of small globular carbides; this state is retained up to a tempering temperature of around 500 °C in certain extent. Correspondingly, lower as-tempered hardness of sub-zero treated steel tempered above 500 °C is referred to much lower contribution of the transformation of retained austenite, and to an expectedly lower amount of precipitated alloy carbides.