Structure and physical properties of grafted jute fiber

Jute fiber was grafted by acrylonitrile and methylmethacrylate monomers in raw and bleached condition. It was also noted that optimum grafting takes place after about 4 h of grafting. It was also noted that in bleached jute fiber, the grafting percentage is higher at all stages of grafting but the tenacity value at the highest add-on is practically the same as that of raw fiber with much less add-on. The crystalline orientation of the grafted jute fiber was correlated with the fiber tenacity. The moisture regain (%) of the fiber after grafting showed a decreasing trend with an increase in grafting percentage. No structural change of the fiber occurred due to grafting. © 1995 John Wiley & Sons, Inc.     

Studies on thermodynamic compatibility of nitrile rubber and polybutadiene by inverse gas chromatography

Inverse gas chromatography technique has been used to study the thermodynamic compatibility of the industrially important elastomers polybutadiene (BR) and polybutadiene copolymerised with acrylonitrile (NBR). The NBR used in this study had nitrile contents of 18 and 34%. The ratio of BR/NBR in blends varied between 1 and 0.25 in both cases and retention volume of twelve probes was measured at 80°C. The Flory-Huggins interaction parameter X′₂₃, computed using a standard procedure, and also the interaction parameter B₂₃ showed that BR and NBR are incompatible in all compositions and that incompatibility increases with nitrile content. © 1995 John Wiley & Sons, Inc.     

On the nature and structure of ‘niobic acid’. Part IV: Formation of sulphatoniobates(V) and the properties of isopolyniobic acid produced therefrom

Formation of sulphatoniobates can be considered as resulting from the high temperature acid-base reaction of isopolyniobic acid and sulphur trioxide. The nature of attachment of the SO₃ group has been adjudged from the properties of the available atomic orbitals on the oxygen atoms of H₈Nb₆O₁₉. The hydrolysis of the sulphatoniobates and the nature and properties of the resulting isopolyniobic acid has been explained. The possible way of stabilisation of the sulphatoniobates and their proper nomenclature have been discussed.     

Studies on the reduction of nitrobenzene to aniline catalysed by pd(acac)2-pyridine system

The complex, bis(acetylacetonato)palladium(II) in pyridine, is used as a homogeneous catalyst for the conversion of nitrobenzene to aniline. From a study of various operational parameters the optimum reduction was found to occur at 1 atm pressure and at room temperature in petroleum ether (b.p. 100–120°C) solvent, yielding 90% of aniline on input nitrobenzene basis. The complex [Pd¹¹(acac)H(C₆H₅NO₂)Py] was isolated under similar experimental conditions and was characterised by elemental analysis, magnetic, thermal and spectral studies. Formation of a phenylnitrene metal complex has been suggested as a hypothetical intermediate in the reduction process.     

Selective corrosion study by anodic stripping of CrNi steel

A method consisting in galvanostatic anodic stripping of layers with thicknesses of the order of nanometers combined with gamma-spectrometric analysis of soluble anodic reaction products has been developed for the purpose of a study of concentration profile of alloy components in the surface of alloys after a corrosion process.Suitable conditions as regards the stripping solution and the electrochemical parameters were investigated to ensure reliable determination of the quantity of stripped metal based on the Faraday relationship and to provide for a uniform removal of metal from the surface. Experimentally verified constants for the conversion of passed electric charge to stripped layer thickness are given for steel grades FeCr17, FeCr18Ni5Mn9, FeCr18Ni9, FrCr18Ni10Mo2 and FeCr20Ni38Mo6, the average accuracy being ±1.5 per cent.Two examples are presented to illustrate the determination of the concentration profile of components in the surface of steel grade FeCr18Ni9.     

On the External Positivity of Linear Time-Invariant Dynamic Systems

This brief is devoted to present a general method to characterize precisely the external positivity property of linear time-invariant continuous-time dynamic systems which is based on the Post formula for Laplace inversion.