Synthesis,thermal degradation and dielectric properties of poly[2-hydroxy,3-(1-naphthyloxy)propyl methacrylate]

2-Hydroxy-3-(1-naphthyloxy)propyl methacrylate (NOPMA) monomer was synthesized from reaction of 2-[(2-naphthyloxy)methyl]oxirane with methacrylic acid in the presence of pyridine. The polymerization of NOPMA was carried out by free radical polymerization method in the presence of AIBN at 60 °C. The structure of monomer and polymer was characterized by ¹H-NMR, ¹³C-NMR and FT-IR spectroscopy techniques. The glass transition temperature and average-molecular weights of poly(NOPMA) were measured using differential scanning calorimetry and gel permeation chromatography, respectively. The thermal degradation behavior of poly(NOPMA) has been investigated by FT-IR studies of the partially degraded polymer and thermogravimetry. The cold ring fractions (CRFs) were collected at two different temperatures, initially fraction-1 (CRF₁) is from room temperature to 320 °C, and the other fraction-2 (CRF₂) is from 320 to 500 °C. The volatile products of the degradation were trapped at ?195 °C (in liquid nitrogen). All the fractions were characterized by FT-IR, ¹H and ¹³C-NMR spectroscopic techniques, and the cold ring fractions (CRFs) were also characterized by GC–MS. For the degradation of polymer, the major compound between products of CRFs is α-naphthol. The GC–MS, FT-IR and NMR data showed that depolymerization corresponding to monomer was not prominent below 320 °C in the thermal degradation of poly(NOPMA). The mode of thermal degradation containing formation of the major products was identified. The dielectric permittivity (ε′), the loss factor (ε″) and conductivity (σ_ac) were measured using a dielectric analyzer in the frequency range of 50 Hz to 20 kHz.     

Investigation of the mechanic behaviours in hollow composite shafts having different fiber reinforcement and orientation angles

This study experimentally investigates the mechanical properties and behaviors of the hollow circular composite shafts, which are widely used in the industry and operated under a variety of environmental influences. Within the context of this study, glass, carbon and kevlar fibers were utilized as fiber materials and epoxy resins were preferred as the matrix material for hollow circular composite shafts. Composite shafts having 80 mm, 200 mm, 250 mm length and different internal diameters were used for three‐point bending tests. Composite hollow shafts were manufactured by utilizing filament winding method at different orientation angles (θ = 45°, 60°, 75°, 80°, 88°). The bending behaviors of the hollow circular composite shafts manufactured were repeated separately for each sample in three‐point bending tests. The results obtained were evaluated inter se, displayed in graphics and necessary considerations were addressed.     

Supercritical fluid extraction of jojoba oil

Supercritical fluid extraction of jojoba oil from Simmondsia chinensis seeds using CO₂ as the solvent is presented in this study. The effects of process parameters such as pressure and temperature of extraction, particle size of jojoba seeds, flow rate of CO₂, and concentration of entrainer (hexane) on the extraction yield were examined. Increases in the supercritical CO₂ flow rate, temperature, and pressure generally improved the performance. The extraction yield increased as the particle size decreased, indicating the importance of decreasing intraparticle diffusional resistance. The maximum extraction yield obtained was 50.6 wt% with a 0.23-mm particle size and a 2 mL/min CO₂ flow rate at 90°C and 600 bar. Use of an entrainer at a concentration of 5 vol% improved the yield to 52.2 wt% for the same particle size and also enabled the use of relatively lower pressure and temperature, i.e., 300 bar and 70°C.     

Mass transfer enhancement factor for chemical absorption of carbon dioxide into sodium metaborate solution

Hydrogen is getting increasing attention as a medium for energy storage, and sodium borohydride is accepted as a suitable carrier for hydrogen. The main product of the process by means of which hydrogen is produced from sodium borohydride is sodium metaborate. Our aim was to find an alternative use for sodium metaborate and specifically investigating the feasibility to use it for carbon dioxide capture from flue gases. The products of this chemical absorption are sodium carbonate, sodium bicarbonate and boric acid, all of which are industrially important chemicals. A bubble column was used in the experiments. Oxygen desorption technique was employed to determine the liquid side physical mass transfer coefficient. Chemical mass transfer coefficient was determined by absorption of carbon dioxide from its mixture with nitrogen into sodium metaborate solution. Enhancement factor was then calculated and a correlation was developed for it.     

Chernobyl fallout in the uppermost (0-3 cm) humus layer of forest soil in Finland, North East Russia and the Baltic countries in 2000--2003

The situation resulting from the Chernobyl fallout in 1987 was compared to that in 2000--2001 in Finland and NW Russia and that in 2003 in the Baltic countries. 786 humus (0-3 cm layer) samples were collected during 2000--2001 in the Barents Ecogeochemistry Project, and 177 samples in the Baltic countries in 2003. Nuclides emitting gamma-radiation in the 0-3 cm humus layer were measured by the Radiation and Nuclear Safety Authority-STUK in Finland. In 1987 the project area was classified by the European Commission into four different fallout classes. 137Cs inventory Bg/m2 levels measured in 2000--2003 were compared to the EU's class ranges. Fitting over the whole project area was implemented by generalizing the results for samples from the Baltic countries, for which Bq/m2 inventories could be calculated. A rough estimation was made by comparing the mass of organic matter and humus with 137Cs concentrations in these two areas. Changes in 137Cs concentration levels are illustrated in both thematic maps and tables. Radionuclide 137Cs concentrations (Bq/kg d.w.) were detected in the humus layer at all the 988 sampling sites. 134Cs was still present in 198 sites 15 years after the nuclear accident in Chernobyl. No other anthropogenic nuclides emitting gamma-radiation were detected, but low levels of 60Co, 125Sb and 154Eu isotopes were found in 14 sites. Fifteen years after the Chernobyl accident, the radioactive nuclide 137Cs was and still is the most significant fallout radionuclide in the environment and in food chains. The results show that the fallout can still be detected in the uppermost humus layer in North East Europe.