The Effect of Flower-Like Magnesium Hydroxide Nanostructure on the Thermal Stability of Cellulose Acetate and Acrylonitrile–Butadiene–Styrene

Flower-like magnesium hydroxide (Mg(OH)₂) nanostructures were synthesized via a simple hydrothermal reaction at relatively low temperature. The Mg(OH)₂ nanostructures were then added to acrylonitrile–butadiene–styrene (ABS) and cellulose acetate (CA) polymers. The effect of Mg(OH)₂ nanostructures on the thermal stability of the polymeric matrixes has been investigated. The thermal decomposition of the nanocomposites shifts towards higher temperature in the presence of the Mg(OH)₂. The enhancement of thermal stability of nanocomposites is due to endothermically decomposition of magnesium hydroxide that releases of water and dilutes combustible gases. Nanostructures and nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), differential thermal analysis (DTA), UL-94 test and limiting oxygen index (LOI) analysis.     

Influence of the Water Content on the Thermal Behaviour of β-Cyclodextrin at Low and Very Low Temperature

Heat capacities of -CD·9.7H₂O weremeasured by adiabatic calorimetry in the temperature range10–300 K. Differential scanning calorimetry wasused to follow the evolution of the thermalbehaviour versus hydration ratio between 170 and300 K. At least three different behaviours wereobserved, according to the number, n, of watermolecules: 0 < n < 7, 7 < n < 10, and n > 10.These macroscopic results are discussed in terms oforganization differences between the most or theleast hydrated -CD. The structuring effectof the hydration water molecules is emphasised. Theexistence of two energetically distinct -CDhydrates (n < 10 and n > 10) seems to be confirmed. Thishypothesis is discussed in comparison with previousspectroscopic and structural studies.     

Thermal Behaviour of Anhydrous α-, β- and γ-Cyclodextrin at Low Temperature

Heat capacities of anhydrous -and -cyclodextrin were measured by adiabaticcalorimetry between 10 K and 300 K. The thermalbehaviour of the two compounds exhibits significantdifferences. -Cyclodextrin shows an anomalousexcess heat capacity in the entire region between 70 Kand 210 K. In the case of -cyclodextrin, anendothermic effect is observed at 240K. This effect isanalysed through the study of the correspondingentropy change and discussed in terms ofintramolecular organization.Using the known heat capacity values of anhydrous-CD, a comparative analysis has been developed.For each cyclodextrin, the average behaviour of abound -D-glucopyranose has been calculated andcompared. From a thermodynamic point of view, thedegree of organization of the dehydrated macrocycliccompounds could be expressed as-CD -CD -CD.     

Effects of Thermal Activation on the Electrocatalysis of the Ru(0001) Surface

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The Effects of Structure on Gene Delivery with Linear β- and γ-Cyclodextrin-Containing Polycations

Cyclodextrin (CD)-containing polycations are prepared bycopolymerization of3^A3^B-dideoxy-3^A,3^B-diamino-- and -CDs with dimethyl suberimidate·2HCl to yieldpolyamidine products. Both alkyl- and alkoxy-diamines are used to vary the spacing between the CDand the amidine charge centers. It is found that the transfection efficiency andtoxicity of such polycations is dramatically affected by the structure of the spacer separatingthe CD ring from the charge centers and less so by the type of CD used.     

Effects of Mechanochemical Activation and α-Fe2O3 Addition on the Formation of Corundum in Thermal Transformations of γ-Al(OH)3

Transformations of hydrargillite -Al(OH)₃ during mechanochemical activation in various grinding mills and further calcination of activated samples at 200-1300°C were studied. The effects of mechano-chemical activation and additions of iron(III) oxide compounds on the temperature of corundum formation and on its crystal size distribution were studied.     

The Influence of β-Diketones on the Hydrolysis and Growth of Particles from Zirconium(IV) n-Propoxide

The influence of low ligand/Zr mole ratios ( = 0–0.1) on the hydrolysis and growth of oligomers from Zr(O ⁿ Pr)₄ modified with a series of -diketones (trifluoroacetylacetone, hexafluoroacetylacetone, benzoylacetone, dibenzoylmethane and dipivaloylmethane), and their subsequent aggregation to form uniform, dense spheres, has been investigated by light scattering and turbidometry. The addition of -diketones results in a large increase in the induction time, t _i (reduction in hydrolysis/condensation rates). A remarkable feature of the data is the dramatic reductions in rate observed even when a maximum of one in forty Zr–OR bonds have been replaced by the -diketone and are no longer available for hydrolysis or further condensation. The largest effect is observed with dibenzoylmethane, which increases t _i by a factor of 26 relative to acetylacetone.A mechanism rationalising the origin of the effect is discussed, which involves segregation of the -diketone ligands on the surface of the growing particle, with subsequent particle growth restricted to those sites not occupied by the chelating ligands.     

The Study on the Thermal Stability of CLA in Egg Yolk

Conjugated linoleic acids (CLA) have been a subject of extensive investigation for their anticarcinogenic, hypolipidemic, antiatherosclerotic and immune-enhancing activities. Stability of CLA in foods has not received much attention by both academics and industry. Although CLA has shown many beneficial effects, its decomposition must be prevented when CLA in foods is processed, stored and transported. However, no study to date has addressed the stability of CLA in foods. The present stud…     

Raman Spectroscopic Studies on the Complexation and Adsorbed Behaviour of Thiourea

Raman spectroscopic studies on thiourea (TU) in highly acidic media (e. g. >3 mol/L HC1O4) show that TU as a solution species is protonated through its sulphur atom and forms complex with anions. However, as an adsorbed species, TU is protonated via the nitrogen atom and adsorbed at the silver electrode surface through the sulphur atom. The distinct effects of pH and anions of the solution on the surface enhanced Raman (SER) spectra of TU were investigated. In acidic and neutral solutions, TU is coadsorbed with anions through its NH3 and - NH2 groups respectively.     

The Effect of Interactions between γ-AlOOH and SiO2 Hydrosols on the Phase Formation in Their Mixed Products during Thermal Treatment

The effect of the sign and the value of a relative change in the -potentials of -AlOOH and SiO₂ sols on the composition homogeneity of the products of their mixing, as well as on the phase formation during thermal treatment of the latter is studied. A sample prepared by mixing -AlOOH and SiO₂ sols at pH 2.5 demonstrates the highest homogeneity of mixed gels and forms the only phase of mullite 3Al₂O₃ · 2SiO₂ during its thermal treatment (1350°C). At this pH value, a slow heterocoagulation of the sol particles with different signs of the -potential takes place. The coagulation of the sols at pH 1.5 and 5.0 results in the preparation of more or less heterogeneous mixed products and the formation of several phases during thermal treatment.     

The influence of γ-rays irradiation on the structure and crystallinity of heteropoly acid doped PVA

This contribution represents the manufacturing of a hybrid organic–inorganic proton conducting compound, which involves the introduction of heteropoly acid (HPA) of different concentrations into poly-vinyl alcohol (PVA). These compounds were irradiated by γ-rays at different doses of 10, 20, 30, and 40 kGy. The unirradiated and irradiated compounds were characterized by XRD and DSC. The XRD results showed that the crystallinity and d-spacing were strongly influenced by the amount of HPA and irradiation doses. The DSC results showed that the melting point was decreased as a result of HPA concentration and irradiation doses. The degree of crystallinity calculated from XRD is in good agreement with that calculated from DSC. The activation energy of the Unirradiated and irradiated compounds was calculated using the Flynn–Wall–Ozawa model.     

Effects of Chain Ends on Thermal and Mechanical Properties and Recyclability of Poly(γ-butyrolactone)

This work investigates effects of poly(γ-butyrolactone) (PγBL) with different initiation and termination chain ends on five types of materials properties, including thermal stability, thermal transitions, thermal recyclability, hydrolytic degradation, and dynamic mechanical behavior. Four different chain-end-capped polymers with similar molecular weights, BnO-[C(=O)(CH₂)₃O]_n-R, R = C(=O)Me, C(=O)CH=CH₂, C(=O)Ph, and SiMe₂CMe₃, along with a series of uncapped polymers R′O-[C(=O)(CH₂)₃O]_n-H (R′ = Bn, Ph₂CHCH₂) with M_n ranging from low (4.95 kg mol⁻¹) to high (83.2 kg mol⁻¹), have been synthesized. The termination chain end R showed a large effect on polymer decomposition temperature and hydrolytic degradation, relative to H. Overall, for those properties sensitive to the chain ends, chain-end capping renders R-protected linear PγBL behaving much like cyclic PγBL. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2271–2279     

Preparation of Cationic Membrane of Polyethylene Film by γ-Irradiation

Grafting of acrylic acid onto PE film by a pre-irradiation method was studied. In order to prevent formation of homopolymer, Mohr salt (NH₄)₂Fe(SO₄)₂ · 6H₂O was used, and the reaction was carried out in the presence of a swelling agent, such as methanol. The influence of different factors, such as dose, dose rate, and temperature, on the kinetics of the reaction was studied. The infrared spectrum of the grafted acrylic acid onto PE shows bands characteristic of carboxylic acids, which demonstrates that grafting has occurred. The grafting sites were shown to be of a semi-spongy shape and irregular structure which is thought to be due to the copolymerization of acrylic acid onto PE film.     

Effects of binders and graphite on the sensitivity of ε-HNIW

In order to optimize formulations of PBX based on Hexanitrohexaazaisowurtzitane (HNIW) and meet the application in mixed explosive, the mold powder of HNIW coated by varied binders was obtained by aqueous suspension technology. Several particle sizes of graphite were added as additive with a 0.5 % mass ratio. The experiment results showed that fluorine resin (FPM) was better than polyurethane and cis-butadiene rubber when the mass percentage of binders was fixed at 4 %. The characteristic height of HNIW/FPM (96/4) mold powder was at 28 cm (2.5 kg hammer), while that of the neat HNIW was at 15 cm merely, and the friction explosion probability fell from 100 to 70 %. The addition of flake graphite with proper grain size would reduce the mechanical sensitivity of HNIW and improved the fluxion property of HNIW-based mold powders. The thermal stability characteristic of HNIW FPM (96/4) and HNIW/FPM/G (96/4/0.5) were studied by thermogravimetric analysis (TG) at 10 °C min^?1, the peak decomposition temperatures were at 251 and 250 °C, which were closed to that of neat HNIW(249 °C) and also identified superior thermal stability of compound.     

Study on Synthesis and Intercalation Behavior of Layered Zirconium Proline-N-methylphosphonate-phosphate

Zirconium proline-N-methylphosphonate-phosphate (α-ZPMPP) was prepared in the presence of HF for the first time. The α-ZPMPP sample is highly crystallized with interlayer distance of 1.52nm. The interlayer distance of complex of α-ZPMPP with n-butylamine (α-ZPMPP-BA) is in 0.45 nm larger than that of α-ZPMPP. The α-ZPMPP possesses different intercalation behavior of host-guest compound from α-ZP.     

Catalytic dehydration of isopropanol on neodymium-Y and X-zeolites and the effect of γ-irradiation

Four different samples of NdX, NdY, NdNH₄X and NdNH₄Y-zeolites were prepared by ionexchange methods. DTA and XRD analyses have been carried out for the samples. The thermally activated zeolites were irradiated by 1.5 and 10.0 Mrad -rays. The catalytic activities of these samples were tested in dehydration of isopropanol. The results of DTA indicated that all samples showed endothermic peaks at about 215 °C related to the release of physically adsorbed water and exothermic peaks at 850–950 °C indicating the collapses of the zeolite. The X-ray analysis revealed that the exchange of sodium by neodymium or ammonium followed by neodymium ions did not change the crystal structure but some decrease in the crystallinity was observed. The catalytic activities of these zeolites were measured in dehydration of isopropanol as a function of temperature. It was found that the activity of the prepared Nd-zeolites depends on the crystallinity of zeolites and on the condensation products formed on catalyst surface. However, the irradiated samples exhibited higher catalytic activities in isopropanol conversion than the unirradiated ones. The observed higher activity for irradiated samples was attributed to the increase of the number of acidic centers responsible for dehydration of alcohols. These centers were formed as a result of the formation of tricoordinate aluminium atoms in -irradiated zeolites.     

Thermal Stability of γ-irradiated Tolbutamide

The thermal stability of tolbutamide before and after exposure to various γ-radiation doses was investigated. The data were followed by studying DTA, X-ray diffraction, IR, and UV absorption spectra before and after γ-irradiation. The results obtained were promising, and were explained, and discussed on the basis of γ-enhanced stabilization through recombination of free radicals. This revised version was published online in August 2006 with corrections to the Cover Date.     

The influence of γ- and UV-radiation dose on the buildup and decay of paramagnetic centers in solid hydrogen cyanide

A decrease in the concentration of paramagnetic centers (PMCs) stabilized at 77 K in crystalline hydrogen cyanide was observed when ionizing radiation doses exceeded 3000 kGy. It was assumed that the decrease is due to a change in the physical properties of the matrix as a result of its deformation, loosening, amorphization, and formation of metastable structures. The decay of the PMCs with an increase in temperature of the irradiated samples depends on the dose and type (UV, γ) of the radiation. The higher the dose of preliminary γ-irradiation, the lower the decay temperature. In UV-irradiated HCN, the paramagnetic centers that occur in the thin photolyzed layer are more stable, since they are localized at defect sites of the crystalline matrix, which hinder the migration of free valence.