Ajit Kumar Chaudhuri

Polymerization of Acrylonitrile with Ceric lon-2-Propanethiol as Initiator System

Abstract The kinetics of the polymerization of arylonitrile with ceric ammonium sulfate in the presence of 2-propanethiol as the redox initiator system in aqueous solution has been investigated. The rate of polymerization was found to be proportional to the square root of both ceric ion and thiol concentrations, and the monomer exponent was close to 1.5. Spectral studies indicated that there is a complex formation between ceric ion and the monomer acrylonitrile. A kinetic scheme, based on initial formation of this complex and its subsequent reaction with the thiol to produce the free radicals (RS.) responsible for initiation has been postulated to account for the observed results. The activation energy and different kinetic and transfer constants for the system have also been evaluated.

Thermal and age-resistance properties of NR gum vulcanizates in EV systems

Abstract A comparative study of the cure behavior of thiocarbamyl sulfenamides both in the presence of MBTS and thiazole sulfenamides has been made at 140 and 170°C. It is observed that most of the NR vulcanizates obtained at 170°C are capable of retaining a considerable portion of torque, modulus, and tensile values obtained at 140°C. This provides information regarding the heat resistance of these vulcanizates. It is observed that ZDCs up to a certain concentration increases the thermal resistance of the NR vulcanizates, the maximum effect being produced by ZBD and ZPD. ZOD and ZPD above a critical concentration, impart a deleterious effect to NR gum vulcanizates where a drop in the R∞ value is observed. The age resistance property of the various combinations of thiocarbamyl sulfenamides plus MBTS and thiazole sulfenamides plus thiocarbamyl sulfenamides has been discussed. It is evident from the study that the former combination generally provides higher physical properties of the vulcanizates and bett...

Studies on the Reaction between Thiocarbamylsulfenamides and Diebenzothiazyl Disulfide

Abstract The use of binary systems as accelerators in the vulcanization of rubber has received considerable attention, since many of them in suitable combinations, have been shown to provide efficient vulcanization systems. Dogadkin and co-workers and Skinner and Watson reported mutual activation with a number of popular accelerator combinations. It was suggested that the mutual activation occurs by the interaction of the accelerators to form intermediate complexes which decompose to produce free radicals responsible for initiating the various reactions involved in the vulcanization process. Recently Krymowski and Taylor studied the reaction between N-oxydiethylenethiocarbamyl-N′-oxydiethylenesulfenamide (OTOS) and N-oxydiethylene-2-benzothiazylsulfenamide (OBTS), a synergistic accelerator system, in tetrachloroethane at 142°C, and identified the various products formed. Many of these reaction products themselves are familiar as vulcanization accelerators and thus may contribute to the synergistic activit...

Amperometric determination of 2-benzothiazole sulphenamide accelerators.

A simple method for the amperometric estimation of N-cyclohexyl-2-benzothiazole sulphenamide, N-dicyclohexyl-2-benzothiazole sulphenamide, 2-(morpholinothio)benzothiazole and N-tert.-butyl-2-benzothiazole sulphenamide is reported. The results are obtained within 5 min and are correct within +/- 2.0%.

Kinetics of diffusion-controlled copolymerization systems

Kinetics of diffusion-controlled copolymerization systems, (i) vinyl acetate and isobutyl methacrylate, (ii) methyl methacrylate and methyl acrylate and (iii) methyl methacrylate and ethyl methacrylate, have been investigated at 30 and 60° C utilizing the equations developed by Atherton and North. The observed termination constant for system (i) at 30°C decreases monotonically with increasing concentration of vinyl acetate in the feed up to about 90 mole % vinyl acetate and then increases rapidly at higher concentration of vinyl acetate. At 60°C, the termination constant remains roughly constant at low vinyl acetate content and also approaches the ideal behaviour. The termination rate for system (ii) at 60°C remains constant up to about 82 mole % methyl acrylate while for system (iii) at 30°C it increases continuously with methyl methacrylate concentration. These results have been interpreted in terms of the relative stiffness of polymeric chains as the controlling factor of termination reactions and support the diffusion-controlled termination mechanism of Benson and North.

Vinyl polymerization with metal ion redox systems as initiators. Manganic laurate-thiol system

Abstract Polymerization of methyl methacrylate was studied using manganic laurate in the presence of organic thiols as initiators. The thiols used were 1-propane thiol and 2-propane thiol and the solvent was carbon tetrachloride. The rate of polymerization satisfied the expression RP = k1 [manganic laurate]1/2 [thiol]1/2 [monomer]3/2 where k1 is a constant. Spectroscopic investigations indicated complex formation between the monomer and manganic laurate. A reaction scheme is suggested.

Determination of thiocarbamyl sulphenamides, thiuram disulphides and dibenzothiazyl disulphide by amperometric titration

An amperometric method for the determination of thiocarbamyl sulphonamides has been developed, based on the cleavage of the S-N bond by hydriodic acid. The method can also be applied for the cleavage of the S-S bond in thiuram disulphides and dibenzothiazyl disulphide, and thus provides a useful means for the estimation of these compounds as well.