V. R. Pai Verneker’s research while affiliated with Indian Institute of Science Bangalore and other places

Metal hydrazine nitrate complexes of the type M(N2H4)Nn (NO3)2 where M = Mg, n = 2; M = Mn, Fe, Co, Ni, Zn and Cd and n = 3; metal dihydrazine azide complexes of the type M(N2H4)2 (N3)2 where M = Mg, Co, Ni and Zn; and Mg(N2H4)2 (C1O4)2 have been prepared by dissolving the respective metal powders in the solution of corresponding ammonium salts (NO3, N3 and C1O4) in hydrazine hydrate. These hydrazine complexes were also prepared by the conventional method involving the addition of alcoholic hydrazine hydrate to the aqueous solution of metal salts. The hydrazine complexes have been characterised by chemical analysis, infrared spectra and differential thermal analysis (DTA). Impact sensitivities of hydrazine complexes were determined by the drop weight method. The reactivity of these hydrazine complexes does not change with the method of preparation.

Polymeric compositions containing Al-Mg alloys show higher reactivities, in comparison with similar compositions containing aluminium. This is observed irrespective of the amount of oxidizer, type of oxidizer used, type of polymeric binder, and over a range of the particle sizes of the metal additive. This is evident from the higher calorimetric values obtained for compositions containing the alloy, in comparison to samples containing aluminium. Analysis of the combustion residue shows the increase in calorimetric value to be due to the greater extent of oxidation of the alloy. The interaction between the polymeric binder and the alloy was studied by coating the metal particles with the polymer by a coacervation technique. On ageing in the presence of ammonium perchlorate, cracking of the polymer coating on the alloy was noticed. This was deduced from differential thermal analysis experiments, and confirmed by scanning electron microscopic observations. The increase in stiffness of the coating, leading to cracking, has been traced to the cross-linking of the polymer by magnesium.

The humid aging of composite propellants containing a terpolymer of polybutadiene, acrylic acid, and acrylonitrile (PBAN) as a binder has been studied as a function of aging temperature, relative humidity, and aging time. Three composite types - AP-PBAN, AP-Al-PBAN, and AP-(Al-Mg) alloy-PBAN - have been studied. While many of the properties of polymeric composites may be affected by aging, those that seem most affected are the mechanical properties, long before any other property is affected.

The participation of aluminum in the decomposition reaction of ammonium perchlorate (AP) is enhanced if magnesium is added—either as a mixture of Al and Mg powders or as an alloy of Mg in Al. The differential thermal analyses of the compositions show a sensitization in the temperatures of decomposition, as well as increase in the heat of reaction. The AP-Mg and Ap-(MgLi) alloy pellets also show increased reactivity. The burning rates of AP-(Al-10% Mg) alloy pellets increase with increase in the alloy content, while calorimetric values peak at 40% alloy content. The combustion product gases of AP-40% (Al-10% Mg) alloy contain large quantities of hydrogen.

This study investigates the mechanism of action of transition metal chromites on the decomposition of ammonium perchlorate.

Coloration in polyacrylonitrile can be induced in three distinct ways: by heat treatment, by treatment with base, or during synthesis of the polymer itself using ionic initiators at relatively higher temperatures. The present investigation employing 1H and 13C NMR spectroscopy has revealed some common features in colored polyacrylonitrile irrespective of its mode of coloration. All colored polyacrylonitriles give an additional peak around δ 2.7 in 1H NMR spectra and, except for heat-treated polyacrylonitrile, one extra group of peaks in the region δ 12-16 in 13C NMR spectra. The former peak has been attributed to methine and/or methylene protons in branched and/or cyclized structures, while the latter peak has been attributed to methylene carbon atoms in the branched structure. Colorless polyacrylonitriles have been found to be predominantly heterotactic, while colored polyacrylonitriles have been found to have appreciable isotactic contribution.

In order to ascertain the behavior of metallic lithium as an initiator for polymerization, we have carried out homopolymerization of acrylonitrile and acrylamide with lithium metal as initiator utilizing temperature as the only variant. The ESR experiments with the lithium-initiated AN system and**1H NMR spectra of the product obtained from lithium-initiated AM in dioxan strongly point to the dual nature - of both anion radical and free radical - lithium metal as an initiator in vinyl polymerization.

Acrylamide undergoes vinyl polymerization via 1,2-addition to give polyacrylamide when heated alone or when treated with a free radical initiator. However, it undergoes hydrogen-transfer (transition) polymerization via 1,4-addition to give poly- beta -alanine when treated with an anionic initiator. The present investigation shows that metallic lithium and sodium can polymerize acrylamide, in its undiluted form, without any free radical inhibitor to give poly- beta -alanine.

Evidence of the initiation process during uncatalyzed thermal polymerization of vinyl monomers is presented. DSC studies reveal a prominent endothermic effect just before the polymerization exotherm, which is substantiated by the identification of the free radicals produced in the initiation by a quick quenching technique and subsequent detection by ESR at low temperatures.