Thermal Analysis of Plastics Used in the Food Industry

Fires in landfills, where used plastic packaging waste is discarded, have shown how great a fire hazard these types of materials pose. In this study, the course of thermo-oxidation of samples made of polypropylene (PP), polystyrene (PS), and polyethylene terephthalate (PET) based plastics was determined. Based on an analysis of the dissociation energy of bonds between atoms in a polymer molecule, the mechanisms responsible for the character and course of degradation were observed. It was found that the degradation rate of PP and PS could be a result of the stability of C-H bonds on the tertiary carbon atom. In the case of PS, due to facilitated intramolecular hydrogen transfer, stabilization of hydroperoxide, and formation of a stable tertiary alcohol molecule, the onset of degradation is shifted towards higher temperatures than in the case of PP. Notably, the PP fragmentation occurs to a greater extent due to the easier course of β-scission. In addition, it was found that during a fire, the least amount of heat would be generated by thermo-oxidation of PS-based plastics. This is a result of the formation of a styrene molecule during decomposition that, due to the high stability of bonds in the aromatic ring, escapes from the combustion zone without oxidation. It has been proven that the greatest thermal effect accompanies PET decomposition, during which a phenyl radical is produced, where the C-H bonds break more easily in comparison with the bonds of an intact ring.

Influence of the nature of organic solvents on the process of separation of antioxidative additive in a transformer oil by a gas-chromatographic method

THE PURPUSE. The paper considers the influence of the nature of organic solvents on the process of separation of an antioxidant additive added to transformer oil at a concentration of up to 0.40% by weight, and organic solvents used as selective extractants. Based on the analysis of literature data, it is shown that mineral transformer oil is a complex hydrocarbon composition that undergoes oxidative degradation during operation, leading to aging of transformer oil and deterioration of technical conditions of operation of transformer electrical equipment. As a result of this process, peroxide compounds appear in transformer oil, which affect its color, oxidation stability, aging resistance, compatibility with structural parts of equipment, etc. Gas -liquid chromatography was used to determine the "Ionol" antioxidant additive and organic extractants in transformer oil. Experiments were performed on a chromatograph of Chromosomes GC -1000 with a flame ionization detector and a quartz capillary column 30 m long, 0.32 mm in diamet er, filled with a fixed liquid phase Valko Bond VB-WAX P/n with a film thickness of 0.5 microns. The sample was dosed into the gas-liquid chromatograph injector using an automatic liquid dispenser DAZH-23, designed for entering up to twenty-three samples of sorbates and controlled by a computer with the appropriate software.METHODS. Aliphatic alcohols from C1 to C5 were studied as extractants of the antioxidant additive, which are well separated from the ionol both under isothermal conditions and in the mode of linear programming of the column temperature from 40 to 220 °C. Under these conditions the chromatogram of the separation of antioxidant additives, and aliphatic alcohols, which are used to calculate their relative retained volumes, the asymmetry of chromatographic peaks and the column efficiency, which depends on the physico -chemical nature of the solutes to be analyzed and the conditions of the chromatographic experiment.RESULTS. The dependence of the relative volume of retention of aliphatic alcohols on their permittivity, which has a nonlinear form, is established. At the same time, with a decrease in the chain length of alkyl substituents in the aliphatic alcohol molecule, there is a tendency to increase their permittivity. The dependence of the relative retained volume of aliphatic alcohols on the selectivity coefficient of separation with Ionol is linear. In this case, the most optimal separation selectivity, approaching one, is characteristic of the Ionol – Butanol-1 pair. It is shown that the dependence of the logarithm of the retention time of aliphatic alcohols on their boiling points is linear both at a low temperature of the chromatographic column (40 °C) and at a higher temperature (more than 100 °C). CONCLUSION. At the same time, the angle of inclination of the corresponding lines changes in the boiling point of organic solvents, which is associated with a change in the sorption mechanism in a capillary chromatographic column filled with a polar stationary phase.

Crystal Structure and Infrared Spectroscopy of trans-[Cr(NCS)2(Me2tn)2][Cr(NCS)4(Me2tn)] Moiety

A novel double complex, trans-[Cr(NCS)2(Me2tn)2][Cr(NCS)4(Me2tn)]·NaSCN·i-PrOH, (1) (Me2tn = 2,2-dimethyl-1,3-propanediamine, C5H14N2; i-PrOH = isopropyl alcohol), was prepared and its structure was determined by single-crystal X-ray diffraction at 95 K. The complex 1 crystallized in the space group P1 of the triclinic system with two nuclear formula units in a cell of dimensions a = 13.220(3), b = 13.699(3), c = 15.087(3) Å and α = 116.193(3), β = 102.73(3) and γ = 104.48(3)°. X-ray structural analysis revealed two crystallo-graphically independent Cr(III) complex cations in the complex 1. The asymmetric unit contains two halves of trans-[Cr(NCS)2(Me2tn)2]+ cations (2 and 3), one cis-[Cr(NCS)4(Me2tn)]− anion (4), one NaSCN salt and one isopropyl alcohol molecule. In two independent complex cations, the chromium(III) ions are coordinated by four N atoms of two chelating Me2tn and two NCS groups in a distorted octahedral geometry while the chromium(III) ion in cis-[Cr(NCS)4(Me2tn)]- has a distorted octahedral coordination with two N atoms of one Me2tn and four NCS groups. The two six-membered rings in trans-[Cr(NCS)2(Me2tn)2]+ cations adopt both anti chair-chair conformations. The Cr–N(Me2tn) bond lengths range from 2.0624(18) to 2.0877(16) Å, while the Cr–N(NCS) bond lengths range from 2.0718(16) to 2.0428 (16) Å. The crystal lattice is stabilized by hydrogen bonding interactions among the NH groups of the Me2tn ligand, OH group of i-PrOH and the S atoms of the NCS groups. The infrared spectral properties are also described.

Strongly diluted dimethyl-imidazolium chloride–alcohol solutions: solvents are structurally different but dynamic heterogeneities are similar

The increase of the alkyl chain length of the alcohol molecule does not affect the motion of the ionic liquid components.

Crystal structure and Hirshfeld surface analysis of 1-methyl-4-(2-methyl-10H-benzo[b]thieno[2,3-e][1,4]diazepin-4-yl)piperazin-1-ium 2,5-dihydroxybenzoate propan-2-ol monosolvate

The asymmetric unit of the title salt, C17H21N4S+·C7H5O4 −·C3H7OH, consists of an olanzapinium cation, an independent 2,5-dihydroxybenzoate anion and a solvent isopropyl alcohol molecule. The central seven-membered heterocycle is in a boat conformation, while the piperazine ring displays a distorted chair conformation. The dihedral angle between the benzene and thiene rings flanking the diazepine ring is 52.58 (19)°. In the crystal, the anions and cations are connected by N—H...O and O—H...O hydrogen bonds, forming a three-dimensional network.

Similar Behavior of Rheological Properties and the Evaluation of the Melting Temperatures of Fluorinated Aliphatic Alcohols

On the basis of experimental data obtained for the viscosity, density, and refractive index of fluorinated alcohols and proceeding from the similarity laws, the structural features of molecules of the researched liquids are determined. A comparison of molecular refraction values determined for fluorinated and non-fluorinated alcohols made it possible to reveal a modification of the structure of fluorinated alcohol molecules. Namely, this is a probable minor change in the arrangement of fluorine atoms in the alcohol molecule, at which the structure of a molecule remains similar to the structure of molecules of aliphatic alcohols. A similarity in the behavior of the rheological properties of 2,2,3,3-tetrafluoropropan-1-ol and 1H,1H-pentafluoropropan-1-ol, on the one hand, and propan-1-ol, on the other hand, as well as 1H,1H,7H-dodecafluoroheptan-1-ol and 1H,1H-tridecafluoroheptan-1-ol, on the one hand, and heptan-1-ol, on the other hand, is found. A method for estimating the melting temperatures of halogenated molecular liquids, which is based on the similarity of the rheological properties of those liquids, is proposed. The melting temperatures for 1H,1H-pentafluoropropan-1-ol, Tm = (244.5 ± 1.0) K, and 1H,1H-tridecafluoroheptan-1-ol, Tm = (255.0 ± 1.0) K, which are not available in the literature, are evaluated.

COMPUTER SIMULATION OF THE POROUS STRUCTURE OF HYDROLYSIS LIGNIN AND ITS HARD COMPO-SITES WITH COMPONENTS OF OIL FUELS AND WATER

A fragment of the supramolecular structure of lignin was simulated by cross-linking the C546H600O196 structural units along the corresponding CH–bonds followed by geometric optimization by the Polac-Ribier’s conjugate gradient method in the MNDO field of the HyperChem 8.0 software and ChemBio 13.0. The pore structure of lignin was simulated as well with optimization by the molecular mechanic’s method according to the MM2 Norman-Alinger’s algorithm taking into account the dipole-dipole interaction. Сoumaric alcohol molecule was a building block. The calculation of the energy parameters of lignin’s pore structure filling by the molecules of organic substances and water were carried out. It included a search for a global minimum of the potential energy by the molecular mechanic’s method according to the MM2 program and by the molecular dynamics method. The calculation had its basis in the “closed” pores existence in lignin. The calculated values of pore volume and specific surface area correlate with the experimental data. The way of prediction of organic substances sorption activity to lignin was proposed. This is evident from their calculated hydrophobicity parameter that correlates with the interaction energy of the molecules in the lignin pore.

Carbyne with finite length: The one-dimensional sp carbon

Carbyne is the one-dimensional allotrope of carbon composed of sp-hybridized carbon atoms. Definitive evidence for carbyne has remained elusive despite its synthesis and preparation in the laboratory. Given the remarkable technological breakthroughs offered by other allotropes of carbon, including diamond, graphite, fullerenes, carbon nanotubes, and graphene, interest in carbyne and its unusual potential properties remains intense. We report the first synthesis of carbyne with finite length, which is clearly composed of alternating single bonds and triple bonds, using a novel process involving laser ablation in liquid. Spectroscopic analyses confirm that the product is the structure of sp hybridization with alternating carbon-carbon single bonds and triple bonds and capped by hydrogen. We observe purple-blue fluorescence emissions from the gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital of carbyne. Condensed-phase carbyne crystals have a hexagonal lattice and resemble the white crystalline powder produced by drying a carbyne solution. We also establish that the combination of gold and alcohol is crucial to carbyne formation because carbon-hydrogen bonds can be cleaved with the help of gold catalysts under the favorable thermodynamic environment provided by laser ablation in liquid and because the unique configuration of two carbon atoms in an alcohol molecule matches the elementary entity of carbyne. This laboratory synthesis of carbyne will enable the exploration of its properties and applications.