Sandeep Rai

Hydro-ecological analysis of a sacred lake watershed system in relation to land-use/cover change from Sikkim Himalaya.

Abstract The hydrology and ecological linkages between Khecheopalri lake and its surrounding watershed (area: 12 km2) in Sikkim were investigated to assess the long-term impacts of land-use/cover change on the hydrology of the lake ecosystem and bog formation around the glaciated lake. Significant land-use/cover change occurred in the past 4 decades. The bog area expanded by 67%, while the area under agriculture land in the lake watershed grew by 63% between 1988 and 1997. Overland flow was highest on the bare land (4.77% of the precipitation) and lowest in areas of cardamom-based agroforestry (1.79%). Soil and nutrient losses were highest in the cultivated area and least in the cardamom agroforestry system. Sediment loads of 345 Mg year−1 were recorded at the lake inlet and of 316 Mg year−1 at the outlet. Annual soil loss from the lake watershed was 502 Mg km−2 and a net sediment deposition in the lake was 141 Mg year−1. The lake received high nutrient loads (organic carbon of 10.2 Mg year−1, total nitrogen of 1.01 Mg year−1 and total phosphorus of 0.51 Mg year−1) from soil erosion and overland flow. The pH, total phosphorus and bulk density of the peat increased from the lake towards the bog-forest edge. This reflects the trapping of sediments and nutrients around the bog forest margin, although their retention is limited. Agricultural practices should be minimized in the upper part of the watershed and agroforestry practices should be encouraged to maintain the health and longevity of the lake.

Synthesis and characterization of coordination polymers of polyesters with pendant amino groups

Oligomeric polyester, namely, poly(tetramethylene aspartate) (PTMA), was synthesized from D,L-aspartic acid and 1,4-butanediol by a melt-condensation technique. Polyester-metal complexes were synthesized by the reaction of PTMA with hydrated acetates of Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II), Mg(II), Ca(II), Pb(II), and Ce( IV) in DMSO. The polyester-metal complexes were characterized by elemental analysis, IR spectral studies, magnetic susceptibility measurements, and thermogravimetry. The metal ions were found to be six-coordinated with two water molecules as additional ligands besides oxygen and nitrogen atoms of polyester repeating units. Thermogravimetric analysis (TGA) showed that coordination polymers are thermally more stable than is polyester.

Synthesis and Characterization of Aliphatic Aromatic Polyamide — Metal Complexes

Synthesis, characterization and physico-chemical studies of metal-chelate polymers are of great importance. Renewed interest in this field has been evinced in the context of obtaining materials with high temperature resistance. The potential applications of metal containing polymers are numerous and well documented. Schiff s base complexes involving low molecular weight diamines and aldehydes were extensively studied. Polyamides are versatile high performance polymers. A variety of aliphatic, aromatic and aliphatic-aromatic polyamides have been synthesised. In order to improve the thermal properties of existing polyamides, we have attempted to synthesise polyamide-Schiff’s base complexes1,2. In the present paper, we are reporting the syntheses of polyamide schiff’s base coordination polymers using amino terminated oligomers of hexamethylene terephthalamide (PHTA) and Co(II), Ni(II) and Cu(II) complexes with salicylaldehyde and 2-hydroxy 1-napthaldehyde.

Heat Resistant Coordination Polymers Based on Amino Group Terminated Oligomer of Hexamethyleneadipamide

Abstract Nylon-6,6 oligomer was prepared from hexamethylenediamine and adipic acid using the conventional phosphorylation technique. The amino terminated oligomer was then converted into Schiff base coordination polymers by interacting it with Co(II), Ni(II) and Cu(II) complexes of salicylaldehyde, [M(SAL)2] and 2-hydroxyl-1-naphthaldehyde, [M(NAPHTHAL)2]. The resulting coordination polymers were characterized by ir spectrescopy, elemental analyses, magnetic susceptibility measurements and thermogravimetric analysis (TGA). Thermogravimetric analysis shows that the coordination polymers were thermally more stable than the oligomer. On the basis of physio-chemical studies a probable structure of the coordination polymers has been proposed. Referee I: T. G. Richmond Referee II: K. Moedritzer

Important Aspects Involved in Pilot Scale Production of Modern Paints and Coatings

Abstract Paint, or coating, is defined as a fluid material that when spread on a surface forms a thin, cohesive, durable, and opaque film. It is a dispersion of powdered material (pigment) in a resin solution (vehicle/medium). It is a mixture of liquid and solid that exists in a stable dispersed condition. Prime parameters in paint or surface coatings are production of polymer emulsion with desired chemical composition and physical properties, and a high speed mixing and tinting to make stable dispersion. The dispersion process has four steps: grinding, wetting, separation, and stabilization. At the pilot plant stage, it is essential to mimic a commercial plant production process such as generating operating data, recording the reaction trends and thermochemical parameters, and optimizing recipes/formulations, for the facile scale-up of paints and coating formulations. This chapter focuses on general engineering aspects involved in Pilot Plant production of waterborne and solvent-based paints and coatings.

Condensation Polymers of Terephthalic Acid and 1,4-Diaminobutane and Their Schiff Base Complexes

Amino-terminated oligomeric poly(tetramethylene terephthalamide) (PTTA) was prepared by condensation of terephthalic acid and 1,4-diaminobutane using phosphorylation technique. Schiff base complexes of this polyamide were synthesized with salicylaldehyde and 2-hydroxy-1-naphthaldehyde complexes of Co(II), Ni(II), and Cu(II). The polyamide as well as Schiff base complexes were characterized by elemental analysis, IR spectroscopy, and magnetic susceptibility measurements. Thermal stabilities of ligand and its various complexes were compared by thermogravimetric analysis.