The Raman and mid-range infrared spectra have been measured on natural limestone and dolomite minerals. The carbonate minerals show four prominent absorption bands in the regions 1450-1420, 890-870, 720-700 and 1000-1100 cm −1 . The positions of the wavenumbers are unique for each carbonate mineral and are thus diagnostic of their mineralogy. Calcite and dolomite groups are characterized by the Raman wavenumbers at 288 and 309 cm −1 and the infrared absorption bands at 712 and 728 cm −1 , respectively. The principal wavenumber at 1092 cm −1 in the limestone spectra is accompanied by two satellites with values of 1062 and 1075 cm −1 . The observed non-split peaks n 2 and n 4 in the infrared spectra of limestone indicate the presence of calcite structure in all these samples. The principal reflections occurring at the d-spacings, 3.03482, 1.91658 and 1.87962Å, confirm the presence of calcite structure in limestone minerals. The principal reflections occurring at the d-spacings, 3.037, 1.79179 and 2.19750Å, confirm the existence of dolomite structure in the dolomite minerals. The calculated lattice parameters for the limestone minerals are: a = 4.9781Å, c = 17.1188Å and V = 367.392(Å) 3 and the corresponding values for the dolomite minerals are: a = 4.8247Å, c = 15.9868Å and V = 322.28 (Å) 3 .

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Thermal decomposition behaviour of dolomite sample has been studied by thermogravimetric (TG) measurements. Differential thermal analysis (DTA) curve of dolomite shows two peaks at 777⋅8°C and 834°C. The two endothermic peaks observed in dolomite are essentially due to decarbonation of dolomite and calcite, respectively. The TG data of the decomposition steps have also been analysed using various differential, difference-differential and integral methods, viz. Freeman-Carroll, Horowitz-Metzger, Coats-Redfern methods. Values of activation entropy, Arrhenius factor, and order of reaction have been approximated and compared. Measured activation energies vary between 97 and 147 kJ mol -1 . The large fluctuation in activation energy is attributed to the presence of impurities such as SiO 2 , Al 2 O 3 , Fe 2 O 3 , Cl -etc in the samples. FTIR and XRD analyses confirm the decomposition reaction. SEM observation of the heat-treated samples at 950°C shows cluster of grains, indicating the structural transformation.

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The present study deals with the characterization of the polymeric materialsviz.,nylon-66 and 30% glass fibre reinforced nylon-66 (GF Nylon-66) by employing FTIR and thermal measurements. The complete vibrational band assignment made available for nylon-66 and GF nylon-66 using FTIR spectra confirm their chemical structure. FTIR spectroscopy provides detailed information on polymer structure through the characteristic vibrational energies of the various groups present in the molecule. The thermal behavior of nylon-66 and GF nylon-66 essential for proper processing and fabrication was studied from TGA and DTA thermograms. The thermal stability of the polymers was studied from TGA and the activation energy for the degradation of the polymeric materials was calculated using Murray-White plot and Coats-Redfern plot. The polymer with high activation energy is more thermally stable. GF nylon-66 is found to be more thermally stable than nylon-66. The major thermal transitions such as crystalline melting temperature (Tm) and degradation temperature (Td) of the polymers were detected from DTA curves. The melting behaviour of the polymer depends upon the specimen history and in particular upon the temperature of crystallization. The melting behaviour also depends upon the rate at which the specimen is heated. The various factors such as molar mass and degree of chain branching govern the value of Tmin different polymers.