Choubisa B.,Sardar Vallabhbhai National Institute of Technology, Surat |
Dholakiya B.,Sardar Vallabhbhai National Institute of Technology, Surat |
Journal of Macromolecular Science, Part A: Pure and Applied Chemistry | Year: 2013
Poly(lactic acid) or PLA was produced by direct condensation polymerization of lactic acid. For the optimization of the reaction conditions, various catalyst systems were examined with constant temperature and different reaction times. In the present study, a solid acid catalyst silica sulfuric acid (SiO2-OSO3H), Keggin type tungstophosphoric acid (H 3[PW12O40], and cellulose sulfuric acid was employed as the polycondensation catalyst for the polymerization of lactic acid. Solid acid catalyst SSA and CSA were synthesized and TPA was modified by a calcine process. The prepared PLA was well characterized by using FT-IR, 1H-NMR and 13C-NMR. The thermal characteristics of the polymer have been studied using DSC analyses. The data relevant to the magnitude of the molecular weight were obtained by GPC analysis in terms weight average molecular weight (Mw) and number average molecular weight. Furthermore, the polydispersity index which is a measure of the molecular weight distribution was obtained by GPC. The obtained PLA exhibited a molecular weight of (Mw) 61250 with silica sulfuric acid. © 2013 Copyright Taylor and Francis Group, LLC.
Bhatt V.D.,NVPAS |
Advanced Materials Letters | Year: 2013
Seven ionic liquids (ILs) based on tetrabutylammonium cation [N+4444] and inorganic anions were tested for their applications in a solar cooker. Thermophysical characteristics like melting point, density, heat of fusion, heat of solid - solid transitions, specific heat capacity and thermal conductivity were used to determine the efficiency of ILs used as phase change materials (PCMs) in solar thermal applications. A delay time of two hours was observed on an average in achieving the highest temperatures. A majority of the ILs extended the time required for achieving ambient temperature to a tune of around four hours. The ILs containing bromide, iodate and nitrate proved to be more efficient than the thiocyanate, bromate and hexafluorophosphate moieties. © 2013 VBRI press.
Srivastava P.K.,University of Bristol |
Kiran G.S.,M. S. University of Baroda |
Gupta M.,Indian Institute of Technology Delhi |
Sharma N.K.,NVPAS |
International Journal of Ecology and Development | Year: 2012
Vegetable fields of sub-urban areas of Vadodara district, Gujarat, continue to receive the large amounts of extraneous heavy metals due to rapid urbanization and industrialization. A study was conducted to analyze the accumulated concentration of heavy metal contents in pea (Pisum sativum), lady's finger (Abelmoschus esculentus) and carrot (Daucus carota). A road density thematic map has been generated using the Geographic Information system (GIS) to visualize the anthropogenic sources of heavy metal contaminations in the vegetables. It has been found that the areas which are nearer to the dense road have higher amount of lead and cadmium content than the lower road density market. It was found that heavy metal contamination in vegetables collected from regular markets of Vadodara district, contains an elevated concentration of metal in comparison to the vegetables grown in biofresh farms. The concentration of Zinc was found to be highest in Pea followed by Lady's finger and Carrot in both suburban as well as biofresh vegetables. However, concentration of Cadmium was found to be highest in carrot. All vegetables either from suburban or biofresh market shows a remarkably lower concentration than Prevention of Food and Adulteration act (PFA) but higher than European Union (EU) standards. © 2011-12 IJED.
Bhatt V.D.,NVPAS |
Thermochimica Acta | Year: 2013
Eight salts, derived from tetrabutylammonium cation [N+ 4444] and inorganic anions like BF4 -, NO 3 -, NO2 -, SCN-, BrO 3 -, IO3 -, PF6 - and HCO3 - were synthesized using the ion exchange method. These ionic liquids (ILs) were characterized using thermogravimetry, differential scanning calorimetry and infrared spectroscopy. Thermophysical properties such as density, volume expansion, heat of fusion, heat of solid-solid transitions, specific heat capacity and thermal energy storage capacity were determined. The total of heat of solid-solid transitions observed below the melting points exceeded the heat of fusion in some cases. The thermal conductivity of the samples was determined both in solid and liquid phases. High values of thermal energy storage capacity and handsome liquid phase thermal conductivities made many of the ionic liquids under investigation were recommended as Thermal Energy Storage Devices (TESDs) as well as heat transfer fluids. © 2013 Elsevier B.V.