Release Of Volatile Substances Research Articles

Effect of ecofriendly grapefruit peel extract on PVC thin films photostabilizing tested under harmful weathering conditions

AbstractExposure to ultraviolet radiation triggers a photooxidative deterioration mechanism in plastics, resulting in bond breakage, release of volatile substances, overall weight reduction, generation of free radicals, and loose crosslinking. The aim of this study was to obtain a plant extract with appropriate concentration and use it to protect polyvinyl chloride (PVC) from photodegradation. PVC films containing different concentrations of naringin that were already extracted and TINUVIN 622 as a commercial stabilizer were investigated in this paper. UV light was used to irradiate PVC films for 300 h to test the photostability. After radiation, infrared spectra, weight loss, molecular weight reduction, and surface morphology examination for PVC films were studied. In comparison to blank film, the photodegradation of PVC films was significantly reduced by the naringin and TINUVIN 622 photostabilizers. The role of photostabilizers includes deactivating excited states (as quenchers), functioning as effective light filters (pigments and absorbers), scavenging radicals, and decomposing hydroperoxides.

Atomic oxygen degradation of a fluorine-containing colorless polyimide

Colorless polyimides (PIs) are regarded as the most feasible lens materials deployed in aerospace optical systems due to their light weight, flexibility, transparency, and excellent mechanical properties. However, durability towards atomic oxygen (AO) exposure is a chief concern for externally deployed colorless PI films in low Earth orbit (LEO) environments. In this work, we investigated the degradation behavior of a fluorine-containing colorless PI film with a combination of ground-based AO exposure experiments and reactive molecular dynamics (ReaxFF-MD) simulations. The fluorine-containing colorless PI showed linear erosion dynamics and a constant erosion yield (Ey) of ∼1.4 × 10−24 cm3 atom−1. Microscopic investigations demonstrated an increased surface roughness and shag-like appearance after continuous AO exposure. In addition, spectroscopic transformations resulted from elimination and oxidation processes occurring at specific reaction active sites (C=O, CN, CH, and CF, and CC) and the release of volatile substances. Moreover, the exposed fluorine-containing colorless PI films exhibited gradually deteriorating visible light transmission with increased AO fluence. Furthermore, the ReaxFF-MD simulations demonstrated physical sputtering and bombardment-enhanced chemical reaction models. Considering the limited-scale slab and the system thermal dissipation, the experimental and ReaxFF-MD computational results were largely consistent.

Effects of poly(vinyl alcohol) matrix on the release of substances from the fragrance composition

The chemical composition of two commercially available lavender fragrance oils was determined and compared. The process of concentration by partial evaporation was carried out and its influence on changes in the content of individual components in the analysed mixtures was examined. The effect of poly(vinyl alcohol)-based polymer matrix on the release of volatile substances from oils was tested as well. The presence and chemical composition of the polymer matrix affects the relative content of volatile substances released from the liquid phase containing the tested fragrance composition.

Variation in longevity of cut and in planta flowers of potted carnation varieties affected by their relationship with ethylene and water

Carnation (<italic>Dianthus caryophyllus</italic> L.) is a typical ethylene-sensitive cut flower, but a few differences in ethylene sensitivity have been reported for different potted carnation species. In this study, we investigated the relationship between vase life, ethylene sensitivity, ethylene biosynthesis gene expression, and flower volatile substance content of 17 different potted carnation varieties. It was found that under the same post-harvest environmental conditions, the vase life of different varieties ranged from 6.2−14.2 d. Among the 17 varieties, 'Cherry' and 'Grace Bay' were highly sensitive to ethylene, and qRT-PCR analysis showed that their ethylene biosynthesis genes <italic>DcACS1</italic> and <italic>DcACO1</italic> expression increased the most, while 'Pink and Purple', 'Bondi Beach', and 'Grane Beach' showed the opposite pattern. In addition, the lower ethylene release was important in leading to longer vase life of potted carnations, and that ethylene release from shorter vase life varieties was 2.5−4.5 times greater than that of longer vase life varieties. Varieties that are more sensitive to ethylene are more likely to have a shorter vase life due to early disruption of water relations, which is mainly the result of reduced stem hydraulic conductivity and transpiration water loss. Analysis of volatile substances showed that ethylene had no significant effect on the release of volatile substances from potted carnations. Therefore, a better understanding of petal senescence in potted carnations will help us to improve measures to extend flower longevity according to the ethylene sensitivity of different varieties.

Кelationship of the parameters of physico-chemical and sorp-tion processes with the emission of coal beds. part II: on the influence of the stages of metamorphism of natural coals on their metanic capacity

In this part of the article, based on the technologies of intelligent data processing (Data Mining), it is shown that the dispersion of the experimental da-ta on the release of volatile substances in depth is associated with the peculiarities of the manifestation of regional thermo-metamorphism of coals. It has been established that the most powerful factors influencing the methane capacity of coal are the depth of coal seams and the release of volatile substances, which is consistent with classical concepts.

Relationship of the parameters of physico-chemical and sorp-tion processes with the emission of coal beds. part I: on the influence of physical and chemical parameters of natural coals on their metane capacity

This part of the article shows shows that methane capacity is closely related to the physicochemical properties of coals and the physical structure of coal matter: porosity, moisture, ash content, petrographic composition and the release of volatile substances. It was found that the porosity of natural coals weakly depends on the stages of metamorphism and its effect on the methane content of coals can be ignored. Based on the catalogs of the physicochemical properties of coals from the developed deposits of Kuzbass, it is shown that differences in ash content and moisture content of coals have very little effect on their me-thane capacity, and the main strongest influencing factors on the methane capacity of coal were the depth of coal seams and the release of volatiles.

Thermal Dissolution of Coals of the Metamorphism Series in the Anthracene Fraction of Coking Tar: An Analysis of Correlations with the Chemical and Technological Properties of Coals

The thermal dissolution of coals of a wide metamorphism series from the deposits of Russia and Mongolia in the anthracene fraction of coking tar at 380°C was studied. According to the data of a correlation analysis, it was found that the reflectivity of vitrinite, the yield of volatile substances, the carbon content, and the temperature Tmax at which the main release of volatile substances occurs in the course of pyrolysis are the most reliable characteristic properties of coal to be used for the prediction of the conversion of its organic matter into quinoline-soluble substances. The dependence of the conversion on the above properties of coal has an extremum. The medium-rank coking coals with a vitrinite reflectance of 0.80–0.90, a vitrinite concentration of higher than 70%, a carbon content of 83–86%, a volatile matter yield of 35–39%, and a temperature of Tmax = 465–475°С had the highest rates of conversion.

Kinetics and thermodynamics evaluation of carbon dioxide enhanced oil shale pyrolysis

The pyrolysis process of oil shale is significantly affected by atmospheric conditions. In this paper, the pyrolysis experiments of oil shale under non-isothermal conditions are carried out using nitrogen and carbon dioxide as heat-carrying fluids. The results show that the activation energy of the second stage of oil shale pyrolysis under carbon dioxide is less than that under nitrogen. The thermodynamic analysis of the second stage of oil shale pyrolysis shows that Gibbs free energy, activation enthalpy and activation entropy are higher under carbon dioxide than those under nitrogen, which obeys the law of carbon dioxide promoting oil shale pyrolysis. In addition, the volatile release characteristics of oil shale in the second stage of pyrolysis were analyzed, which proves that the volatile release characteristics of oil shale under carbon dioxide are higher than that under nitrogen. Therefore, carbon dioxide is helpful to promote the pyrolysis of oil shale and increases the release of volatile substances during pyrolysis.

ПРО РОЗРОБКУ ЗАГАЛЬНОЇ МЕТОДИКИ ДЛЯ ПРОГНОЗУ НЕБЕЗПЕЧНИХ ВЛАСТИВОСТЕЙ ВУГІЛЬНИХ ШАХТОПЛАСТІВ

Purpose: to establish a quantitative effect on the dust-generating ability of mine layers of the degree of metamorphic transformations of fossil coals, mining-geological and mining conditions of mining operations and to provide proposals for the development of a general methodology for predicting other hazardous properties of mine layers. Methodology: research is based on the experience of using regulatory documents and analysis of the results of experimental and calculated data on dust formation of fine fractions for various observation conditions. Results: based on the analysis of statistical models of shallow and steeply dipping mine layers by groups of their dustiness, the effect of specific dust release, dust content in broken coal, moisture and thickness of the seams was established. Of all the possible factors that determine the specific dust release, the main ones are the design features of mining machines. The yield of small grades when tested by the falling weight method can serve as an indicator of the strength of coal. The use of such methods eliminates the errors caused by determining the degree of coal change during the transition from its actual destruction by a coal mining machine to the reference mode. The use of carbon content as one of the main indicators of the degree of metamorphism makes it possible to analyze the level of influence of both the sum of the remaining main components of the organic mass (hydrogen, nitrogen, sulfur, oxygen) and their separate influence. In order to bring the state of coal as close as possible to production conditions, it is necessary to additionally take into account moisture, mineral inclusions and their composition. The petrographic composition and some physical and mechanical properties are reliably characterized by the vitrinite reflectance index. The extreme limits of influence on dust formation of the design features of mass-produced combines differ by 43.4 times. The influence of metamorphic transformations at the extreme limits of the yield of the 1-0 mm class when testing coals in a pile driver is estimated by a difference of 5.6 times. The release of volatile substances taken as the main indicator of the degree of metamorphism in the normative base for the safe conduct of mining operations does not unambiguously characterize the gradation of mine layers according to their dustiness groups. The thickness of the mines being developed and the angles of occurrence do not determine their tendency to dust formation, but are the main criteria for choosing mining equipment for crushing coal in the massif. The general methodology for predicting the hazardous properties of coal mine layers, using the example of their dust-forming ability, should take into account the influence of factors of three blocks – metamorphic transformations, mining and geological and mining technical conditions. Scientific novelty: for the first time, a quantitative assessment of the effect on the dust-generating capacity of mine layers of a combination of factors of metamorphic transformation of fossil coals, mining-geological and mining-technical conditions of mining operations has been established. Practical value: the results obtained make it possible to substantiate and develop a general methodology for predicting the hazardous properties of mine layers, which will contribute to improving the regulatory framework for the safe conduct of mining operations.

Effective and green tire recycling through microwave pyrolysis

Waste tire rubber has become a severe environmental issue, which calls for a green method to recycle this rubber. Microwave thermolysis serves as an ideal recycling process for used tires. By surveying the dielectric characteristics from 25 to 700 °C under microwave frequencies of 915 and 2466 MHz, the microwave absorption ability of waste tire rubbers was studied. At temperatures below 350 °C, the dielectric characteristics were relatively steady. Both the loss factor and relative dielectric constant (DC) increased sharply with the rise in temperature. The reason for this is the release of volatile substances, which increases the electrical conductivity. The performance of microwave absorption of tire rubber during thermolysis, and thus the efficiency of microwave tire rubber thermolysis, can be largely impacted by the specimen dimension. The calculation of the reflection loss (RL) of the tire rubber specimens suggests that when the waste tire rubber is 5 mm thick, the highest microwave absorption can be achieved at 915 MHz and 592.1 °C, with RL of −17.30 dB. The product after microwave pyrolysis of waste tire rubber comprises 35% carbon black, 40% oil, and 25% gas. Based on this investigation of the optimal condition of microwave absorption, a proper microwave pyrolysis recycling system was designed for waste tire. This system is efficient at recycling the waste tire rubber into valuable carbon black, oil, and gas products.

Thermal decomposition and combustion of coals, fuel wood, and hydrolytic lignin, as studied by thermal analysis

Different biofuel woods (spruce, pine, and spruce and pine bark), hydrolytic lignin, and coals from different deposits [D coal from Inta, Zh coal from Vorkuta, and D coal from Khakassia] were studied on a synchronous thermal analyzer at heating rates of 5, 10, and 20 K/min in inert and air atmospheres. Classical thermogravimetric and differential thermogravimetric curves were obtained to describe the thermal decomposition of hemicellulose, cellulose, and lignin and the combustion of a carbon residue as the main components of the biofuel woods. The decomposition of the coal fuels from different deposits was studied, and the temperature ranges of drying, the release of volatile substances, and the combustion of carbon residues were obtained. The results of thermal analyses were processed with the use of an isoconversional method based on the Friedman and Ozawa–Flynn–Wall models and with the aid of an extended independent parallel reaction (EIPR) model. A satisfactory repeatability of the results was obtained to indicate the applicability of both of these methods. The subsequent study of wood, hydrolytic lignin and, coals from different deposits was carried out with the aid of the EIPR model. The activation energies of biofuel woods varied in a range from 62 to 93 kJ/mol, which are much lower than those of coals (104–116 kJ/mol).

A Chamber for Testing the Release of Volatile Substances Secreted by Animals, Especially Mammals, as Exemplified by Substances Released by Rats in Response to Stress

The success of the testing of volatile organic compounds emitted by animals is dependent on the creation of appropriate conditions for air sampling subsequently used to assay and identify the compounds. These conditions play a particularly important role in the investigation of pheromones, which are secreted in extremely low concentrations. The authors have not come across any previous work which offers constructional solutions, which would allow avoidance of contamination of the air samples containing volatile substances secreted by animals. A constructional solution was developed, which provides optimal conditions for their sampling and isolation. Its main advantages are as follows: the exposure chamber (the chamber in which the animal is studied) is filled with synthetic air; the exposure chamber is separated from the atmospheric air with a synthetic air “jacket”; the exposure chamber has been constructed using materials which do not release chemicals and absorb them in trace quantities.

Water – an important parameter for the preparation and proper use of certified reference materials

Property values of powdered certified reference materials (CRMs) are very often related to dry mass. The dry mass is indirectly determined by measuring the moisture content of the sample. The most commonly used methods are the drying oven method and the Karl Fischer titration (KFT). It is well known that these two methods may give different values for the moisture/water content. In this study thermogravimetry was used to simulate the drying oven method and to investigate the reasons of the differences between both moisture/water content determination methods. A mass spectrometer coupled to a thermobalance (TGMS) added further useful information regarding the release of volatile substances and the decomposition of the material during the drying process. The relative humidity of the laboratory may influence the water content of powdered CRMs because of their more or less pronounced tendency to take up water (hygroscopicity). This fact can lead to biased property values. The water adsorption kinetics and the water uptake capacity vary, depending on the constitution of the sample. This was studied analysing several powdered food CRMs and individual constituents thereof. The speed of water uptake and the water uptake capacity were described using an exponential function. The findings have consequences both for the producer and for the user of certified reference materials.

False positive results in cytotoxicity testing due to unexpectedly volatile compounds.

We investigated the cytotoxicity of different dental materials according to the study protocol adopted by our lab for the screening of new materials. Experimental parameters used in such testing are addressed mainly in documents EN 30993 "Biological evaluation of medical devices, Part 5: Tests for cytotoxicity: in vitro methods" and "Biological evaluation of medical devices, Part 12: Sample preparation and reference materials." Cells were cultured in microplates and challenged with aqueous extracts of the materials. The assay methods were neutral red- and propidium iodide-uptake assays, both indicative of cell viability and able to provide quantitative data. The observation of contrasting results for one material using the above-mentioned methods raised some concern about the assay system used. With further experimentation, it appeared that a sustained release of volatile substances still present in one extract exerted a toxic effect in neighboring cultures. It is concluded that in the microenvironment of a microplate the distribution of samples cannot be disregarded, as it may be responsible for toxicity cross-contamination. Moreover, the use of more than one single method has to be recommended in cytotoxicity testing, in order to avoid false positive results due to experimental artifacts.