P. Vasudevan

Indian Institute of Technology Delhi, New Dilli, NCT, India

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Publications (54)23.65 Total impact

  • U. S. Tewari, S. K. Sharma, P. Vasudevan
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    ABSTRACT: Polyphenylene sulphide is a polymer with good thermal stability and high crystallinity. This paper summarizes the results of friction and wear studies of polyphenylene sulphide and its composites made with conventional solid lubricants to ascertain the suitability of the material as a matrix for solid lubricant additives. The polymer itself has a high coefficient of friction. Wear rate increases with load and speed. Addition of solid lubricant additives helps in improving the friction and wear of the polymer. Composites with MoS2-Sb2O3 and PTFE gave better results than composites made by the addition of graphite and MoS2 graphite. Wear rate of these composites increased with load and speed; but load and speed had little effect on friction.
    Journal of Synthetic Lubrication 02/2006; 4(3):219 - 228.
  • J. Bijwe, U. S. Tewari, P. Vasudevan
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    ABSTRACT: Polyetherimide (PEI) is one of the latest generic high-performance engineering thermoplastics. PEI (developed by General Electric (USA) under the trade name ULTEM) is an amber and amorphous polymer with a heat distortion temperature between those of polyarylate resin and thermally stable crystalline polymers such as polyether-ether ketone (PEEK) and polyamideimide (PAI). It has excellent thermal, mechanical and electrical properties along with easy processability. In the work reported here, a wear-resistant formulated composite supplied by GEC (ULTEM 4001) was selected for tribological investigations on a pin on disc machine under unlubricated conditions, against mild steel. Analysis of the composite revealed that this grade contained PTFE (13–15%), which is the most promising polymeric lubricant.A very low and stable frictional coefficient was observed against moderately finished surfaces. However, its specific wear resistance (⋍10−14 m3/Nm) was comparatively lower than that of fibre-reinforced thermoplastics. The wear mechanism was found to be significantly dominated by the presence of PTFE. The friction coefficient was in the range of 0.2 and reduced to a still lower value (0.1) as the apparent contactpressure increased. Scanning electron microscopy was used to investigate the underlying wear mechanism. Film transfer of PTFE was observed to be the principal factor responsible for reduced friction.
    Journal of Synthetic Lubrication 02/2006; 6(3):179 - 202.
  • U. S. Tewari, S. K. Sharma, P. Vasudevan
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    ABSTRACT: Bismaleimides are the addition type of polyimide resin. They are synthesized by reaction of diamino compounds with maleic anhydride. By varying the structure of the diamino compound it is possible to make various bismaleimides. This paper discusses improvement of the friction and wear properties of bismaleimide resin, by the addition of solid lubricant additives such as MoS2, graphite and PTFE.The bismaleimide tested has the following structure: On heating, bismaleimide cross links through its unsaturated bonds, thus producing a highly cross linked polyimide. The friction and wear measurements were done on a Plint friction and wear machine (pin on disc type), wherein polymer pins slid against a steel disc at different loads and speeds.The polymer itself had a high coefficient of friction, ranging from 0.3 to 0.6 and a higher wear rate. Solid lubricant additives helped in improving its friction and wear characteristics. The addition of graphite brought the coefficient of friction to 0.3 but wear remained high at high loads. Best results were obtained with additions to the resin of MoS2-Sb2O3 and PTFE. Composites with MoS2-Sb203 and PTFE had low coefficient of friction and low rate of wear, at low as well as at high loads. It appears that these solid lubricant additives transfer to the counterface, thereby reducing effective counterface roughness, hence reducing both friction and wear.
    Journal of Synthetic Lubrication 02/2006; 4(2):147 - 158.
  • Hari Singh Nalwa, Padma Vasudevan
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    ABSTRACT: A thiourea-formaldehyde polycondensate was synthesized in acidic medium using glacial acetic acid. It was characterized by elemental analysis, infrared spectroscopy and thermal techniques. The thermally stimulated depolarization (TSD) current characteristics were studied under different polarization and depolarization conditions. The TSD results indicate a transition at 126°C. Depolarization kinetics data of the thermoelectret are reported. The polarization and depolarization phenomena were correlated with physical as well as chemical changes occurring in the material.
    Die Makromolekulare Chemie 03/2003; 186(6):1255 - 1261.
  • P. S. Viswanathan, P. Vasudevan
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    ABSTRACT: In this paper we report some of the physico-chemical changes occurring in poly(phenylene sulphide) prepared by the homopolycondensation of thiophenol. The various electrical properties measured on these polymers were used to identify the temperatures at which these transitions occur.In dieser Arbeit wird über einige physiko-chemische Veränderungen berichtet, die in Polyphenylensulfid auftreten, das durch Homopolykondensation von Thiophenol hergestellt wurde. Die an diesen Polymeren gemessenen verschiedenen elektrischen Eigenschaften wurden zur Bestimmung der übergangstemperaturen benutzt.
    Angewandte Makromolekulare Chemie 03/2003; 102(1):17 - 28.
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    ABSTRACT: Thiourea formaldehyde polymers were synthesized by condensing thiourea with formaldehyde under alkaline conditions and were characterized by infrared spectroscopy. The stability of the samples was determined by thermogravimetric analysis. Electrets were prepared by polarizing the polymer at 100–300 kV m−1 and at 303–353 K. The complex thermal depolarization spectra were recorded and analysed. The results are correlated with studies on the variation of the dielectric constant and d. c. conductance as a function of the temperature.Thioharnstoff-Formaldehyd-Polymere wurden durch Kondensation von Thioharnstoff mit Formaldehyd unter alkalischen Bedingungen synthetisiert und durch Infrarotspektroskopie charakterisiert. Die Stabilitt der Proben wurde durch thermogravimetrische Analyse bestimmt. Es wurden Elektrete hergestellt, indem das Polymere bei 100-300 kV · m−1 und bei 303–353 K polarisiert wurde. Die komplexen thermischen Depolarisationsspektren wurden aufgezeichnet und analysiert. Die Ergebnisse wurden korreliert mit Untersuchungen über die Abhngigkeit der Dielektrizittskonstante und der Gleichstromleitfhigkeit von der Temperatur.
    Angewandte Makromolekulare Chemie 03/2003; 82(1):39 - 53.
  • Hari S. Nalwa, Jai M. Sinha, Padma Vasudevan
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    ABSTRACT: A set of experimental conditions are described for the synthesis of monomeric and polymeric iron-phthalocyanines and compared with those reported in the literature. The dielectric constant and resistivity of characterised samples are studied as a function of temperature. The data indicate possible transitions at 90 and 180°C for monomeric iron-phthalocyanine whereas polymeric iron-phthalocyanine shows no breaks.
    Die Makromolekulare Chemie 03/2003; 182(3):811 - 816.
  • S Sharma, M Madan, P Vasudevan
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    ABSTRACT: Mycorrhizae have been shown to increase growth and yield of plants. They have been identified with both nutrient mobilization and nutrient cycling. Arbuscular (or endo-) mycorrhizae play a significant role in agriculture and most natural ecosystems, whereas ectomycorrhizae have a great potential in forestry and wasteland regeneration. The use of mycorrhizal fungi would reduce dependence on chemical fertilizers besides minimizing environmental pollution. The present review addresses the progress that there has been in the area of the ecto- and endomycorrhizae. It also examines the potential of field applications of mycorrhizal biotechnology in agriculture and forestry.
    Microbiología (Madrid, Spain) 01/1998; 13(4):427-36.
  • Source
    Ragini Bisaria, Mira Madan, Padma Vasudevan
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    ABSTRACT: Bioconversion of agro-residues, rice straw and wheat straw, was carried out with the edible mushroom Pleurotus sajor-caju, with a view to increasing nutritive values and digestibilities for animal feed. Amongst the inorganic and organic nitrogen sources tested, soyabean meal and ficus fruits, in which nitrogen is present in complex form, were the best supplements in enhancing the in vitro dry matter digestibilities of the residues.
    Bioresource Technology 01/1997; · 5.04 Impact Factor
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 01/1996; 35:894-899.
  • Journal of Materials Science Letters 12/1995; 15(14):1221-1224.
  • S. Sharma, P. Vasudevan, M. Madan
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    ABSTRACT: The insecticidal value of the castor oil plant (Ricinus communis) in controlling the termites which damage the wood of Mangifera indica and Pinus longifolia was examined. In comparative trials, the order of insecticidal activity was DDT=BHC > castor oil + castor cake (1:1) > castor oil > castor leaves > castor cake > neem oil > neem leaves. All treatments significantly reduced weight loss in wood pieces exposed to termites.
    International Biodeterioration. 01/1991; 27(3):249-254.
  • Ragini Bisaria, Padma Vasudevan, V. S. Bisaria
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    ABSTRACT: Various spent agro-residues obtained after cultivation of the edible mushroom Pleurotus sajor-caju were used in anaerobic digestors for production of biogas. The changes that take place in the residues during bioconversion were quantified in terms of composition of cellulose, hemicellulose, lignin, carbon and nitrogen. These mycostraws resulted in increased biogas production over the untreated ones, which varied from 21.5% in the case of spent bagasse to 38.8% in the case of spent paddy straw. The increased biogas generation by the spent residues seems to be due to the increased susceptibility to digestion and more favourable C/N ratio of the residues.
    Applied Microbiology and Biotechnology 07/1990; 33(5):607-609. · 3.69 Impact Factor
  • Arvind Singh, Mira Madan, Padma Vasudevan
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    ABSTRACT: Estimation of above-ground biomass of Adhatoda vasica on a fresh-weight basis has been done, using observed weight (W0) as dependent variable and basal radius (p) of stem just above ground and height (H) of plant as independent variables, through linear regression techniques. Basal radius indicated an almost linear relationship with weight, while height appeared to be a redundant factor. The best estimates were obtained using the equation W0=bp2 × H+C, though reasonably accurate estimation can be done also through equation W0=bp+C, where C is the regression constant. Adhatoda exhibited fairly uniform distribution of moisture content along the height.
    Forest Ecology and Management. 01/1990;
  • S.K. Jain, P. Vasudevan, N.K. Jha
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    ABSTRACT: The uptake of lead and zinc by Azolla pinnata R.Br. (water velvet) and Lemma minor L. (duckweed) was investigated in solutions, enriched with and 8.0 mg/l of these two metal ions, which were renewed on alternate days over a 14 day test period. The uptake rate of both metal ions was highest when the initial concentration in the test solution was 1.0 mg/l. The concentration of lead or zinc remaining in the residual solutions after treatment with duckweed or water velvet at 1.0 and 2.0 mg/l levels, increased with the passage of time. At 4.0 and 8.0 mg/l levels, the concentration of lead or zinc remaining in the residual solutions either continuously increased with the passage of time or, first sharply increased (8–10 days) and then remained almost constant. The presence of one metal ion in solution decreased the uptake rate of the other; e.g. when water velvet was kept in a solution containing lead alone at 8.0 mg/l level, the value of the concentration factor was 54.5. However, in the presence of equal concentrations of zinc (mixed metal group), the value of the concentration factor for lead decreased to 35.44, indicating the influence caused by the presence of the zinc ion. The effect of these metal ions on biomass growth rate was also studied.
    Water Research. 01/1990; 24(2):177-183.
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    ABSTRACT: Polyetherimide (PEI) is a high performance thermoplastic polymide with good thermal, mechanical and electrical (insulating) properties with the added advantage of easy processability. Hence, for tribological studies, a short-glass-fibre-reinforced and internally solid lubricated composite of PEI was selected. Its friction and wear properties (in dry conditions) were tested for various experimental parameters such as load, sliding distance, speed and fibre orientation against a mild steel counterface. A very good combination of friction and wear properties was displayed by the composite. Its performance was compared with that of other PEI composites and bulk PEI for a better understanding of the role of fillers. Also, scanning electron microscopy studies were carried out on the worn pin and disc surfaces.
    Wear. 01/1990; 138:61-76.
  • J. Bijwe, U. S. Tewari, P. Vasudevan
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    ABSTRACT: Polyetherimide, ULTEM 1000, was studied as a neat resin for investigating its friction and wear behaviour while sliding against mild steel, under unlubricated conditions on a pin on disc machine. Experimental parameters selected were different loads, sliding distances and counterface roughness. It was observed that unlike other semicrystalline highly linear thermoplastics and some thermoplastic thermosetting polyimides, this polyimide does not transfer a film on the counterface under the conditions of the study. It seems that it wears mainly by fatigue mechanism but crack propagation could not be observed in SEM micrographs of pin surfaces. The frictional coefficient was low as compared with other polyimides and varied with contact pressure from 0.4 to 0.22, although the initial value was high. The cycles required to initiate wear particles were around 90 kcycles at 13 N cm–2 contact pressure. Once the wear started, the specific wear rate was high (K 0=10–13m3N–1 m–1).
    Journal of Materials Science 12/1989; 25(1):548-556. · 2.16 Impact Factor
  • U. S. Tewari, S. K. Sharma, P. Vasudevan
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    ABSTRACT: To meet the stringent demands placed on lubricants by the progress of modern technology, it has become necessary to supplement conventional mineral oils and greases. New kinds of lubricants are also needed where products of petroleum crudes cannot even be considered. For example, new and special types of lubricants are required in environments subjected to extreme temperatures, high vacuum, nuclear radiation, and chemically oxidizing or reducing effects. The attention of scientists is therefore being focused on the development of synthetic lubricants for more demanding physical, chemical, and thermal requirements.
    Journal of Macromolecular Science—Reviews in Macromolecular Chemistry and Physics. 02/1989; C29(1):1-38.
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    ABSTRACT: In adopting any technology it is important to consider the waste utilisation aspect so that better returns are obtained and the pollution of the environment by waste is minimised. In sericulture industry the waste from rearing trays, i.e. the silkworm litter, is available in large quantities. The present study has shown that silkworm litter could be used as a nitrogen source in replacing chemical fertilisers for vegetable crop production and as a substrate for mushroom cultivation.
    Biological Wastes - BIOL WASTE. 01/1989; 27(3):209-216.
    Agriculture Ecosystems & Environment - AGR ECOSYST ENVIRON. 01/1989; 26(1):75-77.

Publication Stats

214 Citations
23.65 Total Impact Points


  • 1982–2006
    • Indian Institute of Technology Delhi
      • • Centre for Polymer Science and Engineering
      • • Department of Chemistry
      • • Centre for Rural Development and Technology
      New Dilli, NCT, India
  • 1985
    • University of Southern California
      • Department of Chemistry
      Los Angeles, California, United States