Vikram Sarabhai Space Centre

About: Vikram Sarabhai Space Centre is a facility organization based out in Thiruvananthapuram, India. It is known for research contribution in the topics: Aerosol & Ultimate tensile strength. The organization has 2092 authors who have published 3058 publications receiving 47975 citations. The organization is also known as: VSSC.

Effect of imide–oxazolidinone modification on the thermal and mechanical properties of HTPB‐polyurethanes

Abstract: Imide- and oxazolidinone-incorporated polyurethanes, based on hydroxy-terminated polybutadiene (HTPB), were synthesized and characterized. Reaction of the blocked isocyanate terminals of the HTPB prepolymer with diepoxy compounds, containing preformed imide groups, was the strategy followed. The diepoxy resins were derived through reaction of an aliphatic and an aromatic dicarboxylic acid with preformed imide groups with a diepoxy resin. The intermediates and the polyurethane–imide–oxazolidinone were characterized by chemical, spectral, and elemental analyses. Incorporation of these heterocyclic groups caused dramatic improvements in the thermal and mechanical properties and the thermomechanical profile of the system. The improvements in properties were proportional to the hard-segment content of the modified polyurethanes. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1731–1738, 1999

Synthesis and characterization of polyamides and poly (amide-imide) s derived from 2, 6-bis (3-aminophenoxy) benzonitrile or 2, 6-bis (4-aminophenoxy) benzonitrile

Abstract: A series of polyamides and poly(amide-imide)s was prepared by direct polycondensation of ether and nitrile group containing aromatic diamines with aromatic dicarboxylic acids and bis(carboxyphthalimide)s respectively in N-methyl 2-pyrrolidone (NMP) using triphenyl phosphite and pyridine as condensing agents. New diamines, such as 2,6-bis(4-aminophenoxy)benzonitrile and 2,6-bis(3-aminophenoxy)benzonitrile, were prepared from 2,6-dichlorobenzonitrile with 4-aminophenol and 3-aminophenol, respectively, in NMP using potassium carbonate. Bis(carboxyphthalimide)s were prepared from the reaction of trimellitic anhydride with various aromatic diamines in N,N′-dimethyl formamide. The inherent viscosities of the resulting polymers were in the range of 0.27 to 0.93 dl g−1 in NMP and the glass transition temperatures were between 175 and 298 °C. All polymers were soluble in dipolar aprotic solvents such as dimethylsulfoxide, dimethylacetamide and NMP. All polymers were stable up to 350 °C with a char yield of above 40 % at 900 °C in nitrogen atmosphere. All polymers were found to be amorphous except the polyamide derived from isophthalic acid and the poly(amide-imide)s derived from diaminodiphenylether and diaminobenzophenone based bis(carboxyphthalimide)s. Copyright © 2004 Society of Chemical Industry

Interannual Variations of Aerosol Optical Depth over Coastal India: Relation to Synoptic Meteorology

Abstract: Interannual variations in spectral aerosol optical depths (AOD) were examined using the data obtained from a chain of ground-based multiwavelength solar radiometers from various locations of the Indian peninsula during the dry winter season (January–March) of 1996–2001. All of the stations revealed significant interannual variations, even though the spatial pattern of the variations differed over the years. These interannual variations were found to be significantly influenced by the extent of the southward excursion of the intertropical convergence zone (ITCZ). The years in which the southward excursion of the ITCZ was less (i.e., the years when the wintertime ITCZ was closer to the equator) showed higher AODs than the years in which the ITCZ moved far southward. The spatial variation was found to be influenced by large-scale vertical descent of an air mass over peninsular India, the Arabian Sea, the Indian Ocean, and the Bay of Bengal.

Poly(methyl methacrylate)-grafted chitosan microspheres for controlled release of ampicillin.

Abstract: Microspheres of 50-500 microm diameter were prepared from a blend of chitosan and chitosan-g-PMMA. Environmental scanning electron microscopic and SEM studies revealed that the microspheres are porous and the pores extend toward the inner core of the microspheres. The microspheres were also found to be hemocompatible and cytocompatible. A model drug ampicillin was used to evaluate the drug loading capacity and the controlled release properties of the microspheres. The system maintained a sustained release of ampicillin for a period of more than 8 days. The drug-loaded chitosan/chitosan-g-PMMA microspheres exhibited higher antibacterial activity for both the gram positive (ATCC 25923 S. aureus) and gram negative (ATCC 25922 E. coli) bacteria than the drug-loaded virgin chitosan microspheres. The percentage release and bioactivity of ampicillin was found to be higher for the chitosan/chitosan-g-PMMA microspheres than the virgin chitosan microspheres. Potential applications such as oral drug delivery, wound dressings, tissue engineering, and so forth, are envisaged from these microspheres.