Authors:P. K. Singh, A. B. Mathur and G. N. Mathur
The thermal behaviours of polystyrene (PS), polymethylacrylate (PMA), polyacrylonitrile (PAN), polystyrene-co-methylacrylate [P(S: MA)](alternate and random), polystyrene-co-acrylonitrile [P(S: AN)] (alternate) and a terpolymer of styrene, methylacrylate and acrylonitrile [P(S: MA: AN)] are discussed on the basis of non-isothermal thermogravimetric studies. The thermal stabilities of the copolymers have been found to be intermediate between of those of the individual homopolymers. The stability of the [P(S: AN)] copolymer is higher than those of the individual homopolymers. The activation energy values are also in accordance with the thermal behaviours of these polymers.
Authors:K. Pandey, K. Debnath, P. Rajagopalan, D. Setua and G. Mathur
Studies have been made on differential scanning calorimetry (DSC), thermogravimetric analysis (TG) and dynamic mechanical
analysis (DMA) of binary blends of isobutylene-isoprene (IIR) copolymer and polychloroprene (CR) elastomers. Blends of IIR
and CR are incompatible and showed separateTg peaks in DSC curves similar to Tanδ peaks. However, addition of chlorinated polyethylene (CM) elastomer, as compatibilizer,
imparts miscibility between IIR and CR which could be judged both through DSC as well as by dynamic loss measurements (Loss
modulusE″ and Tanδ). The storage modulus (E′) showed variation of stiffness due to structural changes associated with the addition of compatibilizer. TG plots for these
blends showed improvement of thermal stability both by addition of a suitable compatibilizer as well as due to formation of
crosslinked structures associated with the vulcanization of the blends by standard curative package.
Authors:D. Chowdhury, S. Saha, Sujit Pal and P.K. Mathur
The rare earth elements (REE), Pr, Sm, Eu, Gd, Ho, Er and Tm have been determined by charged particle activation analysis using 40 MeV a-particles through radiochemical approach. The radiochemical separation of REE as a group has been carried out from the bulk matrix. It has been shown from the theoretical computation that the products obtained from (a,xn) reactions (x = 1, 2, 3) are more suitable compared to those from (a,pyn) reactions (y = 0, 1, 2) due to the former having higher cross section (of the order of thousand millibarns).
Authors:N. Raje, K. Swain, S. Kumar, S. Kayasth, R. Parthasarathy and P. Mathur
A simple and efficient method has been developed to preconcentrate natural protactinium from large quantity of monazite (5–10 g) and thorium concentrates (5–100 g), obtained from thorium plant stream on Dowex 1X8 in acid medium. Gamma-spectrometry, a powerful determination technique, has been used for quantitative determination of protactinium and uranium. Various parameters like sample preparation, optimization of the resin and sample size for 231Pa recovery, 231Pa/235U ratio have been studied in detail and are discussed.
Authors:J. Mathur, M. Murali, P. Natarajan, L. Badheka, A. Banerji, K. Michael, S. Kapoor and R. Dhumwad
The tail-end purification of Am from Pu loading effluents in 7.5M HNO3 containing 160 mg l–1 Am and 1.2 mg l–1 Pu has been carried out. With 0.2M CMPO+1.2M TBP in dodecane as the extractant and stripping by 0.04M HNO3+0.05M NaNO2, the Pu level is brought down to 31.2 g l–1. When the acidity was reduced to 4.2M HNO3, one contact with 20% TLA/dodecane and subsequent extraction by a mixture of CMPO and TBP and stripping with 0.04M HNO3+0.05M NaNO2 gave Am samples without any detectable amounts of Pu. The recovery of Am was 90% by the first procedure and 98% by the second one.
Authors:P. Rajagopalan, L. Kandpal, A. Tewary, R. Singh, K. Pandey and G. Mathur
PEEK is characterised by high impact and fatigue resistance andTg of 145‡C. Blends of PEEK and PEI have been made and scanning electron micro-graphs of the broken specimen show that the two
polymers are completely miscible in all proportions. The study also shows that PEEK∶PEI 50∶50 blend, can be used as matrix
for composite applications with appreciable enhancement ofTg to 177‡C.