Reološko ponašanje termoplastičnih poli(estar-siloksana)

Two series of thermoplastic elastomers (TPES), based on poly(dimethylsiloxane) (PDMS) as the soft segment and poly(butylene terephthalate) (PBT) as the hard segment, were analyzed by dynamic mechanical spectroscopy. In the first TPES series the lengths of both hard and soft segments were varied while the mass ratio of the hard to soft segments was nearly constant (about 60 mass%). In the second series, the mass ratio of hard and soft segments was varied in the range from 60/40 to 40/60, with a constant length of soft PDMS segments. The influence of the structure and composition of TPESs on the rheological properties, such as complex dynamic viscosity, μ*, the storage, G', and loss, G', shear modulus as well as the microphase separation transition temperature, TMST, was examined. The obtained results showed that the storage modulus of the TPESs increased in a rubbery plateau region with increase in degree of crystallinity. The rheological measurements of TPESs also showed that a microphase reorganization occurred during the melting process. The microphase separation transition temperatures were in the range from 220 to 234°C. In the isotropic molten state, the complex dynamic viscosity increased with increasing both the content and length of hard PBT segments.Dve serije termoplastičnih elastomera (TPES) na bazi poli(dimetilsiloksana) kao mekog segmenta i poli(butilentereftalata) kao tvrdog segmenta su analizirane dinamičko-mehaničkom spektroskopijom. U prvoj TPES seriji varirane su dužine tvrdih i mekih segmenata dok je njihov maseni odnos bio skoro konstantan (oko 60 mas%). U drugoj seriji, odnos tvrdih i mekih segmenata je variran u opsegu od 60/40 do 40/60, dok je dužina mekih PDMS segmenata bila konstantna. Ispitan je uticaj strukture i sastava TPES kopolimera na reološka svojstva, kao što su kompleksni dinamički viskozitet, μ*, moduli sačuvane, G', i izgubljene energije, G', i temperatura mikrofaznog razdvajanja, TMST. Dobijeni rezultati su pokazali da su uzorci sa većim stepenom kristaliničnosti imali i veće module sačuvane energije u gumolikom platou. Reološka merenja su takođe pokazala da svi TPES uzorci ispoljavaju mikrofaznu reorganizaciju u procesu topljenja. Temperature mikrofaznog razdvajanja su bile u opsegu od 220 do 234°C. U izotropskom rastopu, kompleksni dinamički viskoziteti su rasli sa povećanjem sadržaja i dužine PBT segmenata

Kvantitativno određivanje poli(vinilpirolidona) primenom 'On-line' pirolize kuplovane sa gasnom hromatografijom

'On-line' pyrolysis coupled with gas chromatography (GC) was performed for quantitative determination of poly(vinylpyrrolidone) (PVP) in wastewater sample. Gas chromatography-mass spectrometry (GC-MS) showed that the main product of pyrolysis of PVP, at high temperatures, was N-vinylpyrrolidone (NVP). After that, different amounts of commercial PVP were pyrolyzed in order to establish the correlation between the amount of generated NVP (its GC peak area) and the initial mass of pyrolyzed PVP. GC-FID analysis was used for construction of the calibration curve and for quantitative determination of PVP. Very good linear correlation was obtained between the area of NVP peak, generated during pyrolysis, and the initial mass of PVP (r2 = 0.998). Further, solutions of known concentration of PVP were prepared in destilled water ('spiked samples'). Spiked samples were preextracted with diethyl ether and n-hexane, after which the water-layer was evaporated and dissolved again in methanol. Analysis of pyrolysates of preextracted spiked samples showed that the 'recovery' of PVP was above 96 mass%. This finding suggested that pre-extraction could be applied to reduce the concentration of organic substances that could also be pyrolyzed, and thus hinder identification and quantitative determination of PVP, without significant loss of polymer. The sample of an industrial wastewater from Pančevo, Serbia was investigated in the last part of this work. The sample was preextracted in the same way as the spiked samples and than pyrolyzed. NVP was identified by GC-MS in obtained pyrolysate, which was the evidence that PVP was present in the wastewater sample. NVP was quantified on the basis of the peak area in GC-FID chromatogram, and than the concentration of PVP in wastewater sample was calculated based on calibration curve. Concentration of PVP in industrial wastewater amounted 2.5 mg/L.U ovom radu je primenjena metoda 'on-line' pirolize u sprezi sa gasnom hromatografijom (GC) za kvantitativno određivanje poli(vinilpirolidona) (PVP) u uzorku otpadne vode. Najpre je gasnomhromatografsko-masenospektrometrijskom analizom (GC-MS) utvrđeno da pirolizom PVP na visokim temperaturama kao glavni proizvod degradacije nastaje monomer, N-vinilpirolidon (NVP). Nakon toga su različite količine komercijalnog PVP pirolizovane da bi se uspostavila korelacija između količine nastalog NVP i inicijalne mase pirolizovanog polimera. Za konstruisanje kalibracione krive i kvantitativno određivanje PVP u rastvorima poznate koncentracije u destilovanoj vodi ('spiked samples'), kao i u uzorku otpadne vode, korišćena je GC analiza. Analizom rastvora komercijalnog PVP poznate koncentracije ustanovljeno je da PVP 'recovery', nakon ekstrakcije n-heksanom i dietil-etrom, iznosi iznad 96 mas.%. U poslednjem delu rada ispitan je uzorak industrijske otpadne vode iz Pančeva, Srbija. Pokazano je da je PVP bio prisutan u otpadnoj vodi i da je njegova koncentracija bila daleko iznad uobičajenih koncentracija niskomolekularnih organskih zagađivača

Synthesis, structure and thermogravimetric analysis of alpha,omega-telechelic polydimethylsiloxanes of low molecular weight

A series of alpha,omega-telechelic polydimethylsiloxanes (PDMS), with predetermined molecular weights of about 2500 g mol(-1), was synthesized by siloxane equilibration reaction. Syntheses were performed using octamethylcyclotetrasiloxane (D-4) and various disiloxanes: hexamethyldisiloxane (HMDS), 1,1,3,3-tetramethyldisiloxane (TMDS), 1,3-divinyltetramethyldisiloxane (DVTMDS), 1,3-bis(3-carboxypropyl) tetramethyldisiloxane (DCPTMDS) and 1,3-bis(3-aminopropyl) tetramethyldisiloxane (DAPTMDS). The role of the disiloxane was to introduce terminal functional groups at the end of the polymer chains and to control the molecular weight of the polymers. Polymers with trimethyl, hydrido, vinyl, carboxypropyl and aminopropyl end-groups were obtained in this way. The structure of the alpha,omega-telechelic PDMSs was confirmed by NMR and IR spectroscopy. The molecular weights of the polymers were determined by H-1-NMR, gel permeation chromatography (GPC) and dilute solution viscometry. Thermogravimetric analysis (TGA) under nitrogen and air showed that the type of the terminal groups significantly influenced the thermal and thermo-oxidative stability, as well as the degradation mechanism of the alpha,omega-telechelic PDMSs

Chemical Composition of the Essential Oils of Three Ocimum basilicum L. Cultivars from Serbia

Basil essential oil (BEO) contains a wide range of chemical compounds whose content may vary depending on chemotypes, environmental conditions, agronomic techniques and particularly the origin of the plant. In our present study, essential oils (EOs) were isolated by hydrodistillation method from dry herbs of three basil cultivars and analyzed by GC-FID and GC-MS. Two of the tested cultivars belong to sweet basil group (B-1 and B-2) while the third one was large leafed 'Genovese' basil (B-3). EO content in the dry herb was 0.65%, 0.41% and 0.62% respectively. The main classes of compounds of B1EO and B3EO were sesquiterpene hydrocarbons (38.39% and 37.95%), oxygenated monoterpenes (25.44% and 28.04%) and phenylpropanoids (17.43% and 15.71%). The main constituents of both EOs were monoterpene alcohol linalool (13.68% and 15.38%), phenoyl derivate eugenol (10.83% and 8.97%) and sesquiterpene hydrocarbon alpha-bergamotene (8.12% and 9.25%). In both EOs, epi-bicyclosesquiphellandrene was detected in considerable amount (7.03% and 8.07%). The most abundant compound classes in B2EO were oxygenated monoterpenes (52.07%), sesquiterpene hydrocarbons (24.27%) and phenylpropanoids (10.95%). Linalool was the dominant compound (40.97%), followed by epi-bicyclosesquiphellandrene (8.70%) and methyl chavicol (7.92%). The results showed complex chemical composition of BEOs and pointed out the presence of biologically active compounds of importance for different branches of the pharmaceutical, chemical and food industry. Although there are differences in the chemical composition of the BEOs, the obtained results show that all of the tested cultivars are rich in compounds which are responsible for biological activities

Sinalbin degradation products in mild yellow mustard paste

Sinalbin degradation products in mild yellow mustard paste were investigated. The analyzed material consisted of a mild yellow mustard paste condiment and ground white mustard seeds which were originally used in the mustard paste production process. The samples were extracted in a Soxhlet extraction system and analyzed by gas chromatography - mass spectrometry (GC-MS) technique. The only sinalbin degradation product in ground mustard seeds was 2-(4-hydroxyphenyl)acetonitrile. The most abundant sinalbin degradation product in yellow mustard paste was 4-(hydroxymethyl)phenol. Other compounds identified in this sample were: 4-methyl phenol, 4-ethyl phenol, 4-(2-hydroxyethyl)phenol and 2-(4-hydroxyphenyl) ethanoic acid

Aqueous extraction of anions from coal and fly ash followed by ion-chromatographic determination

Three different techniques were applied for the aqueous extraction of anions from coal and fly ash: rotary mixer-and ultrasonic-assisted extraction with different duration time, and microwave-assisted extraction at different temperatures. Validation showed that the ion-chromatographic method was suitable for the analysis of anions in coal and fly ash extracts. The variations in the amounts of anions using different extraction times during rotary-assisted extraction were minimal for all investigated anions. The efficiency of ultrasound-assisted extraction of anions from coal depended on the sonication time and was highest at 30 min. The ultrasound-assisted extraction was less efficient for the extraction of anions from fly ash than rotary-assisted extraction. Increase of temperature in the microwave-assisted extraction had a positive effect on the amounts of all anions extracted from coal and sulphate from fly ash, while the amounts of fluoride and chloride in fly ash extracts decreased. The microwave-assisted extraction of coal at 150 degrees C was compared with standard ASTM methods, and results were in good agreement only for chloride. Changes in the pH value and conductivity during ultrasound-assisted extraction were measured in order to explain changes on the surface of coal particles in contact with water and different processes that occur under environmental conditions

Comparison of sequential and single extraction in order to estimate the environmental impact of metals from fly ash

The aim of this paper is to simulate leaching of metals from fly ash in different environmental conditions using ultrasound and microwave-assisted extraction techniques. Single-agent extraction and sequential extraction procedures were used to determine the levels of different metals leaching. The concentration of metals (Al, Fe, Mn, Cd, Co, Cr, Ni, Pb, Cu, As and Be) in fly ash extracts were measured by inductively coupled plasma-atomic emission spectrometry. Single-agent extractions of metals were conducted at sonication times of 10, 20, 30, 40 and 50 min. Single-agent extraction with deionized water was also performed by exposing samples to microwave radiation at temperature of 50 degrees C. The sequential extraction was conducted according to the BCR procedure which was modified and applied to study the partitioning of metals in coal fly ash. The microwave-assisted sequential extraction was performed at different extraction temperatures: 50, 100 and 150 degrees C. The partitioning of metals between the individual fractions was investigated and discussed. The efficiency of the extraction process for each step was examined. In addition, the results of the microwave-assisted sequential extraction are compared to the results obtained by standard ASTM method. The mobility of most elements contained in the fly ash is markedly pH sensitive

Supplementary material for the article: Samelak, I.; Balaban, M.; Vidović, N.; Koljančić, N.; Antić, M.; Šolević-Knudsen, T.; Jovančićević, B. Application of Alkane Biological Markers in the Assessment of the Origin of Oil Pollutants in the Soil and Recent River Sediments (River Vrbas, Bosnia and Herzegovina). Journal of the Serbian Chemical Society 2018, 83 (10), 1167–1175. https://doi.org/10.2298/JSC180501061S

Supplementary material for: [https://doi.org/10.2298/JSC180501061S]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/2237

Application of alkane biological markers in the assessment of the origin of oil pollutants in the soil and recent river sediments (River Vrbas, Bosnia and Herzegovina)

In this paper, an attempt was made to contribute to the use of biological markers, n-alkanes, and polycyclic alkanes of the sterane and terpane type, in the assessment of the source of oil pollutants in the environment using the example of the correlation between recent river and coastal sediments,. Four samples of recent river sediments of the Vrbas River and four samples of adjacent bank sediments (soils), in the part of the River that belongs to the city of Banja Luka (Bosnia and Herzegovina) were analyzed. In the alkane fractions of isolated extracts, a bimodal distribution of the n-alkanes was observed. Lower homologues dominated in the recent river sediments with maximum at C15, but higher n-alkanes dominated in the soil samples, with a maximum at n-C29 or at n-C31. The higher concentration of steranes and terpanes with oil type distributions in the recent/fresh river sediments (compared to the bank sediments) represents evidence that lower n-alkanes originate from oil sources. The higher content of total hydrocarbons in the recent river sediments than in the bank sediments further confirms this conclusion. At the same time, these fundamental considerations provide evidence that oil pollution primarily occurred in the water flow and then the oil pollutants propagated towards the riverbank

Determination of bisphenol A traces in water samples from the Vrbas River and its tributaries, Bosnia and Herzegovina

The bisphenol A (BPA) concentration was determined in 12 surface water samples of the Vrbas River and its five tributaries. The samples were taken in the area that belongs to the city of Banja Luka (Bosnia and Herzegovina). BPA was isolated using micro liquid-liquid extraction followed by derivatization and gas chromatography-mass spectrometry analysis (GC-MS). Silylation was used as a derivatization method to increase volatility and allow the GC-MS determination of BPA. The limits of detection (LOD) and quantification (LOQ), obtained by validating the procedure, were determined at 4 and 10 ng L-1, respectively. The concentrations of BPA were ranged between 33 and 354 ng L-1, and all were above the LOQ value. The lowest amount of BPA was found in the sample collected in the river Vrbas, near Švrakava estuary upstream from the city of Banja Luka. The highest concentration of BPA was recorded at the confluence of the Crkvena and Vrbas rivers, which is located in the city center. This study shows that population and human activity could affect the level of BPA in the environment