Two biocomposites based on cellulose (UFC) and starch modified urea formaldehyde (UFS) resin (F/U ratio of 0.8) were synthesized using the same procedure. The hydrolitical, thermal, and radiation stability of biocomposites are determined. Also, released formaldehyde during the acid hydrolysis is determined. Biocomposites based on modified UF resin have been irradiated with (50 kGy). Cellulose modified UF resin after γ‐radiation has 1.38% released formaldehyde; unmodified UF resin has 2.21% released formaldehyde. Thermal stability of biocomposites is determined using nonisothermal thermogravimetric analysis, differential thermal gravimetry (DTG), and differential thermal analysis with IR spectroscopy. Moving the DTG peak to higher temperatures indicates an increased thermal stability of cellulose modified UF resin, which is confirmed by the FTIR analysis. Gamma radiation most often causes a decrease in the intensity of the peaks in the FTIR spectrum. POLYM. COMPOS., 40:1287–1294, 2019. © 2018 Society of Plastics Engineers
In this paper an applied organic geochemical approach in studying the nature of organic matter (OM) in water and sediments of the River Ibar (upsteream and downstream of towns Kosovska Mitrovica and Kraljevo) was used. A forensic approach that relies on the fact that the composition of OM of recent sediments and oil varies due to geological age and maturity was applied. The content of bitumen, its group composition of saturated, aromatic and NSO compounds (nitrogen, sulphur, and oxygen compounds) and the distribution of n-alkanes in saturated fractions identified by gas chromatography-mass spectrometry (in almost all samples incorporated into the colloidal micelles formed by water and NSO compounds) could not answer the question whether OM in isolated extracts has native or anthropogenic origin. However, the presence of sterane and terpane, with the distribution of structural and stereochemical isomers characteristic of oil, as a form of most matture OM in sediments, unambiguously confirmed presence of oil type pollutants in anlayzed samples. Based on significant differences in the distributions of these polycyclic alkane (water--water, sediment-sediment and water-sediment), it was concluded that they have more than one source of pollution, and that the River Ibar is permanently exposed to this form of pollution.
The main objective of this study was to determine whether there are the spatial and temporal changes in physico-chemical properties of water and concentrations of heavy metals in water and sediment of the River Ibar upstream and downstream of Kosovska Mitrovica and Kraljevo. The following physicochemical parameters were determined: pH, electrical conductivity, suspended matter content, biological oxygen demand, chemical oxygen demand, total organic carbon, contents of nitrates, ammonium ion, total phosphorous, sulphates. Concentrations of heavy metals in water and sediment samples were determined using an inductively coupled plasma optical emission spectrometry (ICP-OES) using a SPEC-TRO AR COS instrument. The water of the Ibar River after flowing through Kraljevo shows a higher degree of pollution than in Kosovska Mitrovica. However, the water upstream and downstream of Kraljevo is of similar quality indicating that the pollution source is not located in Kraljevo, but along the river section between the two towns. This study has also proved that the water quality in Kraljevo did not significantly change during the period 2010-2016. The highest concentrations of nitrates, nitrites, ortophosphates and ammonium ion are found in colder months. During spring-summer change electrical conductivity, pH and concentration of sulphates has most prominent change in the analyzed Ibar River water in Kraljevo.
The elastomeric materials based on NR/BR/SBR ternary rubber blend were investigated. The polyisoprene (NR), butadiene (BR) and styrene butadiene (SBR) rubbers were used as network precursors and carbon black (CB) as an active filler (60 phr) for elastomeric materials preparation. For sample preparation, the mass ratio of NR to BR was constant, 1:1, but the SBR content was varied from 0 to 80 phr. The morphological, mechanical and thermal properties of prepared elastomeric materials were determined using scanning electron microscopy (SEM), mechanical tensile measurements and thermogravimetric analysis (TGA). Mechanical properties were assessed before and after thermooxidative aging during 168 h at 100 °C. The values of tensile strength, elongation at break, and hardness decrease up to 40 phr of SBR content and after that are increasing, but abrasion resistance of ternary rubber blends increases. Тhe thermal decomposition temperature obviously shifted to a higher temperature for the sample with 40 phr of SBR.
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