Comparison of carbon nanotube and soot reinforced rubber mixtures and their mechanical-morphological properties
Abstract— In our study, we investigated 2 different natural rubber mixtures with CNT’s and shoot. The aim was to compare the results of samples and their mechanical effects with a shore. A hardness tester, a tensile strength instrument before and after vulcanisation (t=30; 60; and 90minutes) during the UV-ageing processes. The hardness results represented the different after the degradation process that was 10 % different between the samples.
Simultaneous analysis of nitro compounds by Voltammetric method combined with the principal component regression (PCR)
Abstract— The ability to simultaneously determine 6 nitro compounds including nitrobenzene (NB), 2-nitrophenol (2-NP), 3-nitrophenol (3-NP), 4-nitrophenol (4-NP), 2,4- dinitrophenol (DNP) and trinitrophenol (TNT) in the same samples was investigated by differential pulse Voltammetry on hanging mercury drop electrodes (HMDE), in acetate buffer of pH 4.6. It was found that peak potentials of voltammetric reduction waves of NB, 2-NP, 3-NP and 4-NP appeared at – 0.297, – 0.251, – 0.267 and – 0.337 V respectively. Under the same conditions there are three peak potentials at -0.076, – 0.161, – 0.267 V for TNT and two peaks at tại – 0.176, – 0.282V for DNT. The peaks of these compounds are very close together. Due to the serious overlapping of Voltammetric peaks of these compounds in the mixtures, so that by a conventional Voltammetry it not possible to individually determine each compound. In this study, the linear multivariate regression method such as principal component regression (PCR) was used to resolve the overlapped Voltammograms. The obtained relative standard error (RSEt) of method is less 10%. The percent of recoveries were within ± 10% of the target value. The developed method was then applied to the analysis of these nitro-substituted aromatic compounds in field samples with similar satisfactory results.
Isopropyl myristate continuous synthesis in a packed-bed reactor using lipase immobilized on magnetic polymer matrix
Abstract— The aim of this study was to synthesize isopropyl myristate, an emollient ester, in a continuous-flow packed-bed reactor using Candida antarctica lipase immobilized on poly(styrene-co-divinylbenzene) matrix prepared by suspension polymerization and magnetized by co-precipitation of Fe2+ and Fe3+ in alkaline medium. To determine the best esterification conditions, we investigated the effects of acid/alcohol molar ratio (1:5, 1:10, and 1:15) on reaction yield in shake flasks. The three tested conditions provided similar results, esterification yields of approximately 80%. An acid/alcohol molar ratio of 1:15 was chosen for further experiments because it allowed for better operability of the bioreactor. Subsequently, we compared the reactor performance in up flow and down flow modes. This experiment showed that greater ease of operation was achieved with down flow operation. We also evaluated the influence of space time (8 and 20 h) on reaction yield and productivity. A space time of 8 h provided better results. An experimental system consisting of two bioreactors and a molecular sieve packed column was used to remove the water formed during esterification and thus increase the yield of isopropyl myristate. There was a significant improvement in performance with the use of the two-stage system, which resulted in almost complete conversion of reagents, an increase of about 150% in biocatalyst half-life, and an isopropyl myristate productivity of 25 g L−1 h−1, confirming the beneficial effect of adding a water extraction column to the experimental system.